CA2119555C - Local area network transmission emulator - Google Patents
Local area network transmission emulatorInfo
- Publication number
- CA2119555C CA2119555C CA002119555A CA2119555A CA2119555C CA 2119555 C CA2119555 C CA 2119555C CA 002119555 A CA002119555 A CA 002119555A CA 2119555 A CA2119555 A CA 2119555A CA 2119555 C CA2119555 C CA 2119555C
- Authority
- CA
- Canada
- Prior art keywords
- datagram
- channel
- switched network
- destination
- switched
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/02—Details
- H04L12/16—Arrangements for providing special services to substations
- H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/02—Details
- H04L12/16—Arrangements for providing special services to substations
- H04L12/18—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast
- H04L12/1886—Arrangements for providing special services to substations for broadcast or conference, e.g. multicast with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S370/00—Multiplex communications
- Y10S370/901—Wide area network
- Y10S370/902—Packet switching
- Y10S370/903—Osi compliant network
- Y10S370/904—Integrated Services Digital Network, ISDN
Abstract
A method and apparatus for using switched telecommunications services to emulate a local area network (LAN) medium. The method and apparatus convert a public switched network or an equivalent priv ate network into an LAN cabling method for connecting distant devices using the same communications software as used in tra ditionally wired LANs.
Description
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switched telecommunications services to emulate a local area 3 network (LAN) medium.
The present invention will be better understood hereinafter 6 as a result of the detailed description of the invention when taken in conjunction with the following drawings in which:
Fig. 1 diagrammatically depicts the OSI Reference Model and g its relation to the invention:
1(? Fig. 2 is a block diagram of an embodiment of the invention 1 ~ for conveying a directed datagram:
1 2 Fig. 3 is a block diagram of an embodiment of the invention 13 for conveying a broadcast datagram; and J.4 Fig. 4 is a block diagram of an embodiment of the invention for conveying a multicast datagram.
i7 Local Area Networks (LANs) provide a method for connecting 18 computers or other devices together to exchange data or to 19 harness groups of computers together to apply their combined power to a single problem. Generally speaking, a LAN includes:
~1 1) a high speed transmission medium, typically metallic or fiber 2'i optic, for connecting each of the devices to the LANs 2) the 23 ability to transmit a message on the transmission medium directed 24 to a single device; and 3) a means known as "broadcast" in which ?5 all devices connected to the LAN medium can receive a message 2fi transmitted on the medium. A standard for the implementation of ?7 LAN devices and systems has been established by the Institute of ?3 Electrical and Electronic Engineers as IEEE Standard 802.
The physical length of the transmission medium and the total :n number of devices connected thereto are typically limited on a 1 LAN due to the physics of high speed transmission systems.
2 Bridges and routers are devices used to connect multiple LANs to 3 provide communications between individual LANs and to construct 4 large networks that transcend the technical size limits of a single individual LAN. When the individual LANs to be 6 interconnected are at geographically remote locations, bridges 7 and routers are used in pairs, one at each site, to provide a 8 path for data to flow from one LAN to another, with a lower speed communication link between the bridge or router pair. Typically the data rates of the long distance communications link fs a 11 fraction of the data rate of the LAN medium. The use of bridges 12 and routers has been limited, however, due to the cost of these 13 devices and the costs of the long distance communications link.
19 An all-digital telephone network, known as the Integrated Services Digital Network ("ISDN"), has become a potential 16 s~stitute for the private long distance lines currently used by 1~ bridges and routers. ISDN provides relatively high speed digital 1g transmission service on an "as needed" basis, and is different 19 from LAN transmission media in that it is a switched transmission media which provides a point-to-point transmission service on an 21 intermittent basis.
22 Modern communications technology can be analyzed with 23 respect to the Open Systems Interconnect (OSI) Reference Model.
24 The OSI model. decomposes a communication system into seven major 2 5 components or layers which are defined by international 26 standards. The OSI model is concerned with the interconnection 2~ between systems, i.e., the way they exchange information, and not 26 with the internal functions that are performed by a given system.
29 The OSI model depicted in Fig. 1 provides a generalized view of a ,~.
~5 1 layered architecture, using an approach where sets of functions Z have been allocated to different layers.
3 The first layer is known as the physical layer and is 4 responsible for the transmission of bit streams across a particular physical transmission medium. This layer involves a 6 connection between two machines that allows electrical signals to 7 be exchanged between them.
8 The second layer is the~data link layer, and is responsible 9 for providing reliable data transmission from one node to another and for shielding higher layers from any concerns about the 11 physical transmission medium. It is concerned with the error-12 free transmission of frames of data.
13 The third layer, the network layer, is concerned with 1~ routing data from one network node to another and is responsible for establishing, maintaining, and terminating the network 15 connection between two users and for transferring data along that 17 connection. There can be only one.network connection between two 18 given users, although there can be many possible routes from 19 which to choose when the particular connection is established.
The fourth layer is the transport layer, and is responsible 21 for providing data transfer between two users at an agreed on 22 level of quality. when a connection is established between two 23 users, the transport layer is responsible for selecting a 2~ particular class of service to be used, for monitoring transmissions to ensure the appropriate service quality is 26 maintained, and for notifying the users if it is not.
r41 w 1 The fifth layer is the session layer, and it focuses on 2 providing services used to organize and synchronize the dialog 3 that takes place bQtween users and to manage the data exchange.
d A primary concern of the session layer is controlling when users can send and receive, based on whether they can send and receive 5 concurrently or alternately.
7 The sixth layer is the presentation layer, and is 8 responsible for the presentation of information in a way that is 9 meaningful to network users. This may include character code translation, data conversion or data compression and expansion.
11 The seventh layer is the application layer, and it provides 12 a means for application processes to access the system 17 interconnection facilities in order to exchange information.
to This includes services used to establish and terminate the connections between users and to monitor and manage the systems 16 being interconnected and the various resources they employ.
17 Different components (or implementations) that conform to a 18 common standard are considered equivalent and interchangeable. A
19 system constructed from components that conform to their respective standard is expected to interoperate (i.e., to be able 21 to communicate) with any other system constructed out of a ~2 different set of components that conform to the standards.
23 Communications between systems are organized into information 2d that is exchanged between entities at each layer.
A layer in the OSI model provides specific services to an ~6 upper layer through service access points ('SAPs'). Take, for 1 example, the situation where Systems A and B are joined by a 2 transmission medium at layer 1. Information from layer x of 7 system A is constrained to communicate with layer x of system B.
4 The information of layer x of system A is transported, however, by requesting service from layer x-1 of system A for delivery to 6 layer x of system B. The mechanism for communication between two 7 systems at a single layer is referred to as a protocol (i.e., 'a 8 layer x protocol'), and a protocol stack is a set of protocols 9 for layers 1 to x. The OSI protocols provide flexibility in l0 usage by incorporating optional features and user determined 11 parameters. Profiles are standards that.specify the selection of 12 options and parameters to ensure compatibility between two 13 compliant systems. Profiles are needed since two compliant 14 systems using different profiles may still not be able to exchange data.
16 In Fig. 1, layer 1 represents the network or transmission 17 medium, and includes token rings, token buses, and interfaces 18 such as RS-232, RS-530 and V.35. Layer 2, the data link layer, 19 has as its primary responsibility the transfer of frames of 2o information between physically linked devices. When only two 21 devices are connected by the network layer medium, the data link 22 layer assumes that the network layer will provide the mechanism 23 of addressing messages to the proper device.
2~ IEEE Standard 802.2 provides a model which divides the data link layer 2 into two sublayers: an upper sublayer for Logical 25 Link Control (LLC) and a lower sublayer for Media Access Control (MAC). The ZEES 802.2 model differs from earlier data link 2 layers of the OSI Reference Model by providing a method for 3 addressing messages to specific destinations. This is required 4 since more than two devices are connected by the medium at layer 1. This mechanism is necessary in the context of a single 6 isolated LAN (or LAN segment) without connections to other LANs 7 (or LAN segments) because many devices are connected to a common 8 transmission medium and a means for directing a message to a 9 single destination is important.
The MAC sublayer regulates station access to the 11 transmission medium that is shared by multiple stations on the 12 LAN. For a given LAN, the MAC sublayer governs a common 13 transmission medium that has one pathway or route between ib communicating network stations. In the context of the IEEE 802.2 model, the network station address is referred to as the MAC
16 address and is sufficient for ensuring delivery of a MAC frame to 17 a destination address on the LAN. The MAC sublayer offers 18 services consistent with those in the OSI data link layer.
19 The LLC sublayer mediates multiple logical connections for upper layer service users. As a service provider, the LLC
21 sublayer offers several Service Access Points (SAP) as logical 22 ports for multiple upper layer entities located at a given 23 network station address. As a service user, the LLC sublayer 2d issues requests through the SAP provided by the MAC sublayer. The LLC sublayer Service Access Points are typically shown situated 26 between layer 3 (network) and layer 2 (data link) of the OSI
1 Reference Model.
2 A significant number of layer 3 protocols bypass the 3 LLC Service Access Point and interface directly to the MAC
4 Service Access Point.
S
8 The disclosed invention provides a method and apparatus 9 for using the IEEE Standard 802 LLC or MAC Service layer as an interface to communicate over the ISDN. The disclosed 11 invention presents the ISDN as a LAN transmission media to 12 upper layer (layer 3 and above) protocols, and permits 13 communication systems designed to operate over LAN to 14 operate over the ISDN. As a result, LAN devices can be dispersed geographically using inexpensive ISDN
16 communications without the geographic limitations of a 17 single LAN and without the cost of bridges, routers, and the 18 associated communications links currently used to 19 interconnect LAN segments.
Fig. 1 shows the relationship of the invention with 21 respect to the OSI Reference Model. The generally accepted 22 role of the ISDN in the communications industry or OSI
23 Reference Model is shown as a stack occurring in layers 1 to 24 3 of Fig. 1 (bottom left). The ISDN has the role of a a layer 3 service with service access points to layer 4 26 protocols. Use of the disclosed invention permits ISDN to 27 be used as an alternative LAN medium, thus permitting 28 existing computer systems and other communication a~
1 devices designed to use LANs to be connected through the ISDN
2 without change of protocols from layer 3 on up. This allows 3 access to the ISDN for a large body of systems and software 4 without requiring modification.
The disclosed embodiment of the invention features a MAC
6 layer interface, packet replication to emulate broadcasting on a 7 common access medium, physical connection during periods with message traffic, physical disconnection during periods with no message traffic, classification of traffic patterns with re direction to circuit and packet switched channels that match the 11 required capacity, a virtual channel interface that utilizes 12 multiple physical channels to service one logical channel, a 13 virtual physical interface that makes multiple physical 14 interfaces appear as a single physical interface, and a method for providing connections to a number of users that exceed the 16 number of physical channels.
i' Accordingly in one aspect the invention provides an 18 apparatus for coupling a source device to a destination device, Z9 comprising: means for receiving, from a logical link control or medium access control service layer, a datagram having a 21 source address identifying a source device and a destination 22 address identifying a destination device; means for retrieving 23 from a storage location an address on a switched network which 24 corresponds to the destination address; means for using the switched network address to obtain access to a channel of the 26 switched network; and means for providing the datagram to the 2~ channel of the switched network for transmission to the 2~ destination device.
29 In a further aspect the invention provides a method for coupling a source device to a destination device, 31 comprising: receiving, from a logical link control or medium 1 access control service layer, a datagram having a source 2 address identifying a source device and a destination address 3 identifying a destination device; retrieving from a storage a location an address on a switched network which corresponds to the destination address; using the switched network address to obtain access to a channel of the switched network; and providing the datagram to the channel of the switched network g for transmission to the destination device.
g ~TAIhED DESCRTPTION OF THE INVENTI9Z1 Three classes of datagrams are typically submitted to a LAN
1 1 medium: directed datagrams, multicast datagrams and all stations 12 broadcast datagrams. The LAN emulator manages LAN datagram 13 traffic by a set of logical channels between every pair of nodes 14 that exchanges datagrams. The actual transmission of datagrams 1 5 between nodes is provided by a physical channel. The LAN
16 emulator only requires a physical channel between nodes When 1~ datagrams are actively being exchanged over a logical channel (between two nodes).
lg Since the hardware interface to the public network (e. g.
ISDN) provides a limited number of physical channels, the LAN
21. emulator provides a monolithic interface to the higher layer 22 protocol process. That process interacts with a single entity, 2 3 ~e ~ emulator, while the total transmission service may be 24 provided by more than one hardware interface to the public 2 5 network.
2 6 All types of datagrams (directed, multicast, and broadcast) 2~ intended for transmission are potentially subject to one or more 2 g filtering mechanisms. A filter can either leave the datagram 2 9 unchanged or remove the datagram from any further transmit 3 0 processing. Datagrams that remain unchanged are termed ordinary WO 93/06674 PCT/U~92/07773 r,...
1 or unfiltered datagrams, while datagrams that are removed by a , 2 filter are termed filtered datagrams. Each filter typically acts 3 on a specific class or type of datagram. ' 4 One generic filtering mechanism used in the invention is termed rate suppression. Rate suppression acts on certain types 6 of datagrams which contain repetitive information, and functions 7 by passing only a certain percentage or ratio of those datagrams 8 it recognizes. The purpose of rate suppression filtering is to 9 minimize transmission charges for those datagrams whose content does not change or changes very slowly over time.
il Another generic filtering mechanism used in the invention is 12 termed response spoofing. Response spoofing acts on those 13 packets which contain repetitive information, but which require a 14 response from the destination or destinations. The response spoofing Filter not only removes these datagrams from further 16 transmission processing, but also simulates the response that 17 would be expected from the destination(s), and delivers the 18 spoofed response to the higher layer protocol processes.
19 With reference to Fig. 2, an embodiment of the invention for conveying a directed datagram with a specific destination address 21 through the LAN Emulator interface to emulate the transmission of 22 a directed datagram on a LAN is described.
23 As mentioned above, a protocol stack is a set of protocols 24 for the various layers. With the disclosed embodiment, and with reference to Fig. 2, a high layer protocol process submits a 26 directed datagram to the LAN Emulator interface 10 accompanied by .
~~119555 A 1 the appropriate LAN MAC layer source and destination addresses.
2 For every device there is at least one LAN MAC address and a ' 3 corresponding switched network address.
4 This disclosed embodiment describes a direct interface from higher layers to the MAC interface, as is commonly found in 6 systems implemented for personal computers. An LLC interface may 7 be required in some systems. The difference between an LLC
8 interface and a MAC interface is not significant with respect to 9 the disclosed invention.
A directed datagram filter 15 makes a determination of the 11 datagram type by comparing the datagram type with the contents of 12 a directed datagram filter list 25. This is a list of protocol 13 specific datagrams specific to the application system. When 14 there is a matching datagram type in the directed datagram filter list 25, the datagram is marked as one which may be discarded 16 from the transmission queue or enqueued for a spoofed response at 17 a later time. The marking is based upon the actions specified 18 within the directed datagram filter list 25.
19 The datagram is then passed to a channel classifier 20 for further qualification. However, datagrams marked for removal 21 from the transmission queue are not given to the channel 22 classifier 20 and so are not sent to any destination node.
23 Instead, they are either discarded or sent to the datagram 24 response handler 30, where a spoofed response is formatted and eventually delivered to the higher layer protocol process.
26 The channel classifier 20 receives unfiltered directed WO 93/06674 ,. ~ ~ PCT/U592/07773 1 datagrams from the directed datagram filter 15. Using the LAN ' 2 MAC address as a search key, the classifier 20 retrieves a 3 switched network address and an associated node channel status 4 from a network definition table 35.
The network definition table 35 has an entry for each node 6 on the emulated LAN. A node may have multiple entries with 7 different LAN MAC addresses. Each entry includes, but is not 8 limited to: the LAN MAC address, which is the node LAN address 9 the device would have if it was connected to a conventional LAN;
the switched network address, which is the address of the device 11 on the switched network (e. g., for devices using ISDN, the public 12 network number on the public switched telephone network): the 13 node type, which is a descriptor which describes the node type or 14 function: suspension timer values, which are the parameters that control the suspension of the network connection: preferred 16 service parameters, which specify the preferred types of 17 transmission service when a connection is created: node channel 18 status parameter, which reflects the operational status of a 19 remote node; and broadcast service selectors, which are parameters that specify the methods by which broadcast messages 21 are distributed to remote nodes.
22 One class of preference is the type of service. The 23 effective bandwidth delivered is determined by the preferred 24 service parameter of the network definition table. The channel classifier can decide whether to transmit low priority 26 information on low bandwidth channels, such as the D-channel ~~~~~5~
1 packet switched service of ISDN. Devices connected to an ISDN
2 may select, among others, a B-channel circuit switched service, 3 B-channel packet switched service, D-channel packet switched 4 service, or HO circuit switched service.
Another class of preference is the minimum and maximum 6 throughput desired. With the disclosed invention, multiple 7 instances of a physical interface may be used under a single 8 service layer. The upper laxer protocols can therefore be 9 presented with a single logical service layer while the actual l0 transmission service may be delivered by more than one physical 11 interface. It is possible to synthesize higher speed 12 transmission service by combining multiple physical interfaces 13 under a single service interface. Thus a device that requires 14 higher speed transmission may specify the minimum and maximum number of transmission channels to be used when communication is 16 established with a remote node. For purposes of description of 17 the invention, the logical channel is the connection service 18 delivered to the upper layers, and the physical channel is the 19 means by which datagrams are delivered.
The datagram is discarded by channel classifier 20 when 21 there is no entry in the table 35 that has the destination LAN
22 MAC address. For LAN MAC addresses that are in the network 23 definition table 35, the four possible values for node channel 24 status are: registered with a logical channel and assigned physical channel(s), registered with a logical channel and no 26 physical channels, registered, or not registered.
1 Where the node channel status for a case is registered node , 2 with datagram traffic on both a logical channel and its physical 3 channels, it is considered a connection that is completely ' 4 active. An unfiltered datagram is immediately submitted to the datagram dispatcher 40.
6 For an unfiltered datagram where the node channel status is 7 registered node with datagram traffic on the logical channel but 8 with no associated physical channel, there is an attempt to 9 establish a connection to the destination node on a new physical channel. This is accomplished by giving the datagram to channel 11 manager 45 which attempts to establish a~connection on a physical 12 channel and then to send the datagram over that connection. The 13 channel manager 45 manages the process of establishing a 14 connection through both a logical and new physical channel.
Node registration is a MAC management function that occurs 16 at the time the LAN Emulator is initialized. When a node is 17 registered with another node it means that it will respond to a 18 request for connection. It also means that another node may 19 attempt a connection with it. There is no implication that the connection attempt will be successful: a connection attempt may 21 fail because the node's circuit resources may be occupied at the 22 time of the attempt.
23 Node de-registration occurs when the LAN Emulator is shut 24 down. This involves the LAN emulator sending de-registration messages to its connection partners. De-registration is not 26 mandatory. A node may also be de-registered when an attempt to In ~119~5~
1 connect to it fails because that node is no longer active.
2 Datagrams addressed to a node which is not registered are 3 discarded by the channel classifier 20.
4 As mentioned above, the channel manager 45 is responsible for initiating a connection on a logical and/or a physical 6 channel. If there is a request for connection on a pre-existing 7 logical channel, the channel manager 45 establishes connections 8 on the requisite physical channel(s). For a connection request 9 when no logical channel exists, the channel manager 45 will set to up a new logical channel as well as new physical channels.
il A logical channel may be supported by more than one 12 connection to the same destination through multiple physical 13 channels. The channel manager 45 uses a user preference 14 contained within the network definition table 35 to determine the number of physical channel resources to allocate for a given 16 connection attempt to the destination node.
1~ There are three possible occurrences when there is an 18 attempt to allocate a physical channel on behalf of the logical 19 channel. In the first, there are either no physical channels available for conveying the datagram or there is a network 21 problem that prevents a call from being offered to the 22 destination node. In the second, there are physical channels 23 available, but when a call request is placed to the remote node 24 at the destination switched network address, a rejected call response gets returned. In these two cases, the logical channel 26 is optionally torn down and network definition table maintenance a 1 is performed.
2 The third possibility is that the call request is accepted 3 by the node at the destination switched network address, at which 4 point the connection is considered physically active.
When the node channel status field shows that no logical or 6 physical channel exists, there is a choice for an appropriate 7 course of action which is dependent upon whether a connection on 8 a physical channel is possible, and which requires a destination 9 node to have registered its LAN MAC address and to be able to accept a connection request. In this case, a logical channel and 11 logical channel reference number are assigned after the physical 12 channel is set up and a connection established.
13 The channel manager 45 will also monitor traffic on the 14 physical channel, and during periods when there is no traffic, it may disconnect the physical channel while maintaining the logical 16 channel. When new datagram traffic begins, the channel manager 17 45 will reassign a physical channel. During this process a 18 physical channel is described as being suspended and later 19 resumed. The channel manager 45 will monitor external events such as incoming calls and determine whether a logical channel 21 will release its physical channel in order to reassign it to the 22 new call. This may be termed release of bandwidth on demand.
23 One consequence of the invention's embodiment of suspend and 24 resume is that the channel manager 45 may maintain more logical channels than the maximum number of physical channels possible.
26 This is known as channel over-subscription. The channel manager ?1.1955 1 45 may associate an idle physical channel to a new logical 2 channel while still maintaining the logical channel that had 3 originally used the physical channel. As a consequence of over-4 subscription, there may be periods when there is more demand for active channels than there is supply of preferred physical 6 channels. In such cases the channel manager 45 will assign 7 alternate (i.e., slower and/or more expensive) physical channels 8 to carry the data. Over-subscription is also tied to the concept 9 of a monolithic interface since the effectiveness of over-l0 subscription is enhanced by the use of a larger number of 11 physical channels.
12 The directed datagram dispatcher 40 receives a list of 13 physical channels to which a datagram must be transmitted. It 14 then manages datagram delivery by sending it through those individual channels. Usually there is only one element in the 16 channel list. If multiple channels are listed and the packet 17 size is sufficiently large, the datagram dispatcher 40 may 18 fragment the datagram and send the marked fragments on different 19 physical channels to the same logical destination.
With reference to Fig. 3, the mechanisms employed to convey 21 an all stations broadcast datagram through the LAN Emulator 22 interface to emulate a local area network are described. An all 23 stations broadcast datagram has a LAN MAC destination address 24 with a format that is a special case in that all bits are set to one in each of the address's octets. This transmission is 26 emulated by sending the datagram to all eligible members of a 1 finite list of recipients.
2 As with the emulation mechanism for the directed datagram, 3 for an all stations broadcast, the higher layer protocol process 4 submits a datagram to the LAN Emulator interface 110 with an all stations broadcast destination LAN MAC address. Because there 6 are several uses for an all station broadcast datagram that are 7 entirely application dependent, several selection mechanisms may 8 be used for separating broadcast datagrams of different origin 9 and directing them into appropriate courses of action. For example, some datagrams may be entirely blocked from transmission 11 by filter 115, some may have a transmission frequency attenuated 12 by the filter, and the filter may have no effect on the 13 transmission frequency of others. The metric for these filters 14 may be a function of either cost, throughput performance, propagation delay or some other factor.
16 The broadcast filter 115 compares the broadcast type against 17 a broadcast filter list 125 to determine whether the broadcast 18 datagram is a candidate for filtering or is an ordinary broadcast 19 datagram. The filtering mechanism 115 affects the transmission 2o frequency of broadcasts either by not transmitting any of the 21 datagrams or by transmitting over time 1 of every n datagrams for 22 each type submitted.
23 The broadcast filter list 125 either specifies a spoofing 24 response or contains the parameters and metrics that specify the appropriate attenuation rate for each type of broadcast datagram.
26 The value of this rate is zero for blocked broadcasts or is ~119~~~
1 expressed as a ratio for reduced broadcast frequencies. The 2 filtering mechanism 115 does not affect the transmission 3 frequency of unfiltered broadcasts, which are automatically given 4 to the channel classifier 120.
The channel classifier 120 receives all unfiltered 6 broadcasts and some reduced frequency broadcasts and qualifies 7 the broadcast eligibility for transmission. When the channel 8 classifier 120 receives a broadcast datagram, it determines a 9 list of destinations to which to send the broadcast and then l0 passes that list to the channel manager 145 to handle delivery.
11 The channel classifier 120 will enqueue unfiltered 12 broadcasts for delivery through all channels that are eligible 13 for this service. This is regulated by the broadcast service 14 parameter of the network definition table 135.
The functions of the channel classifier 120 may be 16 accomplished by software, hardware, or through packet replication 17 services provided by the network. There may be several reference 18 criteria that are useful for deciding which destinations receive 19 a particular broadcast datagram, and the network definition table 135 can hold values for these criteria including node type and 21 node channel status.
22 The channel manager 145 receives information from the 23 network definition table 135 to discriminate between those 24 logical channels with active physical channels and those for which a physical channel must be first reestablished. For 26 logical channels with active physical channels, the channel ~~
1 manager 145 submits the broadcast frame to the datagram 2 dispatcher 140 with a request for transmission. The datagram 3 dispatcher 140 receives a list of physical channels to which a 4 broadcast must be transmitted and then manages broadcast delivery by sending the broadcast through the individual physical 6 channels.
7 For logical channels without active physical channels, the 8 channel manager 145 enqueues the broadcast datagram for delivery 9 to those logical channels that can establish a new physical channel.
11 With reference to Fig. 4, the mechanisms employed to convey 12 a multicast datagram through a LAN emulator interface to emulate 13 a local area network are described. A multicast destination MAC
14 address is represented by a '1' in the Individual/Group Bit (the LSB) and a '0' in the Universal/Local Administration Bit (the 16 LSB+1) of the first octet, thus denoting a Group address within 17 the universally administered address space. As with broadcasts, 18 this class of transmission is emulated by sending the datagram to 19 a list of recipients. The list may be same as the list maintained for the all stations broadcast datagram.
21 Again, as with the directed datagrams and broadcast 22 datagrams, the higher layer protocol process submits a datagram 23 with a multicast LAN MAC address to the LAN Emulator interface 24 210, which in turn submits it, after filtering in filter 215 based on infonaation in the multicast filter list 225, to the 26 channel classifier 220. When the channel classifier 220 receives ~1~.95~~
1 a multicast that is enqueued for transmission, it uses the 2 network table 235 to determine a list of destinations to which to 3 send the multicast and passes that list to the channel manager 4 245 to handle delivery.
There are several reference criteria that may be useful for 6 deciding which destinations receive a particular multicast 7 datagram. The network definition table 235 holds values for 8 these criteria which include node type, node channel status, and 9 multicast filter lists.
Channel manager 245 examines the network definition table il 235 to discriminate between those logical channels with active 12 physical channels and those for which a physical channel must be 13 first reestablished. For logical channels with active physical 14 channels, the channel manager 245 submits the multicast frame to the datagram dispatcher 240 with a request for transmission. The 16 datagram dispatcher 240 receives a list of channels to which a 17 multicast must be transmitted. It then manages multicast 18 delivery by sending it through the individual channels.
19 It should be apparent to one skilled in the art that the invention contains a message receive function which will perform 21 complementary processing on received messages. All received 22 directed datagrams, as well as broadcast and multicast datagrams, 23 will be passed up to the higher layer protocol process.
24 It should also be readily apparent to one skilled in the art that the disclosed invention is not limited to any specific 26 computer architecture or hardware device. For example, the '~~~.~-~'~~~
1 disclosed embodiment works not only on IBM compatible personal 2 computers with the Novell network operating system, but with 3 other computer architectures as well, including IBM microchannel 4 personnel computers, SUN SPARC workstations, Apple Macintosh computers, minicomputers and mainframes. In addition, although 6 the embodiment disclosed herein simulates LANs over ISDN, the 7 invention is applicable to other switched networks such as pre 8 ISDN switched digital networks, X.25 networks, and frame relay 9 networks.
Although it may be preferred to implement the described 11 procedures using software, they can also be implemented using 12 well-known hardware elements. Similarly, the disclosed invention 13 can be applied to other communication devices which use LAN
14 interfaces, including LAN bridges and routers.
Although an embodiment of the invention has been illustrated 16 and described, it is anticipated that various changes and 17 modifications will be apparent to those skilled in the art, and 18 that such changes may be made without departing from the scope of 19 the invention as defined by the following claims:
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switched telecommunications services to emulate a local area 3 network (LAN) medium.
The present invention will be better understood hereinafter 6 as a result of the detailed description of the invention when taken in conjunction with the following drawings in which:
Fig. 1 diagrammatically depicts the OSI Reference Model and g its relation to the invention:
1(? Fig. 2 is a block diagram of an embodiment of the invention 1 ~ for conveying a directed datagram:
1 2 Fig. 3 is a block diagram of an embodiment of the invention 13 for conveying a broadcast datagram; and J.4 Fig. 4 is a block diagram of an embodiment of the invention for conveying a multicast datagram.
i7 Local Area Networks (LANs) provide a method for connecting 18 computers or other devices together to exchange data or to 19 harness groups of computers together to apply their combined power to a single problem. Generally speaking, a LAN includes:
~1 1) a high speed transmission medium, typically metallic or fiber 2'i optic, for connecting each of the devices to the LANs 2) the 23 ability to transmit a message on the transmission medium directed 24 to a single device; and 3) a means known as "broadcast" in which ?5 all devices connected to the LAN medium can receive a message 2fi transmitted on the medium. A standard for the implementation of ?7 LAN devices and systems has been established by the Institute of ?3 Electrical and Electronic Engineers as IEEE Standard 802.
The physical length of the transmission medium and the total :n number of devices connected thereto are typically limited on a 1 LAN due to the physics of high speed transmission systems.
2 Bridges and routers are devices used to connect multiple LANs to 3 provide communications between individual LANs and to construct 4 large networks that transcend the technical size limits of a single individual LAN. When the individual LANs to be 6 interconnected are at geographically remote locations, bridges 7 and routers are used in pairs, one at each site, to provide a 8 path for data to flow from one LAN to another, with a lower speed communication link between the bridge or router pair. Typically the data rates of the long distance communications link fs a 11 fraction of the data rate of the LAN medium. The use of bridges 12 and routers has been limited, however, due to the cost of these 13 devices and the costs of the long distance communications link.
19 An all-digital telephone network, known as the Integrated Services Digital Network ("ISDN"), has become a potential 16 s~stitute for the private long distance lines currently used by 1~ bridges and routers. ISDN provides relatively high speed digital 1g transmission service on an "as needed" basis, and is different 19 from LAN transmission media in that it is a switched transmission media which provides a point-to-point transmission service on an 21 intermittent basis.
22 Modern communications technology can be analyzed with 23 respect to the Open Systems Interconnect (OSI) Reference Model.
24 The OSI model. decomposes a communication system into seven major 2 5 components or layers which are defined by international 26 standards. The OSI model is concerned with the interconnection 2~ between systems, i.e., the way they exchange information, and not 26 with the internal functions that are performed by a given system.
29 The OSI model depicted in Fig. 1 provides a generalized view of a ,~.
~5 1 layered architecture, using an approach where sets of functions Z have been allocated to different layers.
3 The first layer is known as the physical layer and is 4 responsible for the transmission of bit streams across a particular physical transmission medium. This layer involves a 6 connection between two machines that allows electrical signals to 7 be exchanged between them.
8 The second layer is the~data link layer, and is responsible 9 for providing reliable data transmission from one node to another and for shielding higher layers from any concerns about the 11 physical transmission medium. It is concerned with the error-12 free transmission of frames of data.
13 The third layer, the network layer, is concerned with 1~ routing data from one network node to another and is responsible for establishing, maintaining, and terminating the network 15 connection between two users and for transferring data along that 17 connection. There can be only one.network connection between two 18 given users, although there can be many possible routes from 19 which to choose when the particular connection is established.
The fourth layer is the transport layer, and is responsible 21 for providing data transfer between two users at an agreed on 22 level of quality. when a connection is established between two 23 users, the transport layer is responsible for selecting a 2~ particular class of service to be used, for monitoring transmissions to ensure the appropriate service quality is 26 maintained, and for notifying the users if it is not.
r41 w 1 The fifth layer is the session layer, and it focuses on 2 providing services used to organize and synchronize the dialog 3 that takes place bQtween users and to manage the data exchange.
d A primary concern of the session layer is controlling when users can send and receive, based on whether they can send and receive 5 concurrently or alternately.
7 The sixth layer is the presentation layer, and is 8 responsible for the presentation of information in a way that is 9 meaningful to network users. This may include character code translation, data conversion or data compression and expansion.
11 The seventh layer is the application layer, and it provides 12 a means for application processes to access the system 17 interconnection facilities in order to exchange information.
to This includes services used to establish and terminate the connections between users and to monitor and manage the systems 16 being interconnected and the various resources they employ.
17 Different components (or implementations) that conform to a 18 common standard are considered equivalent and interchangeable. A
19 system constructed from components that conform to their respective standard is expected to interoperate (i.e., to be able 21 to communicate) with any other system constructed out of a ~2 different set of components that conform to the standards.
23 Communications between systems are organized into information 2d that is exchanged between entities at each layer.
A layer in the OSI model provides specific services to an ~6 upper layer through service access points ('SAPs'). Take, for 1 example, the situation where Systems A and B are joined by a 2 transmission medium at layer 1. Information from layer x of 7 system A is constrained to communicate with layer x of system B.
4 The information of layer x of system A is transported, however, by requesting service from layer x-1 of system A for delivery to 6 layer x of system B. The mechanism for communication between two 7 systems at a single layer is referred to as a protocol (i.e., 'a 8 layer x protocol'), and a protocol stack is a set of protocols 9 for layers 1 to x. The OSI protocols provide flexibility in l0 usage by incorporating optional features and user determined 11 parameters. Profiles are standards that.specify the selection of 12 options and parameters to ensure compatibility between two 13 compliant systems. Profiles are needed since two compliant 14 systems using different profiles may still not be able to exchange data.
16 In Fig. 1, layer 1 represents the network or transmission 17 medium, and includes token rings, token buses, and interfaces 18 such as RS-232, RS-530 and V.35. Layer 2, the data link layer, 19 has as its primary responsibility the transfer of frames of 2o information between physically linked devices. When only two 21 devices are connected by the network layer medium, the data link 22 layer assumes that the network layer will provide the mechanism 23 of addressing messages to the proper device.
2~ IEEE Standard 802.2 provides a model which divides the data link layer 2 into two sublayers: an upper sublayer for Logical 25 Link Control (LLC) and a lower sublayer for Media Access Control (MAC). The ZEES 802.2 model differs from earlier data link 2 layers of the OSI Reference Model by providing a method for 3 addressing messages to specific destinations. This is required 4 since more than two devices are connected by the medium at layer 1. This mechanism is necessary in the context of a single 6 isolated LAN (or LAN segment) without connections to other LANs 7 (or LAN segments) because many devices are connected to a common 8 transmission medium and a means for directing a message to a 9 single destination is important.
The MAC sublayer regulates station access to the 11 transmission medium that is shared by multiple stations on the 12 LAN. For a given LAN, the MAC sublayer governs a common 13 transmission medium that has one pathway or route between ib communicating network stations. In the context of the IEEE 802.2 model, the network station address is referred to as the MAC
16 address and is sufficient for ensuring delivery of a MAC frame to 17 a destination address on the LAN. The MAC sublayer offers 18 services consistent with those in the OSI data link layer.
19 The LLC sublayer mediates multiple logical connections for upper layer service users. As a service provider, the LLC
21 sublayer offers several Service Access Points (SAP) as logical 22 ports for multiple upper layer entities located at a given 23 network station address. As a service user, the LLC sublayer 2d issues requests through the SAP provided by the MAC sublayer. The LLC sublayer Service Access Points are typically shown situated 26 between layer 3 (network) and layer 2 (data link) of the OSI
1 Reference Model.
2 A significant number of layer 3 protocols bypass the 3 LLC Service Access Point and interface directly to the MAC
4 Service Access Point.
S
8 The disclosed invention provides a method and apparatus 9 for using the IEEE Standard 802 LLC or MAC Service layer as an interface to communicate over the ISDN. The disclosed 11 invention presents the ISDN as a LAN transmission media to 12 upper layer (layer 3 and above) protocols, and permits 13 communication systems designed to operate over LAN to 14 operate over the ISDN. As a result, LAN devices can be dispersed geographically using inexpensive ISDN
16 communications without the geographic limitations of a 17 single LAN and without the cost of bridges, routers, and the 18 associated communications links currently used to 19 interconnect LAN segments.
Fig. 1 shows the relationship of the invention with 21 respect to the OSI Reference Model. The generally accepted 22 role of the ISDN in the communications industry or OSI
23 Reference Model is shown as a stack occurring in layers 1 to 24 3 of Fig. 1 (bottom left). The ISDN has the role of a a layer 3 service with service access points to layer 4 26 protocols. Use of the disclosed invention permits ISDN to 27 be used as an alternative LAN medium, thus permitting 28 existing computer systems and other communication a~
1 devices designed to use LANs to be connected through the ISDN
2 without change of protocols from layer 3 on up. This allows 3 access to the ISDN for a large body of systems and software 4 without requiring modification.
The disclosed embodiment of the invention features a MAC
6 layer interface, packet replication to emulate broadcasting on a 7 common access medium, physical connection during periods with message traffic, physical disconnection during periods with no message traffic, classification of traffic patterns with re direction to circuit and packet switched channels that match the 11 required capacity, a virtual channel interface that utilizes 12 multiple physical channels to service one logical channel, a 13 virtual physical interface that makes multiple physical 14 interfaces appear as a single physical interface, and a method for providing connections to a number of users that exceed the 16 number of physical channels.
i' Accordingly in one aspect the invention provides an 18 apparatus for coupling a source device to a destination device, Z9 comprising: means for receiving, from a logical link control or medium access control service layer, a datagram having a 21 source address identifying a source device and a destination 22 address identifying a destination device; means for retrieving 23 from a storage location an address on a switched network which 24 corresponds to the destination address; means for using the switched network address to obtain access to a channel of the 26 switched network; and means for providing the datagram to the 2~ channel of the switched network for transmission to the 2~ destination device.
29 In a further aspect the invention provides a method for coupling a source device to a destination device, 31 comprising: receiving, from a logical link control or medium 1 access control service layer, a datagram having a source 2 address identifying a source device and a destination address 3 identifying a destination device; retrieving from a storage a location an address on a switched network which corresponds to the destination address; using the switched network address to obtain access to a channel of the switched network; and providing the datagram to the channel of the switched network g for transmission to the destination device.
g ~TAIhED DESCRTPTION OF THE INVENTI9Z1 Three classes of datagrams are typically submitted to a LAN
1 1 medium: directed datagrams, multicast datagrams and all stations 12 broadcast datagrams. The LAN emulator manages LAN datagram 13 traffic by a set of logical channels between every pair of nodes 14 that exchanges datagrams. The actual transmission of datagrams 1 5 between nodes is provided by a physical channel. The LAN
16 emulator only requires a physical channel between nodes When 1~ datagrams are actively being exchanged over a logical channel (between two nodes).
lg Since the hardware interface to the public network (e. g.
ISDN) provides a limited number of physical channels, the LAN
21. emulator provides a monolithic interface to the higher layer 22 protocol process. That process interacts with a single entity, 2 3 ~e ~ emulator, while the total transmission service may be 24 provided by more than one hardware interface to the public 2 5 network.
2 6 All types of datagrams (directed, multicast, and broadcast) 2~ intended for transmission are potentially subject to one or more 2 g filtering mechanisms. A filter can either leave the datagram 2 9 unchanged or remove the datagram from any further transmit 3 0 processing. Datagrams that remain unchanged are termed ordinary WO 93/06674 PCT/U~92/07773 r,...
1 or unfiltered datagrams, while datagrams that are removed by a , 2 filter are termed filtered datagrams. Each filter typically acts 3 on a specific class or type of datagram. ' 4 One generic filtering mechanism used in the invention is termed rate suppression. Rate suppression acts on certain types 6 of datagrams which contain repetitive information, and functions 7 by passing only a certain percentage or ratio of those datagrams 8 it recognizes. The purpose of rate suppression filtering is to 9 minimize transmission charges for those datagrams whose content does not change or changes very slowly over time.
il Another generic filtering mechanism used in the invention is 12 termed response spoofing. Response spoofing acts on those 13 packets which contain repetitive information, but which require a 14 response from the destination or destinations. The response spoofing Filter not only removes these datagrams from further 16 transmission processing, but also simulates the response that 17 would be expected from the destination(s), and delivers the 18 spoofed response to the higher layer protocol processes.
19 With reference to Fig. 2, an embodiment of the invention for conveying a directed datagram with a specific destination address 21 through the LAN Emulator interface to emulate the transmission of 22 a directed datagram on a LAN is described.
23 As mentioned above, a protocol stack is a set of protocols 24 for the various layers. With the disclosed embodiment, and with reference to Fig. 2, a high layer protocol process submits a 26 directed datagram to the LAN Emulator interface 10 accompanied by .
~~119555 A 1 the appropriate LAN MAC layer source and destination addresses.
2 For every device there is at least one LAN MAC address and a ' 3 corresponding switched network address.
4 This disclosed embodiment describes a direct interface from higher layers to the MAC interface, as is commonly found in 6 systems implemented for personal computers. An LLC interface may 7 be required in some systems. The difference between an LLC
8 interface and a MAC interface is not significant with respect to 9 the disclosed invention.
A directed datagram filter 15 makes a determination of the 11 datagram type by comparing the datagram type with the contents of 12 a directed datagram filter list 25. This is a list of protocol 13 specific datagrams specific to the application system. When 14 there is a matching datagram type in the directed datagram filter list 25, the datagram is marked as one which may be discarded 16 from the transmission queue or enqueued for a spoofed response at 17 a later time. The marking is based upon the actions specified 18 within the directed datagram filter list 25.
19 The datagram is then passed to a channel classifier 20 for further qualification. However, datagrams marked for removal 21 from the transmission queue are not given to the channel 22 classifier 20 and so are not sent to any destination node.
23 Instead, they are either discarded or sent to the datagram 24 response handler 30, where a spoofed response is formatted and eventually delivered to the higher layer protocol process.
26 The channel classifier 20 receives unfiltered directed WO 93/06674 ,. ~ ~ PCT/U592/07773 1 datagrams from the directed datagram filter 15. Using the LAN ' 2 MAC address as a search key, the classifier 20 retrieves a 3 switched network address and an associated node channel status 4 from a network definition table 35.
The network definition table 35 has an entry for each node 6 on the emulated LAN. A node may have multiple entries with 7 different LAN MAC addresses. Each entry includes, but is not 8 limited to: the LAN MAC address, which is the node LAN address 9 the device would have if it was connected to a conventional LAN;
the switched network address, which is the address of the device 11 on the switched network (e. g., for devices using ISDN, the public 12 network number on the public switched telephone network): the 13 node type, which is a descriptor which describes the node type or 14 function: suspension timer values, which are the parameters that control the suspension of the network connection: preferred 16 service parameters, which specify the preferred types of 17 transmission service when a connection is created: node channel 18 status parameter, which reflects the operational status of a 19 remote node; and broadcast service selectors, which are parameters that specify the methods by which broadcast messages 21 are distributed to remote nodes.
22 One class of preference is the type of service. The 23 effective bandwidth delivered is determined by the preferred 24 service parameter of the network definition table. The channel classifier can decide whether to transmit low priority 26 information on low bandwidth channels, such as the D-channel ~~~~~5~
1 packet switched service of ISDN. Devices connected to an ISDN
2 may select, among others, a B-channel circuit switched service, 3 B-channel packet switched service, D-channel packet switched 4 service, or HO circuit switched service.
Another class of preference is the minimum and maximum 6 throughput desired. With the disclosed invention, multiple 7 instances of a physical interface may be used under a single 8 service layer. The upper laxer protocols can therefore be 9 presented with a single logical service layer while the actual l0 transmission service may be delivered by more than one physical 11 interface. It is possible to synthesize higher speed 12 transmission service by combining multiple physical interfaces 13 under a single service interface. Thus a device that requires 14 higher speed transmission may specify the minimum and maximum number of transmission channels to be used when communication is 16 established with a remote node. For purposes of description of 17 the invention, the logical channel is the connection service 18 delivered to the upper layers, and the physical channel is the 19 means by which datagrams are delivered.
The datagram is discarded by channel classifier 20 when 21 there is no entry in the table 35 that has the destination LAN
22 MAC address. For LAN MAC addresses that are in the network 23 definition table 35, the four possible values for node channel 24 status are: registered with a logical channel and assigned physical channel(s), registered with a logical channel and no 26 physical channels, registered, or not registered.
1 Where the node channel status for a case is registered node , 2 with datagram traffic on both a logical channel and its physical 3 channels, it is considered a connection that is completely ' 4 active. An unfiltered datagram is immediately submitted to the datagram dispatcher 40.
6 For an unfiltered datagram where the node channel status is 7 registered node with datagram traffic on the logical channel but 8 with no associated physical channel, there is an attempt to 9 establish a connection to the destination node on a new physical channel. This is accomplished by giving the datagram to channel 11 manager 45 which attempts to establish a~connection on a physical 12 channel and then to send the datagram over that connection. The 13 channel manager 45 manages the process of establishing a 14 connection through both a logical and new physical channel.
Node registration is a MAC management function that occurs 16 at the time the LAN Emulator is initialized. When a node is 17 registered with another node it means that it will respond to a 18 request for connection. It also means that another node may 19 attempt a connection with it. There is no implication that the connection attempt will be successful: a connection attempt may 21 fail because the node's circuit resources may be occupied at the 22 time of the attempt.
23 Node de-registration occurs when the LAN Emulator is shut 24 down. This involves the LAN emulator sending de-registration messages to its connection partners. De-registration is not 26 mandatory. A node may also be de-registered when an attempt to In ~119~5~
1 connect to it fails because that node is no longer active.
2 Datagrams addressed to a node which is not registered are 3 discarded by the channel classifier 20.
4 As mentioned above, the channel manager 45 is responsible for initiating a connection on a logical and/or a physical 6 channel. If there is a request for connection on a pre-existing 7 logical channel, the channel manager 45 establishes connections 8 on the requisite physical channel(s). For a connection request 9 when no logical channel exists, the channel manager 45 will set to up a new logical channel as well as new physical channels.
il A logical channel may be supported by more than one 12 connection to the same destination through multiple physical 13 channels. The channel manager 45 uses a user preference 14 contained within the network definition table 35 to determine the number of physical channel resources to allocate for a given 16 connection attempt to the destination node.
1~ There are three possible occurrences when there is an 18 attempt to allocate a physical channel on behalf of the logical 19 channel. In the first, there are either no physical channels available for conveying the datagram or there is a network 21 problem that prevents a call from being offered to the 22 destination node. In the second, there are physical channels 23 available, but when a call request is placed to the remote node 24 at the destination switched network address, a rejected call response gets returned. In these two cases, the logical channel 26 is optionally torn down and network definition table maintenance a 1 is performed.
2 The third possibility is that the call request is accepted 3 by the node at the destination switched network address, at which 4 point the connection is considered physically active.
When the node channel status field shows that no logical or 6 physical channel exists, there is a choice for an appropriate 7 course of action which is dependent upon whether a connection on 8 a physical channel is possible, and which requires a destination 9 node to have registered its LAN MAC address and to be able to accept a connection request. In this case, a logical channel and 11 logical channel reference number are assigned after the physical 12 channel is set up and a connection established.
13 The channel manager 45 will also monitor traffic on the 14 physical channel, and during periods when there is no traffic, it may disconnect the physical channel while maintaining the logical 16 channel. When new datagram traffic begins, the channel manager 17 45 will reassign a physical channel. During this process a 18 physical channel is described as being suspended and later 19 resumed. The channel manager 45 will monitor external events such as incoming calls and determine whether a logical channel 21 will release its physical channel in order to reassign it to the 22 new call. This may be termed release of bandwidth on demand.
23 One consequence of the invention's embodiment of suspend and 24 resume is that the channel manager 45 may maintain more logical channels than the maximum number of physical channels possible.
26 This is known as channel over-subscription. The channel manager ?1.1955 1 45 may associate an idle physical channel to a new logical 2 channel while still maintaining the logical channel that had 3 originally used the physical channel. As a consequence of over-4 subscription, there may be periods when there is more demand for active channels than there is supply of preferred physical 6 channels. In such cases the channel manager 45 will assign 7 alternate (i.e., slower and/or more expensive) physical channels 8 to carry the data. Over-subscription is also tied to the concept 9 of a monolithic interface since the effectiveness of over-l0 subscription is enhanced by the use of a larger number of 11 physical channels.
12 The directed datagram dispatcher 40 receives a list of 13 physical channels to which a datagram must be transmitted. It 14 then manages datagram delivery by sending it through those individual channels. Usually there is only one element in the 16 channel list. If multiple channels are listed and the packet 17 size is sufficiently large, the datagram dispatcher 40 may 18 fragment the datagram and send the marked fragments on different 19 physical channels to the same logical destination.
With reference to Fig. 3, the mechanisms employed to convey 21 an all stations broadcast datagram through the LAN Emulator 22 interface to emulate a local area network are described. An all 23 stations broadcast datagram has a LAN MAC destination address 24 with a format that is a special case in that all bits are set to one in each of the address's octets. This transmission is 26 emulated by sending the datagram to all eligible members of a 1 finite list of recipients.
2 As with the emulation mechanism for the directed datagram, 3 for an all stations broadcast, the higher layer protocol process 4 submits a datagram to the LAN Emulator interface 110 with an all stations broadcast destination LAN MAC address. Because there 6 are several uses for an all station broadcast datagram that are 7 entirely application dependent, several selection mechanisms may 8 be used for separating broadcast datagrams of different origin 9 and directing them into appropriate courses of action. For example, some datagrams may be entirely blocked from transmission 11 by filter 115, some may have a transmission frequency attenuated 12 by the filter, and the filter may have no effect on the 13 transmission frequency of others. The metric for these filters 14 may be a function of either cost, throughput performance, propagation delay or some other factor.
16 The broadcast filter 115 compares the broadcast type against 17 a broadcast filter list 125 to determine whether the broadcast 18 datagram is a candidate for filtering or is an ordinary broadcast 19 datagram. The filtering mechanism 115 affects the transmission 2o frequency of broadcasts either by not transmitting any of the 21 datagrams or by transmitting over time 1 of every n datagrams for 22 each type submitted.
23 The broadcast filter list 125 either specifies a spoofing 24 response or contains the parameters and metrics that specify the appropriate attenuation rate for each type of broadcast datagram.
26 The value of this rate is zero for blocked broadcasts or is ~119~~~
1 expressed as a ratio for reduced broadcast frequencies. The 2 filtering mechanism 115 does not affect the transmission 3 frequency of unfiltered broadcasts, which are automatically given 4 to the channel classifier 120.
The channel classifier 120 receives all unfiltered 6 broadcasts and some reduced frequency broadcasts and qualifies 7 the broadcast eligibility for transmission. When the channel 8 classifier 120 receives a broadcast datagram, it determines a 9 list of destinations to which to send the broadcast and then l0 passes that list to the channel manager 145 to handle delivery.
11 The channel classifier 120 will enqueue unfiltered 12 broadcasts for delivery through all channels that are eligible 13 for this service. This is regulated by the broadcast service 14 parameter of the network definition table 135.
The functions of the channel classifier 120 may be 16 accomplished by software, hardware, or through packet replication 17 services provided by the network. There may be several reference 18 criteria that are useful for deciding which destinations receive 19 a particular broadcast datagram, and the network definition table 135 can hold values for these criteria including node type and 21 node channel status.
22 The channel manager 145 receives information from the 23 network definition table 135 to discriminate between those 24 logical channels with active physical channels and those for which a physical channel must be first reestablished. For 26 logical channels with active physical channels, the channel ~~
1 manager 145 submits the broadcast frame to the datagram 2 dispatcher 140 with a request for transmission. The datagram 3 dispatcher 140 receives a list of physical channels to which a 4 broadcast must be transmitted and then manages broadcast delivery by sending the broadcast through the individual physical 6 channels.
7 For logical channels without active physical channels, the 8 channel manager 145 enqueues the broadcast datagram for delivery 9 to those logical channels that can establish a new physical channel.
11 With reference to Fig. 4, the mechanisms employed to convey 12 a multicast datagram through a LAN emulator interface to emulate 13 a local area network are described. A multicast destination MAC
14 address is represented by a '1' in the Individual/Group Bit (the LSB) and a '0' in the Universal/Local Administration Bit (the 16 LSB+1) of the first octet, thus denoting a Group address within 17 the universally administered address space. As with broadcasts, 18 this class of transmission is emulated by sending the datagram to 19 a list of recipients. The list may be same as the list maintained for the all stations broadcast datagram.
21 Again, as with the directed datagrams and broadcast 22 datagrams, the higher layer protocol process submits a datagram 23 with a multicast LAN MAC address to the LAN Emulator interface 24 210, which in turn submits it, after filtering in filter 215 based on infonaation in the multicast filter list 225, to the 26 channel classifier 220. When the channel classifier 220 receives ~1~.95~~
1 a multicast that is enqueued for transmission, it uses the 2 network table 235 to determine a list of destinations to which to 3 send the multicast and passes that list to the channel manager 4 245 to handle delivery.
There are several reference criteria that may be useful for 6 deciding which destinations receive a particular multicast 7 datagram. The network definition table 235 holds values for 8 these criteria which include node type, node channel status, and 9 multicast filter lists.
Channel manager 245 examines the network definition table il 235 to discriminate between those logical channels with active 12 physical channels and those for which a physical channel must be 13 first reestablished. For logical channels with active physical 14 channels, the channel manager 245 submits the multicast frame to the datagram dispatcher 240 with a request for transmission. The 16 datagram dispatcher 240 receives a list of channels to which a 17 multicast must be transmitted. It then manages multicast 18 delivery by sending it through the individual channels.
19 It should be apparent to one skilled in the art that the invention contains a message receive function which will perform 21 complementary processing on received messages. All received 22 directed datagrams, as well as broadcast and multicast datagrams, 23 will be passed up to the higher layer protocol process.
24 It should also be readily apparent to one skilled in the art that the disclosed invention is not limited to any specific 26 computer architecture or hardware device. For example, the '~~~.~-~'~~~
1 disclosed embodiment works not only on IBM compatible personal 2 computers with the Novell network operating system, but with 3 other computer architectures as well, including IBM microchannel 4 personnel computers, SUN SPARC workstations, Apple Macintosh computers, minicomputers and mainframes. In addition, although 6 the embodiment disclosed herein simulates LANs over ISDN, the 7 invention is applicable to other switched networks such as pre 8 ISDN switched digital networks, X.25 networks, and frame relay 9 networks.
Although it may be preferred to implement the described 11 procedures using software, they can also be implemented using 12 well-known hardware elements. Similarly, the disclosed invention 13 can be applied to other communication devices which use LAN
14 interfaces, including LAN bridges and routers.
Although an embodiment of the invention has been illustrated 16 and described, it is anticipated that various changes and 17 modifications will be apparent to those skilled in the art, and 18 that such changes may be made without departing from the scope of 19 the invention as defined by the following claims:
Claims (35)
1. A method for using a switched network as a data path between devices connected to local area networks (LANs), comprising:
receiving a datagram having a LAN source address identifying a source device on its associated LAN and a LAN destination address identifying at least one destination device on its associated LAN from a logical link control or medium access control service layer of the source device;
for each of the destination devices, retrieving, from a network definition table having an entry for each device on the switched network, a switched network address corresponding to the LAN destination address and identifying the destination device on the switched network;
for each of the destination devices, establishing, based on the switched network address, a connection on at least one physical channel of said switched network for transmittal of said datagram to the destination device; and for each of the destination devices, providing said datagram to said at least one physical channel for transmission to the destination device over the switched network.
receiving a datagram having a LAN source address identifying a source device on its associated LAN and a LAN destination address identifying at least one destination device on its associated LAN from a logical link control or medium access control service layer of the source device;
for each of the destination devices, retrieving, from a network definition table having an entry for each device on the switched network, a switched network address corresponding to the LAN destination address and identifying the destination device on the switched network;
for each of the destination devices, establishing, based on the switched network address, a connection on at least one physical channel of said switched network for transmittal of said datagram to the destination device; and for each of the destination devices, providing said datagram to said at least one physical channel for transmission to the destination device over the switched network.
2. The method of claim 1, further comprising comparing said datagram with information stored in a reference list to determine the datagram type.
3. The method of claim 2, further comprising retrieving a node channel status from the network definition table.
4. The method of claim 2 wherein at least one logical channel receives the datagram and the at least one physical channel of the switched network comprises multiple circuit or packet switched channels which are selectively mapped into one logical channel.
5. The method of claim 2 wherein a single logical channel receives the datagram, the at least one physical channel of the switched network comprises multiple circuit or packet switched channels, and the logical channel is mapped onto the multiple circuit or packet switched channels to provide incremental capacity for datagrams received by the logical channel.
6. The method of claim 1 wherein the received datagram is a low bandwidth datagram that has periodic infrequent arrival characteristics and which is intended for delivery to multiple destination devices, wherein the low bandwidth datagram is delivered to each of the destination devices at a rate less than or equal to an original rate at which the low bandwidth datagram is received.
7. The method of claim 1 wherein the received datagram is a low bandwidth datagram that has periodic infrequent arrival characteristics and is provided to a physical channel other than the at least one physical channel for which the connection was established.
8. The method of claim 1 further comprising maintaining at least one logical channel for receiving the datagram while each of the physical channels are disconnected.
9. The method of claim 1 wherein the at least one physical channel comprises a plurality of circuit or packet switched channels and the connection to said channels is de-established and re-established when datagram traffic patterns demand the services of a particular circuit or packet switched channel which is unavailable.
10. A system for using a switched network as a data path between devices connected to local area networks (LANs), comprising:
means for receiving a datagram having a LAN source address identifying a source device on its associated LAN and a LAN destination address identifying at least one destination device on its associated LAN from a logical link control or medium access control service layer of the source device;
means for retrieving, for each of the destination devices and from a network definition table having an entry for each device on the switched network, a switched network address corresponding to the LAN
destination address and identifying the destination device on the switched network;
means for establishing, for each of the destination devices and based on the switched network address, a connection on at least one physical channel of said switched network for transmittal of said datagram to the destination device; and means for providing, for each of the destination devices, said datagram to said at least one physical channel for transmission to the destination device over the switched network.
means for receiving a datagram having a LAN source address identifying a source device on its associated LAN and a LAN destination address identifying at least one destination device on its associated LAN from a logical link control or medium access control service layer of the source device;
means for retrieving, for each of the destination devices and from a network definition table having an entry for each device on the switched network, a switched network address corresponding to the LAN
destination address and identifying the destination device on the switched network;
means for establishing, for each of the destination devices and based on the switched network address, a connection on at least one physical channel of said switched network for transmittal of said datagram to the destination device; and means for providing, for each of the destination devices, said datagram to said at least one physical channel for transmission to the destination device over the switched network.
11. The system of claim 10, further comprising means for comparing said datagram with information stored in a reference list to determine the datagram type.
12. The system of claim 11, further comprising means for retrieving a node channel status from the network definition table.
13. The system of claim 11 wherein at least one logical channel receives the datagram and the at least one physical channel of the switched network comprises multiple circuit or packet switched channels which are selectively mapped by means for selectively mapping into one logical channel.
14. The system of claim 11 wherein a single logical channel receives the datagram, the at least one physical channel of the switched network comprises multiple circuit or packet switched channels, and the logical channel is mapped onto the multiple circuit or packet switched channels by means for mapping to provide incremental capacity for datagrams received by the logical channel.
15. The system of claim 10 wherein the received datagram is a low bandwidth datagram that has periodic infrequent arrival characteristics and which is intended for delivery to multiple destination devices, wherein the low bandwidth datagram is delivered to each of the destination devices by means for delivering at a rate less than or equal to an original rate at which the low bandwidth datagram is received.
16. The system of claim 10 wherein the received datagram is a low bandwidth datagram that has periodic infrequent arrival characteristics and is provided by means for redirecting to a physical channel other than the at least one physical channel for which the connection was established.
17. The system of claim 10 further comprising means for maintaining at least one logical channel for receiving the datagram while each of the physical channels are disconnected.
18. The system of claim 10 wherein the at least one physical channel comprises a plurality of circuit or packet switched channels and the connection to said channels is de-established and re-established by means for re-dedicating when datagram traffic patterns demand the services of a particular circuit or packet switched channel which is unavailable.
19. Apparatus for coupling a source device to a destination device, comprising:
means for receiving, from a logical link control or medium access control service layer, a datagram having a source address identifying a source device and a destination address identifying a destination device;
means for retrieving from a storage location an address on a switched network which corresponds to the destination address;
means for using the switched network address to obtain access to a channel of the switched network; and means for providing the datagram to the channel of the switched network for transmission to the destination device.
means for receiving, from a logical link control or medium access control service layer, a datagram having a source address identifying a source device and a destination address identifying a destination device;
means for retrieving from a storage location an address on a switched network which corresponds to the destination address;
means for using the switched network address to obtain access to a channel of the switched network; and means for providing the datagram to the channel of the switched network for transmission to the destination device.
20. The apparatus of claim 19 wherein the switched network comprises a switched telecommunications service.
21. The apparatus of claim 19 wherein the channel of the switched network comprises a physical channel.
22. The apparatus of claim 21 wherein the physical channel comprises multiple circuit or packet switched channels.
23. The apparatus of claim 22 wherein a logical channel receives the datagram.
24. The apparatus of claim 23 further comprising means for selectively mapping the multiple circuit or packet switched channels into the logical channel.
- 27b -
- 27b -
25. The apparatus of claim 23 wherein the physical channel is disconnected while the logical channel receives the datagram.
26. The apparatus of claim 22 further comprising means for de-establishing and re-establishing access to the physical channel when data traffic patterns over the switched network demand the services of a particular circuit or packet switched channel that is unavailable.
27. The apparatus of claim 19 wherein the source device and the destination device are computer network devices designed to communicate over one or more computer networks.
28. The apparatus of claim 19 wherein the storage location comprises a network definition table which includes one or more entries which identify devices on the switched network.
29. Apparatus for allowing communication between two computer network devices via a switched network, comprising:
means for receiving, from a logical link control or medium access control service layer, a datagram having a source address identifying a source device and a destination address identifying a destination device, the source device and the destination device being designed to communicate over one or more computer networks;
means for retrieving from a storage location an address on a switched network which corresponds to the destination address;
means for using the switched network address to obtain access to a channel of the switched network; and means for providing the datagram to the channel of the switched network for transmission to the destination device.
- 27c -
means for receiving, from a logical link control or medium access control service layer, a datagram having a source address identifying a source device and a destination address identifying a destination device, the source device and the destination device being designed to communicate over one or more computer networks;
means for retrieving from a storage location an address on a switched network which corresponds to the destination address;
means for using the switched network address to obtain access to a channel of the switched network; and means for providing the datagram to the channel of the switched network for transmission to the destination device.
- 27c -
30. The apparatus of claim 29 wherein the switched network comprises a switched telecommunications service.
31. The apparatus of claim 29 wherein the storage location comprises a network definition table which includes one or more entries which identify devices on the switched network.
32. A method for coupling a source device to a destination device, comprising:
receiving, from a logical link control or medium access control service layer, a datagram having a source address identifying a source device and a destination address identifying a destination device;
retrieving from a storage location an address on a switched network which corresponds to the destination address;
using the switched network address to obtain access to a channel of the switched network; and providing the datagram to the channel of the switched network for transmission to the destination device.
receiving, from a logical link control or medium access control service layer, a datagram having a source address identifying a source device and a destination address identifying a destination device;
retrieving from a storage location an address on a switched network which corresponds to the destination address;
using the switched network address to obtain access to a channel of the switched network; and providing the datagram to the channel of the switched network for transmission to the destination device.
33. The method of claim 32 wherein the switched network comprises a switched telecommunications service.
34. The method of claim 32 wherein the source device and the destination device are computer network devices designed to communicate over one or more computer networks.
35. The method of claim 32 wherein the storage location comprises a network definition table which includes one or more entries which identify devices on the switched network.
- 27 d -
- 27 d -
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US763,340 | 1991-09-20 | ||
| US07/763,340 US5280481A (en) | 1991-09-20 | 1991-09-20 | Local area network transmission emulator |
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| CA2119555A1 CA2119555A1 (en) | 1993-04-01 |
| CA2119555C true CA2119555C (en) | 1998-12-08 |
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| CA002119555A Expired - Fee Related CA2119555C (en) | 1991-09-20 | 1992-09-14 | Local area network transmission emulator |
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| CA (1) | CA2119555C (en) |
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| DK (1) | DK0604523T3 (en) |
| ES (1) | ES2099834T3 (en) |
| GR (1) | GR3023822T3 (en) |
| WO (1) | WO1993006674A1 (en) |
Families Citing this family (84)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6847611B1 (en) * | 1990-12-10 | 2005-01-25 | At&T Corp. | Traffic management for frame relay switched data service |
| US5280481A (en) * | 1991-09-20 | 1994-01-18 | Extension Technology Corp. | Local area network transmission emulator |
| ATE207679T1 (en) * | 1992-04-20 | 2001-11-15 | 3Com Corp | DEVICE FOR EXPANSION OF NETWORK MEANS TO REMOTE NETWORKS |
| JPH0653965A (en) * | 1992-07-29 | 1994-02-25 | Sony Corp | Network system |
| US6018771A (en) * | 1992-11-25 | 2000-01-25 | Digital Equipment Corporation | Dynamic assignment of multicast network addresses |
| GB9300942D0 (en) * | 1993-01-19 | 1993-03-10 | Int Computers Ltd | Parallel computer system |
| US5630061A (en) * | 1993-04-19 | 1997-05-13 | International Business Machines Corporation | System for enabling first computer to communicate over switched network with second computer located within LAN by using media access control driver in different modes |
| US5386412A (en) * | 1993-05-11 | 1995-01-31 | Park; Jung S. | Telecommunication system protocol for asynchronous data communication between multiport switch control processor and information support personal computer terminal |
| US5434850A (en) | 1993-06-17 | 1995-07-18 | Skydata Corporation | Frame relay protocol-based multiplex switching scheme for satellite |
| US6771617B1 (en) | 1993-06-17 | 2004-08-03 | Gilat Satellite Networks, Ltd. | Frame relay protocol-based multiplex switching scheme for satellite mesh network |
| US5448566A (en) * | 1993-11-15 | 1995-09-05 | International Business Machines Corporation | Method and apparatus for facilitating communication in a multilayer communication architecture via a dynamic communication channel |
| US5519640A (en) * | 1994-01-26 | 1996-05-21 | Hughes Aircraft Company | Multimedia frame relay codec |
| GB9406477D0 (en) * | 1994-03-31 | 1994-05-25 | D2B Systems Co Ltd | Interconnection of local communication bus systems |
| WO1996000468A1 (en) * | 1994-06-24 | 1996-01-04 | Metricom, Inc. | Method for using point-to-point protocol over an imperfect mesh network |
| IL110537A (en) * | 1994-08-01 | 1998-01-04 | 3Com Corp | Network switch |
| US5588148A (en) * | 1994-09-06 | 1996-12-24 | Motorola, Inc. | Method for managing data transfer between computing devices |
| SE515815C2 (en) * | 1994-09-08 | 2001-10-15 | Telia Ab | Device for ATM networks |
| US5541911A (en) * | 1994-10-12 | 1996-07-30 | 3Com Corporation | Remote smart filtering communication management system |
| US5742670A (en) * | 1995-01-09 | 1998-04-21 | Ncr Corporation | Passive telephone monitor to control collaborative systems |
| US5659684A (en) * | 1995-02-03 | 1997-08-19 | Isdn Systems Corporation | Methods and apparatus for interconnecting personal computers (PCs) and local area networks (LANs) using packet protocols transmitted over a digital data service (DDS) |
| ATE224620T1 (en) * | 1995-05-08 | 2002-10-15 | Koninkl Kpn Nv | ARRANGEMENT AND METHOD FOR PROTOCOL IMPLEMENTATION |
| US5752003A (en) * | 1995-07-14 | 1998-05-12 | 3 Com Corporation | Architecture for managing traffic in a virtual LAN environment |
| US6041166A (en) | 1995-07-14 | 2000-03-21 | 3Com Corp. | Virtual network architecture for connectionless LAN backbone |
| US6005864A (en) | 1995-07-14 | 1999-12-21 | 3Com Corporation | Protocol for optimized multicast services for a connection oriented network providing lan emulation |
| US5805805A (en) * | 1995-08-04 | 1998-09-08 | At&T Corp. | Symmetric method and apparatus for interconnecting emulated lans |
| US5850536A (en) * | 1996-05-01 | 1998-12-15 | Mci Communications Corporation | Method and system for simulated multi-tasking |
| US5809286A (en) * | 1996-05-01 | 1998-09-15 | Mci Communications Corporation | Method and apparatus for emulating a dynamically configured digital cross-connect switch network |
| US5748617A (en) * | 1996-05-01 | 1998-05-05 | Mci Corporation | Method and apparatus for emulating a digital cross-connect switch network |
| US5867689A (en) * | 1996-05-01 | 1999-02-02 | Mci Communications Corporation | Method and apparatus for emulating a digital cross-connect switch network using a flexible topology to test MCS network management |
| US6400681B1 (en) | 1996-06-20 | 2002-06-04 | Cisco Technology, Inc. | Method and system for minimizing the connection set up time in high speed packet switching networks |
| US6490247B1 (en) | 1996-06-26 | 2002-12-03 | Gateway, Inc | Ring-ordered dynamically reconfigurable network using an existing communications system |
| US5812826A (en) * | 1996-06-27 | 1998-09-22 | Mci Communications Corporation | Method and apparatus for emulating a network of state monitoring devices |
| US5805594A (en) * | 1996-08-23 | 1998-09-08 | International Business Machines Corporation | Activation sequence for a network router |
| CA2187239A1 (en) * | 1996-10-07 | 1998-04-07 | Rakesh Prasad | Remote on-demand applications server |
| DE19700357C2 (en) * | 1996-12-10 | 2003-07-31 | Siemens Ag | Method for connecting a communication terminal to a data network |
| US5954829A (en) * | 1996-12-30 | 1999-09-21 | Mci Communications Corporation | System, method, and computer program product for digital cross connect testing |
| US5854930A (en) * | 1996-12-30 | 1998-12-29 | Mci Communications Corporations | System, method, and computer program product for script processing |
| US6226297B1 (en) | 1997-01-30 | 2001-05-01 | International Business Machines Corporation | Method and system for providing redundancy to asynchronous transfer mode emulated local-area networks |
| US6934249B1 (en) | 1997-04-01 | 2005-08-23 | Cisco Technology, Inc. | Method and system for minimizing the connection set up time in high speed packet switching networks |
| DE19713956C2 (en) * | 1997-04-04 | 1999-02-18 | Ericsson Telefon Ab L M | Method, communication network and service access interface for communications in an environment for connections of open systems |
| DE19720086A1 (en) * | 1997-05-14 | 1998-11-19 | Alsthom Cge Alcatel | Subscriber line network, switching center, service control device and connection establishment method |
| US6081524A (en) | 1997-07-03 | 2000-06-27 | At&T Corp. | Frame relay switched data service |
| US6625158B1 (en) * | 1997-07-31 | 2003-09-23 | International Business Machines Corporation | Method and system for enhanced communication involving emulated local area networks |
| US6091732A (en) | 1997-11-20 | 2000-07-18 | Cisco Systems, Inc. | Method for configuring distributed internet protocol gateways with lan emulation |
| US6246669B1 (en) | 1997-11-28 | 2001-06-12 | Cisco Technology, Inc. | Method and system for optimizing connection set-up operations in a high speed digital network |
| US6256659B1 (en) | 1997-12-09 | 2001-07-03 | Mci Communications Corporation | System and method for performing hybrid preemptive and cooperative multi-tasking in a computer system |
| US5974532A (en) * | 1997-12-09 | 1999-10-26 | Mci Communications Corporation | System and method for generating responses for inputs using a hybrid state engine table |
| US7013467B1 (en) | 1997-12-09 | 2006-03-14 | Mci Communications Corporation | System and method for managing computer system resources using command control vectors |
| US6222848B1 (en) | 1997-12-22 | 2001-04-24 | Nortel Networks Limited | Gigabit ethernet interface to synchronous optical network (SONET) ring |
| US6157635A (en) * | 1998-02-13 | 2000-12-05 | 3Com Corporation | Integrated remote data access and audio/visual conference gateway |
| US6188691B1 (en) | 1998-03-16 | 2001-02-13 | 3Com Corporation | Multicast domain virtual local area network |
| FI107365B (en) | 1998-04-27 | 2001-07-13 | Nokia Mobile Phones Ltd | A method and system for detecting variable data processing in a communication link |
| US6201792B1 (en) | 1998-05-14 | 2001-03-13 | 3Com Corporation | Backpressure responsive multicast queue |
| US6269076B1 (en) | 1998-05-28 | 2001-07-31 | 3Com Corporation | Method of resolving split virtual LANs utilizing a network management system |
| US6223149B1 (en) | 1998-05-28 | 2001-04-24 | 3Com Corporation | Non-distributed LAN emulation server redundancy method |
| US6289017B1 (en) | 1998-05-29 | 2001-09-11 | 3Com Corporation | Method of providing redundancy and load sharing among multiple LECs in an asynchronous mode network |
| US6104870A (en) * | 1998-07-02 | 2000-08-15 | International Business Machines Corporation | Method and system for improving communications in data communications networks that provide network emulation |
| US6081848A (en) * | 1998-08-14 | 2000-06-27 | Intel Corporation | Striping packets of data across multiple virtual channels |
| US6480891B1 (en) | 1999-01-04 | 2002-11-12 | 3Com Corporation | Embedded code memory size reduction in asynchronous mode transfer devices |
| US6532237B1 (en) | 1999-02-16 | 2003-03-11 | 3Com Corporation | Apparatus for and method of testing a hierarchical PNNI based ATM network |
| US6487171B1 (en) | 1999-05-19 | 2002-11-26 | 3Com Corporation | Crossbar switching matrix with broadcast buffering |
| US6470022B1 (en) | 1999-05-19 | 2002-10-22 | 3Com Corporation | Method of distributing network resources fairly between users in an asynchronous transfer mode network |
| US6580693B1 (en) | 1999-05-24 | 2003-06-17 | 3Com Corporation | Methods and apparatus for detecting leaks in ATM networks |
| US6539019B1 (en) | 1999-05-24 | 2003-03-25 | 3Com Corporation | Methods and apparatus for automatically connecting a dynamic host configuration protocol (DHCP) client network device to a virtual local area network (VLAN) |
| US6574232B1 (en) | 1999-05-26 | 2003-06-03 | 3Com Corporation | Crossbar switch utilizing broadcast buffer and associated broadcast buffer management unit |
| US6614792B1 (en) | 1999-05-27 | 2003-09-02 | 3Com Corporation | Proxy MPC for providing MPOA services to legacy lane clients in an asynchronous transfer mode network |
| US6671253B1 (en) | 1999-09-21 | 2003-12-30 | International Business Machines Corporation | Method and system for providing peer redundancy to asynchronous transfer mode emulated local-area networks |
| US6526034B1 (en) * | 1999-09-21 | 2003-02-25 | Tantivy Communications, Inc. | Dual mode subscriber unit for short range, high rate and long range, lower rate data communications |
| US6678241B1 (en) | 1999-11-30 | 2004-01-13 | Cisc Technology, Inc. | Fast convergence with topology switching |
| EP1128602B1 (en) * | 2000-02-23 | 2006-10-04 | Tektronix Berlin GmbH & Co. KG | Apparatus for building a protocol stack and corresponding method |
| US7266490B2 (en) | 2000-12-28 | 2007-09-04 | Robert Marc Zeidman | Apparatus and method for connecting hardware to a circuit simulation |
| US8160863B2 (en) * | 2000-03-28 | 2012-04-17 | Ionipas Transfer Company, Llc | System and method for connecting a logic circuit simulation to a network |
| US7050962B2 (en) * | 2000-03-28 | 2006-05-23 | Zeidman Robert M | Method for connecting a hardware emulator to a network |
| DE50103788D1 (en) | 2000-07-31 | 2004-10-28 | Siemens Ag | METHOD FOR ERROR CORRECTION IN A PACKET-ORIENTED DATA TRANSFER |
| US7905900B2 (en) * | 2003-01-30 | 2011-03-15 | Integrated Vascular Systems, Inc. | Clip applier and methods of use |
| US6975913B2 (en) * | 2001-07-13 | 2005-12-13 | Siemens Aktiengesellschaft | Database system and method for industrial automation services |
| US7603289B2 (en) * | 2001-07-13 | 2009-10-13 | Siemens Aktiengesellschaft | System and method for electronic delivery of content for industrial automation systems |
| US6932929B2 (en) * | 2001-12-21 | 2005-08-23 | Kimberly-Clark Worldwide, Inc. | Method of forming composite absorbent members |
| DE10205901A1 (en) * | 2002-02-13 | 2003-08-28 | Tenovis Gmbh & Co Kg | Method and arrangement for data transmission with a multipoint connection |
| US20030191453A1 (en) * | 2002-04-03 | 2003-10-09 | Velez Omar E. | Catheter assembly |
| US7724671B2 (en) * | 2003-05-13 | 2010-05-25 | Intel-Tel, Inc. | Architecture for resource management in a telecommunications network |
| US7921216B2 (en) * | 2005-02-01 | 2011-04-05 | Microsoft Corporation | System and method for building and using communication binding objects |
| JP4701152B2 (en) * | 2006-10-20 | 2011-06-15 | 富士通株式会社 | Data relay apparatus, data relay method, and data relay program |
| CN104159306B (en) | 2014-07-22 | 2018-05-29 | 华为技术有限公司 | A kind of method, equipment and system for controlling interface-free resources |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4868866A (en) * | 1984-12-28 | 1989-09-19 | Mcgraw-Hill Inc. | Broadcast data distribution system |
| US4787082A (en) * | 1986-07-24 | 1988-11-22 | American Telephone And Telegraph Company, At&T Bell Laboratories | Data flow control arrangement for local area network |
| US4818984A (en) * | 1986-11-26 | 1989-04-04 | American Telephone And Telegraph Company, At&T Bell Laboratories | Broadcasting messages in a distributed processing system |
| US4823338B1 (en) * | 1987-08-03 | 1998-11-10 | At & T Information Systems Inc | Virtual local area network |
| DE68925300T2 (en) * | 1988-03-04 | 1996-05-30 | Nec Corp | Procedure for controlling the address parameters for the connection between LAN and ISDN systems |
| JP2550642B2 (en) * | 1988-03-04 | 1996-11-06 | 日本電気株式会社 | Packet frame transmission method |
| US5093827A (en) * | 1989-09-21 | 1992-03-03 | At&T Bell Laboratories | Control architecture of a multi-node circuit- and packet-switching system |
| US5280481A (en) * | 1991-09-20 | 1994-01-18 | Extension Technology Corp. | Local area network transmission emulator |
-
1991
- 1991-09-20 US US07/763,340 patent/US5280481A/en not_active Expired - Lifetime
-
1992
- 1992-09-14 AT AT92919914T patent/ATE151932T1/en not_active IP Right Cessation
- 1992-09-14 EP EP92919914A patent/EP0604523B1/en not_active Expired - Lifetime
- 1992-09-14 DE DE69219141T patent/DE69219141T2/en not_active Expired - Lifetime
- 1992-09-14 ES ES92919914T patent/ES2099834T3/en not_active Expired - Lifetime
- 1992-09-14 DK DK92919914.9T patent/DK0604523T3/en active
- 1992-09-14 WO PCT/US1992/007773 patent/WO1993006674A1/en active IP Right Grant
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- 1992-09-14 JP JP50615993A patent/JP3390434B2/en not_active Expired - Lifetime
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1993
- 1993-07-27 US US08/097,851 patent/US5323388A/en not_active Expired - Lifetime
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1994
- 1994-06-03 US US08/253,753 patent/US5577033A/en not_active Expired - Lifetime
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1997
- 1997-06-19 GR GR970401460T patent/GR3023822T3/en unknown
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| WO1993006674A1 (en) | 1993-04-01 |
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| CA2119555A1 (en) | 1993-04-01 |
| EP0604523A1 (en) | 1994-07-06 |
| DE69219141D1 (en) | 1997-05-22 |
| US5577033A (en) | 1996-11-19 |
| DK0604523T3 (en) | 1997-05-26 |
| JP3390434B2 (en) | 2003-03-24 |
| US5280481A (en) | 1994-01-18 |
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