WO1997004569A1 - Port and link identification - Google Patents

Port and link identification Download PDF

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Publication number
WO1997004569A1
WO1997004569A1 PCT/US1996/011963 US9611963W WO9704569A1 WO 1997004569 A1 WO1997004569 A1 WO 1997004569A1 US 9611963 W US9611963 W US 9611963W WO 9704569 A1 WO9704569 A1 WO 9704569A1
Authority
WO
WIPO (PCT)
Prior art keywords
cell
logical link
link
processing port
received
Prior art date
Application number
PCT/US1996/011963
Other languages
French (fr)
Inventor
Stephen A. Caldara
Stephen A. Hauser
Thomas A. Manning
Original Assignee
Fujitsu Network Communications, Inc.
Fujitsu Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Fujitsu Network Communications, Inc., Fujitsu Limited filed Critical Fujitsu Network Communications, Inc.
Priority to PCT/US1996/011963 priority Critical patent/WO1997004569A1/en
Priority to JP9506895A priority patent/JPH11510329A/en
Priority to AU65035/96A priority patent/AU6503596A/en
Publication of WO1997004569A1 publication Critical patent/WO1997004569A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
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    • H04L49/25—Routing or path finding in a switch fabric
    • H04L49/253—Routing or path finding in a switch fabric using establishment or release of connections between ports
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F15/00—Digital computers in general; Data processing equipment in general
    • G06F15/16—Combinations of two or more digital computers each having at least an arithmetic unit, a program unit and a register, e.g. for a simultaneous processing of several programs
    • G06F15/163—Interprocessor communication
    • G06F15/173—Interprocessor communication using an interconnection network, e.g. matrix, shuffle, pyramid, star, snowflake
    • G06F15/17356—Indirect interconnection networks
    • G06F15/17368—Indirect interconnection networks non hierarchical topologies
    • G06F15/17375—One dimensional, e.g. linear array, ring
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    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/46—Interconnection of networks
    • H04L12/4604—LAN interconnection over a backbone network, e.g. Internet, Frame Relay
    • H04L12/4608—LAN interconnection over ATM networks
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5685—Addressing issues
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/04—Speed or phase control by synchronisation signals
    • H04L7/041—Speed or phase control by synchronisation signals using special codes as synchronising signal
    • H04L7/046—Speed or phase control by synchronisation signals using special codes as synchronising signal using a dotting sequence

Definitions

  • This invention relates generally to the field of communication systems, and more particularly to port and link identification.
  • a communication system includes a collection of components that communicate, manipulate, and process information in a variety of ways.
  • This system may support different access technologies, such as frame relay, circuit services, and new and evolving connection-based or connectionless services, that communicate information, such as data, voice, and video.
  • Switches in the communication system employ hardware and software to route information generated by access technologies to an intended destination.
  • a control cell can be used to establish communication on a connection or link.
  • a control cell of a particular type such as a cell relating to an interim local management interface (ILMI)
  • the switch control module SCM
  • the switch control module must be able to identify the port and link of origin for the control cell in order to establish communication.
  • the virtual path identification (VPI) field and the virtual channel identification (VCI) field of the control cell typically will be the same as the VPI field and VCI field, respectively, of other control cells of the same type.
  • the VPI/VCI identifier of a control cell cannot be used to identify a link and a port of origin for the control cell in a communication switch.
  • the disadvantages and problems associated with identifying a port and link of origin for a cell in a communication switch have been substantially reduced or eliminated.
  • a system for identifying a processing port and a link at which a cell is received.
  • the system includes a logical link table having a plurality of logical link entries. Each logical link entry, which corresponds to a particular link of a processing port associated with the logical link table, specifies a numerical value.
  • the processing port may receive a cell at one of a plurality of links.
  • the processing port can convert the cell by replacing a numerical value of an identification field, such as a virtual channel identification field, of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received.
  • a switch control module which is connected to the processing port, may receive the converted cell. The switch control module can identify the link and the processing port at which the cell corresponding to the converted cell was received by referencing a reverse mapping table using the numerical value of the logical link entry in the converted cell.
  • a method for identifying a processing port and a link at which a cell is received.
  • the method includes receiving a cell at one of a plurality of links of a processing port.
  • a logical link table associated with the processing port is then referenced.
  • the logical link table includes a plurality of logical link entries, each logical link entry corresponding to a particular link of the processing port and specifying a numerical value.
  • the received cell is converted by replacing a numerical value of an identification field, such as a virtual channel identification field, of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received.
  • the link and the processing port at which the cell was received can be identified by referencing a reverse mapping table using the numerical value specified by the logical link entry in the converted cell .
  • An important technical advantage of the present invention includes replacing a VCI value of a control cell with a specific logical link number corresponding to the link and port at which the control cell is received.
  • a reverse mapping table contains information specifying which link and port are associated with each logical link number. The reverse mapping table may be accessed by the switch control module.
  • the switch control module processes the control cell, the switch control module is able to identify the link and port of origin for the cell using the reverse mapping table. This alleviates the need to set up a separate connection to receive control cells uniquely at each input link.
  • a connection requires resources (queues, topology information) and is a resource to be conserved. This method allows there to be a single multipoint to point connection.
  • FIGURE 1 illustrates a system for identifying a port and link of origin for a control cell in a communication switch
  • FIGURE 2 is a flow chart of a method for identifying a link and port of origin for a control cell in a communication switch.
  • FIGURES 1 and 2 of the drawings like numerals being used for like and corresponding parts of the various drawings.
  • FIGURE 1 illustrates a system 10 for identifying a link and a processing port of origin for a control cell in a communication switch.
  • System 10 includes at least one to-switch processing port (TSPP) 12, at least one logical link table 14, switching fabric 16, a switch control module (SCM) 18, and a reverse mapping table 20.
  • TSPP to-switch processing port
  • SCM switch control module
  • system 10 includes two TSPPs 12, labeled as TSPP0 and TSPPI.
  • Each TSPP 12 can be implemented as an application specific integrated circuit (ASIC) .
  • Each TSPP 12 may include a number of connections or links 22.
  • Links 22 may support asynchronous transfer mode (ATM) cell relay (OC-12, OC-3c, 155 Mbps UTP) , frame relay (Tl, El, T3, E3, V.35) , circuit emulation (Tl, El, T3 , E3) , internetworking using Ethernet, Fast Ethernet, Internet Protocol (IP) , or IP over ATM, or any other communications protocol or access technology.
  • ATM synchronous transfer mode
  • IP Internet Protocol
  • each TSPP 12 may support or include eight links 22, which are labeled as LINK0-LINK7.
  • Each link 22 is operable to receive a data cell, including control cells 24 which are labeled as CELL1, CELL2, and CELL3.
  • control cells refers to cells that contain signaling or administration information.
  • Each control cell 24 includes a virtual path identification (VPI) field 26 and a virtual channel identification (VCI) field 28.
  • VPI field 26 and VCI field 28 may be numerical values. For a particular type of control cell 24, the numerical values for VPI field 26 and the VCI field 28 are specific.
  • CELL1 , CELL2 and CELL3 may each be an interim local management interface (ILMI) control cell where VPI field 26 has a value of "0" and VCI field 28 has a value of "16.” These values for VPI field 26 and VCI field 28 are the same for every ILMI control cell, regardless of the link 22 or TSPP 12 at which the control cell 24 is received.
  • each TSPP 12 is operable to convert the control cells 24 that it receives into converted cells 38, which are labeled as CCELL1, CCELL2, and CCELL3 in FIGURE 1.
  • Each of these converted cells 38 may have a VPI 40 and a VCI 42.
  • the values of the VCI 42 in converted cells 38 differ even if the converted cells 38 all correspond to the same type of control cell 24.
  • a separate logical link table 14 is associated with each TSPP 12.
  • the logical link tables 14 shown in FIGURE 1 are labeled as LLTO and LLT1.
  • LLTO and LLT1 are associated with TSPPO and TSPPI, respectively.
  • Each logical link table 14 may be implemented on a memory internal or external to its associated TSPP 12, such as an external random access memory (RAM) .
  • Logical link tables 14 each comprise a plurality of logical link entries 30, which are labeled as LL#0-LL#7 in FIGURE 1.
  • Each logical link entry 30 corresponds to a particular link 22 in the TSPP 12 associated with the logical link table 14.
  • LL#0-LL#7 in LLTO correspond to LINKO-LINK7 in TSPPO, respectively.
  • Each logical link entry 30 may specify a numerical value, which is unique to a particular link 22 of a particular TSPP 12. In one embodiment, each numerical value may be implemented as a nine-bit binary number. Consequently, five hundred and twelve numerical values may be supported for the various logical link entries 30.
  • the logical link entries 30 are used in converting control cells 24 to converted cells 38, as described below.
  • the information in logical link tables 14 can be configured or initialized by software.
  • Switch fabric 16 is connected to each TSPP 12. Switch fabric 16 is operable to transfer a data cell, such as control cells 24, from a TSPP 12 to a from-switch processing port (FSPP) . Switch fabric 16 can be implemented as an ECL cross-point device for transferring signals. In one embodiment, switch fabric 16 supports sixteen TSPPs 12.
  • SCM 18 is connected to switch fabric 16.
  • SCM 18 may be implemented as one or more ASICs.
  • SCM 18 includes an FSPP 32 having a special queue 34.
  • FSPP 32 may also be implemented as an ASIC.
  • Special queue 34 may be dedicated to receiving converted cells 38 corresponding to control cells of a particular type, such as ILMI control cells. As shown in FIGURE 1, special queue 34 receives or contains CCELL1, CCELL2, and CCELL3.
  • Reverse mapping table 20 may be associated with special queue 34 in FSPP 32 of SCM 18.
  • Reverse mapping table 20 may be implemented on memory (e.g., RAM) internal or external to FSPP 32.
  • Reverse mapping table 20 comprises a plurality of reverse mapping entries 36. Each of reverse mapping entries 36 comprises information identifying a specific link 22 and TSPP 12 at which a control cell 24 can be received.
  • Reverse mapping table 20 can be indexed by the numerical values specified in logical link entries 30. Like logical link tables 14, the information in reverse mapping table 20 can be configured or initialized by software.
  • the TSPPs 12 may receive control cells 24 at various links 22. As shown in FIGURE 1, CELL1 and CELL2 may be received at LINK2 and LINK7 of TSPPO, respectively, and CELL3 may be received at LINK6. If these control cells 24 are the same type, the numerical value for the VPI field 26 of all cells will be the same. Likewise, the numerical value for the VCI field 28 of all cells will be the same. VPI field 26 and VCI field 28 of the cells shown in FIGURE 1 have numerical values of 0 and 16, respectively.
  • the TSPP 12 replaces the numerical value for VCI field 28 of the received cells with a numerical value stored in the logical linking table 14 associated with that TSPP 12.
  • the TSPP 12 uses the logical link entry 30 corresponding to the link 22 at which the control cell 24 is received to replace the numerical value of the VCI field 28. In this manner, TSPP 12 converts control cells 24 to converted cells 38.
  • CELL1 is received at LINK2 of TSSPO
  • the numerical value of "285" specified in LL#2 of LLTO is used to replace the VCI value of "16".
  • CELL2 is received at LINK7 of TSPPO
  • the VCI value of "16" in CELL2 is replaced with a VCI value of "220" specified in LL#7 of LLTO.
  • CELL3 is receive at LINK6 of TSPPI
  • the VCI value of "16” in CELL3 is replaced with the value of "96" specified in LL#6 of LLT1. In this manner, CELL1, CELL2, and CELL3 may be converted into CCELL1, CCELL2, and CCELL3.
  • TSPPs 12 transmit the converted cells 38 to SCM 18, which receives the converted cells 38 at special queue 34 dedicated to this particular type of control cell.
  • SCM 18 receives a converted cell 38, it is able to identify the link and processing port at which the corresponding control cell 24 was received using reverse mapping table 20.
  • a separate set comprising one or more logical link tables 14, a special queue 34, and a reverse mapping table 20 can be maintained for each type of control cell in a switch.
  • FIGURE 2 is a flow chart of a method 100 for identifying a link 22 and a TSPP 12 of origin for a control cell 24 in a communication switch.
  • Method 100 which corresponds to the operation of system 10 shown in FIGURE 1, is described with particular reference to the processing of exemplary CELL1.
  • Method 100 begins at step 102, where a TSPP 12 receives an information cell 24 at one of its links 22. For example, TSPPO receives CELL1 at. LINK2.
  • TSPP 12 determines whether the cell is a control cell 24. For example, in one embodiment, a queue number associated with the cell is used to look-up a queue descriptor.
  • the queue descriptor may contain a logical link (LL) bit that specifies whether the cell should be converted.
  • LL logical link
  • TSPP 12 references its associated logical link table 14 and converts the control cell 24 into a converted cell 38.
  • TSPP 12 replaces the value of VCI field 28 in the control cell 24 with a numerical value specified by the logical link entry 30 corresponding to the link 22 at which control cell 24 was received.
  • CELL1 was received at LINK2 of TSPPO
  • TSPPO replaces the VCI field 28 value of "16" with a value of "285" specified by LL#2 in LLTO. This results in CCELL1, a converted cell 38 having a VCI 42 value of "285.
  • TSPP 12 transmits the converted cell 38 to special queue 34 of FSPP 32 in SCM 18.
  • Special queue 34 receives only information cells of a particular type, such as cells relating to ILMI control.
  • SCM 18 receives the converted cell 38 from special queue 34 at step 114.
  • SCM 18 extracts the VCI 42 value from the converted cell 38.
  • the VCI 42 value is used to index a reverse mapping entry 36 in reverse mapping table 20 at step 118.
  • the reverse mapping entry 36 specifies the link 22 and TSPP 12 at which the control cell 24 corresponding to the converted cell 38 was received. Accordingly, SCM 18 is able to identify the TSPP 12 and link 22 of origin for the control cell 24 at step 128.
  • the VCI 42 value of "285" is used to reference the reverse mapping entry 30 specifying "LINK2 TSPPO.” SCM 18 may then respond at the link 22 and TSPP 12 of origin if appropriate.

Abstract

A system (12-42) is provided for identifying a processing port (12) and a link (22) at which a cell (24) is received. The system (10) includes a logical link table (14) having a plurality of logical link entries (30). The processing port (12) can convert the cell (24) by replacing a numerical value of an identification field, such as a virtual channel identification field (28), of the cell (24) with the numerical value specified by the logical link entry (30) corresponding to the link (22) at which the cell (24) is received. A switch control module (18), which is connected to the processing port (12), may receive the converted cell (38) and identify the link (22) and the processing port (12) at which the cell (24) corresponding to the converted cell (38) was received by referencing a reverse mapping table (20) using the numerical value of the logical link entry (30) in the converted cell (38).

Description

PORT AND LINK IDENTIFICATION
RELATED PATENT APPLICATION
This application is related to United States Provisional Patent Application Serial No. 60/001,498, filed July 19, 1995.
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of communication systems, and more particularly to port and link identification.
BACKGROUND OF THE INVENTION
A communication system includes a collection of components that communicate, manipulate, and process information in a variety of ways. This system may support different access technologies, such as frame relay, circuit services, and new and evolving connection-based or connectionless services, that communicate information, such as data, voice, and video. Switches in the communication system employ hardware and software to route information generated by access technologies to an intended destination.
In such switches, different types of data cells are utilized to control switching connections. For example, a control cell can be used to establish communication on a connection or link. When a control cell of a particular type, such as a cell relating to an interim local management interface (ILMI) , is processed at a switch control module, the switch control module (SCM) must be able to identify the port and link of origin for the control cell in order to establish communication. However, regardless of which link and processing port in a switch receives the cell of a particular type, the virtual path identification (VPI) field and the virtual channel identification (VCI) field of the control cell typically will be the same as the VPI field and VCI field, respectively, of other control cells of the same type. Thus, in some instances, the VPI/VCI identifier of a control cell cannot be used to identify a link and a port of origin for the control cell in a communication switch. SUMMARY OF THE INVENTION
In accordance with the present invention, the disadvantages and problems associated with identifying a port and link of origin for a cell in a communication switch have been substantially reduced or eliminated.
In accordance with one embodiment of the present invention, a system is provided for identifying a processing port and a link at which a cell is received. The system includes a logical link table having a plurality of logical link entries. Each logical link entry, which corresponds to a particular link of a processing port associated with the logical link table, specifies a numerical value. The processing port may receive a cell at one of a plurality of links. The processing port can convert the cell by replacing a numerical value of an identification field, such as a virtual channel identification field, of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received. A switch control module, which is connected to the processing port, may receive the converted cell. The switch control module can identify the link and the processing port at which the cell corresponding to the converted cell was received by referencing a reverse mapping table using the numerical value of the logical link entry in the converted cell.
In accordance with another embodiment of the present invention, a method is provided for identifying a processing port and a link at which a cell is received. The method includes receiving a cell at one of a plurality of links of a processing port. A logical link table associated with the processing port is then referenced. The logical link table includes a plurality of logical link entries, each logical link entry corresponding to a particular link of the processing port and specifying a numerical value. The received cell is converted by replacing a numerical value of an identification field, such as a virtual channel identification field, of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received. The link and the processing port at which the cell was received can be identified by referencing a reverse mapping table using the numerical value specified by the logical link entry in the converted cell .
An important technical advantage of the present invention includes replacing a VCI value of a control cell with a specific logical link number corresponding to the link and port at which the control cell is received. A reverse mapping table contains information specifying which link and port are associated with each logical link number. The reverse mapping table may be accessed by the switch control module. Thus, when the switch control module processes the control cell, the switch control module is able to identify the link and port of origin for the cell using the reverse mapping table. This alleviates the need to set up a separate connection to receive control cells uniquely at each input link. A connection requires resources (queues, topology information) and is a resource to be conserved. This method allows there to be a single multipoint to point connection. Other important technical advantages are readily apparent to one skilled in the art from the following FIGURES, descriptions, and claims. BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, and for further features and advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:
FIGURE 1 illustrates a system for identifying a port and link of origin for a control cell in a communication switch; and
FIGURE 2 is a flow chart of a method for identifying a link and port of origin for a control cell in a communication switch.
DETAILED DESCRIPTION OF THE INVENTION
The preferred embodiment of the present invention and its advantages are best understood by referring to FIGURES 1 and 2 of the drawings, like numerals being used for like and corresponding parts of the various drawings.
FIGURE 1 illustrates a system 10 for identifying a link and a processing port of origin for a control cell in a communication switch. System 10 includes at least one to-switch processing port (TSPP) 12, at least one logical link table 14, switching fabric 16, a switch control module (SCM) 18, and a reverse mapping table 20.
As shown in FIGURE 1, system 10 includes two TSPPs 12, labeled as TSPP0 and TSPPI. Each TSPP 12 can be implemented as an application specific integrated circuit (ASIC) . Each TSPP 12 may include a number of connections or links 22. Links 22 may support asynchronous transfer mode (ATM) cell relay (OC-12, OC-3c, 155 Mbps UTP) , frame relay (Tl, El, T3, E3, V.35) , circuit emulation (Tl, El, T3 , E3) , internetworking using Ethernet, Fast Ethernet, Internet Protocol (IP) , or IP over ATM, or any other communications protocol or access technology. In the embodiment shown in FIGURE 1, each TSPP 12 may support or include eight links 22, which are labeled as LINK0-LINK7. Each link 22 is operable to receive a data cell, including control cells 24 which are labeled as CELL1, CELL2, and CELL3. The term "control cells" refers to cells that contain signaling or administration information. Each control cell 24 includes a virtual path identification (VPI) field 26 and a virtual channel identification (VCI) field 28. VPI field 26 and VCI field 28 may be numerical values. For a particular type of control cell 24, the numerical values for VPI field 26 and the VCI field 28 are specific. For example, as shown in FIGURE 1, CELL1 , CELL2 and CELL3 may each be an interim local management interface (ILMI) control cell where VPI field 26 has a value of "0" and VCI field 28 has a value of "16." These values for VPI field 26 and VCI field 28 are the same for every ILMI control cell, regardless of the link 22 or TSPP 12 at which the control cell 24 is received. As described below in more detail, each TSPP 12 is operable to convert the control cells 24 that it receives into converted cells 38, which are labeled as CCELL1, CCELL2, and CCELL3 in FIGURE 1. Each of these converted cells 38 may have a VPI 40 and a VCI 42. The values of the VCI 42 in converted cells 38 differ even if the converted cells 38 all correspond to the same type of control cell 24.
A separate logical link table 14 is associated with each TSPP 12. The logical link tables 14 shown in FIGURE 1 are labeled as LLTO and LLT1. LLTO and LLT1 are associated with TSPPO and TSPPI, respectively. Each logical link table 14 may be implemented on a memory internal or external to its associated TSPP 12, such as an external random access memory (RAM) . Logical link tables 14 each comprise a plurality of logical link entries 30, which are labeled as LL#0-LL#7 in FIGURE 1. Each logical link entry 30 corresponds to a particular link 22 in the TSPP 12 associated with the logical link table 14. For example, LL#0-LL#7 in LLTO correspond to LINKO-LINK7 in TSPPO, respectively. Likewise, LL#0-LL#7 in LLT1 correspond to LINK0-LINK7 in TSPPI, respectively. Each logical link entry 30 may specify a numerical value, which is unique to a particular link 22 of a particular TSPP 12. In one embodiment, each numerical value may be implemented as a nine-bit binary number. Consequently, five hundred and twelve numerical values may be supported for the various logical link entries 30. The logical link entries 30 are used in converting control cells 24 to converted cells 38, as described below. The information in logical link tables 14 can be configured or initialized by software. Switch fabric 16 is connected to each TSPP 12. Switch fabric 16 is operable to transfer a data cell, such as control cells 24, from a TSPP 12 to a from-switch processing port (FSPP) . Switch fabric 16 can be implemented as an ECL cross-point device for transferring signals. In one embodiment, switch fabric 16 supports sixteen TSPPs 12.
SCM 18 is connected to switch fabric 16. SCM 18 may be implemented as one or more ASICs. SCM 18 includes an FSPP 32 having a special queue 34. FSPP 32 may also be implemented as an ASIC. Special queue 34 may be dedicated to receiving converted cells 38 corresponding to control cells of a particular type, such as ILMI control cells. As shown in FIGURE 1, special queue 34 receives or contains CCELL1, CCELL2, and CCELL3.
Reverse mapping table 20 may be associated with special queue 34 in FSPP 32 of SCM 18. Reverse mapping table 20 may be implemented on memory (e.g., RAM) internal or external to FSPP 32. Reverse mapping table 20 comprises a plurality of reverse mapping entries 36. Each of reverse mapping entries 36 comprises information identifying a specific link 22 and TSPP 12 at which a control cell 24 can be received. Reverse mapping table 20 can be indexed by the numerical values specified in logical link entries 30. Like logical link tables 14, the information in reverse mapping table 20 can be configured or initialized by software.
In operation, the TSPPs 12 may receive control cells 24 at various links 22. As shown in FIGURE 1, CELL1 and CELL2 may be received at LINK2 and LINK7 of TSPPO, respectively, and CELL3 may be received at LINK6. If these control cells 24 are the same type, the numerical value for the VPI field 26 of all cells will be the same. Likewise, the numerical value for the VCI field 28 of all cells will be the same. VPI field 26 and VCI field 28 of the cells shown in FIGURE 1 have numerical values of 0 and 16, respectively. If the control cells 24 received by a TSPP 12 are of a certain type as determined by the VPI and VCI, then the TSPP 12 replaces the numerical value for VCI field 28 of the received cells with a numerical value stored in the logical linking table 14 associated with that TSPP 12. In particular, the TSPP 12 uses the logical link entry 30 corresponding to the link 22 at which the control cell 24 is received to replace the numerical value of the VCI field 28. In this manner, TSPP 12 converts control cells 24 to converted cells 38.
For example, because CELL1 is received at LINK2 of TSSPO, the numerical value of "285" specified in LL#2 of LLTO is used to replace the VCI value of "16". Likewise, because CELL2 is received at LINK7 of TSPPO, the VCI value of "16" in CELL2 is replaced with a VCI value of "220" specified in LL#7 of LLTO. Similarly, because CELL3 is receive at LINK6 of TSPPI, the VCI value of "16" in CELL3 is replaced with the value of "96" specified in LL#6 of LLT1. In this manner, CELL1, CELL2, and CELL3 may be converted into CCELL1, CCELL2, and CCELL3. TSPPs 12 transmit the converted cells 38 to SCM 18, which receives the converted cells 38 at special queue 34 dedicated to this particular type of control cell. When SCM 18 receives a converted cell 38, it is able to identify the link and processing port at which the corresponding control cell 24 was received using reverse mapping table 20.
It should be understood that a separate set comprising one or more logical link tables 14, a special queue 34, and a reverse mapping table 20 can be maintained for each type of control cell in a switch.
FIGURE 2 is a flow chart of a method 100 for identifying a link 22 and a TSPP 12 of origin for a control cell 24 in a communication switch. Method 100, which corresponds to the operation of system 10 shown in FIGURE 1, is described with particular reference to the processing of exemplary CELL1. Method 100 begins at step 102, where a TSPP 12 receives an information cell 24 at one of its links 22. For example, TSPPO receives CELL1 at. LINK2. At step 104, TSPP 12 determines whether the cell is a control cell 24. For example, in one embodiment, a queue number associated with the cell is used to look-up a queue descriptor. The queue descriptor may contain a logical link (LL) bit that specifies whether the cell should be converted.
If the received cell is not a control cell 24, method 100 ends. Otherwise, if the received cell is a control cell 24, then at step 108 TSPP 12 references its associated logical link table 14 and converts the control cell 24 into a converted cell 38. In particular, TSPP 12 replaces the value of VCI field 28 in the control cell 24 with a numerical value specified by the logical link entry 30 corresponding to the link 22 at which control cell 24 was received. Thus, because CELL1 was received at LINK2 of TSPPO, TSPPO replaces the VCI field 28 value of "16" with a value of "285" specified by LL#2 in LLTO. This results in CCELL1, a converted cell 38 having a VCI 42 value of "285. "
At step 110, TSPP 12 transmits the converted cell 38 to special queue 34 of FSPP 32 in SCM 18. Special queue 34 receives only information cells of a particular type, such as cells relating to ILMI control.
SCM 18 receives the converted cell 38 from special queue 34 at step 114. At step 116, SCM 18 extracts the VCI 42 value from the converted cell 38. The VCI 42 value is used to index a reverse mapping entry 36 in reverse mapping table 20 at step 118. The reverse mapping entry 36 specifies the link 22 and TSPP 12 at which the control cell 24 corresponding to the converted cell 38 was received. Accordingly, SCM 18 is able to identify the TSPP 12 and link 22 of origin for the control cell 24 at step 128. Thus, with regard to the example, the VCI 42 value of "285" is used to reference the reverse mapping entry 30 specifying "LINK2 TSPPO." SCM 18 may then respond at the link 22 and TSPP 12 of origin if appropriate.
Although the present invention and its advantages have been described detail, it should be understood that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

WHAT IS CLAIMED IS:
1. A system for identifying a processing port and a link at which a cell is received, comprising: a logical link table comprising a plurality of logical link entries, each logical link entry corresponding to a particular link of a processing port associated with the logical link table, each logical link entry specifying a numerical value; the processing port operable to receive a cell at one of a plurality of links, the processing port operable to convert the cell by replacing a numerical value of an identification field of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received; and a switch control module connected to the processing port, the switch control module operable to receive the converted cell, the switch control module operable to identify the link and the processing port at which the cell corresponding to the converted cell was received by referencing a reverse mapping table using the numerical value of the logical link entry in the converted cell.
2. The system of Claim 1, wherein the cell is a control cell.
3. The system of Claim 1, wherein the reverse mapping table comprises a plurality of reverse mapping entries, each reverse mapping entry specifying a particular link of the processing port.
4. The system of Claim 1, further comprising a switching fabric connected to the processing port and the switch control module.
5. The system of Claim 1, wherein the switch control module further comprises a special queue operable to receive the converted cell.
6. The system of Claim 1, wherein the processing port is further operable to determine whether the received cell is a control cell.
7. The system of Claim 1, wherein the processing port comprises an application specific integrated circuit.
8. The system of Claim 1, wherein the logical link table is stored in a random access memory external of the processing port.
9. The system of Claim 1, wherein the identification field comprises a virtual channel identification field.
10. The system of Claim 1, wherein the switch control module comprises an application specific integrated circuit.
11. A system for identifying a processing port and a link at which a cell is received, comprising: a logical link table comprising a plurality of logical link entries, each logical link entry corresponding to a particular link of a processing port associated with the logical link table, each logical link entry specifying a numerical value; a reverse mapping table comprising a plurality of reverse mapping entries, each reverse mapping entry specifying a particular link of the processing port, the logical link table operable to be indexed using the numerical values specified by the logical link entries of the logical link table; the processing port operable to receive a cell at one of a plurality of links, the processing port further operable to access the logical link table, the processing port further operable to convert the cell by replacing a numerical value of a virtual channel identification field of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received; and a switch control module coupled to the processing port and operable to access the reverse mapping table, the switch control module further operable receive the converted cell, the switch control module operable to identify the link and the processing port at which the cell corresponding to the converted cell was received by referencing the reverse mapping table using the numerical value of the logical link entry.
12. The system of Claim 11, wherein the cell is control cell.
13. The system of Claim 11, wherein the switch control module further comprises a special queue operable to receive the converted cell.
14. The system of Claim 11, wherein the processing port is operable to determine whether the received cell is a control cell.
15. A method for identifying a processing port and a link at which a cell is received, comprising the steps of: receiving a cell at one of a plurality of links of a processing port; referencing a logical link table associated with the processing port, the logical link table comprising a plurality of logical link entries, each logical link entry corresponding to a particular link of the processing port, each logical link entry specifying a numerical value; converting the cell by replacing a numerical value of an identification field of the cell with the numerical value specified by the logical link entry corresponding to the link at which the cell is received; and identifying the link and the processing port at which the cell was received by referencing a reverse mapping table using the numerical value specified by the logical link entry in the converted cell.
16. The method of Claim 15, further comprising the step of determining whether the received cell is a control cell.
17. The method of Claim 15, further comprising the step of receiving the converted cell at a special queue.
18. The method of Claim 15, wherein the identification field comprises a virtual channel identification field.
PCT/US1996/011963 1995-07-19 1996-07-18 Port and link identification WO1997004569A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
PCT/US1996/011963 WO1997004569A1 (en) 1995-07-19 1996-07-18 Port and link identification
JP9506895A JPH11510329A (en) 1995-07-19 1996-07-18 Port and link identification
AU65035/96A AU6503596A (en) 1995-07-19 1996-07-18 Port and link identification

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US149895P 1995-07-19 1995-07-19
US60/001,498 1995-07-19
PCT/US1996/011963 WO1997004569A1 (en) 1995-07-19 1996-07-18 Port and link identification

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Also Published As

Publication number Publication date
JPH11510329A (en) 1999-09-07
AU6503596A (en) 1997-02-18

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