Clad having majority decision address table controller

• US 5,450,399 A
• Filed: 06/23/1994
• Issued: 09/12/1995
• Est. Priority Date: 06/23/1993
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sugita, Masahiro
• Primary Examiner(s): Hsu, Alpus
• Application Number:
  US08/264,431
• Time in Patent Office: 446 Days
• Field of Search: 370/58.1, 370/58.2, 370/58.3, 370/60, 370/60.1, 370/85.1, 370/85.13, 370/85.14, 370/94.1, 370/94.2, 370/110.1
• US Class Current: 370/392
• CPC Class Codes: H04L 2012/5615 Network termination, e.g. NT1, NT2, PBX
• CPC Class Codes: H04L 2012/5652 Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A cell assembly disassembly facility for interconnecting a local area network and an ATM switch includes an address table and a cell buffer for receiving ATM cells from the switch. A cell disassembler, connected to the cell buffer, disassembles the ATM cells into a packet for coupling to the LAN. The source address, VPI and VCI of each BOM (beginning-of-message) or SSM (single-segment-message) ATM cell in the cell buffer are stored into the DA, VPI and VCI fields of an entry of the table. Entries having identical source addresses (SA) are detected. If the same SA entries have different VPIs and VCIs, they are divided into at least two groups of entries. A majority decision is made on the entry groups to determine a winner. If one of the groups is determined to be a winner, the rest of the groups is erased and all the entries of the remaining group are then erased except for one entry. If there are two or more groups of largest number, all the entries of the groups are erased except for one that is most recently stored, or if at least one group of smaller number is present in addition to the groups of largest number, the smaller group is erased before erasing all entries other than the most recent one. When a packet is received by a packet buffer, the address table is searched for a DA field using the destination of the packet as a search key, and a VPI and a VCI are read from the entry of the DA field into each ATM cell that is sent to the ATM switch.

Claims

1. A cell assembly disassembly facility for interconnecting a local area network and an Asynchronous Transfer Mode (ATM) switch, comprising:

a cell buffer connected to the ATM switch for receiving ATM cells therefrom, each of the ATM cells containing a source address, a virtual path identifier (VPI) and a virtual channel identifier (VCI);

a cell disassembler connected to the cell buffer for disassembling ATM cells therefrom into a packet for coupling to said local area network;

an address table having a plurality of entries each having a destination address (DA) field, a VPI field and a VCI field;

registration means for storing the source address, VPI and VCI of each ATM cell of said cell buffer into the DA, VPI and VCI of fields one of the entries of the address table, respectively;

majority decision means for detecting entries having identical DA fields, erasing all of said detected entries except for one entry if the VIPs and VCIs of the detected entries are identical to each other, dividing the detected entries into at least two groups if the VIPs and VCIs of the detected entries differ from each other, making a majority decision on said at least two groups to determine a winner, leaving the group determined to be the winner in said table by erasing the rest of said groups, and erasing entries other than most recent one of entries remaining in said table, erasing all of the entries of the group of said winner except for one entry;

a packet buffer connected to the local area network for receiving packets therefrom, each of the packets containing a destination address;

search means for making a search through said address table for detecting a match between a source address stored in one of said entries and the destination address of each packet from said packet buffer and reading a VPI and VCI from said one entry; and

a cell assembler for utilizing the read VPI and VCI for assembling each packet from the packet buffer into one or more ATM cells for coupling to said ATM switch.

2. A cell assembly disassembly facility as claimed in claim 1, wherein said majority decision means is operative when the address table is full.

3. A cell assembly disassembly facility as claimed in claim 1, wherein said majority decision means is operative when the number of ATM cells in said cell buffer is smaller than a predetermined value.

4. A cell assembly disassembly facility as claimed in claim 2, wherein said majority decision means is operative when the number of ATM cells in said cell buffer is smaller than a predetermined value.

5. A cell assembly disassembly facility as claimed in claim 1, wherein said majority decision means includes means for sorting all the entries of said address table using the source address of each entry as a sortkey for rearranging the entries into groups having identical source addresses.

6. A cell assembly disassembly facility as claimed in claim 2, wherein said majority decision means includes means for sorting all the entries of said address table using the source address of each entry as a sortkey for rearranging the entries into groups having identical source addresses.

7. A cell assembly disassembly facility as claimed in claim 3, wherein said majority decision means includes means for sorting all the entries of said address table using the source address of each entry as a sortkey for rearranging the entries into groups having identical source addresses.

8. A cell assembly disassembly facility as claimed in claim 1, wherein said registration means includes means for storing said source address, VPI and VCI of each ATM cell of said cell buffer into said table entries before an error check is made on a plurality of the ATM cells which comprises a packet.

9. A cell assembly disassembly facility as claimed in claim 1, wherein each entry of said address table includes an entry number identifying the entry.

10. In a cell assembly disassembly facility for interconnecting a local area network and an Asynchronous Transfer Model (ATM) switch, comprising an address table having a plurality of entries each having a destination field (DA), a VPI field and a VCI field, a method comprising the steps of:

a) storing a source address, VPI and CVI of ATM cells received from said ATM switch into the DA, VPI and VCI fields of one of the entries of the address table;

b) dividing the stored entries of said table into at least two groups of same DA field according to the VPIs and VCIs of the groups, if there is more than one entry having an identical DA field but a different VPI or VCI, and counting the number of entries of each of said group;

c) making a first decision if there is only one group of largest number, a second decision if there are more than one group of same largest number and at least one group of smaller number, and a third decision if there is exclusively more than one group of largest number;

d) responsive to either of said first and second decisions, erasing groups other than one group of the largest number;

e) responsive to said third decision, or following the step (d), erasing one or more entries other than a most recently stored one of the entries which remain in said table;

f) making a search through said address table for detecting a match between one of said DA fields and the destination address of each packet from the packet buffer and reading a VPI and a VCI corresponding to said one DA field; and

g) utilizing the read VPI and VCI for assembling each packet from the local area network into one or more ATM cells for coupling to said ATM switch.

11. In a cell assembly disassembly facility for interconnecting a local area network and an Asynchronous Transfer Model (ATM) switch, comprising:

a cell buffer connected to the ATM switch for receiving ATM cells therefrom, each of the ATM cells containing a source address, a virtual path identifier (VPI) and a virtual channel identifier (VCI);

a cell disassembler connected to the cell buffer for disassembling ATM cells therefrom into a packet for coupling to said local area network;

a packet buffer connected to the local area network for receiving packets therefrom, each of the packets containing a destination address; and

an address table having a plurality of entries each having a destination field (DA), a VPI field and a VCI field, a method comprising the steps of;

a) storing the source address, VPI and VCI of each ATM cell of said cell buffer into the DA, VPI and VCI fields of one of the entries of the address table;

b) dividing the stored entries of said table into at least two groups of same DA field according to the VPIs and VCIs of the groups, if there is more than one entry having an identical DA field but a different VPI or VCI, and counting the number of entries of each of said group;

c) making a first decision if there is only one group of largest number, a second decision if there are more than one group of same largest number and at least one group of smaller number, and a third decision if there is exclusively more than one group of largest number;

d) responsive to either of said first and second decisions, erasing groups other than one group of the largest number;

e) responsive to said third decision, or following the step (d), erasing one or more entries other than a most recently stored one of the entries which remain in said table;

f) making a search through said address table for detecting a match between one of said DA fields and the destination address of each packet from the packet buffer and reading a VPI and a VCI corresponding to the said one DA field; and

g) utilizing the read VPI and VCI for assembling each packet from the local area network into one or more ATM cells for coupling to said ATM switch.

12. A method as claimed in claim 11, further comprising the step of determining whether the address table is full or not, and wherein the steps (b) to (e) are performed if the address table is determined to be full.

13. A method as claimed in claim 12, further comprising the step of sorting all of the entries of said address table using the source address of each entry as a sortkey and rearranging the entries into groups having identical source addresses before the step (b) is performed.

14. A method as claimed in claim 11, further comprising the step of determining whether the number of cells in said cell buffer are smaller than a predetermined number or not, and wherein the steps (b) to (e) are performed if the number of cells in said cell buffer are determined to be smaller than said predetermined number.

15. A method as claimed in claim 14, further comprising the step of determining whether the address table is full or not, and wherein the steps (b) to (e) are performed if the address table is determined to be full.

16. A method as claimed in claim 14, further comprising the step of sorting all of the entries of said address table using the source address of each entry as a sortkey and rearranging the entries into groups having identical source addresses before the step (b) is performed.

17. A method as claimed in claim 11, further comprising the step of sorting all of the entries of said address table using the source address of each entry as a sortkey and rearranging the entries into groups having identical source addresses before the step (b) is performed.

18. A method as claimed in claim 11, wherein the step (a) is performed before an error check is made on a plurality of ATM cells which comprise a packet.