Topology independent broadcast of cells in an ATM network or the like

• US 5,345,558 A
• Filed: 11/23/1992
• Issued: 09/06/1994
• Est. Priority Date: 11/23/1992
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: SynOptics Communications, Inc. (Nortel Networks Corporation)
• Inventors: Chatwani, Dilip, Opher, Ayal, Subramanian, Rajan
• Primary Examiner(s): Shaw, Dale M.
• Assistant Examiner(s): Meky, Moustafa M.
• Application Number:
  US07/980,253
• Time in Patent Office: 652 Days
• Field of Search: 395/200, 370/14, 370/54, 370/60, 370/61, 370/91, 370/94.1, 370/95.1, 370/105.1, 370/105.2, 370/94.2, 370/94.3
• US Class Current: 709/236
• CPC Class Codes: H04L 2012/5619 Network Node Interface, e.g. tandem connections, transit switching
• CPC Class Codes: H04L 2012/5652 Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
• CPC Class Codes: H04L 49/203 ATM switching fabrics with multicast or broadcast capabilities
• CPC Class Codes: H04Q 11/0478 Provisions for broadband connections

Abstract

A topology-independent method and apparatus for avoiding continuous looping of transmission of cells and for allowing broadcast of cells in a network implementing Asynchronous Transfer Mode ("ATM") or similar networking architectures. The disclosed method and apparatus provides for "misusing" fields in a cell header in order to provide for information identifying a cell as a broadcast cell and to provide for "expiration information" in the cell header. More specifically, a first station stores data in a first area of a cell intended for transmission on the network, where the first area is defined by standards to store certain information (in particular, it is defined in the preferred embodiment to store virtual path identifier information, VPI). The information stored identifies the cell as a broadcast cell. In other words, the field is "misused" to store this information. The first station further stores in a second field, also defined by the standard to store certain information (in particular, virtual channel identifier information, VCI), information which allows for expiration of the cell. Thus, this second field is also "misused". The cell is then transmitted onto the network, copied and forwarded out of multiple ports of each switch, until the cell "expires". In the described embodiment, the "expiration information" is implemented as a hop count.

Claims

1. A method for broadcast of cells in a network implementing Asynchronous Transfer Mode comprising the steps of:

(a) a first station on said network formatting a cell for broadcast, said step of formatting said cell comprising the steps of;

i) assembling a header area comprising a first area and a second area, said first area being set to a predetermined value to indicate said cell is a broadcast cell, said second area being set to contain expiration information;

ii) assembling a third area having therein user information;

(b) said first station transmitting said cell onto said network;

(c) said cell being received by a fast switch;

(d) said first switch determining if said fast area is set to said first predetermined value; and

, if said fast switch is so set;

(e) said fast switch accessing said second area to determine if said cell should be forwarded.

2. The method as recited by claim 1 wherein said fast area is a virtual path identifier, also referred to with the acronym VPI.

3. The method as recited by claim 1 wherein said predetermined value is all 1'"'"'s.

4. The method as recited by claim 1 wherein said second area is a virtual channel identifier, also referred to with the acronym VCI.

5. The method as recited by claim 1 wherein said step (e) of accessing said expiration information comprises the step of decrementing said expiration information.

6. The method as recited by claim 1 wherein said step (e) of accessing said expiration information comprises the step of decrementing said expiration information by 1.

7. The method as recited by claim 1 wherein said step (e) of accessing said expiration information comprises the step of decrementing said expiration information by greater than 1.

8. The method as recited by claim 1 wherein said step (e) of accessing said expiration information comprises the step of incrementing said expiration information.

9. A network implementing Asynchronous Transfer Mode comprising:

(a) a fast station on said network for formatting and transmitting a cell, said cell comprising;

i) a first area being a header, said header having a first identifier field and a second identifier field, said fast identifier field set to a predetermined value to indicate said cell is a broadcast cell, said second identifier field set to a count value;

ii) a second area having therein user information; and

(b) a first switch for determining if said fast identifier is set to said fast predetermined value and, if said first switch is so set, for altering the count value in said second identifier field.

10. The network as recited by claim 9 wherein said first identifier field is a virtual path identifier, also referred to with the acronym VPI.

11. The network as recited by claim 9 wherein said predetermined value is all 1'"'"'s.

12. The network as recited by claim 9 wherein said second identifier field is a virtual channel identifier, also referred to with the acronym VCI.

13. The network as recited by claim 9 wherein said count value is altered by decrementing said count value.

14. The network as recited by claim 9 wherein said count value is altered by decrementing said count value by 1.

15. The network as recited by 9 wherein said count value is altered by decrementing said count value by greater than 1.

16. A method for broadcast of a packet in a computer network implementing Asynchronous Transfer Mode, where said packet having a first area comprising information about said packet and a second area comprising user information, said first area having a plurality of fields including a first field and a second field, said method comprising the steps of:

a) a first node on said network formatting said packet for broadcast, said step of

formatting said packet for broadcast including the steps of;

i) populating said first field with a predetermined value, and

ii) populating said second field with a count value,

b) said first node transmitting said packet onto said network;

c) said packet being received by a first switch;

d) said first switch determining if said first field is set to said predetermined value; and

, if said first field is set to said predetermined value,

e) said first switch altering said count value in said second field.

17. The method as recited by claim 16 wherein said first field is a virtual path identifier, also referred to with the acronym VPI.

18. The method as recited by claim 16 wherein said second field is a virtual channel identifier, also referred to with the acronym VCI.

19. The method as recited by claim 16 wherein said predetermined value is all 1'"'"'s.

20. The method as recited by claim 16 wherein said step (e) of altering said count value comprises the step of decrementing said count value.

21. The method as recited by claim 16 wherein said step (e) of altering said count value comprises the step of decrementing said count value by 1.

22. The method as recited by claim 16 wherein said step (e) of altering said count value comprises the step of decrementing said count value by greater than 1.

23. A computer network implementing Asynchronous Transfer Mode providing for broadcast of a packet, where said packet having a first area comprising information about said packet and a second area comprising user information, said first area having a plurality of fields including a first field and a second field, said computer network comprising:

a) a first node on said network for formatting a packet for broadcast by;

i) populating said first field with a predetermined value, and

ii) populating said second field with a count value,

b) said first node transmitting said packet onto said network;

c) a first switch for receiving said packet;

d) said first switch determining if said first field is set to said predetermined value; and

, if said first field is set to said predetermined value and,

e) said first switch altering said count value in said second field.

24. The computer network as recited by claim 23 wherein said first field is as a virtual path identifier, also referred to with the acronym VPI.

25. The computer network as recited by claim 23 wherein said second field is a virtual channel identifier, also referred to with the acronym VCI.

26. The computer network as recited by claim 23 wherein said predetermined value is all 1'"'"'s.

27. The computer network as recited by claim 23 wherein said said first switch alters said count value by decrementing said count value.

28. The computer network as recited by claim 23 wherein said said first switch alters said count value by decrementing said count value by 1.

29. The computer network as recited by claim 23 wherein said said first switch alters said count value by decrementing said count value by greater than 1.

30. A method for avoiding continuous forwarding of cells in a network implementing Asynchronous Transfer Mode comprising the steps of:

(a) a first station on said network formatting a cell for broadcast, said step of

formatting said cell comprising the steps of;

i) assembling a header area comprising a first area and a second area,

said first area being set to a predetermined value to indicate said cell is

a broadcast cell, said second area being set to a count value;

ii) assembling a third area having therein user information;

(b) said first station transmitting said cell onto said network;

(c) said cell being received by a first switch;

(d) said first switch determining if said first area is set to said predetermined

value; and

, if said first switch is so set;

(e) said first switch altering the count value in said second area.

31. The method as recited by claim 30 wherein said Fast area is a virtual path identifier, also referred to with the acronym VPI.

32. The method as recited by claim 30 wherein said predetermined value is all 1'"'"'s.

33. The method as recited by claim 30 wherein said second area is a virtual channel identifier, also referred to with the acronym VCI.

34. The method as recited by claim 30 wherein said step (e) of altering said count value comprises the step of decrementing said count value.

35. A computer network implementing Asynchronous Transfer Mode providing for broadcast of a cell, where said cell having a first area comprising information about said cell and a second area comprising user information, said first area having a plurality of fields including a first field for storing first information and a second field for storing second information, said computer network comprising:

a) a first node on said network for formatting a cell for broadcast by;

i) populating said first field with a first predetermined value, said first predetermined value representing said cell is a broadcast cell; and

ii) populating said second field with a second predetermined value, said second predetermined value further representing said cell is a broadcast cell;

b) said first node transmitting said cell onto said network;

c) a first switch for receiving said cell;

d) said first switch determining if said first field is set to said first predetermined value and if said second field is set to said second predetermined value; and

, if so set,

e) said first switch further altering said second field to contain a count value.

36. The computer network as recited by claim 35 wherein said first field is as a virtual path identifier, also referred to with the acronym VPI and said first predetermined value is 0.

37. The computer network as recited by claim 35 wherein said second field is a virtual channel identifier, also referred to with the acronym VCI, and said second predetermined value is 2.

38. The computer network as recited by claim 35 further comprising the step of altering said first field after step (e).

39. The computer network as recited by claim 38 wherein said first field is altered to contain all 1'"'"'s.