Reducing delays in a communication network using a re-fragmentation pipeline

• US 6,785,239 B1
• Filed: 06/01/1999
• Issued: 08/31/2004
• Est. Priority Date: 06/01/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Tasker, Michael
• Primary Examiner(s): PHAN, MAN U
• Application Number:
  US09/322,907
• Time in Patent Office: 1,918 Days
• Field of Search: 370/238, 370/347, 370/389, 370/395, 370/352, 370/401, 370/428, 370/392, 370/462, 370/463, 370/465, 370/397, 370/471, 370/473, 455/515, 709/203, 709/218, 709/225, 709/249
• US Class Current: 370/238
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04M 7/006 Networks other than PSTN/ISDN providing telephone service, e.g. Voice over Internet Protocol (VoIP) , including next generation networks with a packet-switched transport layer H04L65/00 takes precedence; aspects not specific to the type of network H04M3/00; special services in those networks H04M3/42

Abstract

A method and apparatus are described to reduce delay in a communication network. A fragmentation unit re-assembles a packet received from a first data link. A refragmentation pipeline is coupled to the fragmentation unit to pipeline the re-assembled data for transmission to a second data link.

Claims

1. A method to reduce delay in a communication network, the method comprising:

(a) receiving a packet from a first data link for transmission to a second data link; and

(b) pipelining data of the received packet via a refragmentation pipeline, comprising;

(b1) adding the received packet to a re-assembly buffer,

(b2) removing data from the re-assembly buffer if an amount of data in the re-assembly buffer is equal to or greater than a fragment size of the second data link, and

(b3) emptying the re-assembly buffer if the received packet is a begin packet.

2. The method of claim 1 wherein (a) comprises:

(a1) storing the packet in a receive queue;

(a2) determining if the received packet is forwarded to the second data link; and

(a3) determining if the second data link is configured for fragmentation.

3. The method of claim 1 wherein (b) further comprises:

(b4) creating a data segment for transmission to the second data link.

4. The method of claim 3 wherein (b) further comprises:

(b5) creating a data segment for transmission using data remaining in the re-assembly buffer if the received packet is an end packet.

5. The method of claim 1 wherein (a) further comprises:

(a4) discarding remaining data in the re-assembly buffer if there is an error in the received packet.

6. An apparatus to reduce delay in a communication network, the apparatus comprising:

a fragmentation unit to re-assemble a packet received from a first data link, the fragmentation unit comprising a re-assembly buffer to store the received packet; and

a refragmentation pipeline coupled to the fragmentation unit to pipeline the re-assembled data for transmission to a second data link;

wherein the re-assembly buffer transfers data to the refragmentation pipeline if an amount of data in the re-assembly buffer is equal to or greater than a fragment size of the second data link, and is emptied if the received packet is a begin packet.

7. The apparatus of claim 6 further comprising:

a receive queue coupled to the fragmentation unit to receive the packet.

8. The apparatus of claim 7 wherein the receive queue transfers the received packet to the re-assembly buffer.

9. The apparatus of claim 8 wherein the data in the re-assembly buffer is transferred to the refragmentation pipeline in overlap with the received packet being transferred from the receive queue to the re-assembly buffer.

10. The apparatus of claim 9 wherein the re-assembly buffer is emptied if the received packet is a begin packet.

11. The apparatus of claim 10 wherein a final segment for transmission to the second data link is created from data in the re-assembly buffer if the received packet is an end packet.

12. The apparatus of claim 9 wherein data in the re-assembly buffer is discarded if the received packet has an error.

13. A computer program product comprising:

a computer usable medium having computer program code embodied therein for reducing delay in a communication network, the computer program product having;

(a) computer readable program code for receiving a packet from a first data link for transmission to a second data link; and

(b) computer readable program code for pipelining data of the received packet via a refragmentation pipeline, the computer readable program code for pipelining comprising;

(b1) computer readable program code for adding the received packet to a re-assembly buffer,

(b2) computer readable program code for removing data from the re-assembly buffer if an amount of data in the re-assembly buffer is equal to or greater than a fragment size of the second data link,

(b3) computer readable program code for emptying the re-assembly buffer if the received packet is a begin packet.

14. The computer program product of claim 13 wherein (a) comprising:

(a1) computer readable program code for storing the packet in a receive queue;

(a2) computer readable program code for determining if the received packet is forwarded to the second data link; and

(a3) computer readable program code for determining if the second data link is configured for fragmentation.

15. The computer program product of claim 13 wherein (b) further comprises:

(b4) computer readable program code for creating a data segment for transmission to the second data link.

16. The computer program product of claim 15 wherein (b) further comprises:

(b5) computer readable program code for creating a data segment for transmission using data remaining in the re-assembly buffer if the received packet is an end packet.

17. The computer program product of claim 16 wherein (a) further comprises:

(a4) computer readable program code for discarding remaining data in the re-assembly buffer if there is an error in the received packet.

18. A system comprising:

first and second network interfaces for receiving and transmitting data over a communication network via first and second data links, respectively;

a processing unit coupled to the first and second network interfaces to reduce delay in data transmission in the communication network, the processing unit comprising;

a fragmentation unit coupled to the first network interface to re-assemble a packet received from the first data link, the fragmentation unit comprising a re-assembly buffer to store the received packet, and

a refragmentation pipeline coupled to the fragmentation unit to pipeline the re-assembled data for transmission to a second data link;

wherein the re-assembly buffer transfers data to the refragmentation pipeline if an amount of data in the re-assembly buffer is equal to or greater than a fragment size of the second data link and is emptied if the received packet is a begin packet.

19. The system of claim 18 wherein the processing unit further comprises a receive queue coupled to the fragmentation unit to receive the packet.

20. The system of claim 19 wherein the receive queue transfers the received packet to the re-assembly buffer.

21. The system of claim 20 wherein the data in the re-assembly buffer is transferred to the refragmentation pipeline in overlap with the received packet being transferred from the receive queue to the re-assembly buffer.

22. The system of claim 21 wherein the re-assembly buffer is emptied if the received packet is a begin packet.

23. The system of claim 21 wherein a final segment for transmission to the second data link is created from data in the re-assembly buffer if the received packet is an end packet.

24. The system of claim 21 wherein data in the re-assembly buffer is discarded if the received packet has an error.

25. An apparatus to reduce delay in a communication network, the apparatus comprising:

a fragmentation means to re-assemble a packet received from a first data link, the fragmentation means comprising a re-assembly buffer means to store the received packet; and

a refragmentation pipeline means coupled to the fragmentation means to pipeline the re-assembled data for transmission to a second data link;

wherein the re-assembly buffer means transfers data to the refragmentation pipeline means if an amount of data in the re-assembly buffer means is equal to or greater than a fragment size of the second data link and is emptied if the received packet is a begin packet.

26. The apparatus of claim 25 further comprising:

a receive queue means coupled to the fragmentation means to receive the packet.

27. The apparatus of claim 26 wherein the receive queue means transfers the received packet to the re-assembly buffer.

28. The apparatus of claim 27 wherein the data in the re-assembly buffer means is transferred to the refragmentation pipeline means in overlap with the received packet being transferred from the receive queue means to the re-assembly buffer means.

29. The apparatus of claim 28 wherein the re-assembly buffer means is emptied if the received packet is a begin packet.

30. The apparatus of claim 29 wherein a final segment for transmission to the second data link is created from data in the re-assembly buffer means if the received packet is an end packet.

31. The apparatus of claim 28 wherein data in the re-assembly buffer means is discarded if the received packet has an error.