TWO STAGE INTERNET PROTOCOL HEADER COMPRESSION

• US 20110032952A1
• Filed: 08/07/2009
• Published: 02/10/2011
• Est. Priority Date: 08/07/2009
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent Canada Incorporated (Nokia Corporation)
• Inventors: Ellsworth, Adrian, Rochon, Michel, Duck, Bradley W.
• Granted Patent: US 8,140,709 B2
• Time in Patent Office: Days
• US Class Current: 370/477
• CPC Class Codes: H04L 69/04 Protocols for data compression, e.g. ROHC
• CPC Class Codes: H04L 69/22 Parsing or analysis of headers

Abstract

Various exemplary embodiments relate to a method and related network system including one or more of the following: receiving a packet having a header and belonging to a flow; identifying a context identifier (CID) associated with the flow; morphing the header into a pseudo-compressed header, the pseudo-compressed header including the CID associated with the flow; determining whether the packet should be transmitted with a compressed header, a full header, or an uncompressed header; morphing the pseudo-compressed header into a compressed header to form an outgoing packet when the packet should be transmitted with a compressed header; morphing the pseudo-compressed header into a full header to form an outgoing packet when the packet should be transmitted with a full header; restoring the uncompressed header to form an outgoing packet when the packet should be transmitted with an uncompressed header; and transmitting the outgoing packet over the communications network.

Claims

1. A system for providing header compression functionality in a communications network, the system comprising:

a first stage device that;

receives a packet having an uncompressed header and belonging to a flow,

identifies a context identifier (CID) associated with the flow,

morphs the uncompressed header into a pseudo-compressed header, the pseudo-compressed header including the CID associated with the flow and an indication that the header is pseudo-compressed, and

transmits the packet having a pseudo-compressed header; and

a second stage device that;

receives the packet having a pseudo-compressed header,

determines that the packet has a pseudo-compressed header by reading the indication that the header is pseudo-compressed,

determines whether the packet should be transmitted over the communications network with a compressed header, a full header, or an uncompressed header,

morphs the pseudo-compressed header into a compressed header when the packet should be transmitted with a compressed header,

morphs the pseudo-compressed header into a full header when the packet should be transmitted with a full header,

morphs the pseudo-compressed header into an uncompressed header when the packet should be transmitted with an uncompressed header, and

transmits the packet over the communications network after morphing the pseudo-compressed header.

2. The system of claim 1, wherein:

the first stage device further determines that a context for the flow has changed by comparing the uncompressed header to a stored context for the flow;

the pseudo-compressed header includes an indication that the context for the flow has changed; and

the second stage device further;

determines that the context for the flow has changed by reading the indication that the context for the flow has changed, and

increments a locally-stored generation number for the flow.

3. The system of claim 1, wherein, in identifying a CID associated with the flow, the first stage device accesses a flow lookup table that associates each flow of a plurality of flows with an assigned CID.

4. The system of claim 3, wherein, in identifying a CID associated with the flow, the first stage device assigns a CID to the flow when the flow lookup table does not store an association for the flow.

5. The system of claim 1, wherein, in morphing the uncompressed header into a pseudo-compressed header, the first stage device changes an original value of a first field of the uncompressed header to the CID and changes an original value of a second field of the uncompressed header to the indication that the header is pseudo-compressed.

6. The system of claim 5, wherein, in morphing the pseudo-compressed header into an uncompressed header, the second stage device:

determines a length and a protocol of the packet;

changes the value of the first field to the length, and

changes the value of the second field to an indication of the protocol.

7. The system of claim 1, wherein, in morphing the pseudo-compressed header into a compressed header, the second stage device removes the pseudo-compressed header from the packet and adds a compressed header to the packet, the compressed header including the CID and a generation number.

8. The system of claim 1, wherein, in determining whether the packet should be transmitted over the communications network with a compressed header, a full header, or an uncompressed header, the second stage device determines whether it is currently operating in slow-start mode for the flow.

9. A method of performing header compression in a communications network, the method comprising:

receiving, in a network node, a packet having an uncompressed header and belonging to a flow;

identifying a context identifier (CID) associated with the flow;

morphing the uncompressed header into a pseudo-compressed header, the pseudo-compressed header including the CID associated with the flow;

determining whether the packet should be transmitted with a compressed header, a full header, or an uncompressed header;

removing the pseudo-compressed header and adding a compressed header to the packet to form an outgoing packet when the packet should be transmitted with a compressed header;

modifying the pseudo-compressed header into a full header to form an outgoing packet when the packet should be transmitted with a full header;

restoring the uncompressed header to form an outgoing packet when the packet should be transmitted with an uncompressed header; and

transmitting the outgoing packet over the communications network.

10. The method of claim 9, wherein the step of identifying a CID comprises referencing a flow lookup table that associates each flow of a plurality of flows with a CID.

11. The method of claim 10, wherein the step of identifying a CID further comprises, when the flow lookup table contains no entry for the flow, assigning a new CID to the flow.

12. The method of claim 9, wherein the step of morphing the uncompressed header into a pseudo-compressed header comprises changing an original value of a field of the uncompressed header to the CID.

13. The method of claim 12, wherein the step of restoring the pseudo-compressed header to the uncompressed header comprises:

determining a length of the packet; and

changing the value of the field to the length.

14. The method of claim 9, further comprising:

determining whether a context for the flow has changed by comparing the uncompressed header to a stored context for the flow;

including an indication that the context for the flow has changed in the pseudo-compressed header when the context for the flow has changed; and

incrementing a generation for the flow when the pseudo-compressed header contains an indication that the context for the flow has changed.

15. The method of claim 9, wherein the step of determining whether the packet should be transmitted with a compressed header, a full header, or an uncompressed header comprises:

determining whether the flow should begin operating in slow-start mode by determining whether the generation for the flow has been incremented;

when the flow should begin operating in slow-start mode, determining that the packet should be transmitted with a full header;

determining whether the flow is currently operating in slow-start mode; and

when the flow is currently operating in slow-start mode, determining whether the packet should be transmitted with a full header or with an uncompressed header.

16. A network device for offloading a portion of work performed by a header compression device, the network device comprising;

a flow lookup table that associates each flow of a plurality of flows with an assigned context identifier (CID);

a receiver that receives a packet having an uncompressed header;

a flow identification module that identifies a flow to which the packet belongs;

a flow-CID lookup module that uses the flow lookup table to identify a CID assigned to the flow;

a pseudo-compression module that morphs the uncompressed header into a pseudo-compressed header, the pseudo-compressed header including the CID and an indication that the header is a pseudo-compressed header; and

a transmitter that transmits the packet having the pseudo-compressed header to the header compression device.

17. The network device of claim 16, wherein the flow lookup table is a content-addressable memory.

18. The network device of claim 16, further comprising a CID storage that stores the contexts and assigned CIDs for each flow and wherein the pseudo-compression module further:

determines whether a context for the flow has changed by comparing the uncompressed header to a context stored in the CID storage, and

inserts an indication that the context for the flow has changed into the pseudo-compressed header.

19. The network device of claim 16, further comprising a CID assignment module that, when the flow lookup table does not contain a record for the flow, assigns a new CID to the flow.

20. The network device of claim 16, wherein, in morphing the uncompressed header, the pseudo-compression module replaces an original value of a first field of the uncompressed header with the CID and replaces an original value of a second field of the uncompressed header with the indication that the header is a pseudo-compressed header.