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Speaker: 邱翰銓 Date:2010/10/4

Using sigcomp to compress SIP/SDP Messages Haipeng Jin and AC Mahendran Qualcomm Inc. San Diego, California, 92121, USA IEEE International Conference on Communication (ICC 2005). Speaker: 邱翰銓 Date:2010/10/4. Outline:. Introduction Signaling compression

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Speaker: 邱翰銓 Date:2010/10/4

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  1. Using sigcomp to compress SIP/SDP MessagesHaipeng Jin and AC Mahendran Qualcomm Inc.San Diego, California, 92121, USAIEEE International Conference on Communication (ICC 2005). Speaker:邱翰銓 Date:2010/10/4

  2. Outline: • Introduction • Signaling compression • Overview of Text Compression Algorithms • Performance Results • Conclusion

  3. Introduction SIP and SDP are used in 3G cellular IP Multimedia Subsystems (IMS) to perform multimedia session setup and maintenance. However, both protocols are text-based and have large messages with sizes frequently exceeding several hundred bytes. SigComp can be used to compress these messages and greatly reduce the call setup and feature invocation delays.

  4. Signaling Compression(sigcomp) SigComp is offered to applications such as SIP as a layer between the application and an underlying transport. The service provided is that of the underlying transport plus compression. • Basic SigComp • Dictionaries for SIP/SDP compression • Extended operations

  5. Basic SigComp • The core feature of SigComp is Universal Decompressor Virtual Machine (UDVM). • The UDVM provides decompression functionalities. • The UDVM is used to decompress SigComp messages.

  6. Dictionaries for SIP/SDP compression • In order to reduce the session setup time as much as possible, the SIPPING Working Group in IETF introduced a static dictionary for SIP and SDP. The dictionary is to be used in conjunction with SIP, SDP and SigComp. • The static SIP/SDP dictionary is a collection of well known strings that appear in most of the SIP and SDP messages.

  7. Extended operations Extended operations make use of UDVM instructions and the feedback mechanisms offered by SigComp to significantly improve the compression efficiency . • Dynamic compression • Shared compression

  8. Dynamic compression • During dynamic compression, a compressor performs compression relative to messages that are sent to the remote end-point prior to the current message. • Shared compression involves compressing the current outgoing message relative to messages received from the remote end-point. Shared compression

  9. 2 Sigcomp message Requesting feedback 1 9 1 3 8 4 Sigcomp message Returning feedback 1 6 7 5

  10. Overview of Text Compression Algorithms • LZ family of algorithms J.Ziv and A.Lempel • BWT Burrow-Wheeler Transform • PPM Prediction by Partial Math

  11. Dictionary-based • LZ family of algorithms • LZ77 • LZW • BWT(Burrow-Wheeler Transform) • RLE(Run-Length Encoding ) Transform-based

  12. Static Dictionary codiog A B B B A B A A B 1 0 1 1 1 0 00 1 0

  13. Model-based • PPM (Prediction by Partial Math) • Prediction by partial matching (PPM) is an adaptive statistical data compression technique based on context modeling and prediction. • Huffman Coding • Arithmetic Coding

  14. A B C D E 15 7 6 6 5 Huffman coding A 15 B 7 C 6 D 6 E 5 0 0 39 13 0 1 1 24 0 0 1 A B C D E 11 1 1 0 0 0 1 1 1 1 1 1 0 1

  15. Arithmetic code 這個編碼的方法是將訊息全部壓縮成一個，範圍在[0﹐1）中由裡面的某一個數來代表這整段訊息 說例﹕假設符號 {00﹑01﹑10﹑11}機率分別為{0.1﹑0.2﹑0.3﹑0.4}，依據這些機率分成個子隔﹕[0﹐0.1) ﹑[0.1﹐0.3) ﹑[0.3 ﹐0.6)﹑[0.6 ﹐1)  如果二進位訊息輸入為﹕10 01 11 00

  16. 1 0.33 0.33 0.3192 從[0.318,0.3192〉中選擇一個數代表輸出：0.3185，所以可以知道0.3185就是代表的編碼過後的訊息。 0.6 0.3 0.1 0.318 0.318 0 0.3

  17. Performance Results

  18. Compression Performance for ConcatenatedSIP Messages, size = 7161Bytes

  19. The following notations are used to indicate what states are used in the compression: • SD: static dictionary • SUD: both static and user dictionary • DC: dynamic compression • SC: shared compression • SDC: both dynamic and shared compression

  20. We use the following notations toindicate what messages are used: • M: message with the maximum size • L: latest sent or received message • ML: both the message with the maximum size and the latest message

  21. Effects of User Defined Dictionary onIndividual Messages (Deflate with DC)

  22. SigComp for IMS Call Setup Messages

  23. Conclusion • It is shown that dictionary-based compression schemes are the ones best suited for SigComp because of their low complexity, fast speed and low memory requirement. • Static and user-defined dictionaries are very useful for compressing the first several messages in a SIP dialog.

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