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ROHC Implementation Experience

ROHC Implementation Experience. Mark West mark.a.west@roke.co.uk. Overview. First steps towards a full ROHC implementation Initial feel for memory and processor load Updating original reference implementation Clean separation of ROHC framework and EPIC packet processing

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ROHC Implementation Experience

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  1. ROHC Implementation Experience Mark West mark.a.west@roke.co.uk 1

  2. Overview • First steps towards a full ROHC implementation • Initial feel for memory and processor load • Updating original reference implementation • Clean separation of ROHC framework and EPIC packet processing • Make use of time and memory efficient algorithms(but still scope for optimisation…) • Designed to be used • In a test environment (e.g. running over UDP or TCP) • For initial tests in a ‘real’ environment • As an extensible test-bed for other protocols 2

  3. ROHC 09 Compatible Headers • Described in draft-price-rohc-epic-compatibility-00.txt • Bitwise identical compressed headers to ROHC 09 Example input table for UOR-2 headers: 3

  4. Architecture • Architecture of ROHC 09 implementation including EPIC Packet stream Decompressed Flows Compressor Flow/packet classification Decompressor Compression front end EPIC decoder ROHC framework HH tree EPIC coder ROHC framework HH tree Decompression front end Feedback Link Compressed headers 4

  5. Processing Requirements • Processing load • Memory usage • Implementation efficiency can be increased 5

  6. Timing Breakdown • Compress 1 header 41s • Decompress 1 header 56s (all timings on 270MHz SUN Ultra-5) 6

  7. Efficient Implementation • Existing techniques such as Canonical Huffman work with Hierarchical Huffman • Most mathematical operations can be simplified • Processing cost includes: • CRC • Reduce by lookup based CRC implementation • Selecting header format • Optimise by looking for most common format 7

  8. A ROHC Bay Cough? 8

  9. A ROHC Bay Cough?‘Interoperability Test’ 9

  10. A ROHC Bay Cough?‘Interoperability Test’ London 10

  11. Questions • When? • Who? • What? • Where? • How? 11

  12. Questions • When? • Just before IETF-51? • Who? • Anyone with enough of an implementation… • What? • Aim for basic interoperability • Where? • Siemens/Roke Manor • How? • Take technical aspects of getting implementations to ‘talk together’ to the list 12

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