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ROHC Implementation Experience. Mark West [email protected] 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

ROHC Implementation Experience

Mark West

[email protected]

1


Overview
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


Rohc 09 compatible headers
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


Architecture
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


Processing requirements
Processing Requirements

  • Processing load

  • Memory usage

  • Implementation efficiency can be increased

5


Timing breakdown
Timing Breakdown

  • Compress 1 header 41s

  • Decompress 1 header 56s

    (all timings on 270MHz SUN Ultra-5)

6


Efficient implementation
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



A rohc bay cough interoperability test

A ROHC Bay Cough?‘Interoperability Test’

9


A rohc bay cough interoperability test1

A ROHC Bay Cough?‘Interoperability Test’

London

10


Questions
Questions

  • When?

  • Who?

  • What?

  • Where?

  • How?

11


Questions1
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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