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

▶

Oct 18, 2022 303 likes •410 views

Research Manor Roke ROHC Implementation Experience mark.a.west@roke.co.uk Mark West 1 s s Roke Manor Overview Research ! First steps towards a full ROHC implementation ! Initial feel for memory and processor load ! Updating original

SLIDE 1

Roke Manor Research

s

ROHC Implementation Experience

Mark West mark.a.west@roke.co.uk

SLIDE 2

Roke Manor Research

s

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

SLIDE 3

Roke Manor Research

s

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:

100% IRREGULAR(7) CRC 100% IRREGULAR(1) M 100% LSB(6,-1) SN 100% IRREGULAR(1) X 100% VALUE(“0”) Tsc TS 100% IRREGULAR(6) Probability Encoding Method Field(s)

SLIDE 4

Roke Manor Research

s

Architecture

! Architecture of ROHC 09 implementation including EPIC

Compressor Flow/packet classification Decompressor Decompression front end Compression front end ROHC framework EPIC coder EPIC decoder ROHC framework Link HH tree Packet stream Decompressed Flows HH tree Compressed headers Feedback

SLIDE 5

Roke Manor Research

s

Processing Requirements

! Processing load ! Memory usage ! Implementation efficiency can be increased

0 .8 ROHC + EPI C 16.0 1.6 14.4 GSM EFR codec Decoder MIPS Total MIPS Encoder MIPS 0 .4 1 3 5 0 ROHC + EPI C 1.6 14.4 GSM EFR codec Static tree data (Kbytes) RAM (Kbytes) Program (Kbytes)

SLIDE 6

Roke Manor Research

s

Timing Breakdown

! Compress 1 header 41µs ! Decompress 1 header 56µs

(all timings on 270MHz SUN Ultra-5)

20% 38% 25% 17% Header CRC Choose field codings Find packet coding HH encode and format 4% 14% 36% 32% 14% Check format HH lookup Unpack data Process fields Check CRC

SLIDE 7

Roke Manor Research

s

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

SLIDE 8

Roke Manor Research

s

A ROHC Bay Cough?

‘I nteroperability Test’ ‘I nteroperability Test’ ‘I nteroperability Test’ ‘I nteroperability Test’

London

SLIDE 9

Roke Manor Research

s

Questions

! When? ! Who? ! What? ! Where? ! How?

SLIDE 10

Roke Manor Research

s

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