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Session Header Compression Scheme Using Differential Run-Length Encoding

IP.com Disclosure Number: IPCOM000119154D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Binding, C: AUTHOR [+3]

Abstract

Disclosed is a protocol header compression scheme which is based on the combination of header differentiation with run-length encoding. The sending process computes the difference between successive headers by xor-ing the header content. The result of the difference is then run-length encoded using well known run-length encoding (1).

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Session Header Compression Scheme Using Differential Run-Length Encoding

      Disclosed is a protocol header compression scheme which is
based on the combination of header differentiation with run-length
encoding.  The sending process computes the difference between
successive headers by xor-ing the header content.  The result of the
difference is  then run-length encoded using well known run-length
encoding (1).

      On the receiver's side, the operations are performed in reverse
order: first, the run-length encoded differentiated packet header is
expanded; second, the resulting header is xor-ed with the previous
header.

      The complexity of the compression is O(n), since the data to be
transmitted is scanned linearly twice.  For cases where subsequent
headers differ only in a few fields, the initial header xor-ing
produces a string with many '0' bytes.  These are then compressed
efficiently using run length encoding.  Unlike the method prosed in
(2), the transmitted data does not contain a bitmask to indicate
which fields of  a header have changed.

      The Figure shows the compression performed by the sender.  (The
example is only illustrative as, in fact, no compression takes place.
An actual implementation detects such cases and transmits the
shorter, unmodified header.)

      In a protocol header with large information fields which
contain per-session constant information, such as a data encoding
scheme, source, or destination, th...