Payload Compression - Comtech EF Data CDM-570L Installation And Operation Manual

CDM-570L Satellite Modem with IP Module
automatically be identified for compression. The only configuration consideration is the Header
Compression Refresh Rate. This is how many compressed header packets will be sent before a single full
header packet is sent. Some compressed header traffic could be lost during deteriorated satellite link
conditions. Sending a full header packet will allow the return of the traffic stream. The Refresh Rate can
be increased for poor satellite link conditions or decreased to further reduce overhead.
Header Compression Statistics - These statistics will display the total bytes of the pre-compressed and
post-compressed traffic and effective compression ratio.

14.4.3 Payload Compression

Traffic optimization through Payload Compression is another optional feature of the CDM-570L/IP
Module modem.
- FAST feature to upgrade
- Uses AHA chip
- Compression algorithm applied to all data (HDLC header excluded).
- Compression statistics are fed back to QoS in order to maximize WAN utilization while
maintaining priority, jitter and latency.
- 1024 simultaneous compression sessions to maximize compression across multiple distinct traffic
flows.
- Compression algorithm not applied to RTP streams because this traffic is already compressed and
would only INCREASE the sat bandwidth if compressed again.
- Additional statistics have been added to the compression statistics menu in order to provide
feedback on the compression efficiency that has been achieved.
- Payload Compression is selectable on a per route basis.
ADLC vs LZS compression comparison
Note: These numbers have been generated by using an internally created test program. This program
takes the target benchmark files and splits the files into payload size chunks and
compresses each chunk in a separate invocation of the compression algorithm. This is
important to note because most compression algorithms are applied to the entire file data
set as a single invocation of the compression algorithm which is easier for other types of
compression algorithms (LZS, GZIP in specific). This, of course, does not apply to
streamed packet data across an IP network (ftp transfer, for example).
ADLC
ADLC
ADLC
ADLC
ADLC
ADLC
ADLC
Algorithm Payload size
1472
1000
500
100
1472
1000
500
File Set
Calgary
Calgary
Calgary
Calgary
Canterbury
Canterbury
Canterbury
163
Revision 1
MN/CDM570L.IOM
Ratio
1.76
1.76
1.77
2.09
1.71
1.72
1.74