Comtech EF Data CDM-570 - Manual (Page 216)

CDM-570/570L Satellite Modem with Optional IP Module Revision 12
Ethernet IP Module Interface MN/CDM570L.IOM
13–10
13.4.4 Payload Compression
Traffic optimization through Payload Compression is an optional feature of the IP Module.
Note the following:
• 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
13.4.4.1 ADLC vs. LZS Compression Comparison
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).
Algorithm
Payload
size
File Set Ratio Algorithm
Payload
size
File Set Ratio
ADLC
1472
Calgary
1.76
LZS
1472
Calgary
1.66
1000 1.76 1000 1.66
500 1.77 500 1.68
100 2.09 100 1.97
1472
Canterbury
1.71 1472
Canterbury
1.61
1000 1.72 1000 1.62
500 1.74 500 1.63
100 2.04 100 1.91