Comtech EF Data cdm-570a - ALDC Vs. LZS Compression Comparison Table; Payload Compression; Table D-1. ALDC Vs. LZS Compression Comparison

CDM-570L/570AL Satellite Modem with Optional Packet Processor
Revision 5
Optional High Performance Packet Processor D–17 MN-CDM570A
• Header Compression Statistics will display the total bytes of the pre-compressed and
post-compressed traffic and effective compression ratio.
D.1.2.7.2.2 Payload Compression
The Packet Processor features industry-leading payload compression for IP traffic. Implemented
in the hardware for maximum throughput and efficiency, payload compression can reduce the
required satellite bandwidth by as much as 40–50%. Traffic optimization through Payload
Compression is an optional feature of the Packet Processor. Note the following:
• Available as a FAST feature
• 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
D.1.2.7.2.3 ALDC vs. LZS Compression Comparison Table
The numbers in Table D-1 were compiled using a test program created in-house
by Comtech EF Data. This program takes the target benchmark files and splits
the files into payload-sized chunks, then 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 specifically). This, of course, does not apply
to streamed packet data across an IP network (e.g., FTP transfer).
Table D-1. ALDC vs. LZS Compression Comparison
Algorithm
Payload
size
File Set Ratio Algorithm
Payload
size
File Set Ratio
ALDC
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