Payload Compression; Aldc Vs. Lzs Compression Comparison Table - Comtech EF Data CDM-570A Installation And Operation Manual

CDM-570L/570AL Satellite Modem with Optional Packet Processor
Appendix D
supported header will 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 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).
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