Comtech EF Data CDD-562L - Manual (Page 61)

CDD-562L/564 Demodulator with IP Module Revision 2
IP Module Ethernet Interface MN/CDD564L.IOM
4–5
4.2.3 Payload Compression
Traffic optimization through Payload Compression is another optional feature of the demodulator.
• 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 satellite 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.
4.2.3.1 ADLC vs LZS Compression Comparison
These numbers have been generated 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 (e.g., FTP transfer).
Algorithm
Payload
size
File Set Ratio Algorithm
Payload
size
File Set Ratio
ADLC 1472 Calgary 1.76 LZS 1472 Calgary 1.66
ADLC 1000 Calgary 1.76 LZS 1000 Calgary 1.66
ADLC 500 Calgary 1.77 LZS 500 Calgary 1.68
ADLC 100 Calgary 2.09 LZS 100 Calgary 1.97
ADLC 1472 Canterbury 1.71 LZS 1472 Canterbury 1.61
ADLC 1000 Canterbury 1.72 LZS 1000 Canterbury 1.62
ADLC 500 Canterbury 1.74 LZS 500 Canterbury 1.63
ADLC 100 Canterbury 2.04 LZS 100 Canterbury 1.91