Appendix F Revision 4
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
F–19
F.3.3 Header Compression
The High-Speed Packet Processor incorporates industry-leading header compression for
Ethernet Layer 2 or Layer 3 IP traffic. Header compression can reduce the 40-byte IP/UDP/RTP
header to as little as 1 byte; for TCP/IP, the 40-byte header is reduced to as little as 3 bytes.
For applications such as Voice-over-IP (VoIP), header compression can provide bandwidth
savings exceeding 60%. For example, the 8 kbps G.729 voice codec requires 24 kbps of IP
bandwidth once encapsulated into an IP/UDP/RTP datagram. With header compression, the
same voice call needs about 8.5 kbps – a saving of almost 65%.
In addition, bandwidth requirements for typical Web/HTTP traffic can be reduced by 10% or
more with TCP/IP header compression.
F.3.4 FAST Options
No FAST options are associated with the High-Speed Packet Processor. Once installed and
enabled, the Packet Processor is already configured for full operation of Routing, QoS, and
Header Compression at the full rate of the modem.
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