CDM-570L/570AL Satellite Modem with Optional Packet Processor
Revision 5
Optional High Performance Packet Processor D–16 MN-CDM570A
From CDM-570A HTTP Interface – Use the Admin | FAST page Demo Mode drop-down list to
set operation as Enabled, and then click [Submit]. The Demo Mode timer decrements via the
Demo Time Remaining: XX days XX hours XX minutes banner. To stop Demo
Mode at any time, use the drop-down list to set operation as Disabled.
Make sure to reboot the unit any time you turn Demo Mode ON (Enabled) or OFF
(Disabled).
D.1.2.7.2 Header and Payload Compression
D.1.2.7.2.1 IP Header Compression
The Packet Processor incorporates industry-leading header compression for 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. Using IP/UDP/RTP Header Compression, the same traffic only
needs 10.8 kbps total WAN satellite bandwidth to cross the link. A total maximum of 64
simultaneous VoIP calls can be compressed. Normal HTTP (Web) traffic can be reduced an
additional 10% via IP/TCP header compression.
In addition, bandwidth requirements for typical Web/HTTP traffic can be reduced by 10% or more
with TCP/IP header compression. The Packet Processor supports Header Compression for the
following Ethernet and Layer 3, 4 & 5 Headers:
Supported Ethernet Headers
Supported Layer 3 & 4 Headers
802.3 + 802.2 + SNAP + VLAN-tag
802.3 + 802.2 + SNAP + MPLS
Note the following:
• Header Compression Configuration is completely independent from QoS, and there is
no configuration required except enabling the Header Compression feature on both the
sending and receiving Comtech EF Data IP modem. Packets with a Header Compression
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.
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