Comtech EF Data CDM-570 - Manual (Page 215)

CDM-570/570L Satellite Modem with Optional IP Module Revision 12
Ethernet IP Module Interface MN/CDM570L.IOM
13–9
13.4.2 3xDES Encryption with Ability to Change Keys
The IP Module optionally supports 3xDES-128 (using NIST certified 3x core) encryption and
decryption, for the highest level security for link encryption. Each unit supports eight encryption
keys and eight decryption keys. The keys are user-configurable. Each route can be assigned to be
encrypted by any of the eight available keys, random key method, or transmitted in clear.
13.4.3 IP Header Compression
Header Compression is an optional feature of the IP Module. The IP Module supports Header
Compression for the following Ethernet and Layer 3, 4 & 5 Headers:
Supported Ethernet Headers Supported Layer 3 & 4 Headers
Ethernet 2.0 IP
Ethernet 2.0 + VLAN-tag TCP
Ethernet 2.0 + MPLS UDP
802.3-raw RTP (Codec Independent)
802.3-raw + VLAN-tag
802.3 + 802.2
802.3 + 802.2 + VLAN-tag
802.3 + 802.2 + SNAP
802.3 + 802.2 + SNAP + VLAN-tag
802.3 + 802.2 + SNAP + MPLS
Header Compression reduces the required VoIP bandwidth by 60 percent. Example: A G.729a
voice codec, operating at 8 kbps, will occupy 32 kbps once encapsulated into IP framing on a
LAN. 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.
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.
• Header Compression Statistics will display the total bytes of the pre-compressed and
post-compressed traffic and effective compression ratio.