Comtech EF Data CDM-570/L Vipersat Parameter Editor - Manual (Page 78)

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2-62 CDM-570/L, CDD-56X Parameter Editor User Guide
lite frame. Therefore, IP headers could be compressed as well. Payload
compression is an optional feature of the modem and has the following features:
• All modems used in a VMS network operate in router mode requiring that
payload compression be set on a per route basis, as described in the
section “Routing” on page 2-7.
• The compression algorithm is applied to all data (HDLC header excluded).
• Compression statistics are fed back to QoS in order to maximize WAN
utilization while optimizing priority, jitter and latency.
• The modem runs 1024 simultaneous compression sessions to maximize
compression across multiple distinct traffic flows.
• Compression algorithm is not applied to RTP streams because this traffic
is already compressed and would only increase the satellite bandwidth if
compressed again.
Receive payload compression is auto-sensed by a bit carried in packet headers
and the modem unit will perform decompression. This function is always avail-
able if the payload compression FAST code option has been purchased.
Triple DES
The Triple DES dialog, shown in figure 2-43, sets the parameters for Data
Encryption Standard in the modem.
Each modulator and demodulator in the modem has a tab for its own unique
DES keys. For example, a CDM-570/570L has one TX Encryption sub-tab and
one Rx Decryption sub-tab, while a CDD-564/564L has no Tx Encryption sub-
tab but has four Rx Decryption sub-tabs. Thus, the DES tab can have sub-tabs
for:
• Tx Encryption Keys
• Rx Decryption Keys
The following discussion applies to the keys on both types of sub-tabs.
A 24 Byte [192-bit] 3xDES key is actually a combination of 3 single DES keys
of 8 Bytes [64-bits]. The DES tab displays each key with spaces separating the
key into 3 sections. In figure 2-43, the Transmit Keys are displayed as:
2222222222222222 4444444444444444 6666666666666666
Note: The sequence 6666666666666666 does not fully show in the window; use the
scroll bar to make it visible. NOTE