Comtech EF Data CDD-56X Series Vipersat - Manual (Page 119)

Appendix B - Automatic Switching B-19
MN/22137, rev 1 ToS Switching
the clear and often provides the only mechanism for identifying and prioritize
traffic within the network.
The ToS switching feature in the SLM-5650A provides a reliable method for
performing automatic dSCPC switching and is the preferred method for most
encrypted environments that leave the IP header intact.
Detection of ToS Stamped Packets
The configuration and detection of ToS stamped packets occurs in the Network
Processor (NP) card of the remote modem. In the remote modem, the user
defines the ToS value to be detected and specifies the bandwidth to be
requested, should that value be detected.
Once a packet with the ToS value is detected, the modem will send a switch
request to the VMS. The VMS will then determine if policy settings, hardware,
and bandwidth are available, before sending out tuning commands to reconfig-
ure transmission communications.
Only IP traffic that is coming from the Ethernet port and is destined for the
Satellite interface will trigger a switch. Traffic coming from the hub or another
remote will not trigger a switch, regardless of the ToS value within the packets.
This means that an application or remarking device located at the remote must
be the source for stamping packets that are transmitted out of the remote site and
over the satellite.
A tear down request is sent by the remote modem to the VMS if no more pack-
ets are detected with the ToS value after a user definable timeout occurs.
ToS switching can also be utilized in non-encrypted networks. One advantage
for this is that each packet associated with the application will have ToS set,
thus making ToS switching extremely reliable. A drawback, however, is that
unless each application can set a different ToS value, granular resolution per
application will be lost.
Note: Only ToS stamped IP traffic that is coming from the Ethernet port of a
remote modem and is destined for the Satellite (WAN) interface will trig-
ger a switch request.
NOTE