Type Of Service (Tos) Switching - Comtech EF Data Vipersat 564L User Manual

T y p e o f S e r v i c e ( T o S ) S w i t c h in g

Type of Service (ToS) Switching

Type of Service (ToS) Switching is typically used on circuits carrying
encrypted traffic where the packets cannot be examined to determine the type of
traffic being carried. Normally, in a non-encrypted Vipersat network, packets
are classified by the Remote modem/router using protocol classification detec-
tion and the results are forwarded to the VMS via ASR messages. The VMS
switch detector service then applies the required or requested bandwidth using
policies which have been pre-configured in the VMS.
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, resolution is lost.
For example, in a non-encrypted network, if a voice application service connec-
tion is started, the Remote's classifier analyzes signaling and data protocols
(H.323, SIP, & Data RTP) being routed through the modem/router. After
connection detection, the process waits for data (RTP). Data is normally sent
after the receiving party answers, which then triggers the system to process an
ASR.
Using the ToS classification, detection function allows application-based
switching in encrypted networks where the signaling protocols are encrypted or
effectively hidden. ToS adds the type of service to the un-encrypted Quality of
Service byte (QoS) in the header which then can be analyzed to determine the
type of service being transmitted. Once the type of service is determined, the
VMS uses this information to perform switching, following the policies estab-
lished for the detected traffic type.
Note: Load switching by the VMS is not affected by enabling ToS detec-
NOTE
tion.
Applying a ToS value to an application (VoIP, IPVC, or priority data) through
either preservation or classification packet stamping allows the VMS to func-
tion in an encrypted network.
A p p e n d i x A u t o m a t i c S w i t c hi n g
B - B-13