Comtech EF Data VMS v3.12.x Vipersat - Manual (Page 271)

Chapter 4 - Configuring Network Modems 4-53
MN/22156, rev 12 Network
Step Up Threshold
The Step Up Threshold establishes the percentage of bandwidth use that will
trigger a switch Up from the present SCPC rate to a higher rate to ensure that
there is sufficient bandwidth available for current conditions.
Valid range is 65–100 %. A typical setting for this parameter is 95%. Note that
this value must be greater than the value specified for the SCPC Step Down
Threshold.
Step Down Threshold
The Step Down Threshold establishes the percentage of bandwidth use that
will trigger a switch Down from the present SCPC rate to a lower rate to ensure
efficient bandwidth usage for current conditions.
Valid range is 1–95 %. A typical setting for this parameter is 65%. Note that this
value must be less than the value specified for the SCPC Step Up Threshold.
Network | Switching | ToS
This menu item appears for CDM-840 units only.
This menu item appears under Switching, and is used to define and make modi-
fications to the ToS switching rules.
Type of Service (ToS) is defined by an eight bit field within an IP packet header
that is used to set up per-hop-based QoS rules for prioritizing packets. Because
the ToS field remains untouched by most encryption methods, ToS switching
provides an alternative means of SCPC switching when encryption prevents the
detection of SIP and H.323 protocols.
ToS detection occurs in the Remote modem which only looks at traffic that is
passed in the LAN-to-WAN (Remote to Hub) direction. Once the ToS switch
detection feature is enabled, the Remote modem will send a switch request to
the VMS when a packet stamped with the ToS is detected. The request contains
the destination IP address of the ToS stamped packet, the desired SCPC rate,
and the VMS Switch Type (policy #). If available hardware and bandwidth
exist, the VMS will establish the SCPC carrier automatically.
Click in the Enable check box to activate this feature (figure 4-34).
Enter the maximum number of sessions per ToS identifier. Note that there is an
overall limit of 127 active sessions in the system.
ToS switch rules are configured by defining table entries. This is done with the
Add Entry, Modify Entry, and Delete Entry buttons.