Cisco Cisco Expressway 维护手册
Field
Description
Usage tips
Downspeed
total mode
total mode
Determines what happens if the total bandwidth restrictions
on a subzone or pipe mean that there is insufficient bandwidth
available to place a call at the requested rate.
on a subzone or pipe mean that there is insufficient bandwidth
available to place a call at the requested rate.
On: the call will be downspeeded.
Off: the call will not be placed.
About Downspeeding
If bandwidth control is in use, there may be situations when there is insufficient bandwidth available to place a call at
the requested rate. By default (and assuming that there is some bandwidth still available) the Expressway will still
attempt to connect the call, but at a reduced bandwidth – this is known as downspeeding.
the requested rate. By default (and assuming that there is some bandwidth still available) the Expressway will still
attempt to connect the call, but at a reduced bandwidth – this is known as downspeeding.
Downspeeding can be configured so that it is applied in either or both of the following scenarios:
■
when the requested bandwidth for the call exceeds the lowest per-call limit for the subzone or pipes
■
when placing the call at the requested bandwidth would mean that the total bandwidth limits for that subzone
or pipes would be exceeded
or pipes would be exceeded
You can turn off downspeeding, in which case if there is insufficient bandwidth to place the call at the originally
requested rate, the call will not be placed at all. This could be used if, when your network is nearing capacity, you
would rather a call failed to connect at all than be connected at a lower than requested speed. In this situation
endpoint users will get one of the following messages, depending on the system that initiated the search:
requested rate, the call will not be placed at all. This could be used if, when your network is nearing capacity, you
would rather a call failed to connect at all than be connected at a lower than requested speed. In this situation
endpoint users will get one of the following messages, depending on the system that initiated the search:
■
"Exceeds Call Capacity"
■
"Gatekeeper Resources Unavailable"
About Subzones
The Local Zone is made up of subzones. Subzones are used to control the bandwidth used by various parts of your
network, and to control the Expressway's registration, authentication and media encryption policies.
network, and to control the Expressway's registration, authentication and media encryption policies.
When an endpoint registers with the Expressway it is allocated to an appropriate subzone, determined by
based on endpoint IP address ranges or alias pattern matches.
page (Configuration > Local Zone > Subzones).
The Expressway automatically creates the following special subzones, which you cannot delete:
■
the Default Subzone
■
the Traversal Subzone
■
the Cluster Subzone (only applies if the Expressway is in a cluster)
Default links between subzones
The Expressway is shipped with the Default Subzone and Traversal Subzone (and Default Zone) already created, and
with links between them. If the Expressway is added to a cluster then default links to the Cluster Subzone are also
established automatically. You can delete or amend these
with links between them. If the Expressway is added to a cluster then default links to the Cluster Subzone are also
established automatically. You can delete or amend these
if you need to model restrictions of your
network.
About the Traversal Subzone
The Traversal Subzone is a conceptual subzone. No endpoints can be registered to the Traversal Subzone; its sole
purpose is to control the bandwidth used by traversal calls.
purpose is to control the bandwidth used by traversal calls.
208
Cisco Expressway Administrator Guide
Bandwidth Control