Cisco Cisco Expressway Maintenance Manual
About bandwidth control
The Expressway allows you to control the amount of bandwidth used by calls passing through the system's
Traversal Subzone. This is done by using
Traversal Subzone. This is done by using
Bandwidth limits may be set on a call-by-call basis and/or on a total concurrent usage basis. This flexibility
allows you to set appropriate bandwidth controls on individual components of your network.
allows you to set appropriate bandwidth controls on individual components of your network.
Calls will fail if links are not configured correctly. You can check whether a call will succeed, and what
bandwidth will be allocated to it, using the command xCommand CheckBandwidth.
bandwidth will be allocated to it, using the command xCommand CheckBandwidth.
Configuring bandwidth controls
The
Bandwidth configuration
page (
Configuration > Bandwidth > Configuration
) is used to specify
how the Expressway behaves in situations when it receives a call with no bandwidth specified, and when it
receives a call that requests more bandwidth than is currently available.
receives a call that requests more bandwidth than is currently available.
The configurable options are:
Field
Description
Usage tips
Default call
bandwidth
(kbps)
bandwidth
(kbps)
The bandwidth to use for calls for which no bandwidth value
has been specified by the system that initiated the call.
has been specified by the system that initiated the call.
It also defines the minimum bandwidth to use on SIP to
H.323 interworked calls.
H.323 interworked calls.
This value cannot be blank. The default value is 384kbps.
Usually, when a call is initiated
the endpoint will include in the
request the amount of
bandwidth it wants to use.
the endpoint will include in the
request the amount of
bandwidth it wants to use.
Downspeed
per call mode
per call mode
Determines what happens if the per-call bandwidth
restrictions on a subzone or pipe mean that there is
insufficient bandwidth available to place a call at the
requested rate.
restrictions 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.
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.
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.
Downspeeding can be configured so that it is applied in either or both of the following scenarios:
Cisco Expressway Administrator Guide (X8.5)
Page 180 of 394
Bandwidth control
About bandwidth control