Cisco Cisco Expressway Maintenance Manual
Policy Server Status and Resiliency
You must specify a Status path when configuring the Expressway's connection to a policy server. It identifies the
path from where the status of the remote service can be obtained. By default this is status.
path from where the status of the remote service can be obtained. By default this is status.
Up to 3 different policy server addresses may be specified. The Expressway polls each address on the specified path
every 60 seconds to test the reachability of that address. The Expressway accepts standard HTTP(S) response status
codes. (Note that the developers of the policy service must ensure that this provides the appropriate status of the
service.)
every 60 seconds to test the reachability of that address. The Expressway accepts standard HTTP(S) response status
codes. (Note that the developers of the policy service must ensure that this provides the appropriate status of the
service.)
If a server does not respond to status requests, Expressway will deem that server's status to be in a failed state and it
will not be queried for policy service requests until it returns to an active state. Its availability will not be checked
again until after the 60 second polling interval has elapsed.
will not be queried for policy service requests until it returns to an active state. Its availability will not be checked
again until after the 60 second polling interval has elapsed.
When the Expressway needs to make a policy service request, it attempts to contact the service via one of the
configured server addresses. It will try each address in turn, starting with Server 1 address, and then if necessary -
and if configured - via the Server 2 address and then the Server 3 address. The Expressway only tries to use a
server address if it is in an active state, based on its most recent status query.
configured server addresses. It will try each address in turn, starting with Server 1 address, and then if necessary -
and if configured - via the Server 2 address and then the Server 3 address. The Expressway only tries to use a
server address if it is in an active state, based on its most recent status query.
The Expressway has a non-configurable 30 seconds timeout value for each attempt it makes to contact a policy
server. However, if the server is not reachable, the connection failure will occur almost instantaneously. (Note that
the TCP connection timeout is usually 75 seconds. Therefore, in practice, a TCP connection timeout is unlikely to
occur as either the connection will be instantly unreachable or the 30 second request timeout will occur first.)
server. However, if the server is not reachable, the connection failure will occur almost instantaneously. (Note that
the TCP connection timeout is usually 75 seconds. Therefore, in practice, a TCP connection timeout is unlikely to
occur as either the connection will be instantly unreachable or the 30 second request timeout will occur first.)
The Expressway uses the configured Default CPL if it fails to contact the policy service via any of the configured
addresses.
addresses.
Note that this method provides resiliency but not load balancing i.e. all requests will be sent to Server 1 address,
providing that server address is functioning correctly.
providing that server address is functioning correctly.
Viewing Policy Server Status via the Expressway
A summarized view of the status of the connection to each policy service can be viewed by going to the Policy
service status page (Status > Policy services).
service status page (Status > Policy services).
The set of policy services includes all of the services defined on the Policy services page (Configuration > Dial plan
> Policy services), plus if a remote service has been selected for either Call Policy or for registration restriction policy
it will also display a Call Policy or a Registration restriction service respectively.
> Policy services), plus if a remote service has been selected for either Call Policy or for registration restriction policy
it will also display a Call Policy or a Registration restriction service respectively.
The following information is displayed:
Field
Description
Name
The name of the policy service.
Clicking on a Name takes you to the configuration page for that service where you can change any of the
settings or see the details of any connection problems.
settings or see the details of any connection problems.
URL
The address of the service. Note that each service can be configured with multiple server addresses for
resiliency. This field displays the server address currently selected for use by the Expressway.
resiliency. This field displays the server address currently selected for use by the Expressway.
Status
The current status of the service based on the last attempt to poll that server.
Last
used
used
Indicates when the service was last requested by the Expressway.
TURN Relay Usage
The TURN relay usage page (Status > TURN relay usage) provides a summary list of all the clients that are
connected to the TURN server.
connected to the TURN server.
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Cisco Expressway Administrator Guide
Overview and Status Information