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.
identifies the 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.)
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.)
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.
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.
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.
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.
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.)
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.)
The Expressway uses the configured Default CPL if it fails to contact the policy service via any of the
configured addresses.
configured 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.
address, 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
).
The set of policy services includes all of the services defined on the
Policy services
page (
Configuration >
Dial plan > Policy services
), plus a Call Policy service if appropriate.
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.
the 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.
Cisco Expressway Administrator Guide (X8.5.2)
Page 270 of 403
Overview and status information
Policy server status and resiliency