Cisco Cisco Expressway Maintenance Manual
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On: the Expressway will fail any branch of a search that contains a loop, recording it as a level 2 "loop
detected" event. Two searches are considered to be a loop if they meet all of the following criteria:
detected" event. Two searches are considered to be a loop if they meet all of the following criteria:
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have same call tag
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are for the same destination alias
—
use the same protocol
—
originate from the same zone
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Off: the Expressway will not detect and fail search loops. You are recommended to use this setting only in
advanced deployments.
advanced deployments.
Identifying Calls
Each call that passes through the Expressway is assigned a Call ID and a Call Serial Number. Calls also have a Call
Tag assigned if one does not already exist.
Tag assigned if one does not already exist.
Call ID
The Expressway assigns each call currently in progress a different Call ID. The Call ID numbers start at 1 and go up to
the maximum number of calls allowed on that system.
the maximum number of calls allowed on that system.
Each time a call is made, the Expressway will assign that call the lowest available Call ID number. For example, if
there is already a call in progress with a Call ID of 1, the next call will be assigned a Call ID of 2. If Call 1 is then
disconnected, the third call to be made will be assigned a Call ID of 1.
there is already a call in progress with a Call ID of 1, the next call will be assigned a Call ID of 2. If Call 1 is then
disconnected, the third call to be made will be assigned a Call ID of 1.
The Call ID is not therefore a unique identifier: while no two calls in progress at the same time will have the same Call
ID, the same Call ID will be assigned to more than one call over time.
ID, the same Call ID will be assigned to more than one call over time.
Note that the Expressway web interface does not show the Call ID.
Call Serial Number
The Expressway assigns a unique Call Serial Number to every call passing through it. No two calls on an Expressway
will ever have the same Call Serial Number. A single call passing between two or more Expressways will be identified
by a different Call Serial Number on each system.
will ever have the same Call Serial Number. A single call passing between two or more Expressways will be identified
by a different Call Serial Number on each system.
Call Tag
Call Tags are used to track calls passing through a number of Expressways. When the Expressway receives a call, it
checks to see if there is a Call Tag already assigned to it. If so, the Expressway will use the existing Call Tag; if not, it
will assign a new Call Tag to the call. This Call Tag is then included in the call’s details when the call is forwarded on.
A single call passing between two or more Expressways will be assigned a different Call Serial Number each time it
arrives at an Expressway (including one it has already passed through) but can be identified as the same call by use of
the Call Tag. This is particularly useful if you are using a
checks to see if there is a Call Tag already assigned to it. If so, the Expressway will use the existing Call Tag; if not, it
will assign a new Call Tag to the call. This Call Tag is then included in the call’s details when the call is forwarded on.
A single call passing between two or more Expressways will be assigned a different Call Serial Number each time it
arrives at an Expressway (including one it has already passed through) but can be identified as the same call by use of
the Call Tag. This is particularly useful if you are using a
Expressways in your network.
feature,
and you can also search the Event Log for all events relating to a single call tag. Loops occur when a query is sent to
a neighbor zone and passes through one or more systems before being routed back to the original Expressway. In this
situation the outgoing and incoming query will have different Call Serial Numbers and may even be for different
destination aliases (depending on whether any transforms were applied). However, the call will still have the same
Call Tag.
a neighbor zone and passes through one or more systems before being routed back to the original Expressway. In this
situation the outgoing and incoming query will have different Call Serial Numbers and may even be for different
destination aliases (depending on whether any transforms were applied). However, the call will still have the same
Call Tag.
Note:
If a call passes through a system that is not an Expressway or TelePresence Conductor then the Call Tag
information will be lost.
Identifying Calls in the CLI
To control a call using the CLI, you must reference the call using either its Call ID or Call Serial Number. These can be
obtained using the command:
obtained using the command:
xStatus Calls
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Cisco Expressway Administrator Guide
Dial Plan and Call Processing