CCM and SIP gateways: Error code when "Out of bandwidth"

Unanswered Question

Dear all,


We have the following configuration:


UCCM [6.0.1] --- 2821 [12.4(11)XW2] --- MPLS --- 2821 --- PSTN


It's a cluster of 2 UCCM with two 2821 working as gateways in a single site. The other two 2821 gateways are in the service provider site and connected via MPLS.

The UCCM have two SIP Trunk configured to the first two gateways, and these gateways use SIP to communicate with service provider's ones. Calls to and from PSTN are send and receive from all gateways in load balancing schema.


There is a strange behaviour in some calls. When someone calls via PSTN to a IP phone on the customer site, and the location assigned to that IP phone has reached its bandwidth limit, publisher CCM always sends SIP Status code 503 (Service Unavailable) to the 2821 (in customer site) that has send the SIP INVITE message. However, subscriber CCM always responses SIP Status code 404 Not Found to one 2821 and 503 code to the other one. This means that caller listen the message “This number doesn't exist” in some situations.


The clusterwide parameter “Out of Bandwidth Cause Code Substitution” has the value 34.


Does anyone know about the source of this problem?


Thanks in advance for your assistance



/Amaia & Ekaitz

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ivillegas Mon, 12/01/2008 - 09:21
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ISUP Cause value for SIP response 404 Not Found:

Unallocated number

No route to network

No route to destination

Non-selected user clearing


ISUP Cause value for SIP response 503 Service unavailable

No circuit available

Network out of order

Temporary failure

Switching equipment congestion

Resource unavailable

Bearer capability not presently available

Incompatible destination


4xx is a Client Error -- the request contains bad syntax or cannot be fulfilled at the server whereas 5xx is a Server Error -- the server failed to fulfill an apparently valid request.


So if Level3 sends a perfectly valid request to the IPIPGW to route a call, and this request fails only because the IPIPGW does not know how to route this call (eg: no matching dial-peer found), then this amounts to a server (IPIPGW) error condition and hence, IMO, 503 Service

Unavailable is the correct response.


It just tells the calling party that their request was valid, but it cannot be fulfilled at this SIP entity. 404 is seen typically if you attempt to REGISTER to a server and the number you are trying to Register is not provisioned / not a valid subscriber on that system.


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