Refused call responses

The Telephony Session service may refuse a call for any one of a number of reasons. For example, there may not be sufficient resources available to accept the call. There may be an internal problem within Voice Platform, or a mismatch of security criteria.

When the Telephony Session service refuses a call, it generates a SIP response to indicate the reason for the refusal. The possible responses are summarized in the table below:

Code

Possible reasons for refusal

408

The Voice Browser service did not respond in a timely manner to the incoming call.

486

The call is refused for one of the following reasons:

  • The Telephony Session service is shutting down.
  • All Telephony Session service channels are busy (the number of channels is defined by the ts.APNumberOfChannels service property).
  • There are no Voice Browser service instances available to answer the call.

4XX

The response itself specifies the reason for the refusal. For example, 413 Request Entity Too Large indicates that the SIP INVITE is too long to be accepted.

503

The Voice Browser service encountered a problem within Voice Platform, and thus could not respond to the incoming call. For example, it may be that the Voice Browser service was unable to load the initial page of the application, or that the Speech Server was unavailable. This response may indicate a configuration problem within Voice Platform.

5XX

The response itself specifies the reason for the refusal. For example, 505 Version Not Supported indicates that the Telephony Session service does not support the SIP protocol version that was used in the request.

606

This code indicates that there was a mismatch between the security settings expected by the Telephony Session service, and those provided in the SIP INVITE.

Check the reason provided in the 606 response for specific details.

For more information about these SIP response codes, see SIP RFC 3261, Section 21, Response Codes. This document is available at a number of locations, including here.