Sentinel VoLTE 4.1 :: Sentinel VoLTE Administration Guide :: OC-Access-Transfer-Procedure Header

The OC-Access-Transfer-Procedure Header header is a custom SIP header used by Sentinel VoLTE SCC-AS to coordinate access transfer procedures across multiple nodes. This header is inserted into handover INVITE requests and special internal MESSAGE requests when they are forwarded between Sentinel VoLTE SCC-AS nodes. It is also inserted into handover INVITE requests when they are forwarded into an existing session on the same node. The header indicates to the receiving session which access transfer procedures it should execute.

Header Format

The header name is OC-Access-Transfer-Procedure and its value is a simple string with no special formatting. The header does not have any special parameters. Possible values are described below.

Example:

OC-Access-Transfer-Procedure: Remove-Superfluous

Header Values

Value

Associated Access Transfer Procedure

eSRVCC-Anchored-Active-Established

Enhanced SRVCC for sessions that are currently active (not held), established (INVITE-200-ACK received), and with media anchored in the ATGW.

eSRVCC-Non-Anchored-Active-Established

Enhanced SRVCC for sessions that are currently active (not held), established (INVITE-200-ACK received), and with media not anchored in the ATGW.

eSRVCC-Anchored-Pre-Alerting

Enhanced SRVCC for sessions that are currently pre-alerting (INVITE-180 not yet received), and with media anchored in the ATGW.

eSRVCC-Non-Anchored-Pre-Alerting

Enhanced SRVCC for sessions that are currently pre-alerting (INVITE-180 not yet received), and with media not anchored in the ATGW.

eSRVCC-Anchored-Alerting

Enhanced SRVCC for sessions that are currently alerting (INVITE-180 received, INVITE-2xx not yet received), and with media anchored in the ATGW.

eSRVCC-Non-Anchored-Alerting

Enhanced SRVCC for sessions that are currently alerting (INVITE-180 received, INVITE-2xx not yet received), and with media not anchored in the ATGW.

SRVCC-Active-Established

SRVCC for sessions that are currently active (not held) and established (INVITE-200-ACK received).

Remove-Superfluous

End a session that has been deemed superfluous and will not be transferred.

Header Usage

The header is used extensively by the Packet Switched to Circuit Switched Access Transfer Features. See the individual feature pages for specifics on where it is set and used.

It is also used by the SCCDetermineSessionType feature.

A call flow diagram showing its use is available on the Shared ATU-STI page.

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