12.2b MO Call without preconditions at both originating UE and terminating UE – 503 Service Unavailable

34.229-13GPPInternet Protocol (IP) multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP)Part 1: Protocol conformance specificationRelease 16TSUser Equipment (UE) conformance specification

12.2b.1 Definition

When a server is temporarily unable to process an INVITE request for an MO call without preconditions due to a temporary overloading or maintenance of the server sends a 503 Service Unavailable response. The server may indicate when the service will be available again in a Retry-After header field. This process is described in 3GPP TS 24.229 [10], clause 5.1.3.1.

12.2b.2 Conformance requirement

[TS 24.229, clause 5.1.3.1]:

Upon receiving a 503 (Service Unavailable) response to an initial INVITE request containing a Retry-After header, then the originating UE shall not automatically reattempt the request until after the period indicated by the Retry-After header contents.

[TS 24.229, clause 6.1.2]:

An INVITE request generated by a UE shall contain a SDP offer and at least one media description. This SDP offer shall reflect the calling user’s terminal capabilities and user preferences for the session.

…

NOTE 2: If the originating UE does not use the precondition mechanism (see subclause 5.1.3.1), it will not include any precondition information in the SDP message body.

Reference(s)

3GPP TS 24.229 [10], clause 5.1.3.1 and 6.1.2.

12.2b.3 Test purpose

To verify that when the UE receives a 503 (Service Unavailable) response to an initial INVITE request for an MO call without preconditions containing a Retry-After header, then the UE shall not automatically reattempt the request until after the period indicated by the Retry-After header contents.

12.2b.4 Method of test

Initial conditions

UE contains either ISIM and USIM applications or only USIM application on UICC. UE has discovered P-CSCF and registered to IMS services, by executing the generic test procedure in Annex C.2 or C.2a (GIBA only) up to the last step.

SS is configured with the shared secret key of IMS AKA algorithm, related to the IMS private user identity (IMPI) configured on the UICC card equipped into the UE. SS has performed AKAv1-MD5 authentication with the UE and accepted the registration (IMS security). UE is configured to not use the precondition mechanism.

Test procedure applicable for a UE with E-UTRA support (TS 34.229-2 [5] A.18/1)

For value of T see specific message content for 503 (Service Unavailable) message.

1-8) UE executes the procedures described in TS 36.508 [94] table 4.5A.6.3-1 steps 1 to 8.

9) The SS responds with a 503 (Service Unavailable) response with the Retry-After header set to T.

10) The SS waits for the UE to send an ACK to acknowledge the reception of the 503 (Service Unavailable) response.

11) SS waits for a duration of time T and checks that the UE does not reattempt sending the INVITE request. After the time T the UE may reattempt sending the INVITE request.

12) The UE may reattempt sending the INVITE request after time T.

Expected sequence

NOTE: Only the IMS procedure relevant to the test purpose is described below.

Step

Direction

Message

Comment

UE

SS

1-2

Steps 1-2 defined in annex C.21f

MTSI MO speech call. Referred from 36.508 [94] table 4.5A.6.3-1 for a UE with E-UTRA support.

3

Void

4

🡨

503 Service Unavailable

Including Retry-After header with period set to T

5

🡪

ACK

The UE acknowledges the reception of the 503 (Service Unavailable) response

6

The SS waits for a duration of time T and checks that the UE does not re-send the INVITE request

7

Step 2 defined in annex C.21f

Optional

NOTE: The default messages contents in annex A are used with condition “IMS security” or “GIBA” when applicable

Specific Message Contents

Steps 1 – 2 as specified in annex C.21f

503 Service Unavailable (Step 4)

Use the default message “503 Service Unavailable” in annex A.4.2.

12.2b.5 Test requirements

At step 6 the UE shall not reattempt the INVITE request before time T from the time the SS receives the ACK from the UE in step 5.