Content for TS 26.517 Word version: 18.4.0
11 MBSSF security protocols (MBS-10) p. 41
11.1 General p. 41
This clause is applicable when the MBS User Plane Security mechanism is provisioned for an MBS User Service. This provisioning is indicated to the MBS Client by the presence of the SecurityDescription object in a DistributionSessionDescription object (see clause 5.2.10) of a User Service Description it has obtained by one of the methods specified in clause 5.3.
11.2 MBS Service Key retrieval from MBSSF p. 41
11.2.1 Overview p. 41
Whenever it needs an MBS Service Key (MSK), the MBSF Client shall interact with the MBSSF at reference point MBS-10 using the protocol specified in clause 6.3 of TS 33.246. The key retrieval protocol is based on HTTP RFC 9110 and the general requirements specified in clause 8.2 and 8.3 of the present document shall apply to all interactions between these two functional entities at this reference point.
11.2.2 MBSF Client procedures p. 41
11.2.2.1 MBSSF endpoint selection by MBSF Client p. 41
Aligned with TS 26.346, before communicating with the MBSSF as part of an MBS User Service Session, the MBSF Client shall first choose an MBSSF endpoint address from those listed in the mBSSFAddresses property of the SecurityDescription object specified in Table 5.2.10-1. The MBSF Client shall use the same endpoint address for all subsequent requests to the MBSSF relating to that MBS User Service Session.
If the MBSSF at the chosen endpoint address proves to be unresponsive after a number of retry attempts, a different endpoint shall be chosen by the MBSF Client from those listed, if any.
11.2.2.2 Back-off time computation p. 42
When the back-off mode parameters are present in the SecurityDescription object, these are used to calculate a random back-off time as specified in clause 6.3.2.1A of TS 33.246 and clause 11.3.1 of TS 26.346 in order to avoid overloading the MBSSF.
In case of an MSK request, the MBSF Client shall calculate the random back-off time according to clause 10.2.2.3 of the present document, using the offsetTime and randomTimePeriod parameters indicated in the backOffParameters object as specified in Table 5.2.10-1.
