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The present document contains a detailed description of the SCC AS restoration procedure to be used in the eSRVCC
network specially. The purpose of the SCC AS restoration procedure, as described in the present document, is to ensure
that the originating or terminating session is continued or resumed as soon as possible when some the SCC AS in the
SCC AS pool is out of service. The document defines the SCC AS failure scenarios, possible solutions and solution
analysis. For the related procedure and functionality of S-CSCF, SCC AS, ATCF and HSS in the IMS and eSRVCC
environment, it is based on the requirement in 3GPP related specifications
As the introduction of eSRVCC, the SCC AS shall exchange eSRVCC related parameters with ATCF and HSS during
initial registration and re-registration procedures as described in TS 24.237
, which is different from all other
ATCF reports its ATCF-Management-URI and ATCF-Path-URI towards the SCC AS, and the SCC AS stores it
for later routing of MESSAGE.
SCC AS shall send MESSAGE to ATCF with its own ATU-STI based on ATCF-Management-URI received, in
order to ensure the routing of eSRVCC procedure triggered by ATCF later.
SCC AS shall also update the received ATCF-Path-URI of ATCF towards HSS, HSS forwards it to MME, and
stores it for subscriber downloading to SCC AS later.
The present document analysis SCC AS failure implications in eSRVCC network, it studies possible solutions and
determines whether any should be standardize.