to avoid further fragmentation of IMS specifications. Common IMS will address the interoperability between the different IMS standards and future IMS-enabled networks. Common IMS is expected to bring economies of scale and reductions in capital and operational costs. The ETSI TISPAN IMS specifications were moved to 3GPP in 2007. All TISPAN Release 1 specs included 'as is' in 3GPP Release 7 while some TISPAN Release 2 specs merged with 3GPP Release 8. The 3GPP2 MMD requirement specifications were merged with 3GPP Release 8. From Release 9 onwards, 3GPP will maintain one common set of IMS IMS, Services and Applications IMS Specs (till R8) Common IMS 3GPP2 MMD (3GPP Rel 9 onwards) Common IMS (3GPP Rel 7/8) TISPAN IMS Specs Figure 9.6 Common IMS concept specifications. Release 9 specifications were frozen in December 2009. The high level Common IMS concept is shown in Figure 9.6. 9.7.1 3GPP2 and TISPAN IMS Specs Transfer Process 3GPP TS 21202 [9] published in March 2009 lists all Common IMS specs pertaining to Release 8, including those created to replicate existing frozen publications in the ETSI Technical Committee TISPAN Next Generation Network (NGN) Release 2 document set. It has also reproduced core IMS specifications that have been transferred from ETSI TISPAN to 3GPP. It also shows the mapping of these TISPAN specifications to 3GPP Release 8 specifications. 9.7.2 3GPP and 3GPP2 IMS Specs Transfer Process 3GPP2 S.R0137-0 v1.0 [10] published in December 2008 provides a mapping between 3GPP2 MMD specifications and 3GPP Common IMS Release 8 specifications. Figure 9.7 shows the 3GPP2 All IP Network Architecture Model with the cdma2000 Access Network and including MMD/IMS elements and reference points. The gray highlighted network elements and heavy line reference points (dashed for signaling and solid for media) are supported by 3GPP2's MMD/IMS related specifications and are included in the first Phase of 3GPP Common IMS work transfer. 9.7.2.1 MMD IMS Versus Common IMS Entities and Reference Points Some key commona