LTE HO : Why two MME UE S1AP IDs present within the S1-AP HO Request message ?
http://tech.queryhome.com/45691/lte-ho-why-two-mme-s1ap-ids-present-within-the-request-message
http://www.3gpp.org/ftp/tsg_ran/WG3_Iu/TSGR3_70bis/Docs/R3-110241.zip
2 Discussionhttp://www.3gpp.org/ftp/tsg_ran/wg3_iu/TSGR3_70/Docs/R3-103812.zip
2.1 X2 HO between HeNBs (Source and Target connected via the GW)
If the GUMMEI IE is contained in the INITIAL CONTEXT SETUP REQUEST message, the eNB shall store this information in the UE context and use it for subsequent X2 handovers.ETSI TS 136 413 V10.0.1 (2011-01 )
If the MME UE S1AP ID 2 IE is contained in the INITIAL CONTEXT SETUP REQUEST message, the eNB shall store this information in the UE context and use it for subsequent X2 handovers.
LTE; Evolved Universal Terrestrial Radio Access Network (E- UTRAN); S1 Application Protocol (S1AP) (3GPP TS 36.413 version 10.0.1 Release 10 )
http://www.etsi.org/deliver/etsi_ts/136400_136499/136413/10.00.01_60/ts_136413v100001p.pdf