1 Scope
2 References
3 Terminology
4 Definitions
  4.1 External definitions
  4.2 Other definitions
      4.2.1 User A
      4.2.2 User B
      4.2.3 User C
      4.2.4 Call transfer
      4.2.5 Single step call transfer
      4.2.6 Call transfer by join
      4.2.7 Call transfer by rerouteing
      4.2.8 Corporate telecommunication Network (CN)
      4.2.9 IP network
      4.2.10 Private Integrated Services Network (PISN)
      4.2.11 Private Integrated services Network eXchange (PINX)
5 Abbreviations and acronyms
6 Background and architecture
7 Procedures
  7.1 Call transfers in QSIG
  7.2 Call transfer in SIP
  7.3 Scope of the interworking functions
      7.3.1 QSIG side
      7.3.2 SIP side
      7.3.3 Discussion over transfer interworking functions
  7.4 Mapping of numbers and URIs
  7.5 UAC Processing
      7.5.1 Receipt of a FACILITY message with callTransferComplete
            invoke APDU
      7.5.2 Receipt of a FACILITY message with callTransferUpdate
            invoke APDU
      7.5.3 Receipt of a FACILITY message with ssctInitiate
            invoke APDU
      7.5.4 Receipt of a SETUP message with ssctSetup invoke APDU
      7.5.5 Receipt of a FACILITY message with subaddressTransfer
            invoke APDU
  7.6 UAS Processing
      7.6.1 Receipt of a SIP REFER request
      7.6.2 Receipt of a SIP INVITE request
      7.6.3 Receipt of a SIP request with revised identity
8 Example message sequences
  8.1 Call transfer by join where User B and C are SIP
      participants
  8.2 Call transfer where User A is a SIP participant
  8.3 Call transfer where User A is a SIP participant and
      where two gateways are used
  8.4 Call transfer where User A and User B are SIP participants
  8.5 Single step call transfer where User B is a SIP participant
  8.6 Unsuccessful Single step call transfer where User A
      and User C are SIP participants
  8.7 Single step call transfer where User A and User B
      are SIP participants
9 Security considerations