nd (2) log the information about this session. Figure 4.5 depicts the SIP- NEMO re-invitation operation. An MN is assumed to locate in a mobile net- work and wants to establish a session with a CN. The detailed steps are as follows: 1. The MN sends an INVITE request to the targeted CN for session estab- lishment. C 2009 by Taylor & Francis Group, LLC SIP Mobility Management 2. The SIP-NMS, which acts as the gateway of this mobile network, would translate the INVITE request, i.e., use the SIP-NMS's contact address instead of the SIP-MN's contact address at the CONTACT field and add the SIP-NMS's URI into the RECORD-ROUTE field, and then forward the request to the destination. 3. Once the CN accepts the INVITE request, it must respond with an OK message. Because the contact address of the INVITE request is translated to the SIP-NMS's contact address, the OK message is routed to the SIP-NMS directly. 4. The SIP-NMS can re-route the OK message to the targeted MN based on the TO field. The session between the MN and the CN is established. 5. The SIP-NMS changes its point of attachment. In other words, the entire mobile network roams from one network to another network. 6. The SIP-NMS must re-invite all on-going sessions by sending an INVITE request with a URI list to a local SIP-FS. All corresponding CNs are indicated in the embedded URI list. 7. Once a SIP-FS receives the INVITE request embedded with a URI list, it reproduces similar INVITE requests destined to different recipients according to the embedded URI list. 8. The SIP-NMS must re-register its new contact address to the corre- sponding SIP-HS for recovering the reachability of the entire mobile network. After the re-invitation operation, any session established before the mobile network moves can be resumed again. One point to note is that each SIP- NMS should translate all received INVITE requests to or from the mobile network. Furthermore, each SIP-HS should also translate received INVITE requests, i.e., add the RECORD-ROUTE field. If a SIP-NMS or a SIP-HS