 details on terminal mobility can be found in Section 17.5.1. SIP has one obvious disadvantage: it cannot support seamless mobility for any other applications, even other TCP-based applications. A proposed archi- tecture [19] supports the complete range of applications by using SIP for real- time communication and MIP for TCP connections. However, recently there have been attempts to support TCP connection with SIP [19] by adding a middleware for spoofing constant endpoints for mobile TCP connections. But most often, the TCP connection duration (e.g., POP or IMAP mail retrieval, HTTP transactions) is short enough to make the cost of reconnection rela- tively small on average. Another drawback of SIP is the large handoff delay incurred in application-layer messaging during mid-call mobility management. A synopsis of the strong and weak points of the mobility solutions, based on the above discussions, is presented in Table 17.1. Thus, our qualitative studies [20-22] have shown that SIP is an eligible can- didate as a mobility management protocol for next generation heterogeneous © 2009 by Taylor & Francis Group, LLC TABLE 17.1 Comparison of Mobility Management Schemes [20-22] Layer Protocols Advantages Disadvantages Subnetwork GPRS or UMTS Mobility within a subnetwork provider's Mobility is restricted to the subnetwork domain - the access mobility service area requires no changes to the user cannot move to another subnetwork without network, transport, or application layers using additional mobility solutions Network Mobile IP Mobility transparent to upper layers Requires deployment of foreign agents in visited networks Requires deployment of home agent in home network Requires changes to mobile host network-layer implementation Triangular routing can add considerable latency, based on the distance between the mobile host and home agent Signaling overhead for location update Provides faster handoff for intra-domain Specific architectural requirements mobility, reduces the signaling load Characteristic routing proto