 the neigh- boring AAA server a priori before handoff is initiated. This can be done in © 2009 by Taylor & Francis Group, LLC SIP Security and Quality of Service Performance TABLE 22.7 Disruption Time VS TmTOc Disruption time (msec) TmTOc MIP-SIP Source: From Jung, J.W., Mudumbai, R., Mont- gomery, D., and Kahng, H.K., Performance evaluation of two layered mobility management using mobile IP and session initiation protocol. Global Telecommuni- cation Conference 2003 (GLOBECOM'03), 3, 1190 1194, IEEE 2003. With permission. TABLE 22.8 Disruption Time VS. Tovertime Disruption time (msec) Tovertime MIP-SIP Source: From Jung, J.W., Mudumbai, R., Montgomery, D., and Kahng, H.K., Performance evaluation of two lay- ered mobility management using mobile IP and session initiation protocol. Global Telecommunication Confer- ence 2003 (GLOBECOM'03), 3, 1190-1194, IEEE 2003. With permission. © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security Radio Foreign access network network network network CN's home network FIGURE 22.9 Handoff delay measurement architecture. (From Kwon, T.T., Gerla, M., Das, S.K., and Das, S. Mobility management for VoIP services: mobile IP VS SIP. IEEE Wireless Communications, 9, 66-75, IEEE October 2002. With permission.) a distributed manner with many known AAA servers or selectively with only the neighboring server. This section does not discuss how this is done. 22.2.3.1 Handoff Delay Disruption of SIP in VoIP Services Handoff delay for SIP-based VoIP services was measured by Kwon et al. [4] for both mobile IP and SIP using the set up illustrated in Figure 22.9. Following Kwon et al. [4], the following variables are defined: 1. ts, the time for message transfer in the wireless link between the mobile node and the foreign agent router (RFA) or DHCP server. 2. tf, the delay between the mobile node and the foreign AAA server (AAAF). This is the time required to send a message in the foreign network. 3. th, the delay between the mobile node and the communicating entit