icate Address Detec- tion (DAD) and router selection. The purpose of DAD is to confirm the uniqueness of the IPv6 address on the link. DAD imposes a delay between C 2009 by Taylor & Francis Group, LLC SIP Security and Quality of Service Performance Detachment from old access point router Attachment to new access point Router Handoff detection advertisement Completion of INVITE 200 OK Completion of handoff FIGURE 22.7 Handoff process in SIP in IPv6 environment. (From Nakajima, N., Dutta, A., Das, S., and Schulzinne, H. Handoff delay analysis and measurement for SIP based mobility in IPv6. International Conference on Communications (ICC'03), 26, 1085-1089, May 2003. With permission.) receiving a router advertisement (RA) and sending a packet out of the inter- face with auto configured IPv address. Nakajima [8] also measured the handoff delay of SIP terminal mobility in the IPv6 testbed. Two different scenarios were considered: (a) SIP mobility without kernel modification (b) SIP mobility with kernel modification. Measurements have been performed for scenarios (a) and (b). Table 22.4 shows the handoff delay T3, which is related to signaling. H12 is the handoff time between mobile nodes 1 and 2, H23 is the handoff time between mobile nodes 2 and 3 and H13 is the handoff delay between mobile nodes 1 and 3 as shown in Figure 22.7. Table 22.5 shows the results of another handoff delay related to voice com- munication using UDP. From Table 22.4 and Table 22.5, modified kernel has reduced handoff delay. Although the delay Figures are unacceptable for real-time multimedia com- munications. For example a delay of 420 ms is likely to result to echo if other delays in the network add to it. This could lead to packets being dropped or played back with significant delays and hence render the playback unsuitable for listening. It was shown by Nakajima et al. [8] that by integrating MIPL MIPv6 in the network for SIP mobility, the handoff delay for signaling was observed to be about 2 ms and the handoff delay for media UDP packet 