009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security TABLE 17.3 System Parameter Values Parameters Values 10-4 sec and for WLAN as DHandoff = DDHCP + DSIP-WLAN (17.10) 3) Numerical results: In this section, we present the results for the handoff delay computation in a SIP-based multimedia session, using the delay mod- els described in the previous section. The values used for different system parameters are given in Table 17.3. We have assumed the SIP message arrival rate (A) and the processing rate at the CSCF servers and the destination server, are the same (i.e., us = u). Also, we have assumed AM = 0.1). The derivation of DDest involves the second moment of the processing delay at the destination, which can be derived once the mean and variance are given. For our analysis, we have assumed the standard deviation of the processing delays at the destination is 5% of the mean. Now X2 = E[X2] and X2 = E[X2]. Also, E[X2] = o2 + (E[X1])2 and E[X2] = o2 (E[Xs])2, where 02 and o? are the respective variances. Substituting MO and Hs for E[X1] and E[Xs] and the values for the variances, we get R = 0.501[p? + p2 As mentioned before, due to the varying nature of the Internet delay and the computing power of the intermediate servers, it is difficult to characterize the end-to-end handoff delay. With proper traffic engineering (e.g., GMPLS), the Internet delay can be made to suit the application requirements. Hence, we focus on the component of the handoff delay introduced due to the wire- less access networks to estimate the minimum handoff delay. Subsequently, we have also estimated the end-to-end handoff delay assuming a constant value for the Internet delay and some representative values for the comput- ing capabilities of the servers as shown in Table 17.3. Figure 17.11 shows the increase of the handoff delay component due to the wireless access only, with the increase of channel Frame Error Rate (FER) for channel bandwidth of 9.6 Kbps, 19.2 Kbps, and 128 Kbps, when the MH moves to a UMT