 Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security TABLE 10.2 Comparison of Average Call Setup Delays* and Average Round-Trip Communication Delays Call Setup Delays [ms] Round-trip Delays [ms] * *Per Figure 10.6 Note: transport = UDP. Notice here that, ET1+T2-X=0-X (10.6d) Consequently, H-SIP outperforms the traditional SIP approach, in general, as long as o > X. Our conducted real-time measurements are listed in Table 10.2. In Table 10.2, we verify the validity of our model by separately comparing the real-time call setup measurements to the round-trip delays, thus asserting Equations 10.6. 10.4.3.3 DNS vs. Handle-DNS Resolution Obviously, the only performance degradation introduced by our approach is the handle resolution overhead. This overhead has been extensively measured by CNRI and its partners and is illustrated in Figure 10.7. The current per- formance of the system that oscillates from 3 to 10 ms makes it comparable to the bind implementation of the DNS protocol. Additionally, due to its intrinsic fully distributed administration and resolution, it avoids the pitfalls Handle C++ implementation Concurrent request number (10^3) FIGURE 10.7 Handle implementation performance measurement as of August 2005. Acquired through the courtesy of Mr. Sam Sun and CN-NIC. (Courtesy of Mr. Sam Sun and CN-NIC. With permission.) C 2009 by Taylor & Francis Group, LLC SIP Mobility Technologies and the Use of Persistent Identifiers Handle-DNS Handle-DNS VS bind 16000 14000 12000 10000 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62 66 70 74 78 82 86 90 94 98 Number of client requests (10^3) FIGURE 10.8 Handle load performance measurement as of August 2005. Acquired through the courtesy of Mr. Sam Sun and CN-NIC. (Courtesy of Mr. Sam Sun and CN-NIC. With permission.) that plague the current DNS implementation where DNS resolution times can extend to over 100 milliseconds [39]. Overall robustness of the handle-DNS implementation has also been exten- sively tested along with load assessment. Results, a