ies in its home network (its home registrar (HR), AAAH or HA). It is therefore the time for the mobile node to send messages to its home network. Generally, ts < tf < th. 4. tmc, the delay between the mobile node and the correspondent node. C 2009 by Taylor & Francis Group, LLC SIP Security and Quality of Service Performance 5. the, the delay between the home network and the correspondent node. These delays are shown in Figure 22.9. 6. tARP, the time required for the ARP (address resolution protocol). 7. tno, the time to send a message between the new foreign agent (NFA) and the old foreign agent (OFA). It is assumed in this diagram that a simple VoIP application, unaware of mobility, is involved in the QoS parameter measurements and the mobile node caches the address of the callee's correspondent node (CN). Furthermore, it is assumed that there was no a priori Internet connection. Hence the mobile node must initiate the connection when it requires a VoIP application. Therefore the initial delay is the sum of the time required for Internet connection and VoIP signaling. These times are different for the MIP and SIP situations. 22.2.3.1.1 Initial registration and session setup The time required by mobile IP for initial registration and session setup is given by three com- ponents: (a) the sum of the delay for router solicitation message and router adver- tisement messages (2ts) as a round trip delay, plus (b) the round trip registration message with the HA (2th) and (c) the time for the simple VoIP application (SVA) to initiate a VoIP service request with the correspondent node. This time consists of the request and the OK response from the CN (2tmc). For mobile IP, the total time is: tMIP_init = 2ts 2tmc (22.8) When SIP is used instead of MIP, the time required to acquire a new address through the DHCP (4ts) and for the ARP (tARP) need to be added to the time for the MIP case. The total time is: tSIP_init = 4ts + tARP + 2th + 2tmc (22.9) When the same networks and nodes are used, the time required to initiate the