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Chapter 24 - Mobile IP. Mobile communication has received a lot of attention in the last decade. The interest in mobile communication on the Internet means that the IP protocol, originally designed for stationary devices, must be enhanced to allow the use of mobile computers, computers that move from one network to another. | Chapter 24 Upon completion you will be able to: Mobile IP Understand the addressing scheme for mobile hosts. To define home, care-of, and co-located care-of addresses Understand the interactions between a home and a foreign agent Know the three phases involved in mobile communication Understand why mobile IP communication can be inefficient Objectives TCP/IP Protocol Suite 24.1 ADDRESSING The main problem that must be solved in providing mobile communication using the IP protocol is addressing. The topics discussed in this section include: Stationary Hosts Mobile Hosts TCP/IP Protocol Suite The IP addresses are designed to work with stationary hosts because part of the address defines the network to which the host is attached. Note: TCP/IP Protocol Suite Figure 24.1 Home address and care-of address TCP/IP Protocol Suite Mobile IP has two addresses for a mobile host: one home address and one care-of address. The home address is permanent; the care-of address changes as the mobile host moves from one network to another. Note: TCP/IP Protocol Suite 24.2 AGENTS To make the change of address transparent to the rest of the Internet requires a home agent and a foreign agent. The specific function of an agent is performed in the application layer. The topics discussed in this section include: Home Agent Foreign Agent TCP/IP Protocol Suite Figure 24.2 Home agent and foreign agent TCP/IP Protocol Suite When the mobile host and the foreign agent are the same, the care-of address is called a co-located care-of address. Note: TCP/IP Protocol Suite 24.3 THREE PHASES To communicate with a remote host, a mobile host goes through three phases: agent discovery, registration, and data transfer. The topics discussed in this section include: Agent Discovery Registration Data Transfer TCP/IP Protocol Suite Figure 24.3 Remote host and mobile host communication TCP/IP Protocol Suite Mobile IP does not use a new packet type for agent advertisement; it uses the router advertisement packet of ICMP, and appends an agent advertisement message. Note: TCP/IP Protocol Suite Figure 24.4 Agent advertisement TCP/IP Protocol Suite Table 24.1 Code bits TCP/IP Protocol Suite Mobile IP does not use a new packet type for agent solicitation; it uses the router solicitation packet of ICMP. Note: TCP/IP Protocol Suite Figure 24.5 Registration request and reply TCP/IP Protocol Suite Figure 24.6 Registration request format TCP/IP Protocol Suite Table 24.2 Registration request flag field bits TCP/IP Protocol Suite Figure 24.7 Registration reply format TCP/IP Protocol Suite A registration request or reply is sent by UDP using the well-known port 434. Note: TCP/IP Protocol Suite Figure 24.8 Data transfer TCP/IP Protocol Suite The movement of the mobile host is transparent to the rest of the Internet. Note: TCP/IP Protocol Suite 24.4 INEFFICIENCY IN MOBILE IP Communication involving mobile IP can be inefficient. A severe case is called double crossing or 2X. A moderate case is called triangle routing or dog-leg routing. The topics discussed in this section include: Double Crossing Triangle Routing Solution TCP/IP Protocol Suite Figure 24.9 Double crossing TCP/IP Protocol Suite Figure 24.10 Triangle routing TCP/IP Protocol Suite
