Jayamoorthi

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mobile IP

Mobile IP (or IP mobility) is an Internet Engineering Task Force (IETF) standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining a permanent IP address. Mobile IPv4 is described in IETF RFC 3344 (Obsoleting both RFC 3220 and RFC 2002), and updates are added in IETF RFC 4721. Mobile IPv6 is described in IETF RFC 3775. The Internet Protocol Suite

Application Layer

BGP • DHCP • DNS • FTP • GTP • HTTP • IMAP • IRC • Megaco • MGCP • NNTP • NTP • POP • RIP • RPC • RTP • RTSP • SDP • SIP • SMTP • SNMP • SOAP • SSH • Telnet • TLS/SSL • XMPP • (more)

Transport Layer

TCP • UDP • DCCP • SCTP • RSVP • ECN • (more)

Internet Layer

IP (IPv4, IPv6) • ICMP • ICMPv6 • IGMP • IPsec • (more)

Link Layer

ARP • RARP • NDP • OSPF • Tunnels (L2TP) • PPP • Media Access Control (Ethernet, MPLS, DSL, ISDN, FDDI) • Device Drivers • (more)

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பொருளடக்கம் [மறை] • 1 Introduction • 2 Applications • 3 How Mobile IP works o 3.1 Future • 4 Definition of terms o 4.1 Home network o 4.2 Home address o 4.3 Foreign network o 4.4 Care-of address o 4.5 Home agent o 4.6 Foreign agent o 4.7 Binding • 5 See also • 6 External links

[தொகு] Introduction

The Mobile IP protocol allows location-independent routing of IP datagrams on the Internet. Each mobile node is identified by its home address disregarding its current location in the Internet. While away from its home network, a mobile node is associated with a care-of address which identifies its current location and its home address is associated with the local endpoint of a tunnel to its home agent. Mobile IP specifies how a mobile node registers with its home agent and how the home agent routes datagrams to the mobile node through the tunnel. Mobile IP provides an efficient, scalable mechanism for roaming within the Internet. Using Mobile IP, nodes may change their point-of-attachment to the Internet without changing their home IP address. This allows them to maintain transport and higher-layer connections while roaming. Node mobility is realized without the need to propagate host-specific routes throughout the Internet routing fabric. [தொகு] Applications Mobile IP is most often found in wired and wireless environments where users need to carry their mobile devices across multiple LAN subnets. It may for example be used in roaming between overlapping wireless systems, for example IP over DVB, WLAN, WiMAX and BWA. Currently, Mobile IP is not required within cellular systems such as 3G, to provide transparency when Internet users migrate between cellular towers, since these systems provide their own data link layer handover and roaming mechanisms. However, it is often used in 3G systems to allow seamless IP mobility between different Packet Data Serving Node (PDSN) domains. In many applications (e.g., VPN, VoIP), sudden changes in network connectivity and IP address can cause problems. [தொகு] How Mobile IP works A mobile node can have two addresses - a permanent home address and a care of address (CoA), which is associated with the network the mobile node is visiting. There are two kinds of entities in Mobile IP: • A home agent stores information about mobile nodes whose permanent home address is in the home agent's network. • A foreign agent stores information about mobile nodes visiting its network. Foreign agents also advertise care-of addresses, which are used by Mobile IP. A node wanting to communicate with the mobile node uses the permanent home address of the mobile node as the destination address to send packets to. Because the home address logically belongs to the network associated with the home agent, normal IP routing mechanisms forward these packets to the home agent. Instead of forwarding these packets to a destination that is physically in the same network as the home agent, the home agent redirects these packets towards the foreign agent through an IP tunnel by encapsulating the datagram with a new IP header using the care of address of the mobile node. When acting as transmitter, a mobile node sends packets directly to the other communicating node through the foreign agent, without sending the packets through the home agent, using its permanent home address as the source address for the IP packets. This is known as triangular routing. If needed, the foreign agent could employ reverse tunneling by tunneling the mobile node's packets to the home agent, which in turn forwards them to the communicating node. This is needed in networks whose gateway routers have ingress filtering enabled and hence the source IP address of the mobile host would need to belong to the subnet of the foreign network or else the packets will be discarded by the router. The Mobile IP protocol defines the following: • an authenticated registration procedure by which a mobile node informs its home agent(s) of its care-of-address"(es); • an extension to ICMP Router Discovery, which allows mobile nodes to discover prospective home agents and foreign agents; and • the rules for routing packets to and from mobile nodes, including the specification of one mandatory tunneling mechanism and several optional tunneling mechanisms. [தொகு] Future Enhancements to the Mobile IP technique, such as Mobile IPv6 and Hierarchical Mobile IPv6 (HMIPv6), are being developed to improve mobile communications in certain circumstances by making the processes more secure and more efficient. Researchers create support for mobile networking without requiring any pre-deployed infrastructure as it currently is required by MIP. One such example is Interactive Protocol for Mobile Networking (IPMN) which promises supporting mobility on a regular IP network just from the network edges by intelligent signalling between IP at end-points and application layer module with improved quality of service. Researchers are also working to create support for mobile networking between entire subnets with support from Mobile IPv6. One such example is Network Mobility (NEMO) Network Mobility Basic Support Protocol by the IETF Network Mobility Working Group which supports mobility for entire Mobile Networks that move and to attach to different points in the Internet. The protocol is an extension of Mobile IPv6 and allows session continuity for every node in the Mobile Network as the network moves. [தொகு] Definition of terms [தொகு] Home network The home network of a mobile device is the network within which the device receives its identifying IP address (home address). [தொகு] Home address The home address of a mobile device is the IP address assigned to the device within its home network. [தொகு] Foreign network A foreign network is the a network in which a mobile node is operating when away from its home network. [தொகு] Care-of address Main article: Care of address The care-of address of a mobile device is the physical IP address of the device when operating in a foreign network. [தொகு] Home agent A home agent is a router on a mobile node’s home network which tunnels datagrams for delivery to the mobile node when it is away from home. It maintains current location (IP address) information for the mobile node. It is used with one or more foreign agents. [தொகு] Foreign agent A foreign agent is a router that stores information about mobile nodes visiting its network. Foreign agents also advertise care-of-addresses which are used by Mobile IP. [தொகு] Binding The association of the home address with a care-of address is called a binding.