Computer Networks, Andrew Tannenbaum, Chapter 5.6. Computer Networking: A Top Down Approach Featuring the

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1 Mobile IP (IPv4 and IPv6) Dr. John Keeney 3BA33 Elements of a wireless Wired infrastructure wireless hosts laptop, PDA, IP phone run applications may be stationary (nonmobile) or mobile wireless does not always mean mobility 3BA33 - J.Keeney Mobile IP Mobility How Mobile IP works Mobile IP for IPv6 Recommended Texts: Intering with TCP/IP Vol.1: Principles, Protocols, and Architecture, Douglas E. Comer, part 18 Computer Networking: A Top Down Approach Featuring the Internet, Jim Kurose & Keith Ross, Chapter 6. Computer Networks, Andrew Tannenbaum, Chapter 5.6 3BA33 - J.Keeney Elements of a wireless Wired infrastructure base station typically connected to wired relay - responsible for sending packets between wired and wireless host(s) in its area e.g., cell towers access points 3BA33 - J.Keeney

2 Elements of a wireless Wired infrastructure wireless link typically used to connect mobile device(s) to base station can also be used as backbone link multiple access protocol coordinates link access various data rates, transmission distance Wireless, mobility: impact on higher layer protocols logically, impact should be minimal best effort service model remains unchanged TCP and UDP can (and do) run over IP on wireless, mobile but performance-wise: packet loss/delay due to bit-errors (discarded packets, delays for link-layer retransmissions), and handoff TCP interprets loss as congestion, will decrease congestion window un-necessarily delay impairments for real-time traffic limited bandwidth of wireless links 3BA33 - J.Keeney BA33 - J.Keeney Mobility: Vocabulary Mobility: more vocabulary home : permanent home of mobile (e.g., /24) home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote Permanent address: remains constant (e.g., ) Care-of-address: address in visited. (e.g., 79, ) visited : in which mobile currently resides (e.g., /24) Permanent address: address in home, can always be used to reach mobile e.g., : wants to communicate with : wants to communicate with mobile mobile 3BA33 - J.Keeney BA33 - J.Keeney foreign agent: entity in visited that performs mobility functions on behalf of mobile.

3 How do you contact a mobile friend: Consider friend frequently changing addresses, how do you find her? search all phone books? call her parents? expect her to let you know where he/she is? I wonder where Alice moved to? 3BA33 - J.Keeney Mobility: registration home visited End result: 2 foreign agent contacts home agent on home : this mobile is resident in my Foreign agent knows about mobile Home agent knows location of mobile 3BA33 - J.Keeney mobile contacts foreign agent on entering visited Mobility: approaches Let routing handle it: routers not advertise permanent address of mobile-nodes-in-residence scalable via usual routing table exchange. to millions of mobiles routing tables indicate where each mobile located no changes to end-systems Let end-systems handle it: indirect routing: communication from to mobile goes through home agent, then forwarded to remote direct routing: gets foreign address of mobile, sends directly to mobile 3BA33 - J.Keeney Mobility via Indirect Routing home home agent intercepts packets, forwards to foreign agent foreign agent receives packets, forwards to mobile 3 visited addresses packets using home address of mobile 1 2 4b 4a mobile either replies directly to, or via home agent 3BA33 - J.Keeney

4 Indirect Routing: comments Mobile uses two addresses: permanent address: used by (hence mobile location is transparent to ) care-of-address: used by home agent to forward datagrams to mobile foreign agent functions may be done by mobile itself triangle routing: -home--mobile inefficient when, mobile are in same 3BA33 - J.Keeney Mobility via Direct Routing home forwards to foreign agent, or even mobile node direct foreign agent receives packets, forwards to mobile 3b visited requests, receives foreign address of mobile 2 3a 4 1 mobile replies directly to 3BA33 - J.Keeney Indirect Routing: moving between s suppose mobile user moves to another registers with new foreign agent new foreign agent registers with home agent home agent update care-of-address for mobile packets continue to be forwarded to mobile (but with new care-of-address) mobility, changing foreign s transparent: on going connections can be maintained! 3BA33 - J.Keeney Mobility via Direct Routing: comments overcome triangle routing problem non-transparent to : must get care-of-address from home agent what if mobile changes visited? 3BA33 - J.Keeney

5 Mobile IP has many features we ve seen: home agents, foreign agents, foreign-agent registration, care-ofaddresses, encapsulation (packet-within-a-packet) three components to standard: indirect routing of datagrams agent discovery registration with home agent bear in mind TCP is connection oriented, For any connection, source address, source port, destination address, destination port cannot change or connection will be lost! 3BA33 - J.Keeney Mobile IP: indirect routing foreign-agent-to-mobile packet packet sent by home agent to foreign agent: a packet within a packet (IP in IP Encapsulation) dest: dest: dest: Permanent address: dest: packet sent by Care-of address: BA33 - J.Keeney Mobile IP Mobile Nodes has two addresses Home Address (constant) Care-of Address (changes as the Mobile Node moves) Mobile Node must be able to detect if it is on its Home Network or has moved to a Foreign Network Home agent On Home Network, makes it appear that the Mobile Node can continually receive Foreign Network When the Mobile Node is connected to a Foreign Network, the Home Agent tunnels traffic to Care-of Address, with the help of the Foreign Agent. Care-of Address MAY BE issued by a Foreign Agent, or discovered automatically. Mobile Node notifies Home Agent of new Care-of Address to facilitate tunnelling of IP traffic. If the Foreign Agent provides the Care-of Address, registration with the Home Agent is done through the Foreign Agent If the Mobile Node discovers its own Care-of Address, it registers directly with the Home Agent 3BA33 - J.Keeney Mobile IPv6 Mobile IP extended for IPv6 What effect does IPv6 have on the operation of Mobile IP? While IPv6 eases node mobility, the ability of a Mobile Mode to generate an address at a Foreign Network does not, by itself, overcome the original problems that Mobile IPv4 sought to overcome nodes still need two addresses IPv6 necessitates the introduction of a new mobility protocol Mobile IPv6. Why? In IPv4 the Foreign Agent provided Care-of Addresses to Mobile Node. Mobile Nodes can now calculate their own Care-of Address in at a Foreign Network. NO specific Foreign Agents in Mobile IPv6. The authentication mechanisms that are built into Mobile IPv4 are not necessary in Mobile IPv6 IPv6 has an inbuilt extension header, the IP Authentication Header. IPv6 s ICMPv6 (control protocol) makes it easier for Mobile Node / Home Network / Foreign Network to automatically detect when the Mobile Node moves Remember: The Routing Extension Header supports specifying a list of routers to be visited by the packet en route to the final destination. 3BA33 - J.Keeney

6 Mobile IPv6 Mobile IP extended for IPv6 Mobile IPv6 defines a new IPv6 Header Extension, the Home Address Option: This allows a mobile node to set the IP Source Address of a packet to its care-of address on the Foreign Network It also puts its Home Address into this Extension Header This allows destination nodes to identify the true source of the packet. The Correspondent Node s IP stack, when it receives a packet, is able to substitute the Mobile Node s Home Address for the Care-of Address when processing the packet, thus making the use of the Care-of Address transparent to upper protocols. Once the Corresponding Node knows the (temporary) Care-of Address of the Mobile Node, Messages to the Mobile Node s Home Address can be routed via the Care-of Address and intercepted if the Mobile Node is still at the Care-of Address (Routing Extension Header) (Optimisation) When a Mobile Node receives a packet it replaces the Care-of Address with its Home Address to make mobility transparent to upper layers. 3BA33 - J.Keeney Mobile IPv6 Mobile IP extended for IPv6 NOTE: Mobile IPv6 requires a IPv6. 3BA33 - J.Keeney