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Mobile IP

Mobile IP. Performance Issues in Practice. Introduction. What is Mobile IP? Mobile IP is a technology that allows a "mobile node" (MN) to change its point of attachment to the Internet while communicating with the "correspondent node" (CN) using IP.

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Mobile IP

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  1. Mobile IP Performance Issues in Practice

  2. Introduction • What is Mobile IP? • Mobile IP is a technology that allows a "mobile node" (MN) to change its point of attachment to the Internet while communicating with the "correspondent node" (CN) using IP. • Portable IP verses Mobile IP = Laptop verses Mobile Phone

  3. Key Issues • Why need Mobile IP? • Implementation of Mobile IP • Mobile IPv4 • IP Routing • IP QoS

  4. So, why Mobile IP? • In original IP routing, mobility of hosts was not considered to be an issue. • Routing methods built for static networks • Hosts were unlikely to move from one subnet to another. • Mobile IP defines protocols and procedures by which packets can be routed to a mobile node, regardless of its current point-of-attachment to the Internet, and without changing its IP address.

  5. Mobility: Vocabulary visited network: network in which mobile currently resides (e.g., 79.129.13/24) Permanent address: remains constant (e.g., 128.119.40.186) Care-of-address: address in visited network. (e.g., 79.129.13.2) wide area network foreign agent: entity in visited network that performs mobility functions on behalf of mobile agent. correspondent hosts: wants to communicate with mobile device

  6. foreign agent receives packets, forwards to mobile home agent intercepts packets, forwards to foreign agent correspondent addresses packets using home (“permanent”) address of mobile mobile unit replies directly to correspondent 3 2 4 1 Mobility via Indirect Routing visited network home network wide area network

  7. Packet Formation Data sent by a node to a Mobile IP HA IP Header with Mobile IP Header Data New Data Packet from Home Agent to MN

  8. Mobile IP v4 – Registration Request Header

  9. Mobile IP v4 – Registration Reply Header

  10. Mobile IP v4 – UDP Packet Header

  11. IP Routing • Two most popular protocols: • Distance Vector Protocol • Link State Protocol

  12. Distance Vector Protocol • In DVP, each node contains a routing table with a list of shortest paths to the other nodes in the network • At start, each node has knowledge of its own address and is able to transmit on all links connecting to neighboring nodes • If distance to the node is shorter than the distance in the routing table, the distance table is updated with the new value • When transmission of distance vector no longer causes an update of the tables, the protocol converges and the topology of the network has been fixed

  13. Link State Routing Protocols • All nodes maintain a distributed map of the network • Maps are updated quickly, when network topology changes using….?? • LSP use Shortest Path First algorithm (Dijkstra’s Algorithm) • Considered better than Distance Vector Protocols. Why ??

  14. Why these protocols Fail in Mobile IP • Cellular Systems and Internet networks supporting mobile users depend on a fixed infrastructure • Base station can always reach all mobile nodes in the cell without routing, via a broadcast • But, Mobile Networks have a special case of Ad-Hoc Networks

  15. Routing in Ad-Hoc Networks • In Ad-hoc networks, • A fixed infrastructure is missing and topologies change quickly • A destination node might be out of range of a source node transmitting packets • Each node must be able to forward data to other nodes

  16. So why do they fail in Ad-Hoc networks • Dynamic routing algorithms assume network topology does not change during transmission • they would react too slowly or generate too much traffic to update the tables – their updating frequency of about 30 sec is too long for ad-hoc networks • Routing algorithms depend on symmetric links in which routing information colleted for one direction can be used for other direction – in ad-hoc networks, links can be asymmetric • Interference amongst close nodes that simultaneously forward transmissions

  17. QoS Issues • Most popular techniques: • IntServ and RSVP • DiffServ • MPLS • IntServ maintains per-flow states in each node • DiffServ approach discriminates amongst datagrams in different classes, not flows • MPLS forces traffic into specific labeled switched paths (LSPs) using routers called as labeled-switching routers (LSRs)

  18. Performance considerations • The RSVP method does not fit into Mobile IP QoS architecture Resv S R1 R2 R3 R Path RSVP Operation

  19. Failure of RSVP • Processing overheads and memory consumption directly proportional to the number of separate RSVP reservations • Also, states reservation is not possible over the tunnel between Home Agent and Foreign Agent… why ??

  20. Solution – RSVP over IP Tunnels • This mechanism enables reservations across all IP-within-IP tunnels • The tunnels are of three types: • Type 1: no QoS guarantees (best effort tunnel) • Type 2: no resource allocation to individual data flows, but QoS guarantees to aggregate flows • Type 3: resource allocation for individual end to end flows

  21. RSVP over IP Tunnels (contd) M3 M1 R1 Intermediate Router Intermediate Router R2 M2 IP TUNNEL M4

  22. Mobility Management in Real Time Services • Makes use of the “mobility notification method” • Working • sender delivers a PATH message to MN • When mobile node not connected to HN, HN captures the RSVP message and replies to sender with a PathChange message containing the COA of MN and its own address (MOBILITY_NOTIFICATION Object) • Source receives PathChange message, caches it and sends new PATH message to mobile node, tunneling it to COA

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