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. Portable IP verses Mobile IP = Laptop verses Mobile Phone

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

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.

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

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

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

Mobile IP v4 – Registration Request Header

Mobile IP v4 – Registration Reply Header

Mobile IP v4 – UDP Packet Header

IP Routing Two most popular protocols: –Distance Vector Protocol –Link State Protocol

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

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 ??

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

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

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

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)

Performance considerations The RSVP method does not fit into Mobile IP QoS architecture R1R1 R2R2 R3R3 S R Resv Path RSVP Operation

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 ??

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

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

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