Mobile IPMobile IP

Performance Issues in Practice

Introduction 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 IssuesKey Issues

Why need Mobile IP?Implementation of Mobile IPMobile IPv4IP RoutingIP QoS

So, why Mobile IP? 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: VocabularyMobility: Vocabulary

Care-of-address: address in visited network.(e.g., 79.129.13.2)

wide area network

visited network: network in which mobile currently resides (e.g., 79.129.13/24)

Permanent address: remains constant (e.g., 128.119.40.186)

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 RoutingMobility via Indirect Routing

wide area network

homenetwork

visitednetwork

3

2

41

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 Packet Formation

Header DataHeader withMobile 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 HeaderMobile IP v4 – Registration Request Header

Mobile IP v4 – Registration Reply Mobile IP v4 – Registration Reply HeaderHeader

Mobile IP v4 – UDP Packet Header Mobile IP v4 – UDP Packet Header

IP RoutingIP Routing

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

Distance Vector ProtocolDistance 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 ProtocolsLink 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 IPWhy 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 NetworksRouting 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 So why do they fail in Ad-Hoc networksnetworks 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 IssuesQoS 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 Performance considerations

The RSVP method does not fit into Mobile IP QoS architecture

R1 R2 R3S R

Resv

Path

RSVP Operation

Failure of RSVPFailure 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 TunnelsSolution – 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)RSVP over IP Tunnels (contd)

R1 R2

M1

M2

IntermediateRouter

IntermediateRouter

M3

M4IP TUNNELIP TUNNEL

Mobility Management in Real Time Mobility Management in Real Time ServicesServices

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