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Mobile Computing CS 4830. Mobile IP Mr. Abdul Haseeb Khan. Outlines. Mobile IP Goals Of Network Layer Terminologies MIP Protocol (Discovery, Registration, Tunneling) Routing Inefficiencies MIPv6 History of Java Why Java ? Some Sample Java Based Applications

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Mobile computing cs 4830

Mobile Computing CS 4830

Mobile IP

Mr. Abdul Haseeb Khan


  • Mobile IP

    • Goals Of Network Layer

    • Terminologies

    • MIP Protocol (Discovery, Registration, Tunneling)

    • Routing

    • Inefficiencies

    • MIPv6

  • History of Java

    • Why Java ?

    • Some Sample Java Based Applications

    • Writing a Basic Java Program

    • Java Program Development and Execution Steps

Goal of network layer
Goal of Network Layer

  • Goal of Routing Protocols

    • decrease routing-related overhead

    • find short routes

    • find “stable” routes (despite mobility)

  • Goal of Mobile IP

    • Supporting end-system mobility while maintaining scalability, efficiency and compatibility in all respects with existing systems.

Mobile ip basics
Mobile IP: Basics

  • Proposed by IETF (Internet Engineering Task Force)

    • Standards development body for the Internet

  • Mobile IP allows a mobile host to move about without changing its permanentIP address

  • Each mobile host has a home agenton its home network

  • Mobile host establishes a care-of address when it's away from home


  • Mobile Node (MN) - is an end-system that can change the point of connection to the network without changing its IP address.

  • Home Network (HN) – is the subnet the MN belongs to with respect to its IP address.

  • Foreign Network (FA) – is the current subnet the MN visits.

  • Correspondent Node (CN) – is a fixed or Mobile Node act as partner for communication with MN.

  • Care-of Address (COA)

    • address of the current tunnel end-point for the MN (at FA or MN)

    • actual location of the MN from an IP point of view

    • can be chosen, e.g., via DHCP

  • Home Agent (HA)

    • Is a system (or router) located in the home network of the MN,

    • registers the location of the MN, then tunnels IP datagrams to the COA

  • Foreign Agent (FA)

    • system in the current foreign network of the MN, typically a router

    • typically the default router for the MN

Mobility vocabulary
Mobility: Vocabulary

home network: permanent “home” of mobile

(e.g., 128.119.40/24)

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

home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote

Permanent address: remains constant (e.g.,

wide area network

Permanent address: address in home network, can always be used to reach mobile


Care-of-address: address in visited network.

(e.g., 79,129.13.2)

correspondent: wants to communicate with mobile

Foreign agent: entity in visited network that performs mobility functions on behalf of mobile.

Mobile computing cs 4830


Network B

Foreign Agent


network A


Home Agent

Network C

Mobile Node


Node C

slide by Konidala M. Divyan [3]

Mobile ip basics cont
Mobile IP: Basics, Cont.

  • Correspondent hostis a host that wants to send packets to the mobile host

  • Correspondent host sends packets to the mobile host’s IP permanent address

  • These packets are routed to the mobile host’s home network

  • Home agent forwards IP packets for mobile host to current care-of address

  • Mobile host sends packets directly to correspondent, using permanent home IP as source IP

Mobile ip care of addresses
Mobile IP: Care-of Addresses

  • Whenever a mobile host connects to a remote network, two choices:

    • care-of can be the address of a foreign agenton the remote network

      • foreign agent delivers packets forwarded from home agent to mobile host

    • care-of can be a temporary, foreign IP address obtained through, e.g., DHCP

      • home agent tunnels packets directly to the temporary IP address

  • Regardless, care-of address must be registered with home agent

Mobile computing cs 4830

Mobile Node registers at its Home Agent

Network B

Foreign Agent

Network A


Mobile Node

Home Agent

Network C

  • Mobile Node sends Binding Update

  • Home Agent replies with Binding Acknowledgement


Node C

slide by Konidala M. Divyan [3]


  • In order to support mobility, Mobile IP includes three capabilities:

    1. Discovery

    2. Registration

    3. Tunneling


  • Mobile Agents send ICMP router advertisements with mobility agent advertisement extension periodically informing mobile nodes of its presence.

  • Mobile node is responsible for the discovery process.

  • In order to receive an advertisement, the mobile node may optionally request one from an agent or simply wait for the next advertisement.


  • Mobile node recognizes that it is on a foreign network, acquires a Care-of-Address and requests its home agent to forward its data packets to the foreign agent.

  • The process of registration requires 4 steps:

    1. Mobile node request forwarding service by

    sending registration request to the foreign


    2. Foreign agent relays this request to the home agent.

    3. Home agent accepts or denies the request and sends registration reply to the foreign agent.

    4. Foreign agent relays this reply to Mobile node.


  • After registration, an IP tunnel is set up between the home agent and care-of-address of the mobile node.

  • Home agent broadcasts gratuitous ARP request which causes all nodes in the subnet to update their ARP caches to map the mobile nodes IP address to the home agents link level address.

  • Thus home agent receives packets destined to the mobile node, and forwards the packets to the foreign agent through the IP tunnel.


  • In the foreign network, decapsulation is done by the foreign agent or by the mobile node itself.

  • A correspondent node assumes that the reply from the mobile node is coming from its home network and continues to send the packet to the home agent.

Issues in mobile ip
Issues in Mobile IP

1. Handoff:

  • When mobile node changes its point of attachment, a handoff sequence is initiated.

  • During or immediately after the handoff , packet losses may occur due to delayed propagation of new location information which degrades the quality of service.

  • Solved by introducing access point probing functionality in the mobile node to identify the current access point it is attached with.

Issues in mobile ip1
Issues in Mobile IP

2. Replay attacks:

  • A Bad Guy could obtain a copy of a valid Registration Request, store it, and then “replay” it at a later time, thereby registering a bogus care-of address for the mobile node

  • To prevent that the Identification field is generated is a such a way as to allow the home agent to determine what the next value should be

  • In this way, the Bad Guy is thwarted because the Identification field in his stored Registration Request will be recognized as being out of date by the home agent (timestamps or nonces are used for Identification field)

Mobile IP: Security Issues [4]

Issues in mobile ip2
Issues in Mobile IP

  • Redundancy: What if the home agent doesn't answer a registration request?

    • Registration request to broadcast address

    • Rejection carries new home agent ID

  • "Ingress" filtering

    • Routers which see packets coming from a direction from which they would not have routed the source address are dropped

Mobile computing cs 4830

Mobile IPv6 Roaming

Network B

Network D

Network A


Network C

Home Agent

  • Mobile Node sends Binding Updates to Home Agent and all Corresp. Nodes, which already received a previous Binding Update from this Mobile Node


Node C

slide by Konidala M. Divyan [3]