COS 420 Day 17

Agenda Assignment 4 Posted Chap Due April 6 Group project program requirements due Individual Project Graded 2 A’s and 1 B Today we will discuss Mobile IP

Project 2 Grading Meeting Timelines 10% Deliverables Program requirements Due March 30 15% Protocol Definition Due April 13 15% Working Network Application Due May 4 25% Final Paper Due May 1 25% User Manual Protocol Program requirements Technical Specifications Presentation Due May 4 10%

Computer Faculty Candidate Presentation 11:00 a.m. on March 31 Campus-wide Presentation-GIS Lab Topic for presentation: 30 min on the Benefits of Object Oriented Programming First year computer students with little to no programming experience. The presentation should be generic and not based on any one programming language itself but on the object oriented programming paradigm. The basic concepts covered should include abstractions, classes, methods, properties, message passing, inheritance, interfaces, encapsulation, and polymorphism.

PART XVIII MOBILE IP

Mobility And IP Addressing Recall: prefix of IP address identifies network to which host is attached Consequence: when moving to a new network either Host must change its IP address All routers install host-specific routes

Mobile IP Technology to support mobility Allows host to retain original IP address Does not require routers to install host- specific routes

Characteristics Of Mobile IP Transparent to applications and transport protocols Interoperates with standard IPv4 Scales to large Internet Secure Macro mobility (intended for working away from home rather than moving at high speed)

General Approach Host visiting a foreign network obtains second IP address that is local to the site Host informs router on home network Router at home uses second address to forward datagrams for the host to the foreign network Datagrams sent in a tunnel Uses IP-in-IP encapsulation

Two Broad Approaches Foreign network runs system known as foreign agent Visiting host registers with foreign agent Foreign agent assigns host a temporary address Foreign agent registers host with home agent Foreign network does not run a foreign agent Host uses DHCP to obtain temporary address Host registers directly with home agent

Foreign Agent Advertisement Extension Sent by router that runs foreign agent Added to ICMP router advertisement Format:

CODE Field In Advertisement Message

Host Registration Request

FLAGS Field In Host Registration Request

Consequence Of Mobile IP Because a mobile uses its home address as a source address when communicating with an arbitrary destination, each reply is forwarded to the mobile’s home network, where an agent intercepts the datagram, encapsulates it in another datagram, and forwards it either directly to the mobile or to the foreign agent the mobile is using.

Illustration Of The Two- Crossing Problem

A Severe Problem Mobile IP introduces a routing inefficiency known as the 2- crossing problem that occurs when a mobile visits a foreign network far from its home and then communicates with a computer near the foreign site. Each datagram sent to the mobile travels across the Internet to the mobile’s home agent which then forwards the datagram back to the foreign site. Eliminating the problem requires propagating host- specific routes; the problem remains for any destination that does not receive the host-specific route.

Summary Mobile IP allows a host to visit a foreign site without changing its IP address A visiting host obtains a second, temporary address which is used for communication while at the site The chief advantage of mobile IP arises from transparency to applications The chief disadvantage of mobile IP arises from inefficient routing known as a 2-crossing problem