Transcript COS 420 day 17

COS 420
Day 17
Agenda
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Assignment 4 Posted
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Group project program requirements due
Individual Project Graded
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Chap 16-20
Due April 6
2 A’s and 1 B
Today we will discuss Mobile IP
Project 2 Grading
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Meeting Timelines
Deliverables
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Program requirements
Protocol Definition
Working Network Application
Final Paper
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10%
Due
Due
Due
Due
March 30
April 13
May 4
May 1
15%
15%
25%
25%
User Manual
Protocol
Program requirements
Technical Specifications
Presentation
Due May 4
10%
Computer Faculty Candidate
Presentation
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11:00 a.m. on March 31
Campus-wide Presentation-GIS Lab
Topic for presentation:
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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
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Recall: prefix of IP address identifies
network to which host is attached
Consequence: when moving to a new
network either
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Host must change its IP address
All routers install host-specific routes
Mobile IP
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Technology to support mobility
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Allows host to retain original IP address
Does not require routers to install hostspecific routes
Characteristics Of Mobile IP
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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
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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
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Datagrams sent in a tunnel
Uses IP-in-IP encapsulation
Two Broad Approaches
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Foreign network runs system known as
foreign agent
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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
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Host uses DHCP to obtain temporary address
Host registers directly with home agent
Foreign Agent Advertisement
Extension
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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
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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 TwoCrossing Problem
A Severe Problem
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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 hostspecific routes; the problem remains for any
destination that does not receive the host-specific
route.
Summary
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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