CS4550 Computer Networks II

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Oct 28, 2013 (3 years and 7 months ago)

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CS4550

Computer Networks II


IP : internet protocol,

part 3 : routing policies, IPv6








IP routing


routing mechanism

-

the mechanics of routing


--

discussed previously


--

review basic routing algorithm


routing policy

-

how the paths in the network
are calculated


--

there is no single required routing policy
on the Internet


--

DV and LS routing already discussed


--

some specific IP policies to follow

IP
-

routing policy

topics


interior gateway protocols (IGPs)


RIP


IGRP, EIGRP


OSPF


autonomous systems


exterior gateway protocols


EGP


BGP


IPv6

references


Feit,
TCP/IP: architecture, protocols and
implementation



many RFCs :


RIP : 1058, 1723, 1582


OSPF : 1583,1793, 1586, 1584, 1403


BGP : 1771, 1773, 1772


IGRP : www.cisco.com

Automated Routing Protocols

Generic Functions



Measure route cost


Send/receive routing updates


compute routes


update routing tables


routing information protocol (RIP)


most widely used; now in 2nd version


free, available with Unix as “routed”


DV routing, each hop assigned cost (usually 1)


strong points: simple and available; good for
small, simple networks


max path length is 15 hops


not good for very large networks (already
discussed DV problems)


IGRP : internet gateway routing protocol


Cisco routers
-
> proprietary


distance vector protocol also


uses split horizon


updates every 90 seconds (default)


triggered updates


if no update from an adjacent router for 270
sec, entry timed out, destinations using it
rerouted


destinations flushed after 540 seconds

more on IGRP


more sophisticated distance metric


delay


bandwidth


congestion (load)


reliability


hop count to destination


biggest MTU (packet) that link/path can carry


can also split traffic over multiple paths


can also support routing between different
autonomous systems

EIGRP
-

enhanced IGRP


same distance metrics and routing calculations


does away with periodic updates; only
updated after change, but reliable updates
used


used an algorithm to detect loops in routes and
remove them


“EIGRP has proven the distance vector routing
is far from dead” (Feit)

OSPF : open shortest path first


link state protocol, developed by IETF; non
proprietary


low overhead; updates report changes rather
than everything


quick detection of topology changes, rap


id updating after changes


traffic splitting over multiple paths


subnet masks supported


authentication supported


widely used, refinements will continue

autonomous systems


a piece of the Internet unified by a routing
policy


“somebody’s network”

early def
:
a collection of subnetworks and hosts,
interconnected by routes


new def
:
a connected group of 1 or more IP prefixes ...
which has a SINGLE and CLEARLY DEFINED
routing policy


autonomous systems


routing
within

ASs is done by IGPs, or interior
gateway protocols; chosen by the controlling
organization



routing
between

ASs is done by EGPs, or
exterior gateway protocols



AS domain is identified by a unique 16
-
bit AS
number administered by ARIN (www.arin.net)

AS

A
S

A
S

RIP

IGRP

EIGRP

EGP

BGP

EIGRP

EIGRP

EIGRP

EIGRP

autonomous systems

exterior gateway protocols

EGP

-

an early version


-

simple distance vector: But NO weight used


-

very limited information passed between
routers


-

useful early when Internet was small; losing
its usefulness now

BGP

-

border gateway protocol


-
report entire paths, avoiding loops


-
similar to link
-
state algorithm


Further Internet topics


IPv6


UDP and TCP (in next class)


domain name system


FTP


Telnet


email


HTTP


internet telephony


integrating TV, voice,video into Internet

Why IP Version 6



IPv4 Proposed in 1975, adopted in 1981


Served well but 24 years old


Address Depletion


Explosion of in growth of routing tables


Non
-
heirarchical in nature


Security Issues


Routing Performance


New Applications


Telephony, video , conferencing


Piece of “the Puzzel” to enable new services


IPv6 Challanges



Backward Compatibility



MUST
work with existing equipment



Perpetual coexistence with IPv4



MUST

Coexist with current standards/protocols


will require new v4/v6 aware protocols to
take advantage of v6 features

IPv6 Routing


Routers CANNOT Fragment


guaranteed minimum 576 byte path


Shorter & Simplified Header


Faster Analysis


Most Optional Headers Ignored during routing


Hierarchical Addressing


Smaller Routing Tables


Like international phone system


Flow Control Lables

IPv6 Packet Format



MUCH Simplified


Fixed Length
-

40 bytes


0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

version

Traffic Class


Flow Label



Payload length



next header


hop limit



Source Address ( 4 lines 16 bytes)


destination Address (4 lines 16 bytes)




Extension Headers 8 Optional headers Defined


Authentication (MDS)


Encapsulating Security Payload


IPv6 Addressing


Address Notation X:X:X:X:X:X:X:X


Where X = 16 bits


Total 0f 128 bits


Three Address Types


Unicast


Multicast


Anycast


Global Unicast Address


3

13

8

24

16



64

001 TLA ID RES NLA ID SLA ID Interface ID