Distance Vector routing protocols

aliveboonevilleΔίκτυα και Επικοινωνίες

28 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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Ch 4 Distance vector routing protocol

Dvrp =
Distance Vector routing protocols

Rip=
Routing Information Protoco
l

IGRP=
Interior Gateway Routing Protocol

EIGRP=
Enhanced Interior Gateway Routing Protocol

Distance vector knows distance and direction.

Characteristics



Periodic updates




Neighbors








Broadcast updates




Entire routing table is included with routing update


They uses nw address



Routing Protocol Algorithm
:


-
Defined as a procedure for accomplishing a certain task

Send receive alg

Calcula
te bp


To detect and react to topology changes



Criteria used to compare routing protocols includes



-
Time to convergence



-
Scalability



-
Resource usage



-
Implementation & maintenance



Router initial start up

(Cold Starts)


Initial nw discovery atomaticly

puts into the rt

Configured routers will talk to each other

Updates with new info updates metric and new info is stored no new info is dropped.( only if
configured.)

Ca uses multi

protocols but it is a pain in the butt



Periodic Updates
: RIPv1 & RIPv2



These are time intervals

in which a router sends
out its entire routing table.

Rip uses 4 timers

Update invalid holddown and flush.

Update is timer to send updates

Invalid timer is for invalid nw like failed network (invalid route)

Holddown

don’t send info (step after invalid

Flush (removed) fish in a toilet. when flush time expires then it is erased

Router convergence

every one agrees on information and will continue to share info till there is no
info new. Then they talk to keep ther tab
les acurate.

Cant shair or reseve info till configerd



Speed of achieving convergence consists of 2 interdependent categories



-
Speed of broadcasting routing information



-
Speed of calculating routes

Bounded Updates
-
Tied to atomonice systems ( inter net
works)


-
Partial updates



-
Triggered by topology changes



-
Bounded



-
Non periodic



-
Triggered

updates
-
Conditions in which triggered updates are sent



-
Interface changes state





-
Route becomes unreachable





-
Route is placed in routing table



Random
Jitter

Synchronized updates

A condition where multiple routers on multi access LAN segments transmit routing updates at the same
time.



Problems with synchronized updates

-
Bandwidth consumption

-
Packet collisions



Solution to problems with



synchronized upd
ates



-

Used of random variable



called RIP_JITTER

random timer

routing loops are a packets black hole



Count to Infinity

is an object in space

To eliminate infinity set a maximum

Split Horizon Rule

is used to prevent routing loops



Purpose of the TT
L field

The TTL field is

found in an IP header and is
used to pr
event packets from endlessly
traveling on a
network



How the TTL field works



-
TTL field contains a numeric value

The numeric value is decreased by one

by
every router on the route to the
destination.

If
numeric value reaches 0

then Packet
is discarded.



RIP



Features of RIP:




-
Supports split

horizon & split horizon with
poison reverse




-
Capable of load balancing




-
Easy to configure




-
Works in a multi vendor router environment



EIGRP



Features of EIGRP:




-
Triggered updates




-
EIGRP hell
o protocol used to establish
neighbor adjacencies




-
Supports VLSM & route summarization




-
Use of topology table to maintain all routes




-
Classless distance vector routing protocol




-
Cisco propr
ietary protocol