11. Distance vector protocol
depends only on Hop count to
determine the nearest next hop
for forwarding a packet. One
major disadvantage is that this
may not always represent the
best route. For example, if you
have a destination connected
through two hops via T1 lines,
and if the same destination is
also connected through a single
hop through a 64KBPS line, RIP
assumes that the link through
64KBPS is the best path!
12. There are broadly three
types of routing protocols:
-
Distance Vector (Number of
hops) - Distance vector
routing determines the
direction (vector) and
distance to any link in the
internetwork. Typically, the
smaller the metric, the
better the path. EX:
Examples of distance vector
protocols are RIP and
IGRP. Distance vector
routing is useful for
smaller networks. The
limitation is that any route
which is greater than 15
hops is considered
unreachable. One important
thing that differentiates
distance vector with Link
state is that distance
vector listens to second
hand information to learn
routing tables whereas, Link
state builds its routing
tables from first hand
information. Distance vector
algorithms call for each
router to send its entire
routing table to each of its
adjacent neighbors.
-
Link State Routing: Link
State algorithms are also
known as Shortest Path First
(SPF) algorithms. SPF
recreates the exact topology
of the entire network for
route computation by
listening at the first hand
information. Link State
takes bandwidth into account
using a cost metric. Link
State protocols only send
updates when a change
occurs, which makes them
more attractive for larger
networks. Bandwidth
and delay are the most
heavily weighed parts of the
metric when using Link-State
protocols. EX: OSPF and
NLSP.
Benefits of Link State protocols: <![endif]>
1.
Allows for a larger
scalable network
2.
Reduces convergence time
3.
Allows “super netting”
3.
Balanced Hybrid -
Balanced Hybrid combines some
aspects of Link State and
Distance Vector routing
protocols. Balanced Hybrid uses
distance vectors with more
accurate metrics to determine
the best paths to destination
networks. EX: EIGRP.
