Distance vector routing is a routing protocol that determines the best route for data packets based on distance. Each router maintains a routing table with the minimum distances to every other node and periodically shares its table with neighbors. When a router receives an update indicating a change, it will recalculate its own routing table and propagate changes. While simple to implement, distance vector routing is prone to counting to infinity problems and slow convergence.

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Distance
Vector
Routing.
Presented To:
Romana Rahman Ema
Senior Lecturer
Department of Computer Science and Engineering,
North Western University, Khulna.
Presented By:
Shouvik Kushal Dhali.
ID: 20181093010
3rd Year, 2nd Semester
Department of Computer Science and Engineering,
North Western University, Khulna.

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Contents….
 Routing Protocols and Types of Routing Protocols
 Distance Vector Routing
 Characteristics and Process
 Algorithm
 Advantages
 Disadvantages

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 Routing Protocols
A routing protocol specifies how routers communicate with each
other to distribute information that enables them to select routes
between any two nodes on a computer network. Routers perform the
"traffic directing" functions on the Internet; data packets are
forwarded through the networks of the internet from router to router
until they reach their destination computer. Routing algorithms
determine the specific choice of route.

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 Types of Routing Protocols
We can find many views of the types of Routing Protocols but the types of
popular routing protocols are given as follows,

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 Distance Vector Routing
 A distance-vector routing protocol in data networks determines the best route for data packets
based on distance and it is one of the routing protocols.
 Distance-vector routing protocols measure the distance by the number of routers a packet has to
pass, one router counts as one hop.
 Some distance-vector protocols also take into account network latency and other factors that
influence traffic on a given route. To determine the best route across a network, routers, on which
a distance-vector protocol is implemented, exchange information with one another, usually routing
tables plus hop counts for destination networks and possibly other traffic information.
 Distance-vector routing protocols also require that a router informs its neighbors of network
topology changes periodically.
 Distance-vector routing protocols use the Bellman–Ford algorithm and Ford–Fulkerson algorithm to
calculate the best route. Another way of calculating the best route across a network is based on
link cost, and is implemented through link-state routing protocols.
 Distance vector describes what a router knows about each route. In this protocol, the least-cost
route between any two nodes is the route with minimum distance and in this, each node maintains
a vector(table) of minimum distances to every node
 Routing Information Protocol (RIP) is one of the examples of Distance Vector Routing.

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 Characteristics and Process
 Characteristics of Distance Vector routing protocols:
 Periodic updates: Each Router will send periodic routing table updates to its
neighbors. Routing Information Protocol (RIP) will send updates every 30
seconds and Cisco’s Interior Gateway Routing Protocol (IGRP) will send
updates every 90 seconds
 Neighbors: Most distance vector routing protocols send a full routing table
update to their neighbors.
 Broadcast updates
 Entire routing table is included with routing update
 Each Distance Vector Protocols employs additional loop prevention mechanism
such as split horizon, route invalidation timers counting to infinity etc

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 Process
 At the beginning, in this protocol each node will be known about distance between itself
and its immediate neighbors or the nearest node and won’t be known about the distance
of the node which is not its neighbor.
 At the time of sharing, each node will share its routing table with its immediate neighbors
periodically or will share when there is a change in the network and by this sharing, one
node will be known about the neighbors of another node and it will be confirmed to that
node that there exists another nodes like it.
 There are some moments when the sharing will happen and those are, (i) Periodic update:
In this, A node sends its routing table after a specific time and (ii) Triggered update: In this,
A node sends its two-column routing table to its neighbors anytime when there is a change
in its routing table and this change can be occurred before or after the specific time.
 At the time of update, a node need to update its routing table when it will receive a two-
column table from a neighbor and for update, (i) a node will choose the smaller cost and if
the costs are same then it will keep the old cost and (ii) if the next-node entry is the same,
the receiving node will choose the new row.

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 Algorithm
 Algorithm:
1. A router transmits its distance vector to each of its neighbors in a routing
packet.
2. Each router receives and saves the most recently received distance vector
from each of its neighbors.
3. A router recalculates its distance vector when:
 It receives a distance vector from a neighbor containing different
information than before.
 It discovers that a link to a neighbor has gone down

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 Advantages of
Distance Vector Routing
 Distance Vector is a relatively simple approach and easy to use,
implement and maintain and does not require High-level
knowledge to deploy.
 It does not demand high bandwidth level to send their periodic
updates as the size of the packets are relatively small.
 Distance Vector Routing protocols do not require a large amount of
CPU resources or memory to store the routing data.

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 Disadvantages of
Distance Vector Routing
 The main drawbacks of Distance Vector Routing are limited scalability due
to slow convergence time, bandwidth consumption and routing loops.
 Another problem with distance vector routing is instability, which means
that a network using this protocol can become unstable.
 This can be at risk from the count-to-infinity problem.
 This routing protocol creates more traffic than link state since a hop count
change must be propagated to all routers and processed on each router.
Hop count updates take place on a periodic basis, even if there are no
changes in the network topology, so bandwidth-wasting broadcasts still
occur.

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