Distance vector routing is a distributed routing protocol that uses the Bellman-Ford algorithm to calculate the shortest paths between nodes. Each router periodically sends its routing table to its neighbors, containing the distance and next-hop information to reach all known destinations. Upon receiving updates from neighbors, routers recalculate path costs and propagate changes to ensure all routers converge on the shortest paths over time. While simple to implement, distance vector routing suffers from slow convergence and potential routing loops during network changes.

1. Distance Vector Routing
Presented by Seema Thapa
Roll no: 27
Computer Networks
Department of Computer Science
Soch College of Information and Technology

2. Contents:
• Basic Introduction
• Distance Vector Routing Protocol
• Working Mechanism with example
• Pros and Cons
• Conclusion

3. Basic Introduction
1. What is Routing?
2. What is Distance Vector?
Hi, I am a packet
data. Where
should I go?
I will guide you by
telling the shortest
distance and direction.
Input Link
Destination
Output Link
Router

4. Routing and Distance Vector
• Simple idea of finding shortest distance:
Source
Destination
Total minimal distance is 4+3+5+2 = 14 mins
Let me
think!

5. Hop count
Distance is defined in terms of hop count and direction.
For example:-
Infinity value is 16 hops.
Routers send vectors every 30 seconds.
Fig: Hop count
Networking
devices such as
router etc

6. Distance Vector Routing Protocol
A distance vector routing algorithm is an
intra-domain(within a network) routing protocol
which is:
i. Iterative
ii. Asynchronous
iii. Distributed
It is based on the Bellman-Ford Equation.

7. Why iterative, distributed and
asynchronous?

8. Bellman-Ford Equation
The Bellman-Ford Equation is based on:-
• Defining distances at each node X :
dx(y) = cost of least-cost path from X to Y.
• Updating distances based on neighbors
dx(y) = min {c(x,v) + dv(y)} over all neighbors V
X Y
Z
V
W

9. Bellman-Ford Equation
dx(y) = min{c(x,y) + dy(y), c(x,z) + dz(y)}
= min{3+0, 4+5} = min{3, 9} = 3
X
Y
Z
V
W
7
2
5

10. Example:-
dx(z) = min{c(x,y) +
dy(z), c(x,z) + dz(z)}
= min{2+1, 7+0}
= min{3, 7} = 3
i.e. 3 < 7
A router “counts
to infinity” marks
the route as
unreachable.

11. Pros and Cons
Pros:-
• Simple implementation and maintenance
• Low resource requirements (memory, CPU)
Cons:-
• Slow convergence (periodic updates)
• Limited scalability
• Routing loops (due to slow convergence)

12. Conclusion
D.V. routing protocols maintains routing tables
through it’s characteristics such that
- Periodic updates which include the entire
routing table.
- Calculate the best path.
- Neighbors are defined as routers that share a
link and are configured to use the same
protocol.
- Detect and react to the topology changes.

13. THANK YOU