Distance Vector Routing

Distance Vector Routing
Course: Computer Networks

1. 1 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 3 rd Year, 2 nd Semester Department of Computer Science and Engineering, North Western University, Khulna.

2. 2 Contents…. Routing Protocols and Types of Routing Protocols Distance Vector Routing Characteristics and Process Algorithm Advantages Disadvantages

3. 3 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.

4. 4 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,

5. 5 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.

6. 6 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

7. 7 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 w hen 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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11. 11 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

12. 12 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. D istance Vector Routing protocols do not require a large amount of CPU resources or memory to store the routing data .

13. 13 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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