Routing Information Protocol version 2 (RIP v2) is a distance-vector routing algorithm that makes use of the hop count as metric for routing (Archana, 2015). The hop count is simply a path between a source and destination, which simply could be the number of intermediate routers, bridges or gateways between the source and the destination. A maximum of 15 hops is allowed in RIP v2, placing a limitation on the size of networks that can be supported by the protocol.
The Bellman-Ford algorithm determines the shortest path to a destination using the principle of relaxation where the correct distance to a point is replaced gradually by more accurate values until an optimum solution is reached. The distance vector to a node on the network is initialized to 0 and all other nodes initialized to infinity. Using the algorithm, a node scans all the edges to all the nodes to it, and if the distance to a node is shorter, the new lower value replaces the older longer value, and the scanning continues in order to update the routing table of the node with the most recent distance vector to all other nodes to it. The node also sends its routing table to all other nodes in the network. An important advantage is that the Bellman-Ford algorithm works on negative edges in the network in determining the best path (shivani et al., 2013)
There are two types of messages used by RIP v2 - request message and response message. A broadcast request message is sent by a router running RIP v2 when it comes online, where all the neighbouring routers receive the request message and send a response message which contains their routing table. The other scenario in which a response message is sent is at the expiration of the update timer.
Enhanced Interior Gateway Routing Protocol (EIGRP)
EIGRP is another distance-vector routing protocol which is proprietary to Cisco Systems and made available only on Cisco routers to automate the process of making routing decisions and route configurations. An autonomous system is pivotal to the working of EIGRP as the protocol is used to share route information with other routers which belong to the same autonomous system (Kalamani et al., 2014). An autonomous system is a collection of routers under the same administrative domain with a collection of routing prefixes based on Internet Protocol (IP).
The routing metric used in EIGRP makes use of a combination of parameters for the estimation. These include Bandwidth, Reliability, Maximum Transmission Unit (MTU), Hop count, Total delay and the load. The minimum bandwidth specified in kilobits per second on the path from the router to the destination, the reliability specified with integers between 1 to 255 with 1 being the least reliable, the delay in microseconds along the path from the router to the destination, the hop count which is the number of routers and gateways that a packet passes through before getting to the destination network, and the load on the path specified between 1 and 255 with 255 being the saturated load level.
Figure 1: A sample network running EIGRP (Cisco, 2015)
In figure 1, in determining the best path to network A, router one advertises the network through router four (minimum bandwidth 56 and delay 2200) and router three (minimum bandwidth 128 and delay 1200). EIGRP thus calculates the metrics using the formula as shown below.
metric = ([K1 * bandwidth + (K2 * bandwidth) / (256 - load) + K3 * delay] * [K5 / (reliability + K4)]) * 256
Using these parameters in the equation, Router One chooses the route through Router Three to reach Network A because of the lower metric.
Route summarization entails the consolidation of multiple routes into one single route in order to reduce the size of the routing table especially for large networks (Patel and Pandey, 2014).The summarization of the route can be either inter-area route summarization or external route summarization.
REFERENCES
Archana, C. (2015). Analysis of RIPv2, OSPF, EIGRP Configuration on router Using CISCO Packet tracer. International Journal of Engineering Science and Innovative Technology (IJESIT), 4(2), Pp 215 - 222.
Cisco (2015). Enhanced Interior Gateway Routing Protocol. Web. Accessed on 28 April, 2016 from http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/16406-eigrp-toc.html
Kalamani, P., Kumar, V.M., Chithambarathanu, M. and Thomas, R. (2014). Comparison of RIP, EIGRP, OSPF, IGRPRouting Protocols in Wireless Local Area Network (WLAN)by using OPNETSimulator tool -A Practical Approach. IOSR Journal of Computer Engineering (IOSR-JCE), 16(4), Pp 57 - 64.
Patel, H.N. and Pandey, R. (2014). Extensive Reviews of OSPF and EIGRP Routing Protocols based on Route Summarization and Route Redistribution. International Journal of Engineering Research and Applications, 9(4), Pp 141 - 144.
Shivani, S., Leena, J. and Bharti, K. (2013). Shortest Path Algorithm. International Journal of Application or Innovation in Engineering & Management, (IJAIEM), 2(7), Pp 316 - 320.
