Saturday, 6 February 2021

Routing Protocol

What is Routing Protocol?

A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between any two devices 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. Therefore, the routing algorithms determine the specific choice of route and each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. However this way, routers gain knowledge of the topology of the network. The ability of routing protocols to dynamically adjust to changing conditions such as disabled data lines and computers and route data around obstructions is what gives the Internet its fault and high availability.

Characteristics of Routing Protocols

  • Selection of Preferred Route
  • Avoiding Routing Loops
  • Using Information about Hop Cost
  • Scalability
  • The time they Require to Reach Routing Convergence
  • Cloud Access Framework Parameters
  • Relay Multiplexing
  • Multilayer Interfacing
  • Preventing Issues with Routing Protocols Loops

Types of Routing Protocols

The following types of routing protocols are

  • IGP - Interior Gateway Protocols (Cisco proprietary)
  • EGP - Exterior Gateway Protocols
  • RIP - Routing Information protocols
  • IGRP - Interior Gateway Routing Protocols
  • RIPv1 - Routing Information protocol Version 1
  • OSPF - Open Shortest Path First
  • NLSP - Network Link Service Protocol
  • IS-IS - Intermediate System-Intermediate System
  • EIGRP - Enhanced Interior Gateway Routing Protocol (Cisco proprietary)

Interior Gateway Protocols (IGP)

It used to exchange information inside the same autonomous system. IGP type 1, Distance Vector Routing Protocol, such as Routing Information protocol (RIP), Routing information protocol Version 1 (RIPv1), and Interior Gateway Routing Protocol (IGRP, IGP type 2, Link State Routing Protocol, such as Open Shortest Path First (OSPF) and Network Link Service Protocol, and IGP type 3, Hybrid Routing Protocol, such as Intermediate System- Intermediate System (IS – IS) and Enhanced Interior Gateway Protocol (EIGP).

Exterior Gateway Protocols (EGP)

Exterior Gateway Protocols are routing protocol used on the internet to communicate between autonomous systems, such as Border Gateway Protocol (BGP) and Path Vector Routing Protocol.

Routing Information Protocols (RIP)

It maximum hop is 15 and the metric is hop. It has no asynchronous and the full route table updates every 30 seconds to 90 seconds. Therefore, an administrative distance is 120, and the route specified by ‘R’.

Interior Gateway Routing Protocols (IGRP)

The maximum hop is 255, default is 100, and composite metric (Bandwidth and Delay) default. Also reliability, load, and maximum transmission unit (MTU) use autonomous system number.  However, an administration distance is 100, and the route specified by ‘I’.

Routing Information Protocol Version 1 (RIPv1)

It maintains one table and also maintains one path to the destination. Advertise can update every 30 seconds, are broadcast packets and the entire routing table advertised. High traffic, bandwidth consumption, and the metric is hop. Therefore the maximum hop is 15 and 16 the unreachable and it doesn’t support classless routing and delay in convergence. However, the administrative distance is 120, and the route specified by ‘R’. It uses Bellmanford Algorithm.

Open Shortest Path First (OSPF)

OSPF calculates the best or shortest path to every network in the same area based upon the information collected in topology database and algorithm called SPF (shortest path first). It maintains three tables such that routing table, topology table, and neighboring table. It maintains multiple paths. Advertise can update every 30 minutes, advertise are multicast packets, and only changed entries advertised. Therefore it consists of less traffic, no bandwidth consumption, and full performance. The metric are bandwidth, time delay, cost and traffic and it support classless routing and no delay in convergence. However, the administrative distance is 110, and the route specified by ‘O’. It uses Dijkstra Algorithm.

Note: OSPF used LSO (Link State Update) to indicate the other router to update with the new link status, when the old fails.

Enhanced Interior Gateway Routing Protocol (EIGRP)

It maintains multiple paths to the destination and support classless routing protocol, Internet Protocol (IP), IPX, and Appletalk. Therefore, it is a Cisco proprietary protocol and it selects the best path via Diffusing Update Algorithm (DUAL) and communicates with other routers via Reliable Transport protocol (RTP). It support multiple autonomous system in same router or single route and metric is bandwidth, time delay, cost, and traffic. However, the administrative distance is 90, and the route specified by ‘D’.

Also learn about Digital Subscriber Line (DSL)


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