ABSTRACT

In all computer network systems when they share different type of data on different devices those data transmission path and medium use what we call Routing protocols which serves a purpose of learning and identifying available routes that exists on a network according to the destination and source addresses and details on place, space, time and distance it will use. In this article we will discuss different types of Routing protocols their characteristics, advantages, disadvantages, algorithms and a network suitable for them.

KEY TERMS: Dynamics protocols, RIP, IGRP, EIGRP, OSPF, IS-IS, BGP

1. INTRODUCTION

1.1 Routing Protocols Basics

A Routing protocol as we can get the word route/road is the language routers use to communicate each other to share information data and status over the network;

People everyday use different network scales sharing different resources over networks from our small Local Area Network to extra-large organization Wide Area Networks they are need and uses Routers and Switch for their user device communication.

Routers forwards packets after considering its own routing table, metric distance, hops numbers and compute by a routing algorithm the best, fast and possible successful path to reach the destination.

1.2 TYPES OF ROUTING PROTOCOLS

Some of the most common routing protocols include RIP, IGRP, EIGRP, OSPF, IS-IS and BGP. All these protocols are classified or grouped into different categories from their performance, algorithm, characteristics... The following figure:

Fig 1 Hierarchical view of dynamic routing protocol classification

2. OVERVIEW OF ROUTING PROTOCOLS

2.1 Routing Information Protocol (RIP)

Routing Information Protocol (RIP) is a dynamic routing protocol which uses hop count as a routing metric to find the best path between the source and the destination network. It is a distance vector routing protocol which has AD value 120 and works on the application layer of OSI model. RIP uses port number 520.

2.2 Interior Gateway Routing Protocol (IGRP)

Interior Gateway Routing Protocol is a distance vector routing protocol developed by Cisco systems for routing multiple protocols across small and medium sized Cisco networks. It is proprietary which requires that you use Cisco routers. This contrasts with IP RIP and IPX RIP, which are designed for multi-vendor networks. IGRP will route IP, IPX, Decnet and Apple-talk which makes it very versatile for clients running many different protocols. It is somewhat more easier to scale than RIP since it supports a hop count of 100, only advertises every 90 seconds and uses a composite of five different metrics to select a best path destination. Note that since IGRP advertises less frequently, it uses less bandwidth than RIP but converges much slower since it is 90 seconds before IGRP routers are aware of network topology changes. IGRP does recognize assignment of different autonomous systems and automatically summarizes at network class boundaries. As well there is the option to load balance traffic across equal or unequal metric cost paths.

2.3 Open Shortest Path First (OSPF)

OSPF is one of the famous IGP protocols, which operate in a single autonomous system number. It uses Dijkstra algorithm, also known as SPF (Shortest Path First) algorithm in order to calculate the best path to the destination. Unlike other dynamic routing protocols, each router of OSPF knows the complete topology. However, the forwarding decision is taken on the basis of Best Route in the routing table. Like EIGRP, OSPF also works on the network layer of the OSI Model and its protocol number is 89.

2.4 Enhanced Interior Gateway Routing Protocol (EIGRP)

EIGRP Protocol is one of the most used Dynamic Routing Protocol as IGP (Interior Gateway Protocol). Especially it is used for Routing purpose inside the networks that is mostly consist of Cisco devices.

EIGRP is a Hybrid Routing Protocol that show both Distance Vector and Link-State Routing Protocol properties. It was developed by Cisco as an enhancement to IGRP (Interior Gateway Routing Protocol) and as a Cisco proprietary protocol and it is only available on Cisco devices.

2.5 Integrated IS-IS

Integrated Intermediate System ?Intermediate System routing protocol is a link state protocol similar to OSPF that is used with large enterprise and ISP customers. An intermediate system is a router and IS-IS is the routing protocol that routes packets between intermediate systems. IS-IS utilizes a link state database and runs the SPF Dijkstra algorithm to select shortest paths routes. Neighbor routers on point to point and point to multipoint links establish adjacencies by sending hello packets and exchanging link state databases. IS-IS routers on broadcast and NBMA networks select a designated router that establishes adjacencies with all neighbor routers on that network. The designated router and each neighbor router will establish an adjacency with all neighbor routers by multicasting link state advertisements to the network itself. That is different from OSPF, which establishes adjacencies between the DR and each neighbor router only. IS-IS uses a hierarchical area structure with level 1 and level 2 router types. Level 1 routers are similar to OSPF intra-area routers, which have no direct connections outside of its area. Level 2 routers comprise the backbone area which connects different areas similar to OSPF area 0. With IS-IS a router can be an L1/L2 router which is like an OSPF area border router (ABR) which has connections with its area and the backbone area. The difference with IS-IS is that the links between routers comprise the area borders and not the router. Each IS-IS router must have an assigned address that is unique for that routing domain. An address format is used which is comprised of an area ID and a system ID. The area ID is the assigned area number and the system ID is a MAC address from one of the router interfaces. There is support for variable length subnet masks, which is standard with all link state protocols. Note that IS-IS assigns the routing process to an interface instead of a network.

2.6 Border Gateway Protocol (BGP)

Border Gateway Protocol (BGP) is used to Exchange routing information for the internet and is the protocol used between ISP which are different ASes.

The protocol can connect together any inter-network of autonomous system using an arbitrary topology. The only requirement is that each AS have at least one router that is able to run BGP and that is router connect to at least one other AS抯 BGP router. BGP抯 main function is to exchange network reach-ability information with other BGP systems. Border Gateway Protocol constructs an autonomous systems,graph based on the information exchanged between BGP routers.

3 ROUTING PROTOCOLS CHARACTERISTICS

Below is a summary table of each protocols and their characteristics

PROTOCOL	RIPv1	RIPv2	OSPF	EIGRP	IS-IS	BGP
Type	Distance-vector	Distance-vector	Link-state	Distance-vector	Link State	Path Vector
Routes	IP	IP	IP	IP, IPX, Decnet, app letalk	IP, CLNS	IP
Convergence time	Slow	Slow	Fast	Fast
VLSM	No	Yes	Yes	Yes	Yes	Yes
Bandwidth Consumption	High	High	Low	Low
Resource Consumption	Low	Low	High	Low		Low
Multi-path Support	No	Yes	Yes	Yes
Scales well	No	No	Yes	Yes
Proprietary	No	No	No	Yes	No	No
Routing Table Advertisements		Network updates exchanged periodically	Partial When Route Changes Occur	Partial When Route Changes Occur	Partial When Route Changes Occur	Partial When Route Changes Occur
Metric			Composite Cost of each router to Destination (100,000,000/interface speed)	Bandwidth, Delay, Reliability, Load, MTU Size	Variable Cost (default cost 10 assigned to each interface)	Weight, Local Preference, Local Originated, AS-Path, Origin Type, MED
Hop Count	15	15	None (Limited by Network)	255	None (Limited by Network)	255
Summarize Network Class Address or Subnet Boundary			Yes	Yes	Yes	Yes
Load Balancing Across			4 Equal Cost Paths	6 Equal or Unequal Cost Paths (IOS 11.0)	6 Equal Cost Paths	6 Equal Cost Paths

Tab 1 Routing Protocols characteristics

Convergence Time: This is the point at which all routers on your network know about all current routes for the network. When a router is added or removed from a network, a convergence time is the time used before this change is propagated to all routers on the network.

Variable length subnet masks (VLSM): This term refers to whether all routers on the network are required to use the same subnet mask. This requirement reduces your flexibility in assigning IP address network IDs to the network segments on your network.

Bandwidth Consumption: This term refers to the amount of necessary network bandwidth to maintain and distribute routing table information on the network. To share and distribute routing table information, all routing protocols need to send an amount of data over the network, and some send more than others.

Resource Consumption: In calculating and maintain routing table information on a router, a certain amount of processing power and memory is used.

Multi-path Support: When routes are discovered on the network that have loops in their paths, some segments have two possible routes, which represent multiple paths. Some routing protocols have support for multiple paths, by storing alternative paths in their routing information.

Scales Well: Some routing protocols operate well on small networks, but as the number of routers increases on the network, the routing protocol does not function as well. Routing protocols that can be used on small to very large networks scale well in size.

Proprietary: The routing protocol based on open standards or a proprietary protocol owned by one company can affect the level of support and the speed of changes.

Summary

In this article, we discussed different Routing protocols categories,characteristics,algorithms,how they work and suitable networks like for example if your network hops is more than 50 or 255 you will know the one to use,network speed,sub-netted classes and so on

REFERENCE

[1] Cisco Networking Academy's Introduction to Routing Dynamically http://www.ciscopress.com/articles/article.asp?p=2180210&seqNum=7

[2] Understanding Network Routing Protocols https://www.routerfreak.com/understanding-network-routing-protocols/

[3] Routing Protocols Summary https://www.dummies.com/programming/networking/cisco/routing-protocols-summary/

[4] Network Routing overview http://EzineArticles.com/?Network-Routing-Protocols桰GRP,-EIGRP,-OSPF,-ISIS,-BGP&id=2891289

ROUTING PROTOCOLS REVIEW AND COMPARISONS Version 0
👤 Author: by ngendahimanamoisehotmailcom 2019-09-26 10:41:07