Running head: IMPORTANCE OF ROUTING PROTOCOL

Importance of Routing Protocol

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IMPORTANCE OF ROUTING PROTOCOL 2

Abstract

Routing may be described as the act of moving information across an internetwork

from a point of origin or a source to a given destination. During this process of transmission

of information, at least one intermediate node is encountered. Often, routing is contrasted

with bridging, both might seemingly be perceived to accomplish the same thing to a non-

technical or networking observer. The topic of routing and routing protocol has been covered

in computer science and networking literatures for more than two or more decades. Routing

did achieve commercial popularity in the early 80s. The principal reason for the time lag in

the popularity of routing as well as routing protocols is that networks in the 70s were

relatively simple and homogenous frameworks. Only recently has large scaled

internetworking become relatively popular hence increased awareness on the concept of

routing and its protocols. This paper examines and explains some of such concepts.

The Concept of Routing Protocols

A routing protocol utilizes software and routing algorithms in the determination of optimal

network package or data transfer and communications path between nodes on the same

network. Routing protocols are responsible for the facilitation of router communications and

overall topology of network understanding (Postel, 1981). Most internet protocols networks

can be said to make use of the following routing protocols: Routing Information protocol and

interior gateway routing protocol. Interior gateway routing are provided via path or distance

vector protocols. Open shortest path first, this is responsible for the provision of interior

gateway routing through link state routing protocols and the final one is the border gateway

protocol. This type of routing protocol is said to provide public internet routing protocols via

exterior gateway routing. Routing protocols implement routing algorithms in such a way that

they tend to facilitate the exchange of routing information between networks. The allow

IMPORTANCE OF ROUTING PROTOCOL 3

routers to create routing tables dynamically and in some situations they have the capabilities

to override routed protocols. A typical citation is the situation where BGP runs over TCP,

extreme caution is taken in the implementation of these kind of systems so as not to create a

circular dependency between the routing and routed protocols. The primary objective or

purpose of a routing protocol is to find the most suitable route to route packets. How this

process or function is established is primarily based on various factors like bandwidth, delay,

load and reliability. It most cases it equally depends on what routing protocol is employed.

Routers share their routing tables with neighbouring routers, this enables them establish new

routes from other routers and uses this information to build routing tables which are

eventually used to route data packets. EIGRP shares routes with routers with which have the

same autonomous numbers. In other words, it is important to set the AS number so that the

router can detect other routers within its environment. Routing protocols aid routers to build

as well as maintain a routing table by establishing the best route in the table and eliminating

routes that are no longer existent.

Distance Vector Routing Protocol is one of the two primary routing protocols utilized for

communications methods that use data packets sent over internet protocol. Distance Vector

Routing Protocol requires routing hardware to report the distance of various workstations or

nodes within an IP topology or a network. This is established as a means of determining the

best and most efficient routes for data packets.

In contrast to Distance Vector Routing Protocol, and the other type of routing protocol

Link state Routing Protocol, which is viewed as the more predominant of the two. DVRP has

the tendency to contemplate two basic factors: Vector and Distance. A vector illustrates the

trajectory of the data packet over a stipulated set of network nodes. The Distance on the other

hand is referred to as the number of steps or data packets that must be transmitted to get to its

destination. DVRP is essentially important in voice over IP and other types of

IMPORTANCE OF ROUTING PROTOCOL 4

communications that make use of routed data packets. As internet protocol infrastructure

becomes more extensive and important to the communications and global markets in general,

it is highly probable that that advances will continue to grow the capacity of IP traffic with

enhanced methods and hardware devices.

The Distance Vector Routing Protocol can be further comprehended through

recollection of the meaning of the word “vector”. This is classified as a value with two

components, direction and magnitude. In a DVRP, neighbouring routers such as router

attached to the same sub networks interchange routing vectors. Each router establishes a list

of all known sub networks and metric relating to cost of the path to that sub network from its

routing table (Mogul, 1984). This information is transmitted to all routers within the

environment or to all neighbours. In this case neighbours are referred to as any system or

node which is connected to the same sub network.

One of the most significant advantages of a Distance Vector Routing Protocol is that,

it is a relatively simple approach. In technology and computing, simple things are easier and

more efficient to implement as well as the fact they place a fair demand on the systems

processing power. This tends to be a critical advantage with the DVRP.

On the down side, DVRPs have the tendency to suffer from a list of essential

limitations. These disadvantages of the DVRP tend to grow as the inter-network grows.

Routing tables in significantly large networks can be proportionally or correspondingly large,

thus there is the consumption of bandwidth in the process of exchange of routing information.

One important factor to note about DVRPs is that it is not essential for this type of

protocol to transmit its updates periodically. Updates can only be transmitted in the event that

there is a change. In large inter-networks Distance Vector Routing Protocols may require

some time to converge due to the changes in the network topology which takes time to

IMPORTANCE OF ROUTING PROTOCOL 5

propagate across the whole network. Each router with the inter-network has to receive an

update and then recalculate its routing table before it can establish and generate an update to

its neighbours. However, it should be noted that most DVRPs support event driven updates.

Most also impose the hold downs to avoid transient cycles or loops. The implication of this

concept is that loss of routes travel at a much faster rate than alternative routes which take

relatively longer to follow. This convergence challenge coupled with a number of other

implications of the exchange process make DVRP particularly prone to the creation of

routing loops. Routing Information Protocol (RIP), which is found in TCP/IP, Netware and

XNS inter-networks, Apple Talks Routing Table Maintenance Protocol and Cisco’s Interior

Gateway Routing Protocol are all examples of popular DVRPs (Almquist, 1994).

Routing Information Protocol, is a DRVP, which implements the hop count model as

a routing metric. Routing loops are prevented by Routing Information Protocol via the

implementation of limiting the amount of hops permitted in a path from the origin

destination. In RIP, there are a total number of fifteen hops allowed. This hop limit equally

puts a restriction on the size of the networks that can be supported by Routing Information

Protocol (RIP). A hop count of sixteen is said to be the infinite distance used in deprecating

inoperable, undesirable or otherwise inaccessible routes in any selection processes. Hold

down, route poising and split horizons are mechanisms all implemented by the Routing

Information Protocol. These mechanisms all aid in the prevention of incorrect routing data or

information from being transmitted or propagated. This is viewed as one of the stability

attributes of this type of DVRP. There is also the possibility of the utilization of the Routing

data or Information Protocol with metric based structure or topology algorithm to deal with

the infinity count challenge. The metric based topology, implements the ability to detect

loops with relatively small computational effort is quite feasible (Baker, 1995).

IMPORTANCE OF ROUTING PROTOCOL 6

Routing Information Protocol (RIP) comes in two versions. Version 1 and version 2.

The first version is a distance vector protocol while the second version is a hybrid protocol.

Routing Information Protocol RIPv1 utilizes local broadcast in the sharing or dissemination

of information. The RIPv1 updates are relatively periodic in nature, they occur by default

every thirty seconds. This is established in a bid to prevent packets from the routing loops

effects. This version of the RIP just like the version 2 solves the issue of counting to infinity

by inculcating approximately a hop count limit of fifteen hops on the data packets. Any data

packet that gets to the 16th

hop automatically gets dropped. Routing Information Protocol

RIPv1 is what is known as a classful protocol. It supports approximately about six equal

paths to one destination. Paths that are denoted as equal paths are paths where metric or hop

count is the same. Routing Information Protocol RIPv1 supports essentially classful routing

but not VLSM. In this version no authentication is required. This version of the RIP uses

broadcast.

Routing Information Protocol RIPv2 is also a vector based protocol incorporated with

routing enhancements and is built on the foundations of the version 1. Thus it is referred to as

a hybrid protocol. RIPv2 utilizes multicasts instead of broadcasts. This form of protocol

supports triggered updates. In the situation that a change occurs, a Routing Information

Protocol RIPv2 server will immediately propagate or transmit its routing information to every

single one of its connected neighbours, which is every node within the sub network. RIPv2 as

earlier mentioned is a classless protocol but equally supports variable length sub net masking

(VLSM). This form of protocol inculcates the implementation of network mask in the update

in a bid to permitting classless routing advertisements. It uses the multicast communications

features to reduce the challenge on the network infrastructure that do not need to listen to

Routing Information Protocol updates (Malkin, 2000).

The limitations associated with Routing Information Protocol (RIP) include:

IMPORTANCE OF ROUTING PROTOCOL 7

Slow Convergence: Because the basic RIP algorithm is relatively slow, router

experience a long time to get the same information. This issue is significantly

pronounced in the event of propagation of route failures. These failures are only

detected via the expiration of the 180 seconds time out. This adds up to 3 minutes

more delay before convergence can begin.

Routing loops: RIP has no specific mechanism to detect routing loops, the best it can

do is to avoid their occurrence.

Other limitations of the RIP are counting to Infinity and Small infinity challenges.

IMPORTANCE OF ROUTING PROTOCOL 8

References

Almquist, J. (1994). Towards Requirements for IP Routers, RFC 1716. Retrieved from <

ftp://ftp.rfc-editor.org/in-notes/rfc922.txt > August 11, 2013.

Baker, F. (1995). Requirements for IP Version 4 Routers, RFC 1812 Retrieved from <

ftp://ftp.rfc-editor.org/in-notes/rfc1812.txt > August 11, 2013.

Floyd, S & Jacobson, V. (1994). The Synchronization of Periodic Routing Message. Print

Malkin, Gary Scott (2000). RIP: An Intra-Domain Routing Protocol. Addison-Wesley

Longman. ISBN 0-201-43320-6. Print.

Mogul, Jeffery. (1984). Broadcasting Internet Datagrams in the Presence of Sub Nets.

Retrieved from < ftp://ftp.rfc-editor.org/in-notes/rfc922.txt > August 11, 2013.

Postel, J. (1981). Internet Protocol, Rfc 791. Retrieved from < ftp://ftp.rfc-editor.org/in-

notes/rfc791.txt > August 11, 2013.