Advantages and Disadvantages of routing protocols.

Many of us work today on networks and most of us didn’t have a chance to work in the network design. We some time feel that what if we got the chance to work on the designing part than which protocol will you choose to implement on the network. So in this condition you have to be well prepared before choosing the correct routing protocol. Every routing protocol has its own advantages and disadvantages. There is no such best or perfect routing protocol. But depending upon the need of you organization you can select the protocol that suits yours company the most.

Here are some advantages and disadvantages of the routing protocols.

RIP V1—Routing Information Protocol
Origin: Based on RFC 1058

Type of protocol: Distance vector, based on the Bellman-Ford distance vector algorithm

Metric: Hop count

Methodology: Selects routers with the lowest hop count; updates other routers by broadcasting the entire routing table to all routers every 30 seconds

Ideal topology: Smaller networks that aren’t very dynamic, have fewer than 15 hops, and are not subnetted from classful boundaries (see Weaknesses)

Strengths:

·         Easy to configure and use

·         Since it has been around so long, it is well known and widely used.

Weaknesses:

·         Limited to a hop count of 15; after a packet travels through 15 routers and still has another router to travel to, it will be discarded.

·         Doesn’t support a variable-length subnet mask (VLSM), which means that it sends routing updates based only on a fixed-length subnet mask (FLSM) or routes that fall on classful boundaries. So RIP V1 will not work with a network that has been subnetted beyond the normal /8, /16, /24 (255.0.0.0, 255.255.0.0, 255.255.255.0) or Class A, B, and C network boundaries.

·         Converges slowly, especially on large networks

·         Doesn’t have knowledge of the bandwidth of a link

·         Doesn’t support multiple paths for the same route

·         Routing updates can require significant bandwidth, as the entire routing table is sent when a link’s status changes

·         Prone to routing loops

RIP V2—Routing Information Protocol
Origin: Based on RFC 1388

Type of protocol: Distance vector, based on the Bellman-Ford distance vector algorithm

Metric: Hop count

Methodology: Selects routers with the lowest hop count; updates other routers by multicasting the entire routing table to all routers every 30 seconds

Ideal topology: Smaller networks that aren’t very dynamic, have fewer than 15 hops

Strengths:

·         Easy to configure and use

·         Since it has also been around so long, it is well known and widely used.

·         Version 2 adds support for VSLM or Classless Internet Domain Routing (CIDR), MD5 Authentication, and route summarization.

Weaknesses:

·         Limited to a hop count of 15; after a packet travels through 15 routers and still has another router to travel to, it will be discarded.

·         Converges slowly, especially on large networks

·         Doesn’t have knowledge of the bandwidth of a link

·         Doesn’t support multiple paths for the same route

·         Routing updates can require significant bandwidth as the entire routing table is sent when a link’s status changes

·         Prone to routing loops

IGRP—Interior Gateway Routing Protocol
Origin: Based only on Cisco’s implementation, not an Internet RFC

Type of protocol: Distance vector, based on the Bellman-Ford distance vector algorithm

Metric: Delay, bandwidth, reliability, and load

Methodology: Sends hello packets every five seconds to neighbors to see if the neighbor is still available; updates other routers by notifying them only when routes change

Ideal topology: Any network, small to very large; all routers must be from Cisco. Cannot subnet network beyond classful boundaries.

Strengths:

·         Easy to configure and use

·         Uses the delay, bandwidth, reliability, and load of a link as its metric. This makes it very accurate in selecting the proper route.

Weaknesses:

·         Not an Internet standard; all routers must be from Cisco Systems

·         Converges slowly; slower than RIP

·         Doesn’t support VLSM

·         Prone to routing loops

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Definition
Convergence: The process that a routing protocol goes through to alert all routers on the network of the next available path when the primary path becomes unavailable.

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EIGRP—Enhanced Interior Gateway Routing Protocol
Origin: Based only on Cisco’s implementation, not an Internet RFC

Type of protocol: Hybrid distance vector

Metric: Delay, bandwidth, reliability, and load, using the Diffusing Update Algorithm (DUAL)

Methodology: Sends hello packets every five seconds to neighbors (can interoperate with IGRP) to see if the neighbors are still available; updates other routers by notifying them only when routes change

Ideal topology: Any network, small to very large; all routers must be Cisco

Strengths:

·         Uses DUAL to provide very quick convergence and a loop-free network

·         Supports IP and IPX

·         Requires less CPU than OSPF (see next section)

·         Requires little bandwidth for routing updates

·         Supports VLSM or CIDR

·         Uses the delay, bandwidth, reliability, and load of a link as its metric; this makes it very accurate in selecting the proper route

·         Offers backward compatibility with IGRP

Weaknesses:

·  Not an Internet standard; all routers must be from Cisco Systems
OSPF V2—Open Shortest Path First
[Note that version 1 of OSPF was never implemented.]

Origin: Based on RFC 2328

Type of protocol: Link-state, runs the Dijkstra algorithm to calculate the shortest-path first (SPF) tree

Metric: Calculates the cost to traverse router links to get to the destination, taking the bandwidth of the links into account

Methodology: Develops adjacencies with its neighbors, periodically sending hello packets to neighbors, flooding changes to neighbors when a link’s status changes, and sending “paranoia updates” to neighbors every 30 minutes of all recent link state changes

Ideal topology: Any network, small to very large

Strengths:

·         Converges quickly, compared to a distance vector protocol

·         Routing update packets are small, as the entire routing table is not sent

·         Not prone to routing loops

·         Scales very well to large networks

·         Recognizes the bandwidth of a link, taking this into account in link selection

·         Supports VLSM or CIDR

·         Supports a long list of optional features that many of the other protocols do not

Weaknesses:

·  More complex to configure and understand than a distance vector protocol
Final word
Just to clarify this comparison, one way routing protocols are classified is according to how they are used. Interior routing protocols are used within a single domain on your interior network. Also called an Interior Gateway Protocol (IGP), this is the type of routing protocol you usually think of using for your internal network. The protocols we looked at in this article are all IGPs. Note that I omitted a few of the lesser-known interior routing protocols to keep the discussion reasonably short. These include IS-IS, NLSP, RTMP, and IPX RIP.

Another type of routing protocol is an exterior routing protocol, or Exterior Gateway Protocol (EGP). These protocols maintain routing information for networks that are external to your network. An EGP doesn’t know how to deliver data within your network, just how to deliver data outside your network. While a variety of IGPs are currently used, about the only EGP in use today is the Border Gateway Protocol (BGP). This is the routing protocol of the Internet.

From talking with administrators who manage a variety of networks, the consensus is that OSPF is becoming the most popular interior routing protocol today. I would recommend OSPF or EIGRP for any new network, based on their popularity, flexibility, and fast convergence. Of course, the choice is yours based on the requirements of your network