Characterizing Routing Protocols and Scalability
|Characterizing Routing Protocols.
Some of the most important characteristics of routing protocols have been
copied from Teare and follow.
Routed Protocols Supported. A specific protocol can typically be used only with one routed protocol. The following table displays the routing protocols available with the three most popular routed protocols.
|Routed Protocol||Routing Protocol|
|IP||IP RIP, IGRP, OSPF, IS-IS, EIGRP|
|IPX||IPX, RIP, NLSP, EIGRP|
|AppleTalk||RTMP, AURP, EIGRP|
|Categories of Routing Protocols. As stated in the last web page there are three main categories for routing protocols, distance vector, link state and hybrid. The following table displays the categorizations for the main routing protocols.|
|Distance Vector||IP RIP, IGRP, IPX RIP, RTMP|
|Link State||OSPF, NLSP, IS-IS|
|Interior and Exterior
Routing Protocols. Different routing protocols are
often typically used either inside autonomous systems or between
Interior routing protocols, such as RIP, IGRP and EIGRP, are used by routers within the same autonomous system. Exterior routing protocols, such as BGP - Border Gateway Protocol, are used between autonomous systems.
Interior routing protocols are designed to find the best path through the network. Although exterior routing protocols also find the best path through the network, they provide additional functionality.
Small to medium sized businesses usually use only interior routing protocols. The businesses then rely on an ISP to connect them to the larger internet.
Bandwidth Overhead. Distance vector protocols, being periodic in nature, use a defined amount of bandwidth for sending their routing updates. Teare's book has a table that characterizes the bandwidth used by a variety of routing protocols.
Administrative Distance. It is probably easiest to think of administrative distance as a numeric measure of the trustworthiness of routes and routing information. In some network designs, more than one routing protocol is configured. Teare's book also has a table illustrating typical administrative distance measures for different sorts of router interactions.
Information Exchanged by Peers. The major types of information is exchanged in different routing protocols is in the bulleted list below.
Scalability Issues. The scalability constraints for routing protocols can be characterized by the following list.
Some protocols have metric limitations that make them incompatible with large networks. Some of the standard metric limitations are in the following table.
Maximum Hop Count
|Link state protocols do not have metric
Routing protocol convergence occurs when routers arrive at consistent understandings of the network topology after a change takes place. The time to convergence depends primarily on the following factors.
In general, EIGRP and the link state protocols converge more quickly than distance vector protocols.
Resource requirements include such things as CPU, memory and bandwidth in routers and the networks they run on. The resource requirements depend on many factors including the following.