Internet Protocol Routing Experiments

Introduction:

U.S. government agencies realised the importance and potential of Internet technology many years ago, and have funded research that has made possible a global Internet. Officially named the TCP/IP Internet Protocol Suite and commonly referred to as TCP/IP, it can be used to communicate across any set of interconnected networks. These networks function via Routers. Interior Gateway Protocol (IGP) is a generic description that refers to an algorithm that interior routers use when the exchange network reachability and routing information. One of the most widely used IGP's is the Routing Information Protocol (RIP). The underlying RIP protocol is a straightforward implementation of distance-vector routing for local networks. OSPF (Open Shortest Path First) is a new protocol that tackles several goals. It is a link-state algorithm which uses SPF to compute shortest paths, and also scales better than a distance-vector algorithm. In this report, I will put these Internetworking techniques into motion by conducting a routing experiment.

In this operation, I will familiarise myself with the performance of RIP and OSPF routing protocols. This will involve having access to an 8 testbed network, which I will configure and execute simultaneously in the network, as rendered in the experiment sheet. The first section of the report consists of six parts that experiment on various methods such as 'Examining Failure and Reconvergence with Rip' and 'Examining Failure and Reconvergence with OSPF' [1]. My report is also experimenting on the effects of 'OSPF Parameter Negotiation and Cost Setting' and 'RIP / OSPF Route Injection' [1]. The 8 PC's that will be used to conduct this experiment run the Zebra routing software. Each of the nodes contains four 100BaseT Fast Ethernet interfaces, labelled ste0, ste1, ste2 and ste3. The experimentation will be undertaken on the computers via cabled Ethernet switches. The Ethernet Switches allow the interconnection topology to be changed under software control. I will demonstrate the software in motion within this report.

The last section of this experiment will be a mini-essay that will describe the functions between RIP and OSPF. Discussions of mechanisms that can be used to improve the reconvergence time of IGP's will be discoursed. Further details of this will be mentioned in Part 7 of the report. This will include and initially cover the Background Theory of the report, so it is only briefly mentioned here. The ELE403 Lab sheets also cover Background aspects.

The objectives that I intend to achieve upon commencing this report is to find the protocol's of the host/client machines to which data is being sent, and to verify if it can be sent under certain circumstances. I also intend to find the successive time delays between messages that are sent from source to destination via a router. Hop counts between the networks are also going to be recorded. Once all the experimentations have been undertaken, I will explain in report format the findings and results, and will then draw a conclusion that will set out the problem and resolve the project specification in greater detail.

Background:

The Routing Information Protocol (RIP) is one of the most bearing protocols of all the routing protocols. RIP is one of the higher obscured protocols due to the fact that a variety of similar routing protocols manifolded, some of which that even used the same name.

The RIP and the uncounted 'RIP-like' protocols were established on the same set of algorithms that use distance vectors to mathematically equate routes to distinguish the best path to any given destination address. Pedantic research that dates as far back as 1957 was known for recognising these algorithms.

A router running RIP in active mode broadcasts a routing update message every 30 seconds. The update contains information that is taken from the routers current routing database. Each update consists of a set of pairs, where each pair consists of an IP network address and an integer distance to that network. The RIP uses a 'hop count metric' to measure distances. In the RIP metric, a router is defined to be one hop from a directly connected network, 2 hops from a network that is reachable through one other router. But other routing protocols define a direct connection to be 0 hops. The hop count along a path from source to destination refers to the number of routers that a datagram encounters along that path.

Open Shortest Path First (OSPF) is another routing protocol that was formulated for Internet Protocol (IP) networks by the Interior Gateway Protocol working group of the Internet Engineering Task Force (IETF). 1988 was the year that the working group was formed and they had designed an IGP based on the Shortest Path First (SPF) algorithm for use in the Internet. Like the Interior Gateway Routing Protocol (IGRP), OSPF was created primarily due to the fact that in the central 1980s, the Routing Information Protocol was increasingly incapable of assisting large, heterogeneous internet works. This chapter analyses the OSPF routing environment, underlying fundamental routing algorithms, and general protocol elements. [2]

OSPF is capable of many services. This includes 'type of service routing'. Users can install multiple routes to a given destination, one for each priority or type of service. When routing a datagram, a router running OSPF uses both the destination address and type of service field in an IP Header to choose a route. OSPF is among the first TCP/IP protocols to offer type of service routing. The OSPF protocol specifies that all exchanges between routers can be authenticated. OSPF allows a variety of authentication schemes, and even allows one area to choose a different scheme than another area.

To permit growth and make the networks at a site simpler to manage, OSPF allows a site to partition its networks and routers into subsets called 'areas'. Each area is self-contained that means an areas topology is usually hidden from other areas. Thus, multiple groups within a given site can cooperate in the use of OSPF for routing even though every group retains the ability to change its internal network topology independently. But OSPF allows routers to exchange routing information learned from other external sites. In simpler terms, one or more routers with connections to other sites learn information about those sites and include it when sending update messages.

As a link-state routing protocol, OSPF demarcates with RIP and IGRP, which are distance-vector routing protocols. Routers that are executing the distance-vector algorithm send all or a part of their routing tables