Data Network

Published Date: 02 Nov 2017

The Data network size can range from small, medium, large to global internetworks. Medium and large networks use dynamic routing protocols to ease operational and administrative overhead. Normally, dynamic routing protocols and static routes are both used in networks. Mostly only one dynamic routing protocol is used within a network but in some cases combination of different routing protocols can be used in different parts of the network. The reasons for running multiple routing protocols on a network include migrating from one routing protocol to another, want to use a new protocol while maintaining the current one, merging departments or divisions or entire companies or internetworks that were designed with different interior gateway protocols and multi-vendor environments. It is often a part of a network design to run different routing protocols. For example if one company is running OSPF and the other company is running ISIS and if these companies merge their networks then combination of OSPF and ISIS is used. All the routing protocols have the same purpose so it should be known which routing protocol is a good choice for a particular environment. Network requirements are rapidly changing and organizations are always looking towards better network performance. Modern networks use routing protocols such as Open shortest path first (OSPF), Enhanced interior gateway routing protocol (EIGRP) and Intermediate system to Intermediate system (ISIS) for dynamic routing.

VOIP can play an important role in reducing infrastructure and communication cost. It is flexible and brings new challenges for service providers and public switched telephone networks. The common approach to support VOIP service is the best effort network. VOIP requires an efficient real-time data delivery. Best effort networks depend on Interior Gateway Protocols (IGPs) for choosing paths to route packets between hosts. IGP are used within an autonomous system that consists of network devices under a single administrative control sharing a common routing strategy. Architects for best effort networks provide services by over-provisioning the links and routes so that network congestion does not introduce unwanted levels of latency, jitter and packet loss [VoIP]. The re-convergence of the network is detrimental to VOIP users especially in the on-going conversation. It impacts both latency and jitter. The two most important operation of routing protocols are routing tables and distribution of knowledge. Different sets of knowledge will be used by different protocols and different information will be stored in the routing tables of different protocols but they are almost the same thing. Routing tables contain information that is used by the router to locate other networks. These include next router information or destination network or information about connected interfaces. The requirements of RAM and CPU power increases with the complexity of routing tables and this factor depends on the speed of the network. The routers become aware of each other by the way of distributing knowledge and the data and its size used for sharing knowledge vary from protocol to protocol. Some use regular updates for maintaining neighboring relationship and some exchange information only when there is a change in the topology.

The motivation of the project is to study and analyze the performance and comparison of OSPF/ISIS and EIGRP/ISIS on the same network and there affect on VOIP performance. These types of scenarios are in used in the real world and will help to apply the project results in such cases.

Problem Description

There are two main points in the problem description.

1. Analysis and comparison of the combination of OSPF/ISIS and EIGRP/ISIS routing protocols on the same network.

2. VOIP performance over these combinations of protocols.

Three routing protocols OSPF, ISIS and EIGRP are mainly used in interior networks. Since OSPF is more scalable than others, it is more widely used routing protocol. Link state protocols i.e. OSPF and ISIS are complicated to setup on a network. In larger networks, OSPF and ISIS are preferred because they are scalable. On the other hand, EIGRP is a hybrid routing protocol and is easy to setup on a network. Its convergence time is faster than OSPF and ISIS. It is a cisco proprietary protocol i.e. it can only be used in Cisco products. The average arrival time of routing update packets in OSPF is 2-10 times longer than in ISIS [ospf vs isis]. If a topological change occurs at any point in a network, all the other routers should know about the change as soon as possible. This depends on the speed of convergence. Route convergence time of EIGRP is faster than all the other protocols.

Network performance is degraded due to link failures, routing instabilities and network congestion [link failure VoIP]. Routing changes mostly cause most of the disruptions. Voice and video is easily disrupted by a few hundred milliseconds of disruption. Data packets are delayed, dropped and reach out-of-order at destination during routing protocol convergence thus degrading network performance. Route re-convergence can have a great impact on both latency and jitter especially to VOIP users.

To utilize network resources more efficiently, different routing protocols and their combinations must be analyzed. Routing protocol plays an important role in speeding up a network and depends on several factors such as convergence time, link throughput and application layer service performance. The most important factor is the convergence time that affects routing protocol performance. Another factor is the link failure. In [link failure voip], it is found that to provide better protection against link failure, new protocols must be introduced and no specific handling of voice packets i.e QOS differentiation is needed. Delay, jitter, packet loss and mean opinion score are the metrics for VOIP performance [VOIP performance]. The delay must be kept less than 150ms in VOIP network for real-time conversation [VOIP performance] and voice jitter must be less than 30ms[VOIP performance]. Packets loss should be less than 1%. Minimum opinion score should be maintained at level 3 for acceptable performance.

The objective is to analyze the network performance using the combination of protocols. It will help in analyzing the advantage of using OSPF and ISIS together or OSPF alone or ISIS alone and similarly using EIGRP and ISIS together or using EIGRP alone or ISIS alone. The objective is to run OSPF and ISIS on a selected topology and then use EIGRP and ISIS on the same topology and analyze the network performance improvement. The research questions are:

1. What will be the performance improvement by running multiple protocols (OSPF with ISIS and EIGRP with ISIS) on a network?

2. Study how combination of protocols such as OSPF/ISIS and EIGRP/ISIS will affect VOIP performance?

Current status and developments of Research or Technology

Literature or Technology Survey and Analysis

To compare the different combination of protocols, different parameters must be analyzed. Convergence time is one of the most important parameter and it depends on the configured timers of the protocol and network design. Other parameters include link throughput and application layer service performance. The comparison between OSPF and ISIS [6] shows that both are appropriate for large networks. OSPF is more appropriate for networks with heterogeneous bandwidth whereas IS-IS is more appropriate for networks with high bandwidths, 64kbps or more [6]. Slow links can cause IS-IS to have some congestion and its convergence time is also affected [6]. IS-IS surpasses OSPF in the longest and average arrival times of LSU packets and in the fraction of transmission time performance measures [1]. OSPF outperforms IS-IS in the number of memory accesses of a router [1]. OSPF outperforms IS-IS for small networks around 10 routers and IS-IS outperform OSPF for large networks [1]. Simulation will be carried out in OPNET to examine how VOIP can affect through different routing behaviours.