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1、Performance Comparison of Two Dynamic Routing Protocols: RIP and OSPFABSTRACT: There are two main classes of adaptive routing protocols in the internet: distance vector and link state. This paper presents the comparison between distance vector and link state. It also outlines the pros and cons of RI
2、P and OSPF protocols and a performance analysis with some possible enhancement is presented. Network Simulator (NS2) is used to obtain the performance results of the two classes using different metrics such as throughput, packet delay and packet loss. Results of the simulation show that OSPF has a b
3、etter performance than RIP in terms of average throughput and packet delay in different network sizes, while RIP is better than OSPF in terms of number of packet loss in large networks.Keywords: Dynamic Routing Protocols, RIP, OSPF, NS21.INTRODUCTION Networks rely on routing protocols to keep the ro
4、uting tables updated. Routing is used in networks to control and forward data. For a router to be efficient and effective, the critical factor is the choice of the routing protocol. Routing protocols find a path between network nodes; if multiple paths exist for a given node then the shortest path i
5、s selected by protocol. Each protocol has a cost metric that it applies to each path. The path with lowest metric is selected by protocol. Metrics to compare one routing protocol with another are based on convergence time to adapt to topology changes, optimality is to choose the best path, not neces
6、sarily at minimum cost but to ensure a minimum delay or to minimize overhead and space requirements to store the routing table 157. The rest of paper is organized as follows: Section 2 is an overview of routing protocols. In Section 3 and 4 RIP and OSPF are discussed. We studied RIP and OSPF because
7、 this interior routing protocol is widely used in the internet. In addition the pros and cons of these routing protocols are studied in brief. In Section 5 the system model used for simulation is examined, and in Section 6 we implement routing protocols using NS2. The results of simulation show that
8、 OSPF is better than RIP in some aspects. But in other aspects RIP is revealed to be better than OSPF in Section 7. Finally we conclude the paper. 2.ROUTING PROTOCOLS There are two types of routing protocols: static or dynamic routing protocols. Dynamic routing protocols are superior over static rou
9、ting protocols because of its scalability and adaptability features.Dynamic routes are learned by communicating each router with another, when a new router is added or an old router is removed, the router learns about changes, updates its routing tables, and informs the other router about the modifi
10、cation. The classification of a routing protocol is either as an interior or exterior gateway protocol. The interior gateway protocol runs an algorithm within an Autonomous System (AS) and the exterior gateway protocol runs an algorithm outside an AS. The interior gateway protocol is classified into
11、 two groups: either distance vector (DV) or link state (LS). The distance vector selects the best routing path based on a distance metric, while link state selects the best routing path by calculating the state of each link in a path and finding the path that has the lowest total metric to reach the
12、 destination 15. The parameters used in order to evaluate the algorithms performance are: 713 . Instantaneous Packet Delay: This is the average delay of all data packets routed successfully from source to destination for a given period during an algorithm simulation. Instantaneous Throughput: This i
13、s the number of packets successfully routed for a given time during an algorithm simulation. Packet Loss: This refers to the number of packets that are lost. Different features of LS and DV protocols are presented in 146. In 14 they enhance the RIP to provide stability and reduce overhead of message
14、 updates. In 12 and 13 they enhance OSPF by using QoS. In 5 it is shown that OSPF is better than RIP in throughput, packet delay, packet loss and other aspects. 3.ROUTING INFORMATION PROTOCOL (RIP) RIP is an interior routing protocol that is based on DV routing. RIP uses hop count to calculate the b
15、est route. It is simple but has many drawbacks. RIP uses hop count as a cost metric for each link, and each link has a cost of 1. The maximum path cost is 15 so RIP is limited to use in ASs that are not larger than 15 hops. Every 30 seconds the router sends copy of the routing table to its neighbors
16、. The routing table is updated whenever the network topology is changed; each router informs its adjacent neighbors about the updating in the routing table. When the router receives an update, first it compares the new route with the current routing table, then adds a new path to the routing table a
17、nd informs its adjacent neighbors about the updating in the routing table 59.The following table summarizes the advantages and disadvantages of RIP 8 9: Table 1: Advantages and Disadvantages of RIP In 14 RIP is enhanced by using Fast Selfhealing Distance Vector Protocol (FS-DVP), FS-DVP suppresses i
18、ts failure notification to provide better stability and reduce the overhead of message updates. In FS-DVP, each node generates a backup node set, for each destination, pre-computes the backup next hop and stores them. If the link has failed, the packet selects the next hop from the backup set. FS-DV
19、P thus eliminates the delay due to re-computation and reroutes packets without any interruption in the presence of link failures. To save bandwidth resources and balance the load in the network, FS-DVP uses a suppression-failure technique to handle link failure, so when a link fails, an adjacent nod
20、e suppresses the update message and sets a timer for a suppression interval, but other nodes are not explicitly notified of the failure. When router R1 detects that router R2 is unreachable, R1 starts a timer, the timer must be less than 60 seconds, if R1 receives a route from R2 before the timer ex
21、pires, the link recovers so that the suppression is successful and no notification is propagated for this failure, otherwise a failure is propagated at the end of suppression interval and new routing tables are computed. FS-DVP is applied on RIP and called FS-RIP. In FS-RIP 99.8756% of packets reach
22、 their destination successfully while in OSPF, 50% of packets reach their destination successfully. FS-RIP has fewer packets dropped than OSPF. 4. OPEN SHORTEST PATH FIRST (OSPF) OSPF is an interior routing protocol that is based on link state routing. OSPF is faster than RIP but is complex. RIP kee
23、ps track of the closest router for each destination, while OSPF keeps track of the complete topology of all connections in the local network 5. In OSPF each node broadcasts the link-cost information about its adjacent links to all other nodes in the network. Each node has a complete view of the netw
24、ork using link-cost information from other nodes. It applies Dijkstras shortest path algorithm to get the shortest route to all nodes in the network. A node broadcasts link-cost information whenever the links state is changed. Every 30 seconds it also broadcasts link-cost information. 1 The followin
25、g table summarizes the advantages and disadvantages of OSPF 8 9: Table 2: Advantages and Disadvantages of OSPF OSPFs cost metric is cost given by the administrator. The cost reflects monetary cost and is a static value. The cost metric can be either bandwidth or link delay. In 13 the cost metric of
26、OSPF is based on bandwidth. Cost is inversely proportional to bandwidth. The higher bandwidth means a lower cost (cost = 108 /bandwidth in bps). In 12 OSPF is extended to use a link delay as QoS metric in order to compute routes. When packets are routed based on the shortest static cost route, this
27、may increase the links delay. In the delay-based routing algorithm, the link delay is the sum of the link propagation delay and its mean queuing delay over the sampling interval of the link. The delay algorithm uses threshold and incremental factors in order to return to the computation algorithm. T
28、he threshold and incremental factors are tuned to improve the stability of flow of traffic with an acceptable trade off of delay. The cost metric based on bandwidth or delay is suitable for its use in multimedia and E-commerce. 5.SIMULATION SYSTEM DESIGN MODEL A network consists of senders and recei
29、vers. The sender sends packets to the receiver by passing intermediate nodes. To choose the path from the source to the destination, the source runs a routing protocol such as DV or LS. The network simulation model has the following characteristic: This model uses a connectionless oriented UDP proto
30、col and constant data rate. Also this model uses a connection oriented TCP protocol and FTP. There are several parameters to evaluate network performance such as throughput, delay and packet loss. 6. SIMULATION The environment of the simulation experiments was Ubuntu 10 and NS-2.34. In order to anal
31、yze data results, the tools AWK and gnuplot were used. We used three different sizes of networks. The smallest network had five nodes and five links. Node0 sent a UDP protocol with constant packet rate to node3. A TCP protocol was used to send FTP from node0 to node3. Node0 connected to node1, node1
32、 to node3, node3 to node4, node3 to node4, node4 to node2, and node2 to node0. Connection from node0 to node1 and connection from node1 to node3 had a bandwidth of 1 Mbps and delay of 5 ms but other connections had a bandwidth of 2 Mbps and delay of 2 ms. The Network Simulator-2 (NS2) has an impleme
33、ntation of the OSPF protocol with static cost is called Link State Routing. Also it has an implementation of the RIP is called Distance Vector. The simulation study was done under Network Simulator (NS2). We first built the network with RIP as the routing protocol and then used the same model with O
34、SPF to evaluate and analyze the results. In 13 they used bandwidth as metric, in our experimental we used the same metric.The connection from node0 to node1 and the connection from node1 to node3 have a cost of 100 while other connections have a cost of 50. To calculate packet loss we downlinked and
35、 uplinked the connection between node0 and node1 in DV, and repeated this between node0 and node2 in LS. The topology is indicated in Figure 1. The same experiment was repeated with a larger network by using 11 nodes and 21 nodes.7. CONCLUSION In this paper, we have introduced a quantitative compara
36、tive study for link state and distance vector routing algorithms in different network settings. We can conclude that OSPF outperforms RIP in terms of average throughput and instant packet delay in different sizes of network. In terms of number of packets lost, OSPF is better compared to RIP in small
37、 networks but RIP is better in large networks. OSPF is better than RIP for many reasons: OSPF uses either bandwidth or delay as metric for shortest path and it does not use the number of hops as in RIP. OSPF can adjust the link and OSPF coverage network more quickly than RIP, but if RIP is enhanced
38、by using FS-RIP, then RIP offers a better performance than OSPF. The work can be extended to other dynamic routing protocols and implemented by NS2. It can also be extended to evaluate other routing protocol criteria such as CPU utilization, jitter, and ability to provide Quality of Service (QoS).RE
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44、 8 HP, “Overview,” Online. Available: 9 H. Pun, “Convergence Behavior of RIP and OSPF Network Protocols,” 2001, Online. Available: http:/www.ensc.sfu.ca/ljilja/cnl/pdf/hubert.pdf 10 “The Network Simulator NS-2: Documentation,” Online. Available: http:/www.isi.edu/nsnam/ns/nsdocumentation.html 11C. H
45、. Hon, N. H. James, “Path Recovery Performances of Routing Protocols,” Online. Available: 12C. Y. Yong, T. Michalareas, Dr. L. Sacks, “Network Stability with Delay Minimisation in a QoS based OSPF Network,” Online. Available: www.ee.ucl.ac.uk/lcs/previous/LCS2001/LCS058.pdf 两种动态路由协议的性能比较：RIP和OSPF摘要：
46、自适应路由在互联网协议有两个主要的类别：距离向量和链路状态。本文介绍比较了距离向量和链路状态。它还概述了RIP和OSPF协议的优缺点和一些可能的增强性能分析。网络仿真器（NS2）是用来获得两种使用不同的度量如吞吐量性能结果，数据包的延迟和丢包。仿真结果表明，OSPF协议比RIP中的平均吞吐量和数据包在不同大小的网络延迟具有更好的性能，而RIP在大型网络丢包数目比OSPF多。关键词：动态路由协议RIP，OSPF，NS21、简介 依靠网络路由协议的路由表更新保持，路由是网络中使用的控制和数据转发。一个路由器是有效的还是无效的，关键是选择的路由协议。路由协议发现网络节点之间的路径，如果对于一个给定的
47、节点，然后选择的最短路径的协议存在多条路径。每一个协议都有一个成本指标，它适用于每个路径。以最低的度量的路径选择协议。比较一个路由协议的另一个指标是基于收敛时间适应拓扑结构的变化，选择最优的路径，以最低的成本，但不一定保证最低的延迟或减少开销和空间来存储路由表 1 5 7。本文的其余部分安排如下：第2节是路由协议综述。在3节和4节对 RIP和OSPF进行了讨论。我们研究RIP和OSPF原因是内部路由协议是在互联网上广泛使用的。此外，这些路由协议的优点和缺点进行了简要的比较。在5节中用于仿真系统模型的研究，并在6节中我们使用NS2路由协议。仿真结果表明，OSPF比RIP在某些方面好，但在另一方面
48、，RIP是显示比OSPF更好。最后我们得出结论。2、 路由协议 有两种类型的路由协议：静态或动态路由协议。动态路由协议是优于静态路由协议在于其可扩展性和适应性强的特点。动态路由与另一通信的每个路由器有关系，当一个新的路由器添加或删除旧的路由器，路由器发生变化，更新其路由表，并通知修改其他有关路由器。一个路由协议的分类，通常是内部或外部网关协议。内部网关协议外部网关协议运行一个算法在一个自治系统（AS）。内部网关协议分为两组：距离向量（DV）或链路状态（LS）。距离矢量在选择最佳路由路径的距离度量的基础上，在链路状态选择最佳的路由路径，通过计算状态的每一个环节中的路径和发现的路径，具有最低的总度量达到目的地 1 5 。要使用的参数来评价算法的性能是： 7 13 。 瞬时数据包延迟：这是所有的数据包发送成功的从源到目的地的一段期间的平均延迟算法仿真