A Survey on Routing Issues and Associated Protocols for Best-effort Delivery in IP Networks

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Volume 119 No. 12 2018, 707-716 ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu ijpam.

1 Volume 119 No , ISSN: (on-line version) url: ijpam.eu A Survey on Routing Issues and Associated Protocols for Best-effort Delivery in IP Networks MajidhaFathima K M Assistant Professor, Sri Krishna College of Engineering and Technology Coimbatore,Tamilnadu India Abstract When a user browses the internet, the request is sent as data and is transformed in the form of packets at the network layer. The data is processed in all the seven layers of OSI (application, presentation, session, transport, network, data link, physical). It is added with headers at all layers i.e encapsulated at the sender and the headers are removed layer by layer i.edecapsulated at the receiver end. This paper focuses on the network layer which does the job of routing. Routing process comprises of delivering a packet from the source to the destination through the best path provided by the routing protocols. This is done by the devices used for WAN (Wide Area Network) connectivity named routers. The routing protocols are classified into exterior routing protocols and interior routing protocols. The interior routing protocols aredistance Vector Routing Protocols namely RIPv1, RIPv2, IGRP, EIGRP and Link-State Routing Protocols namely OSPF and IS-IS. BGP is the example of Path-Vector Routing Protocol. These protocols are used for the core backbone routers. Keywords: Routing Information Protocol (RIP), Border Gateway Protocol (BGP), Open Shortest Path First (OSPF), metrics 1.Introduction 707

2 The packet travelling across the internet has various paths as listed by several routing protocols. The best path is decided by the metrics defined. The metrics (measurable parameters) vary depending on the choice of routing protocols. Routing Information Protocol (RIP) uses hop count as the metric. Hop count is defined as the number of devices in between the source and the destination. The devices may be switches, routers or firewalls. Open Shortest Path First (OSPF) uses cost as the metric. The formula for calculating cost is o Cost = (10^8)/bandwidth Interior Gateway Routing Protocol calculates metric as o Metric = Bandwidth + Delay Intermediate System to Intermediate System (IS IS) uses cost as metric which arbitrarily varies from 1 to 63 Border Gateway Protocol (BGP) uses composite metric as AS (Autonomous System) and med values In addition to metrics, static routes may also be configured on the routers. They are written with higher metric; the reason being if any of the routing protocols fail,the static route is chosen. The metric with lowest value has high priority over other routes. The classification of routing protocols is shown in the figure 1. Dynamic Routing Protocols Interior Gateway Protocols (IGPs) Exterior Gateway Protocols (EGPs) Distance Vector Routing Protocols Link-State Routing Protocols Path-Vector Routing Protocol RIPv1 IGRP OSPF IS-IS BGP 708

3 RIPv2 EIGRP Figure 1. Classification of dynamic routing protocols The routing protocols construct routing tables which show the path and the intermediate hops from the source to the destination. The router s routing table is shown in figure / /24 PC1.10 G0/ /30.10 PC2 G0/ S0/0/ / /24.10 D /24 [90/ ] Via :00:05 Serial0/0/0 Figure 2. End to end delivery of packets The structure of a packet consists of destination network, administrative distance, next hop ip, time elapsed and the exit interface. Through advertisement, the route to the the destination network reaches the source. The contents of the routing table entries are depicted in table 1. Table 1. Discovery of routes from source to destination D Identifies how the network was learned by the router /24 Identifies the destination network [90/] Identifies the administrative distance (trustworthiness) of the route source Identifies the metric to reach the remote network Identifies the next hop ip address to reach the remote network 709

4 00:00:05 Identifies the amount of elapsed time since the network was discovered Serial0/0/0 Identifies the outgoing interface on the router to reach the destination network 2. Literature Survey The customized routing protocols which form an overlay routing layer are analysed as shown in table 2 Table 2. Related systems of overlay routing Approaches Topology Infrastructure Topology Methods Navigation Cost Information VMesh [2] Index overlay Less Global View Popularity based segment storage BulletMedia [4] Distributed hash table Less Partial View Structured DHT Overlay Kangaroo [1] Link hops, High Partial View Gossip transfer rate protocol PPLive [3] Latency (distributed) Centralized tracker Partial View Neighbour selection BitTorrent [5] Latency, AS Less Global view Tit-for-tat hops In addition to the traditional routes provided by the routing protocols, there are overlay routes which take the alternative path. This happens in case of heavy bandwidth consuming applications such as video streaming. As shown in table 2, VMesh maintains an index table to find the next hop in the network. BulletMedia uses a hashing mechanism. Kangaroo, as the name implies calculates the number of hops inbetween and chooses the nearest hop. PPLive calculates the total latency in reaching a peer. BitTorrent,in addition takes into account the number of AS involved between peer networks, Hence it has a global routing table. The cost of building the infrastructure is high for Kangaroo as it takes into account the transfer rate. 3. Architecture of Routing 710

The hubs and repeaters are devices which function at physical layer, layer 1 of OSI (Open Systems Interconnection). The switches and bridges belong to datalink layer, layer 2 of OSI.

5 The hubs and repeaters are devices which function at physical layer, layer 1 of OSI (Open Systems Interconnection). The switches and bridges belong to datalink layer, layer 2 of OSI. Routers operate at network layer, layer 3 of OSI. Figure 3. Architecture of routing As shown in the figure 3, the ISPs (Internet Service Provider) are identified by their corresponding Autonomous System (AS) numbers. The user connects to the Customer Premises Equipment (CPE) i.e the router. The traffic is forwarded to the edge router which redirects to the edge router of another Autonomous System. The routes are learnt via the routing protocols. RIP,OSPF,EIGRP,IS IS are the routing protocols configured on routers within Autonomous Systems. Hence they are called interior routing protocols. BGP,the protocol of the internet is configured on the gateway routers of the AS. It is so called the exterior routing protocol. While trying to fetch a content, the router takes it from its own cache. If its unavailable in the cache,it can take the content from its edge router. If its unavailable, the edge router may take it from the proxy server maintained at the edge of the ISPs network. It can also extract the content from the neighboring peer router as the last chance. The network addresses are denoted as /8 711

which belongs to class A address. It is identified from the fact that the first octet falls in the range as 1 126 Class A 128 191 Class B 192 223 Class C 3.

6 which belongs to class A address. It is identified from the fact that the first octet falls in the range as Class A Class B Class C 3.1 Open Shortest Path First (OSPF) Figure 4 Shortest path calculation in OSPF The intranet cloud is formed by the grouping of routers by enabling OSPF in them. As shown in figure 4, the new routers enter the network. They participate in the OSPF DR(Designated Router) and BDR(Backup Designated Router) election. They initiate communication by exchanging the HELLO packets. The routing updates are exchanged as LSAs (Link State Advertisements). The best path is chosen as the one with the lowest cost calculated as (10^8)/bandwidth. The OSPF routes in a routing table are shown in figure 5. The commands for enabling OSPF in a router is 1. enable 2. configureterminal 3. routerospfprocess-id 4. networkip-addresswildcard-maskareaarea-id 5. end Device> enable Device# configure terminal 712

Device(config)# router ospf 109 Device(config-router)# network 192.168.129.16 0.0.0.3 area 20 Device(config-router)# end Figure 5. OSPF routes 3.

7 Device(config)# router ospf 109 Device(config-router)# network area 20 Device(config-router)# end Figure 5. OSPF routes 3.2 Border Gateway Protocol (BGP) The BGP can be configured on a router while exchanging customer routes and AS routes. The BGP routes in a routing table are shown in figure

Figure 6. BGP routes The path attribute in the routing table refers to the number of AS it has travelled before reaching the corresponding destination.

8 Figure 6. BGP routes The path attribute in the routing table refers to the number of AS it has travelled before reaching the corresponding destination. To enable BGP in a network, the following commands are used switch(config)# router bgp switch(config-router)# vrfvrf_a switch(config-router-vrf)# BGP supports Virtual Routing and Forwarding (VRF). If VRFs are used in the network,it can be configured with BGP. The external routes received from other ISPs at the gateway routers are redistributed into the interior network of an ISP. Then OSPF is used for internal routing within an AS. The routing table is built based on the advertisements and shortest path is chosen based on metrics. 4. Conclusion The various routing protocols are compared and their exclusive features are identified in this paper. The results of the command execution are shown in the routing table. There are certain metrics which decide the best effort delivery provided by IP routing protocol. The end to end delivery of packets is taken care by both the routed protocols like IP and routing protocols like OSPF and BGP. The BGP routes received by the gateway routers are injected inside an AS and advertised to the interior of the ISPs network. 714

9 5. Future Work The routing protocols OSPF and BGP which function at layer 3 of OSI also have certain enhancements. They are used for the advertisement and exchange of core routes and customer routes respectively. They can also be enhanced to be employed in MANETS (Mobile Adhoc Networks). References [1] Ma KJ, A survey of schemes for Internet-based video delivery, Journal of Network and Computer Applications,2011. [2] Zhang W, An overlay multicast protocol for live streaming and delayguaranteed interactive media, Journal of Network and Computer Applications,2011. [3] Yun-Shuai Yu, Ce-KuenShieh, Chun-Hsiang Lin, Szu-Yu Wang, A playback offset aware multicast tree for on-demand video streaming with VCR functions, Journal of Systems Architecture, vol.57, pp ,2011. [4] Ana Paula Couto da Silva, Emilio Leonardi, Marco Mellia, and MichelaMeo, Chunk distribution in mesh-based large-scale P2P streaming systems: A fluid approach, IEEETransactions on Parallel and Distributed Systems,Vol.22, No.3, March [5] Y.He, I.Lee, and L.Guan, Distributed throughput maximization in P2P VoD applications, IEEE Transaction Multimedia, vol.11, no.3, pp , Apr [6] Xiaodong Lu, Ookayama, Meguro, Kinji Mori, "Autonomous demand-oriented streaming system architecture and fault-tolerant technology for service continuity", International Journal of Critical Computer-Based Systems archive,volume 2 Issue 1, March [7] Brinkman, Rickson, "A survey of QoE assurance in converged networks", Computer Networks: The International Journal of Computer and Telecommunications Networking archive, Volume 55 Issue 7, May, [8] html#wp [9] MukulGoyal,K. K. Ramakrishnan, Wu-chi Feng, "Achieving Faster Failure Detection in OSPF Networks", Citeseer. 715

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BTEC Level 3 Extended Diploma

BTEC Level 3 Extended Diploma Unit 9 Computer Network Routing and Routing Protocols BTEC Level 3 Extended Diploma Introduction to Routing Routing is the process that a router uses to forward packets toward