FASTEST METHOD TO FIND ALTERNATIVE RE-ROUTE

Routing is the concept of sending the packets from the source to destination through the certain paths.
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INTERNATIONAL JOURNAL OF RESEARCH IN COMPUTER APPLICATIONS AND ROBOTICS www.ijrcar.com

Vol.2 Issue.12, Pg.: 41-47

December 2014

INTERNATIONAL JOURNAL OF RESEARCH IN COMPUTER APPLICATIONS AND ROBOTICS ISSN 2320-7345

FASTEST METHOD TO FIND ALTERNATIVE RE-ROUTE 1

M.JothiLakshmi, M.Sc., M.Phil. 2C.Theebendra, M.Sc., M.Phil. 3M.K.Pavithra, 4S.Yuvabarathi Asst. Professor1+2, Research scholar3+4, Department of Computer Science, Vivekanandha College Of Arts & Sciences For Women (Autonomous), Elayampalayam, TamilNadu, India1+2+3+4.

Abstract Routing is the concept of sending the packets from the source to destination through the certain paths. In some cases before the Interior Gateway Protocol (IGP) there may be a link failure between the source and destination. To reach the target the regional sub network service provider encountered to find a new path which already exists. Certainly multicast nodes are involved and spare links are used. In our scheme Ring Topology are used to overcome the single path failure. We illustrate the method and prove that it will find a path if one exists.

Keywords: Ring Topology, Routing Protocols, Alternate Routing, Interior Gateway Protocol, Node Failure. 1. INTRODUCTION A Routing Protocol select route between two nodes on a computer network. Each router has a priori knowledge about the networks attached to it directly. A routing protocol shares this information first among immediate neighbours, and then throughout the network. This way, routers gain knowledge topology of the network. Consider a source node s sending data to destination node d .Suppose some link (i, j) on the shortest path from s to d fails. An IGP will find an alternate path from s to d that avoids (i,j). To overcome this we implementing Ring Topology network in which each node connected with to other nodes to provide continuous path between source and destination. If any one of a node is failure or break, the alternative route or multipath can be introduced. The source-specific multicast is the simplest model for multicast where source node is fixed and the receivers will never send data to the multicast. Any failed link in the path will disrupt the service to some nodes. The number of nodes affected could be very large especially when the failure is at the proximity of the root node. The standard solution is to reconstruct the multicast node after a link failure is detected. The fast reroute restores the multicast node without route re-convergence and therefore, shortened the disruption. This scheme pre installs another set of routes on each multicast routers.

2. BODY TEXT 2.1. Failure recovery Techniques developed for fast recovery from single-link failures provide more than one forwarding edge to route a packet to a destination. Whenever the default forwarding edge fails or a packet is received from the node

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Vol.2 Issue.12, Pg.: 41-47

December 2014

attached to the default forwarding edge for the destination, the packets are rerouted on the backup ports. In the authors present a framework for IP fast reroute detailing three candidate solutions for IP fast reroute that have all gained considerable attention. When a forwarding link on a tree fails, the packet may be switched to the other node. Types of failure: i)

Link Failure

a

c b

Figure 1: Link Failure ii) Node Failure

a

c b

Figure 2: Node Failure

2.1. Fast re-route method We now present the details of the method. Let G = (N,A) be an undirected connected graph with node set N and arc set A. For x ∈ N, let N(x) be the set of neighbors of x, where a neighbour of x is a node one arc away from x. We associate with each undirected arc (i, j) ∈ A a cost c(i, j), and require each c(i, j) to be a positive integer. (The integer valued restriction can always be met by approximating, to the desired accuracy, each arc cost by an improper fraction, and then multiplying all the fractions by the least common multiple of the fraction denominators.) For i, j ∈ N, let c_(i, j) be the cost of the shortest path in G between i and j. When using Route(s, d) for fast re-route in the event of an arc failure, which is the target application, c_(i, j) represents the shortest path cost before the IGP has re-converged in response to the link failure.

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Vol.2 Issue.12, Pg.: 41-47

December 2014

a

f

b

e

c d

Figure 3: Fast Reroute Source: a, Destination: b, Failed Path: ab, Re Route Path: ad.

2.3. Multipath routing Multipath routing is a promising routing scheme to accommodate these requirements by using multiple pairs of routes between a source and a destination. Multipath routing is the routing technique of using multiple alternative paths through a network, which can yield a variety of benefits such as increased bandwidth, or improved security. The multiple paths computed might be overlapped, edge-disjointed or node-disjointed with each other. Extensive research has been done on multipath routing techniques.

a

c

d b e

g

f

Figure 4: Multipath Routing Source: a, Destination: g, Failed Path: bg. Multipath: 1st path is a-b-e-f-g 2nd path is a-c-d-e-f-g.

2.4. Method Procedure Route(s, d) 1 initialize: P = 0, Δ(n) = 0 for n ∈ N, and x = s;

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INTERNATIONAL JOURNAL OF RESEARCH IN COMPUTER APPLICATIONS AND ROBOTICS www.ijrcar.com

Vol.2 Issue.12, Pg.: 41-47

December 2014

2 while (x _= d) { 3 Let Y = {y ∈ N(x) | Δ(y) = min n∈ N(x)Δ(n)}; 4 Pick any y ∈ Y for which the sum C (x, y) + c*(y, d) is smallest; 5 Set Δ(x) ← Δ(x) + 1, P ← {P, x}, and send the packet and P from x to y; 6 Set x ← y; 7}

Explanation: Let s and d be the source and destination which is connected to directed graph with node N. If x ∈ N then x is a node away from arc (i, j). The arc should be positive integer. If i, j ∈ N then cost is c*(i, j) be the shortest path. If the route s, d is used for fast re-route in arc failure the target application, c*(i, j) represents the shortest path cost before IGP. If route (s, d) < p then order of list node have to visit p{p,x} means that x is inserted after the rightmost element in P. Also, ∆ (n) is the multiplicity of node n, indicating how many times n has been visited by the current packet.

Figure 5: Finding re-route with low cost

Source: f, Destination: a. Failure path: f-e-c-a. Available path: 1st path: f-e-c-b-a=15. 2nd path: f-e-c-d-a=14. The 2nd path is the shortest re-route path from source to destination with low cost.

2.5 link failure algorithm description In our algorithm is based on sequential search in the primary link, which we call SS LINK. It contains the following steps. 1) Init: Set the backup port of each node to null, i.e., bn = 0(n = 2; : : : ;N).

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Vol.2 Issue.12, Pg.: 41-47

December 2014

2) Explore the primary link T(1) using depth-first search. For each node n (n = 2; : : : ;N), assume its primary port pn fails (i.e., link n ! pn fails) and do the following: a) If bn 6= 0, the backup port of node n is already found, go back to step 2 to process the next node; otherwise, continue to the next step. b) The failure disconnects a sub-link T(n) from the primary link, where n is the root of the sub-link. Dye the nodes in T(n) black and all the other nodes in the topology white. The forwarding path from each white node is not affected by the failure. c) In T(n), use breadth-first search to find the first node i that has a direct link to a white node j, set its backup port bi = j. We call this port i,j an exit of sub-tree T(n). d) If i ≠ n, find the path from n to i in T (n). Suppose the path is n -> m1 ->m2 …->mL -> i. Set the corresponding backup ports as bn = m1, bm1 = m2, . , bmL = i. Go back to step 2.

Figure: 6(a) Primary nodes , 6(b) Failure 2-1 6(c) failure 7–5, 6(d) failure 9–7. Figure 6 shows the procedure of using LINK on the depth-first search path 2–5–7–9. 1) Failure 2–1 detaches sub-tree T(2) from the primary link. Using breadth-first search, an exit 5-> 6 is found and the rerouting path is 2->5->6. Thus, we set b2 = 5 and b5 = 6 (Figure 6(b)). 2) Failure 5–2 creates sub-tree T(5), the search is skipped since b5 ≠ 0. 3) Failure 7–5 dyes T(7) black, and the search immediately yields b7 = 4 (Figure 6(c)). 4) Failure 9–7 dyes T(9) black, the algorithm sets b7 = 4(Figure 6(d)).

2.6. Algorithm properties optimality Theorem 1: LINK minimizes the number of switchovers in (1) if the primary tree is obtained using minimum hop routing.

Proof: When the primary port of node k fails, the exit of T(k) is found using breadth first search. Therefore, the hop count from node k to the exit is minimized (since the primary tree is based on minimum hop routing). This minimizes the number of switch-overs because choosing any other exit requires more nodes to use backup ports. Since LINK minimizes the number of switch-overs under any possible failure, it achieves the optimality in (1). Complexity: The algorithm has low computation complexity. Although it contains two nested searches in the tree, the CPU cycles consumed by each step is very limited. In step 2a, a node is immediately skipped if its backup port is

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December 2014

already found. In step 2c, the algorithm only checks if a node has a white neighbor ,thus requires very little computation. In step 2d, the path from n to i is exactly the reverse of the primary path from i to n, which does not require complicated route calculation. In particular, each router only runs a part of the algorithm when link is implemented in a distributed manner. For node n, it finds its backup port...

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