Shree Murthy

An efficient routing protocol for wireless networks

We present the Wireless Routing Protocol (WRP). In WRP, routing nodes communicate the distance and secondto-last hop for each destination. WRP reduces the number of cases in which a temporary routing loop can occur, which accounts for its fast convergence properties. A detailed proof of correctness is presented and its performance is compared by simulation with the performance of the distributed Bellman-Ford Algorithm (DBF), DUAL (a loop-free distance-vector algorithm) and an Ideal Link-state Algorithm (ILS), which represent the state of the art of internet routing. The simulation results indicate that WRP is the most efficient of the alternatives analyzed.

A routing protocol for packet radio networks

Abstract : The authors present a new distance-vector routing protocol for a packet radio network. The new distributed routing protocol, Wireless Routing Protocol (WRP), works on the notion of second-to-last hop node to a destination. WRP reduces the number of cases in which a temporary routing loop can occur and also provides a mechanism for the reliable transmission of update messages. The performance of WRP has been compared quantitatively by simulations with that of distributed Bellman-Ford (DBF), DUAL (a loop-free, distance-vector algorithm), and an ideal link-state algorithm (ILS) that represents the state of the art of Internet routing in a highly dynamic environment. The simulation results indicate that WRP is the most efficient of the algorithms simulated in a wireless environment.

Securing distance-vector routing protocols

We analyze the security requirements of distance-vector routing protocols, identify their vulnerabilities, and propose countermeasures to these vulnerabilities. The innovation we propose involves the use of mechanisms from the path-finding class of distance-vector protocols as a solution to the security problems of distance-vector protocols. The result is a proposal that effectively and efficiently secures distance-vector protocols in constant space.

A path-finding algorithm for loop-free routing

A loop-free path-finding algorithm (LPA) is presented; this is the first routing algorithm that eliminates the formation of temporary routing loops without the need for internodal synchronization spanning multiple hops of the specification of complete or variable-size path information. Like other previous algorithms, the LPA operates by specifying the second-to-last hop and distance to each destination; this feature is used to ensure termination. In addition, the LPA uses an interneighbor synchronization mechanism to eliminate temporary routing loops. A detailed proof of the LPAs correctness and loop-freedom property is presented and its complexity is evaluated. The LPAs average performance is compared by simulation with the performance of algorithms representative of the state of the art in distributed routing, namely an ideal link-state (ILS) algorithm, a loop-free algorithm that is based on internodal coordination spanning multiple hops (DUAL) and a path-finding algorithm without the interneighbor synchronization mechanism. The simulation results show that the LPA is a more scalable alternative than DUAL and ILS in terms of the average number of steps, messages, and operations needed for each algorithm to converge after a topology change.

Congestion-oriented shortest multipath routing

We present a framework for the modeling of multipath routing in connectionless networks that dynamically adapt to network congestion. The basic routing protocol uses a short-term metric based on hop-by-hop credits to reduce congestion over a given link, and a long-term metric based on end-to-end path delay to reduce delays from a source to a given destination. A worst-case bound on the end-to-end path delay is derived under three architectural assumptions: each router adopts weighted fair queueing (or packetized generalized processor sharing) service discipline on a per destination basis, a permit-bucket filter is used at each router to regulate traffic flow on a per destination basis, and all paths are loop free. The shortest multipath routing protocol regulates the parameters of the destination-oriented permit buckets and guarantees that all portions of a multipath are loop free.

Loop-free Internet routing using hierarchical routing trees

We present a new hierarchical routing algorithm that combines the loop-free path-finding algorithm (LPA) with the area-based hierarchical routing scheme first proposed by McQuillan (1974) for distance-vector algorithms. The new algorithm, which we call the hierarchical information path-based routing (HIPR) agorithm, accommodates an arbitrary number of aggregation levels and can be viewed as a distributed version of Dijkstras algorithm running over a hierarchical graph. The HIPR is verified to be loop-free and correct. Simulations are used to show that the HIPR is much more efficient than the OSPF in terms of speed, communication and processing overhead required to converge to correct routing tables. The HIPR constitutes the basis for future Internet routing protocols that are as simple as RIPv2, but with no looping and better performance than protocols based on link-states.

A loop-free path-finding algorithm: specification, verification and complexity

The loop-free path-finding algorithm (LPA) is presented. LPA specifies the second-to-last hop and distance to each destination to ensure termination; in addition, it uses an inter-neighbor synchronization mechanism to eliminate temporary loops. A detailed proof of LPAs correctness is presented and its complexity is evaluated. LPAs average performance is compared by simulation with the performance of algorithms representative of the state of the art in distributed routing, namely an ideal link-state (ILS) algorithm and a loop free algorithm that is based on internodal coordination spanning multiple hops (DUAL). The simulation results show that LPA is a more scalable alternative than DUAL and ILS in terms of the average number of steps, messages, and operations needed for each algorithm to converge after a topology change. LPA is shown to achieve loop freedom at every instant without much additional overhead over that incurred by prior algorithms based on second-to-last hop and distance information.

A more efficient path-finding algorithm

Presents a new routing algorithm, which the authors call a path-finding algorithm (PFA). It drastically reduces the possibility of temporary routing loops, which accounts for its fast convergence properties. Like other path-finding algorithms, the PFA operates by specifying the second-to-last hop to each destination, in addition to the distance to the destination. A detailed proof of correctness and complexity is presented elsewhere. The PFAs performance is compared quantitatively by simulation with DUAL (a loop-free routing algorithm) and an ideal link-state algorithm (ILS). A number of parameters, including the length of the messages and the number of steps required for convergence, are used in the comparison. The simulation results indicate that the PFA constitutes a very efficient distance-vector algorithm. It provides about 50% improvement in performance compared to DUAL in terms of the convergence time and the number of updates after single link failures, and provides comparable or better convergence speed and traffic overhead than ILS, with orders of magnitude fewer CPU cycles.<<ETX>>

A routing architecture for mobile integrated services networks

A drawback of the conventional Internet routing architecture is that its route computation and packet forwarding mechanisms are poorly integrated with congestion control mechanisms. Any datagram offered to the network is accepted; routers forward packets on a best-effort basis and react to congestion only after the network resources have already been wasted. A number of proposals improve on this to support multimedia applications; a promising example is the Integrated Services Packet Network (ISPN) architecture. However, these proposals are oriented to networks with fairly static topologies and rely on the same conventional Internet routing protocols to operate. This paper presents a routing architecture for mobile integrated services networks in which network nodes (routers) can move constantly while providing end-to-end performance guarantees. In the proposed connectionless routing architecture, packets are individually routed towards their destinations on a hop by hop basis. A packet intended for a given destination is allowed to enter the network if and only if there is at least one path of routers with enough resources to ensure its delivery within a finite time. Once a packet is accepted into the network, it is delivered to its destination, unless resource failures prevent it. Each router reserves resources for each active destination, rather than for each source–destination session, and forwards a received packet along one of multiple loop-free paths towards the destination. The resources and available paths for each destination are updated to adapt to congestion and topology changes. This mechanism could be extended to aggregate dissimilar flows as well.

Dynamics of a loop-free path-finding algorithm

The dynamics of a loop-free path-finding algorithm (LPA) based on predecessor information and a single-hop internodal synchronization mechanism is investigated. LPA is compared with a loopfree algorithm based on diffusing computations, DUAL, and an ideal link-state (ILS) algorithm based on topology broadcast. Comparisons include the dynamic response of the algorithms to a single and multiple link-cost changes as well as single link and router failures and recoveries. The results show that LPA requires a significantly smaller number of messages than ILS and DUAL to update routing tables when multiple changes in link costs occur. LPAs performance is always significantly better than DUALs and significantly better than ILSs after node failures and resource additions (in some instances, ILS requires almost four times as many messages). After a link failure, LPA requires approximately the same time to converge as ILS and at most twice as many messages.