Hierarchical Routing Protocol Research Articles

New hierarchical approach to reactive routing protocols for wireless ad hoc networks with cross-layer design

A hierarchical routing protocol is designed for reactive ad hoc networks. In the hierarchical architectures network nodes are classified as Mobile Nodes (MNs) and Forwarding Nodes (FNs). FNs are selected from MNs during the route discovery phase of the reactive routing. This FN selection algorithm is distributed, dynamic and requires no additional protocol messaging other than used during the route discovery. The FN selection algorithm is further improved by using network congestion information from Medium Access (MAC) layer. The protocol is implemented using Dynamic Source Routing (DSR) protocol, and the new protocol is called HDSR. Simulation results show that HDSR significantly improves the routing efficiency in wireless ad hoc networks.

DOA: DSR over AODV Routing for Mobile Ad Hoc Networks

We present a lightweight hierarchical routing model, way point routing (WPR), in which a number of intermediate nodes on a route are selected as waypoints and the route is divided into segments by the waypoints. The waypoints, including the source and the destination, run a high-level intersegment routing protocol, while the nodes on each segment run a low-level intrasegment routing protocol. One distinct advantage of our model is that when a node on the route moves out or fails, instead of discarding the whole original route and discovering a new route from the source to the destination, only the two waypoint nodes of the broken segment have to find a new segment. In addition, our model is lightweight because it maintains a hierarchy only for nodes on active routes. On the other hand, existing hierarchical routing protocols such as CGSR and ZRP maintain hierarchies for the entire network. We present an instantiation of WPR, where we use DSR as the intersegment routing protocol and AODV as the intrasegment routing protocol. This instantiation is termed DSR over AODV (DOA) routing protocol. Thus, DSR and AODV - two well-known on-demand routing protocols for MANETs - are combined into one hierarchical routing protocol and become two special cases of our protocol. Furthermore, we present two novel techniques for DOA: one is an efficient loop detection method and the other is a multitarget route, discovery. Simulation results show that DOA scales well for large networks with more than 1,000 nodes, incurring about 60 percent-80 percent less overhead than AODV, while other metrics are better than or comparable to AODV and DSR

Two-layer hierarchical wavelength routing for islands of transparency optical networks

Although significant advances have been achieved towards the deployment of all-optical networks, optical–electrical–optical (OEO) regeneration is still required due to the lack of proper all-optical processing and all-optical buffering. In order to have a practical, reliable, and cost effective optical transport network, the combination of both all-optical and OEO technologies is necessary. The “islands of transparency” network architecture has been proposed as a solution. This paper presents a two-layer hierarchical wavelength routing (THWR) protocol for the island of transparency optical network. The proposed THWR is a link state protocol that uses a two-layer hierarchy that partitions the network into routing areas, each of which represents an island of transparency. The proposed THWR implements a dynamic wavelength routing capability to balance the network load and avoid the congested area automatically. The complexity analysis and the simulation results of THWR are shown in the paper. The results show THWR is an effective protocol that meets the requirements for optical networks.

Adaptive Inter Vehicle Communications

Inter Vehicle Communications (IVC) have the potential to significatively increase the safety in our highways. In such communications, the quality and reliability of service becomes a very critical issue. In particular, it is important that in case of emergencies, when the inter vehicle traffic increases exponentially, the message delay should be kept low. We present a reliable hierarchical routing protocol that uses load balancing to keep message delay low even in presence of high level of traffic. Our protocol is based on geographical routing. The protocol is designed for highway travelers but can be used in other mobile ad-hoc scenarios. The highway is divided in virtual cells, which moves as the vehicles moves. The cell members might choose one or more Cell_Leaders that will behave for a certain time interval as Base Stations. We assume that every node knows its geographical position, given by Global Positioning System (GPS) or some other method. Cell_Leaders form a virtual backbone that is used to forward messages among nodes on different cells. The traffic is distributed among Cell_Leaders in order to optimize the communication delay. We study the effect of load balancing in minimizing delay. Our simulation results show that our proposed protocol improves the delay and the network utilization compared to existing inter vehicles protocols.

센서 네트워크에서 에너지 효율성을 고려한 two-tier 라우팅 프로토콜

Since sensor node has a limited energy supply in a wireless sensor network, it is very important to maximize the network lifetime through energy-efficient routing. Thus, many routing protocols have been developed for wireless sensor networks and can be classified into flat and hierarchical routing protocols. Recent researches focus on hierarchical routing scheme and LEACH is a representative hierarchical routing protocol. In this paper, we investigated the problems of the LEACH and proposed a novel energy efficient routing scheme, called ENTER(ENergy efficient Two-tiEr Routing protocol), to resolve the problem. ENTER reduces an energy consumption and increases a network lifetime by organizing clusters by the same distributed algerian as in the LEACH and establishing paths among cluster-heads to transmit the aggregated data to the sink node. We compared the performance of the ENTER with the LEACH through simulation and showed that the ENTER could enhance the network lifetime by utilizing the resources more efficiently.

An Autonomous Clustering-Based Hierarchical Multicast Routing for Mobile Ad Hoc Networks

This paper discusses multicast routing in ad hoc networks. In multicast routing, a node delivers the same message to the other nodes within a multicast group along with a multicast tree. Since nodes are moving around in ad hoc networks, the links between the nodes change frequently. However, the multicast tree must be maintained to deliver the messages regardless of the link changes. This paper gives a description of an autonomous clustering-based hierarchical multicast routing protocol in ad hoc networks. Since the autonomous clustering scheme is adaptive to the node movement, the proposed multicast routing can maintain the multicast tree in despite of link changes. This paper shows the effectiveness of autonomous clustering-based hierarchical multicast routing from the point of view of adaptability to link changes and scalability to multicast members.

Implementation and comparison of distributed caching schemes

Shared Web Caches allow multiple clients to quickly access a pool of popular web pages. An organization that provides shared caching to its web clients will typically have a collection of shared caches rather than a single cache. If a collection of shared caches is used, it is required to coordinate the caches so that all cached pages in the collection are shared among the clients of the organization. In this paper, two protocol schemes for coordinating the collection of shared caches are investigated. The first scheme is based on Internet Caching Protocol (ICP) (D. Wessels, K. Claffy, ICP and the Squid WebCache, National Laboratory for Applied Network Research, http://www.nlanr.net/(wessels/papers/icp-squid.ps.gz). In the ICP scheme, the web caches query other caches for the web pages and fetch the web pages from the neighbors if they have cached the requested page. The second scheme is the hash routing scheme in which the client (browser) has to find the hash value for the URL of the requested page and send the request to the corresponding cache server (D. Wessels, K. Claffy, IEEE Network magazine, November–December (1997); G. Thalur, C.V. Ravishankar, IEEE/ACM Trans. Networking (1997); V. Valloppillil, J. Cohen, Hierarchical HTTP Routing Protocol, Internet Draft, http://ww.nlanr.net/Cache/ICP/draft-vinod-icp-traffic-dist00.txt; Super proxy script, How to make Distributed Proxy Servers by URL Hashing, White Paper, http://naragw.sharp.co.jp/sps, August (1996)). These two schemes have been implemented, and compared with respect to the page retrieval latency and the adaptability of the cache servers when a peer cache server fails. Our analysis shows that the hash routing schemes have significant performance advantages over ICP with respect to the average latency under normal conditions but when failure rate of the cache server is significant the ICP provides good adaptability. Also, we observe that the hashing function used in the hash routing scheme must have certain features such as quick calculation of the hash value and uniform distribution of the web pages (among cache servers).

Optimization of hierarchical routing protocols

This paper concentrates on hierarchical routing protocols and their optimization. In a hierarchical routing protocol the network is divided into independent routing areas so that a node has complete routing information on its partition, but only reduced routing information of the “outside world” (i.e. the other partitions). Such routing protocols have been introduced in the early 1980s in order to decrease the overhead of dynamic routing protocols in large networks. However, such an approach may degrade the network performance. The aim of this work is to understand and quantify some aspects of the influence of this clustering process on network performance, and to determine how a given network (of a given topology) should be clustered under some optimization criteria. This problem has been already considered in the past, using a deterministic worst-case approach, for different optimization criteria. We generalize and refine the known results using a random geometric approach. This framework allows us to calculate explicitly the averages of various relevant variables (such as the size of the routing table and connection set-up latency) as a function of the topological parameters (such as the number of hierarchical levels). Optimum structures are then easily deduced.

The effect of network hierarchy structure on performance of ATM PNNI hierarchical routing

Networks deploying hierarchical routing are recursively partitioned into sub-networks that do not reveal full details of their internal structure outside their domains. Instead, an aggregated view of certain parameters that are associated with traversal within such sub-networks between their border nodes is advertised. The ATM PNNI standard and the Internet Nimrod architecture both adopt this approach for routing. This paper studies the effectiveness of ATM hierarchical routing protocols on networks with different hierarchical structures by simulation. Our study shows that, in general, the hierarchical source routing performs well, compared to the global routing strategy which imposes no hierarchy, while utilizing less storage and communication overheads. For certain networks and topologies, the hierarchical routing performs better than the global routing. Different hierarchies imposed on the same topologies have significantly different performance on the throughput and routing delay. This suggests the necessity of studying the hierarchy design for communication networks using hierarchical routing.

A routing protocol for dynamic and large computer networks with clustering topology

The routing decision is one of the important research issues in the network fields. With the rapid development of high-speed networks, multimedia communication networks and mobile computer networks, the hierarchical routing techniques for the dynamic and large networks or high-speed networks have triggered interests among many people worldwide. This paper proposes a hierarchical dynamic routing protocol (HDRP), which can adapt to dynamic and large computer networks (DLCN) with clustering topology. It also gives the main procedures for realizing routing update and routing decision, and the proof of correctness and complexity analysis of the protocol. The performance measures of HDRP, including throughput and average message delay, are evaluated using simulation. The study shows that HDRP provides a new available approach to routing decision for DLCN with clustering topology.

KHIP—a scalable protocol for secure multicast routing

We present Keyed HIP (KHIP), a secure, hierarchical multicast routing protocol. We show that other shared-tree multicast routing protocols are subject to attacks against the multicast routing infrastructure that can isolate receivers or domains or introduce loops into the structure of the multicast routing tree. KHIP changes the multicast routing model so that only trusted members are able to join the multicast tree. This protects the multicast routing against attacks that could form branches to unauthorized receivers, prevents replay attacks and limits the effects of flooding attacks. Untrusted routers that are present on the path between trusted routers cannot change the routing and can mount no denial-of-service attack stronger than simply dropping control messages. KHIP also provides a simple mechanism for distributing data encryption keys while adding little overhead to the protocol.

On the distribution of routing computation in hierarchical ATM networks

ATM private network-to-network interface (PNNI) is a hierarchical and dynamic link-state routing protocol, designed to scale to the largest possible ATM networks, encompassing thousands of nodes. This paper investigates the route computation load imposed by the PNNI routing scheme, and shows that this load is unevenly distributed among the network nodes. More specifically, the routing computation load associated with the setup of a single virtual path grows exponentially with the hierarchy level. As a result, some of the network nodes-mainly those that function as border nodes of high levels-may be overloaded with route computation, while other nodes are rarely involved in this process. This paper also proposes a possible scheme for spreading the route computation burden more evenly. According to this scheme, heavily loaded nodes transfer route computation tasks to lightly loaded nodes.

Open shortest path first (OSPF) routing protocol simulation

Open Shortest Path First (OSPF) is a dynamic, hierarchical routing protocol designed to support routing in TCP/IP networks. A simulation of the OSPF Election Protocol shows three results: (1) The Designated Router (DR) can be elected in constant time. (2) If a router has a limited number of input buffers, a competition for buffers between the Election and the Flooding Protocols increases the election time and causes an oscillatory behavior.At each router, the Router-ID of the DR continuously changes causing instability. (3) In the worst case, when the DR and the BDR fail at the same time, the DR-agreement-time is bounded above by twice the HelloInterval. A simulation of the OSPF Flooding Protocol, using 20, 50 and 80 router point-to-point networks, shows three results: (1) For the 50 router network, as link speed exceeds 4000 Kbps, the probability of overflowing the input buffers increases causing retransmissions. The increase in bootup-convergence-time from retransmissions is bounded by two and three times the RxmtInterval for link speeds of 4000 to 6000 Kbps and above 50 Mbps respectively. The increase in the bootup-convergence-time is due to large number of unacknowledged flooding packets received within RxmtInterval. (2) For 20 and 50 router networks, the input buffer size has little impact on the bootup-convergence-time. For the 80 router network, a small change in the input buffer size drastically changes the bootup-convergence-time. (3) Reducing the value of the RxmtInterval lowers the bootup-convergence-time at high link speeds.

An adaptive hierarchical routing protocol

An adaptive hierarchical routing protocol based on the extension of the new Arpanet scheme is proposed and its simulated performance is presented. The protocol can adapt to rapidly changing environments and works for arbitrarily large networks. A number of existing schemes as well as the proposed scheme are simulated under many different environments and clustering structures. The proposed protocol is found to be superior to the other protocols tested in many different types of network traffic and topological configurations. The results indicate that intercluster links must be reliable, because (1) the failure of these links can significantly degrade the routing performance, even though the protocol does not degrade as badly as the existing scheme and (2) hierarchical routing protocols usually prefer small clusters, which means that there will be many intercluster links. The tradeoff between two conflicting performance criteria, response speed and communication overhead, is shown. >