An efficient innovative method to decrease routing table size in packet switched networks

In simulating large-scale networks, due to the limitation of available resources on computers, the size of the networks and the scale of simulation scenarios are often restricted. Especially, routing tables, which indicate the directions to forward packets, are considered to consume memory space. A simple general routing table requires O(N/sup 2/) space where N is the number of nodes. An algorithmic routing approach recently proposed by Heung et al. only requires O(N) space for representing routing tables, however this can be applied in the case that all the routes between two nodes are contained in a spanning tree (i.e. very limited routing strategies are allowed). We propose a new method to reduce the size of routing tables under any routing strategy. Given a general simple routing table, our method represents a routing table as the combination of an algorithmic routing based table and a general routing table, by translating a part of the given general routing table into the algorithmic routing based one. In order to reduce the size of the routing table, we find a (near-optimal)algorithmic routing based table that represents most part of the given routing table. Our experimental results have shown that our method could reduce the size of the table to 10 % of the given routing table in hierarchical networks.

The recent trend of rapid increase in routing table sizes at routers comprising the Internet's core is posing a serious challenge to the current Internet's scalability, availability, and stability. Multihoming is a prime contributor to this table size explosion. This paper argues that it is possible to a) scale the Internet's routing table sub-linearly with degree of multihoming, and b) improve routing convergence times even under pervasive multihoming using simple and incrementally deployable extensions to today's routing protocols. We present an addressing and routing protocol called SIMPLER (scalable IP multihoming protocol leveraging routing), which is designed to minimize and contain the propagation in space and time of non-aggregatable routes. SIMPLER's prefix containment property results in lower lookup and route processing costs (promotes scalability), and faster convergence time (helps network availability and stability). SIMPLER vastly diminishes the number of non-aggregatable prefixes appearing in the Internet core due to multihoming (to zero in the absence of network faults, and O(number of faults) otherwise), and always leaks fewer non-aggregatable prefixes than today's dominant multihoming strategy of hole punching. Additionally, SIMPLER provides transport-layer survivability (TLS) and better routing policy management, while offering the same routing robustness as today's multihoming. The main cost of SIMPLER is the increased use of address space (O(log(network size)) in the average case). SIMPLER is carefully designed to be useful to both multihomed transit providers and multihomed leaf sites.

In this paper, we compare the proactive MANET routing schemes of OLSR and OSPF-MDR via high-fidelity simulation, and consider their suitability for large-scale airborne networks. A successful MANET routing scheme must be bandwidth efficient and robust to frequent topology changes. To assess the two protocols, we simulate them in networks with up to 400 mobile nodes, under a variety of network densities. We evaluate them on the basis of the amount of routing overhead generated, the rate of successful packet delivery, and the time it takes until all of the routing tables converge. We find that OLSR requires up to an order magnitude higher router overhead than OSPF-MDR, while providing only a marginal benefit in packet delivery success rates. The largest difference between the two protocols is the time it takes for their routing tables to converge in the presence of packet loss. OLSR has consistent convergence times for networks of all sizes, while the convergence time of OSPF-MDR increases with network size.

Bluetooth mesh (BM) is increasingly growing and appearing in Internet of Things (IoT) systems. BM uses a managed flooding mechanism to transmit the message. Nodes with a relay feature will receive and forward the message to neighboring nodes, so that the message can be spread to the whole network. The default configuration of BM is that all nodes are relays, ensuring that every node in the network can connect to each other. However, when all nodes act as relays, it results in a lot of messages being transmitted through the network at a time, which increases the possibility of packet collisions, thereby reducing the packet delivery rate (PDR) and increasing the end-to-end delay (E2E delay). These issues will greatly affect the user experience, especially in smart home systems where users interact near the device. Therefore, it is necessary to choose the relay nodes in the network appropriately to improve the quality of the network. This paper will select and analyze some relay node selection algorithms in the BM network applied in the smart home system, and compare them with the default configuration of the network (all relays) in terms of PDR and E2E delay criteria.

In this paper, an engineering interpretation of small world effects in networks is given. After briefly summarizing the main features of small world networks, an attempt is made to investigate the relevance that small world effects can have in communication networks. The aim is that of investigating the relationship between small world behaviour and some of the characteristic parameters associated to the overall performance of the network. It is shown that the performance of a communication network is indeed affected by the presence or absence of small world effects. Namely, the link between these effects and the average throughput and delivery time on the network is established and assessed through numerical simulations.

In this paper, an improved hybrid location-based Ad hoc routing protocol (IHLAR) has been proposed. This hybrid approach combines geographic routing with topology-based routing protocol. It overcomes the major problems of reactive routing and the end-to-end delay is reduced by this algorithm. In addition, the path length performance of geographic routing is also improved. Simulation results show that our routing protocol outperforms the pure reactive routing in terms of average delay and packet delivery rate.

Critical node discovery plays a vital role in assessing the vulnerability of a computer network to malicious attacks and failures and provides a useful tool with which one can greatly improve network security and reliability. In this paper, we propose a new metric to characterize the criticality of a node in an arbitrary computer network which we refer to as the Combined Banzhaf & Diversity Index (CBDI). The metric utilizes a diversity index which is based on the variability of a node׳s attributes relative to its neighbours and the Banzhaf power index which characterizes the degree of participation of a node in forming shortest paths. The Banzhaf power index is inspired from the theory of voting games in game theory. The proposed metric is evaluated using analysis and simulations. The criticality of nodes in a network is assessed based on the degradation in network performance achieved when these nodes are removed. We use several performance metrics to evaluate network performance including the algebraic connectivity which is a spectral metric characterizing the connectivity robustness of the network. Extensive simulations in a number of network topologies indicate that the proposed CBDI index chooses more critical nodes which, when removed, degrade network performance to a greater extent than if critical nodes based on other criticality metrics were removed.

The transmission rate between two nodes is usually very low in underwater acoustic networks due to the low available bandwidth of underwater acoustic channels. Therefore, increasing the transmission parallelism among network nodes is one of the most effective ways to improve the performance of underwater acoustic networks. In this paper, we propose a new collision-free hybrid medium access control (MAC) protocol for distributed multi-channel underwater acoustic networks. In the proposed protocol, handshaking and data transmission are implemented as a pipeline on multiple acoustic channels. Handshaking is implemented using the time division multiple access (TDMA) technique in a dedicated control channel, which can support multiple successful handshakes in a transmission cycle and avoid collision in the cost of additional delay. Data packets are transmitted in one or multiple data channels, where an algorithm for optimizing the transmission schedule according to the inter-nodal propagation delays is proposed to achieve collision-free parallel data transmission. Replication computation technique, which is usually used in parallel computation to reduce the requirement of communication or execution time, is used in the data packet scheduling to reduce communication overhead in distributed environments. Simulation results show that the proposed protocol outperforms the slotted floor acquisition multiple access (SFAMA), reverse opportunistic packet appending (ROPA), and distributed scheduling based concurrent transmission (DSCT) protocols in throughput, packet delivery rate, and average energy consumption in the price of larger end-to-end delay introduced by TDMA based handshaking.

Address Fragmentation plays a key role in the exponential growth of DFZ routing table, known as the scalability problem of current Internet. In this paper, we measure the severity of address fragmentation, and try to figure out the relationship between Prefix-Distance and Network-Distance of current Internet by taking Geographic-Distance as an approximation of Network-Distance. We focus our measurement on the prefixes with relatively small Geographic-Distance, and get Prefix Groups from BGP routing dynamics. This method reduces the number of active probes required in active measurement, and results a more detailed prefixes’ distribution analysis. We find out that there are two extreme allocations of IP address blocks in current Internet. Some of the blocks with small Geographic-Distances have small Prefix-Distances, while others with small Geographic-Distances have rather big Prefix-Distances. This is the direct reason of the BGP routing table’s inflation. We further conclude that by reallocating IP address blocks according to geography, we could significantly reduce the size of the global routing tables.

Parallel Optical Burst Switching (POBS) is a variant of Optical Burst Switching (OBS) which is proposed as a new optical switching strategy for Ultra-Dense Wavelength Division Multiplexing (U-DWDM) to support the enormous bandwidth demand of the next generation Internet. As opposed to OBS, POBS transmits bursts in two dimensions: the wavelength dimension and the time dimension. POBS network uses an one-way resource reservation mechanism to set up the resources for each data burst transmission. The use of this mechanism may cause bursts to contend for the same resources at the same time at core (intermediate) nodes of the network. Therefore, the performance of POBS networks depends on the contention resolution policies to reach acceptable levels for bandwidth usage. These policies may increase both the cost and complexities of the core nodes in POBS networks. Most literatures on OBS networks apply contention resolution at the core nodes based on reactive strategies that are activated after contention takes place in core nodes. This study proposes the use of a proactive contention resolution technique at ingress nodes of POBS network as well as reactive contention resolution technique at core nodes for reducing the probability of burst drop in the network in order to increase the performance of the network. The simulation results show that the use of POBS network with the proposed Reactive Odd/Even Node ID Wavelength Assignment Technique (POBS-ROENIDWAT) shows a better performance in terms of reduced data loss rate and increased throughput compared to the performances of both POBS network with Sequential Wavelength Assignment Technique (POBS-SWAT) and OBS network with Burst Segmentation (OBS-BS).

Heuristic algorithms for efficient allocation of multicast-capable nodes in sparse-splitting optical networks

Vehicular Ad Hoc Networks (VANET) are key to realizing Intelligent Transportation Systems (ITS). Although VANETs belong to the class of Mobile Ad Hoc Networks (MANET), and there are numerous routing protocols for MANETs, none of these protocols are applicable for VANETs. In particular, VANETs are highly dynamic due to high speed mobility of vehicles and traditional routing algorithms for MANETs cannot deal with such dynamicity of network nodes. Several comparative studies have suggested AODV (Ad hoc On-Demand Distance Vector), a well known MANET protocol that is adaptive to dynamic changes in network and makes efficient utilization of network resources, to be the best candidate for dealing with VANETs. However, verbatim adoption of AODV is not an efficient routing solution for VANETs. Recent works therefore proposed various modifications and/or additions to AODV to make it suitable for VANETs. It is particularly important to control congestion in VANETs by efficiently dealing with the AODV "Route Request" (RREQ) packets. In this paper, we propose Pro-AODV (Proactive AODV), a protocol that uses information from the AODV routing table to minimize congestion in VANETs, yet sustains other performance metrics at acceptable levels. The novelty and elegance in Pro-AODV comes from the fact that it does not require the execution of any additional logic, it is sufficient to know only the size of the routing table at each node.

IoT resource registration and lookup interfaces have been specified for Resource Directory (RD) with defined resource link format in IETF standard. However, it has many drawbacks due to the nature of the centralized architecture. This paper proposes an ICN-based distributed RD architecture. The proposed distributed IoT resource discovery and routing mechanisms allow and reuse the existing RD resource registration and lookup interfaces, which aligns with the IETF standard. Routers do not maintain routing table for every IoT resource, but keep routing tables on the aggregated resource attributes. A client does not need to know the resource names in advance for the routing. Resource advertisement and routing table advertisement are triggered by the updates, which prevents the network congestion due to the control messages. It also allows the client to specify how many resources would be returned. Our simulation results indicate substantial performance improvement of the proposed ICN-based distributed RD architecture in terms of network overhead and routing table size compared to the existing distributed RD deployments.

Research and discussion on the Internets addressing and routing scalability problems has been for more than a decade. IP aware growing population, and learned needs in terms of site multi-homing, traffic engineering, non-aggregatable address allocations and policy based routing have resulted in the continuous alarming growth of the routing tables in the Default Free Zone (DFZ). Constraints posed by the existing router technology, address allocation and architectural history have made identifying and deploying an effective solution difficult. These sources that influence the core routing table growth can lead to fragmentation or de-aggregation of address prefixes. Much of the growths of the routing tables in the DFZ are a result of de-aggregation of address prefixes. Aggressive topological aggregation is the solution to scale the routing system, that is, IP address allocations should follow topology. IP address allocation and management and the scalability of the routing system are interrelated and only certain IP address allocation and management policies yield scalable routing. The Regional Internet Registries (RIRs) individually use various allocation techniques within their respective regional pools of address space. Proper choice of address allocation algorithm would help in reducing fragmentation, thus reducing routing table size and hence increase Internet addressing and routing scalability. This paper analyzes the various address allocation algorithms used by the RIR’s and based on the lessons learnt proposes a hybrid address allocation scheme for IPv6 that would achieve appreciable address aggregation compared to the existing IPv6 address allocation algorithms, and effectively reduce routing table size in the DFZ. This would help in increasing the Internet addressing and routing scalability and thus enhance the performance of the Internet.

The paper presents a new node architecture for an all-optical packet router employing multiple pulse position modulation (PPM) routing table with a hybrid packet header correlation scheme. Most existing routing tables within a node contain a large number of entries, thus resulting in a long packet header address correlation time before delivering the incoming packet to its destination. In the proposed multiple PPM routing tables (PPRTs) the packet header address is based on the binary and PPM formats which leads to a much reduced routing table size. The packet header address correlation is carried out using only a single optical AND gate, thus offering reduced system complexity. It is also shown that the proposed scheme offers unicast/multi-cast/broadcast transmitting capabilities. The propose scheme is simulated and its characteristics are investigated. The output inter-channel crosstalk (CXT) of up to -18 dB and output packet power fluctuation of 2 dB have been achieved, which largely depend on the guard time between the arriving packets.