Reducing the size of routing tables for large-scale network simulation

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.

Appropriate routing for supporting the requirements of various high quality applications emerged in current communication networks is a challenging problem that can lead to improved routing algorithms. Taking into consideration the highly distributed character of networks, numerous multi-agent based algorithms, and particularly ant colony based algorithms, have been proposed in recent years. However, considering the need for decreasing overhead and increasing the scalability of these algorithms remains an elusive challenge. Our goal here is to reduce the overhead and the process complexity in nodes by decreasing the size of routing tables of network nodes in an innovative manner. More specifically, data routing tables which are established in the AntNet algorithm and keep the information of all destination nodes in network convert to tables that only keep the information of popular destinations of network. The resulting algorithm, the ‘‘D-T-SAntNet,’’ is then simulated via Omnet++ onUUNET network topology. The network performance is evaluated under various node-failure and node added conditions. Statistical analysis of results confirms that the new method can significantly reduce the average packet delivery time and rate of convergence to the optimal route when compared with standard AntNet.

With the widely deployed cloud services, data center networks are evolving toward large-scale and multi-path networks, which cannot be supported by conventional routing methods, such as OSPF and RIP. To alleviate this issue, some new routing methods, such as PortLand and BSR, are proposed for data center networks. However, these routing methods are typically designed for a specific network architecture, and thus lacking adaptability while complex in fault-tolerance. To address this issue, this paper proposes a generic routing method, named fault-avoidance routing (FAR), for data center networks that have regular topologies. FAR simplifies route learning by leveraging the regularity in a topology. FAR also greatly reduces the size of routing tables by introducing a novel negative routing table (NRT) at routers. The operations of FAR is illustrated by an example Fat-tree network and the performance of FAR is analyzed in detail. The advantages of FAR are verified through extensive OPNET simulations.

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.

Nowadays, the commonly used table lookup scheme for IP routing is based on the so-called classless interdomain routing (CIDR). With CIDR, routers must find out the best matching prefix (BMP) for IP packet forwarding, which complicates the IP lookup. Since the IP lookup performance is a major design issue for the new generation routers, we investigate the properties of the routing table and present a new IP lookup scheme. By adopting the extreme compression, the size of the forwarding table can be compressed to 360 Kbytes for a large routing table with 58,000 routing entries. It can accomplish one IPv4 route lookup within maximum nine memory accesses. Consequently, the data structure for the incremental update is introduced. With the new data structure, the proposed scheme can accomplish one route update within 500 ns. Even under the circumstance with 4000 route updates per second, the performance degradation is as low as 0.2 %.

Recent peer-to-peer (P2P) systems research has focused on building highly usable P2P overlay networks. Short query paths, small routing tables, and robustness constitute the most prominent design objectives for the overlay topology. In this paper, we introduce a general group theoretic method and define a new Cayley graph. We then use these constructs to derive a novel P2P overlay structure. CayleyCCC, our proposed overlay network, has many desirable features, including short query paths, compact routing tables, high clustering, and robustness. Because of its symmetry, our design offers simpler routing (searching) and several other desirable properties compared with many previously proposed overlay networks, such as Chord and Ulysses. Performance evaluation results, reported in this paper, quantify the advantages of CayleyCCC in terms of query path length, routing table size, and robustness relative to some recent proposals. CayleyCCC is particularly useful in distributed computing under relatively stable conditions.

One of the key design issues for IP routers is the IP lookup mechanism. IP lookup is an important action in router that is to find the next hop of each incoming packet with a longest-prefix-match address in the routing table. In this paper, we put the routing table on a longest prefix first search tree. The tree is constructed as a heap by the prefix length. That makes a router executing IP lookup have the minimal number of memory accesses as compared with Trie [Sklower, K 1991], Patricia [Nilsson, S 1999] and Prefix tree [Berger, M 2003]. Some nodes of our tree can contain two entries of the routing table to reduce the number of tree nodes. For example, a 138286 of a routing table can be stored in 132050 nodes of our tree. Furthermore, the proposed scheme makes the tree can be updated without being reconstructed from scratch when the routing table is changed, and it can be applied in both the IPv4 and IPv6 routers.

Network-on-Chip (NoC) is evolving as an efficient and scalable interconnect architecture for current and future CMP, MPSoC systems. An important challenge in NoC design is to choose an appropriate routing algorithm, as it impacts the NoC performance. As technology scales down to Deep-Submicron (DSM), on-chip networks are becoming increasingly prone to failures. At higher level these failures are handled by fault tolerant routing algorithms. Fault tolerant routing algorithms avoid faulty regions and route traffic through safe regions. Currently, routing algorithms are implemented as source or distributed routing. To handle faults, both source and distributed routing make use of routing tables. Algorithms implemented with routing tables do not scale well with network size. Scalable routing implementation, such as Logic Based Distributed Routing (LBDR) has been proposed for efficient and compact implementation of routing. LBDR handles faults without using routing table. In this paper we propose a fault tolerant routing scheme based on LBDR which aims to handle faults while at the same time addressing network congestion. Proposed method integrates deterministic and adaptive routing schemes to avoid congestion as well as faults that may be present in the network. Experimental results show the effectiveness of proposed method in case of single and multiple link failures.

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.

In this paper, we focus on the efficient routing of data among different areas in delay tolerant networks (DTNs). In current algorithms, packets are forwarded gradually through nodes with higher probability of visiting the destination node or area. However, the number of such nodes usually is limited, leading to insufficient throughput performance. To solve this problem, we propose an inter-landmark data routing algorithm, namely DTN-FLOW. It selects popular places that nodes visit frequently as landmarks and divides the entire DTN area into subareas represented by landmarks. Nodes transiting between landmarks relay packets among landmarks, even though they rarely visit the destinations of these packets. Specifically, the number of node transits between two landmarks is measured to represent the forwarding capacity between them, based on which routing tables are built on each landmark to guide packet routing. Each node predicts its transits based on its previous landmark visiting records using the order- k Markov predictor. When routing a packet, the landmark determines the next-hop landmark based on its routing table and forwards the packet to the node with the highest probability of transiting to the selected landmark. Thus, DTN-FLOW fully utilizes all node movements to route packets along landmark-based paths to their destinations. We analyzed two real DTN traces to support the design of DTN-FLOW. We deployed a small DTN-FLOW system on our campus for performance evaluation. We also proposed advanced extensions to improve its efficiency and stability. The real deployment and trace-driven simulation demonstrate the high efficiency of DTN-FLOW in comparison to state-of-the-art DTN routing algorithms.

The global routing system has seen a rapid increase in table size and routing changes in recent years, mostly driven by the growth of edge networks. This growth reflects two major limitations in the current architecture: (a) the conflict between provider-based addressing and edge networks’ need for multihoming, and (b) flat routing’s inability to provide isolation from edge dynamics. In order to address these limitations, we propose A Practical Tunneling Architecture (APT), a routing architecture that enables the Internet routing system to scale independently from edge growth. APT partitions the Internet address space in two, one for the transit core and one for edge networks, allowing edge addresses to be removed from the routing table in the transit core. Packets between edge networks are tunneled through the transit core. In order to automatically tunnel the packets, APT provides a mapping service between edge addresses and the addresses of their transit-core attachment points. We conducted an extensive performance evaluation of APT using trace data collected from routers at two major service providers. Our results show that APT can tunnel packets through the transit core by incurring extra delay on up to 0.8% of all packets at the cost of introducing only one or a few new or repurposed devices per AS.

Ordered interval routing schemes

Key-based workload partitioning is a common strategy used in parallel stream processing engines, enabling effective key-value tuple distribution over worker threads in a logical operator. It is likely to generate poor balancing performance when workload variance occurs on the incoming data stream. This paper presents a new key-based workload partitioning framework, with practical algorithms to support dynamic workload assignment for stateful operators. The framework combines hash-based and explicit key-based routing strategies for workload distribution, which specifies the destination worker threads for a handful of keys and assigns the other keys with the hash function. When short-term distribution fluctuations occur to the incoming data stream, the system adaptively updates the routing table containing the chosen keys, in order to rebalance the workload with minimal migration overhead within the stateful operator. We formulate the rebalance operation as an optimization problem, with multiple objectives on minimizing state migration costs, controlling the size of the routing table and breaking workload imbalance among worker threads. Despite of the NP-hardness nature behind the optimization formulation, we carefully investigate and justify the heuristics behind key (re)routing and state migration, to facilitate fast response to workload variance with ignorable cost to the normal processing in the distributed system. Empirical studies on synthetic data and real-world stream applications validate the usefulness of our proposals.