Routing table

About: Routing table is a research topic. Over the lifetime, 16589 publications have been published within this topic receiving 336842 citations. The topic is also known as: routing information base & RIB.

Technology-Driven, Highly-Scalable Dragonfly Topology

Abstract: Evolving technology and increasing pin-bandwidth motivate the use of high-radix routers to reduce the diameter, latency, and cost of interconnection networks. High-radix networks, however, require longer cables than their low-radix counterparts. Because cables dominate network cost, the number of cables, and particularly the number of long, global cables should be minimized to realize an efficient network. In this paper, we introduce the dragonfly topology which uses a group of high-radix routers as a virtual router to increase the effective radix of the network. With this organization, each minimally routed packet traverses at most one global channel. By reducing global channels, a dragonfly reduces cost by 20% compared to a flattened butterfly and by 52% compared to a folded Clos network in configurations with ≥ 16K nodes.We also introduce two new variants of global adaptive routing that enable load-balanced routing in the dragonfly. Each router in a dragonfly must make an adaptive routing decision based on the state of a global channel connected to a different router. Because of the indirect nature of this routing decision, conventional adaptive routing algorithms give degraded performance. We introduce the use of selective virtual-channel discrimination and the use of credit round-trip latency to both sense and signal channel congestion. The combination of these two methods gives throughput and latency that approaches that of an ideal adaptive routing algorithm.

Routing lookups in hardware at memory access speeds

Abstract: The increased bandwidth in the Internet puts great demands on network routers; for example, to route minimum sized Gigabit Ethernet packets, an IP router must process about 1.5/spl times/10/sup 6/ packets per second per port. Using the "rule-of-thumb" that it takes roughly 1000 packets per second for every 10/sup 6/ bits per second of line rate, an OC-192 line requires 10/spl times/10/sup 6/ routing lookups per second; well above current router capabilities. One limitation of router performance is the route lookup mechanism. IP routing requires that a router perform a longest-prefix-match address lookup for each incoming datagram in order to determine the datagram's next hop. We present a route lookup mechanism that when implemented in a pipelined fashion in hardware, can achieve one route lookup every memory access. With current 50 ns DRAM, this corresponds to approximately 20/spl times/10/sup 6/ packets per second; much faster than current commercially available routing lookup schemes. We also present novel schemes for performing quick updates to the forwarding table in hardware. We demonstrate using real routing update patterns that the routing tables can be updated with negligible overhead to the central processor.

Characterizing the Internet hierarchy from multiple vantage points

Abstract: The delivery of IP traffic through the Internet depends on the complex interactions between thousands of autonomous systems (AS) that exchange routing information using the border gateway protocol (BGP). This paper investigates the topological structure of the Internet in terms of customer-provider and peer-peer relationships between autonomous systems, as manifested in BGP routing policies. We describe a technique for inferring AS relationships by exploiting partial views of the AS graph available from different vantage points. Next we apply the technique to a collection of ten BGP routing tables to infer the relationships between neighboring autonomous systems. Based on these results, we analyze the hierarchical structure of the Internet and propose a five-level classification of AS. Our characterization differs from previous studies by focusing on the commercial relationships between autonomous systems rather than simply the connectivity between the nodes.

Pipelined packet switching and queuing architecture

Abstract: An architecture for a line card in a network routing device is provided. The line card architecture provides a bi-directional interface between the routing device and a network, both receiving packets from the network and transmitting the packets to the network through one or more connecting ports. In both the receive and transmit path, packets processing and routing in a multi-stage, parallel pipeline that can operate on several packets at the same time to determine each packet's routing destination is provided. Once a routing destination determination is made, the line card architecture provides for each received packet to be modified to contain new routing information and additional header data to facilitate packet transmission through the switching fabric. The line card architecture further provides for the use of bandwidth management techniques in order to buffer and enqueue each packet for transmission through the switching fabric to a corresponding destination port. The transmit path of the line card architecture further incorporates additional features for treatment and replication of multicast packets.

Internet routing instability

Abstract: This paper examines the network interdomain routing information exchanged between backbone service providers at the major US public Internet exchange points. Internet routing instability, or the rapid fluctuation of network reachability information, is an important problem currently facing the Internet engineering community. High levels of network instability can lead to packet loss, increased network latency and time to convergence. At the extreme, high levels of routing instability have led to the loss of internal connectivity in wide-area, national networks. We describe several unexpected trends in routing instability, and examine a number of anomalies and pathologies observed in the exchange of inter-domain routing information. The analysis in this paper is based on data collected from border gateway protocol (BGP) routing messages generated by border routers at five of the Internet core's public exchange points during a nine month period. We show that the volume of these routing updates is several orders of magnitude more than expected and that the majority of this routing information is redundant, or pathological. Furthermore, our analysis reveals several unexpected trends and ill-behaved systematic properties in Internet routing. We finally posit a number of explanations for these anomalies and evaluate their potential impact on the Internet infrastructure.