IP Routing Table Research Articles

A power-saving pre-classifier for TCAM-based IP lookup

Ternary Content Addressable Memory (TCAM) is widely used for designing high-throughput forwarding engines on most of today's high-end routers. Despite its capability for line-speed queries, it is very power hungry and space inefficient. By making use of a pre-classifier to activate TCAM blocks selectively, MEET-IP, a recently proposed TCAM based IP lookup scheme, significantly improves the utilization of TCAMs. However, it suffers from performance degradation because it uses a two-level pre-classifier. In this paper, we propose SplitIP, a memory and power efficient TCAM-based scheme for IP routing table lookup. We first transform the IP lookup problem to a point location problem through a routing table projection. Based on the projection, we propose a top-down splitting algorithm to separate routing table prefixes evenly into TCAM blocks. Finally, a simpler one-level classifier is constructed for fast pre-classification using improved range encoding techniques. The top-down prefix partitioning algorithm combined with the database independent encoding scheme provides an incremental update for SplitIP. Experimental results show that our design achieves more than 97% power reduction with a TCAM storage overhead of less than 3% on average.

Multi-Inherited Search Tree for Dynamic IP Router-Tables

IP lookup and routing table update affect the speed at which a router forwards packets. This study proposes a new data structure for dynamic router tables used in IP lookup and update, called the Multi-inherited Search Tree (MIST). Partitioning each prefix according to an index value and removing the relationships among prefixes enables performing IP lookup operations efficiently. Because a prefix trie is used as a substructure, memory can be consumed and dynamic router-table operations can be performed efficiently. Experiments using real IPv4 routing databases indicated that the MIST uses memory efficiently and performs lookup, insert, and delete operations effectively.

FTCAM: An Area-Efficient Flash-Based Ternary CAM Design

This paper presents a Ternary Content-addressable Memory (TCAM) design which is based on the use of floating-gate (flash) transistors. TCAMs are extensively used in high speed IP networking, and are commonly found in routers in the internet core. Traditional TCAM ICs are built using CMOS devices, and a single TCAM cell utilizes 17 transistors. In contrast, our TCAM cell utilizes only two flash transistors, thereby significantly reducing circuit area. We cover the chip-level architecture of the TCAM IC briefly, focusing mainly on the TCAM block which does fast parallel IP routing table lookup. Our flash-based TCAM (FTCAM) block is simulated in SPICE, and we show that it has a significantly lowered area compared to a CMOS based TCAM block, with a speed that can meet current ( $\sim$ 400 Gb/s) data rates that are found in the internet core.

Poptrie

Internet of Things leads to routing table explosion. An inexpensive approach for IP routing table lookup is required against ever growing size of the Internet. We contribute by a fast and scalable software routing lookup algorithm based on a multiway trie, called Poptrie. Named after our approach to traversing the tree, it leverages the population count instruction on bit-vector indices for the descendant nodes to compress the data structure within the CPU cache. Poptrie outperforms the state-of-the-art technologies, Tree BitMap, DXR and SAIL, in all of the evaluations using random and real destination queries on 35 routing tables, including the real global tier-1 ISP's full-route routing table. Poptrie peaks between 174 and over 240 Million lookups per second (Mlps) with a single core and tables with 500--800k routes, consistently 4--578% faster than all competing algorithms in all the tests we ran. We provide the comprehensive performance evaluation, remarkably with the CPU cycle analysis. This paper shows the suitability of Poptrie in the future Internet including IPv6, where a larger route table is expected with longer prefixes.

Scalability of information centric networking using mediated topology management

Information centric networking is a new concept that places emphasis on the information items themselves rather than on where the information items are stored. Consequently, routing decisions can be made based on the information items rather than on simply destination addresses. There are a number of models proposed for information centric networking and it is important that these models are investigated for their scalability if we are to move from early prototypes towards proposing that these models are used for networks operating at the scale of the current Internet. This paper investigates the scalability of an ICN system that uses mediation between information providers and information consumers using a publish/subscribe delivery mechanism. The scalability is investigated by extrapolating current IP traffic models for a typical national-scale network provider in the UK to estimate mediation workload. The investigation demonstrates that the mediation workload for route determination is on a scale that is comparable to, or less than, that of current IP routing while using a forwarding mechanism with considerably smaller tables than current IP routing tables. Additionally, the work shows that this can be achieved using a security mechanism that mitigates against maliciously injected packets thus stopping attacks such as denial of service that is common with the current IP infrastructure.

GPU-accelerated name lookup with component encoding

Named Data Networking (NDN) aims at redesigning the current Internet: using names to identify the wanted contents instead of using IP addresses to locate the end hosts, with the goal of substantially improving the data retrieval efficiency. Different from IP routers, NDN routers forward packets by names. An NDN name is composed of a number of length-variable components, causing the name to be tens or even hundreds of characters in length. Meanwhile, NDN routing tables could be several orders of magnitude larger than the current IP routing tables. This kind of complex name constitution plus the huge-sized name table makes wire speed name lookup an extremely challenging task.In pursuit of overcoming this challenge, we propose a Name Component Encoding (NCE) solution that assigns codes (integers) to name components. Along with an elaborate one-dimensional transition array and a local code allocation algorithm, NCE performs every node transition by a single memory access to boost lookup speed besides greatly compressing storage space. Moreover, we implement the name lookup engine on a GPU platform to exploit GPU’s massive parallel processing power; furthermore, pipeline and CUDA multi-stream techniques are applied to GPU to increase lookup throughout while reducing lookup latency. Experimental results demonstrate that, under the constraint of 100μs latency, our GPU-based name lookup engine can achieve 51.78 million searches per second on a name table containing 10 million prefixes. NCE also saves 59.57% memory cost comparing with the character trie and supports around 900K prefix insertions and 1.2 million prefix deletions per second.

Practical Network-Wide Compression of IP Routing Tables

The memory Internet routers use to store paths to destinations is expensive, and must be continually upgraded in the face of steadily increasing routing table size. Unfortunately, routing protocols are not designed to gracefully handle cases where memory becomes full, which arises increasingly often due to misconfigurations and routing table growth. Hence router memory must typically be heavily overprovisioned by network operators, inflating operating costs and administrative effort. The research community has primarily focused on clean-slate solutions that cannot interoperate with the deployed base of protocols. This paper presents an incrementally-deployable Memory Management System (MMS) that reduces associated router state by up to 70%. The MMS coalesces prefixes to reduce memory consumption and can be deployed locally on each router or centrally on a route server. The system can operate transparently, without requiring changes in other ASes. Our memory manager can extend router lifetimes up to seven years, given current prefix growth trends.

EXPERIMENTAL EVALUATIONS OF ALGORITHMS FOR IP TABLE MINIMIZATION

Reducing the size of IP routing tables is one of the most compelling scaling problems affecting the Internet because of massive growth of routing table entries, increased traffic, and the migration to 128 bit IPv6 addresses. Various algorithms for IP table minimization have been proposed in the literature both for a single and for multiple tables, also with the possibility of performing address reassignments. In this paper we first introduce two new compression heuristics, the BFM and its evolution called BFM-Cluster, that exploit address reassignments for the minimization of multiple routing tables, and then we experimentally evaluate their performances together with the already existing techniques. Since a main problem posed by the growth of the routing tables sizes is the consequent general increase of the table lookup time during the routing of the IP packets, the aim is twofold: to measure and compare the compression ratios of the different algorithms, and to estimate the effects of the compression on the lookup times by measuring the induced improvement on the time of the main algorithms and data structures for the fast IP address lookup from the original tables to the compressed ones. Our point is that the existing techniques are efficient in different situations, with BFM-Cluster heuristic outperforming all other ones.

Stable Routing With Virtual Topology Capacity Adjustment: A Novel Paradigm for Operating Optical Networks

Advances in optical equipment permit network carriers to offer lightpath-on-demand services to Internet service providers (ISPs). These services are the key for constructing cost-efficient virtual topology capacity adjustment (VTCA) schemes, where ISPs dynamically adapt the number of lightpaths contracted between their IP routers, according to time-varying traffic volumes. An existing technique called lightpath bundling offers ISPs the possibility of grouping lightpaths between the same pair of routers into so-called bundles, perceived by the IP layer as single virtual links of aggregated capacity. Consequently, new lightpaths added or removed from bundles are not seen by the IP layer as new links necessary to advertise, but simply as capacity adjustments of already existing links. Adding lightpath bundling to the picture opens the door for developing VTCA schemes which maintain stability in the IP routing tables, a major requirement for ISPs. In this paper, we present and evaluate the merits of the proposed stable routing VTCA (SR-VTCA) paradigm and present algorithms for designing such a scheme. The results clearly show that SR-VTCA gives an advantageous trade-off between the fully static network with no capacity adjustment and the fully dynamic VTCA scheme where both the IP routing and the VT are reconfigured over time.

SUSE: Superior Storage-Efficiency for Routing Tables Through Prefix Transformation and Aggregation

A novel storage design for IP routing table construction is introduced on the basis of a single set-associative hash table to support fast longest prefix matching (LPM). The proposed design involves two key techniques to lower table storage required drastically: 1) storing transformed prefix representations; and 2) accommodating multiple prefixes per table entry via prefix aggregation, achieving superior storage-efficiency (SUSE). With each prefix (p(x)) maneuvered as a polynomial, p(x) - q(x) x g(a;) + r(x) based on a divisor g(x), SUSE keeps only q(x) rather than full and long p(x) in an r(x)-indexed table with 2degree(g(x)) entries, because q(x) and r(x) uniquely identify p(x). Additionally, using r(x) as the hash index exhibits better distribution than do original prefixes, reducing hash collisions, which can be tolerated further by the set-associative design. Given a set of chosen prefix lengths (called treads), all prefixes are rounded down to nearest treads under SUSE before hashed to the table using their transformed representations so that prefix aggregation opportunities abound in hash entries. SUSE yields significant table storage reduction and enjoys fast lookups and speedy incremental updates not possible for a typical trie-based design, with the worst-case lookup time shown upper-bounded theoretically by the number of treads (?) but found experimentally to be 4 memory accesses when ? equals 8. SUSE makes it possible to fit a large routing table with 256 K (or even 1 M) prefixes in on-chip SRAM by today's ASIC technology. It solves both the memory- and the bandwidth-intensive problems faced by IP routing.

DOM: a scalable multicast protocol for next-generation internet

In this article we propose a scalable and efficient destination-oriented multicast protocol for next-generation Internet. With DOM, each packet carries explicit destinations information, instead of an implicit group address, to facilitate the multicast data delivery; and each router leverages the unicast IP routing table to determine necessary multicast copies and next-hop interfaces. The fundamental issue is that we need to limit the bandwidth overhead for such explicit addressing, since it is impractical to attach all the destination addresses to each packet. We resort to the Bloom filter technique to encode the destination information carried by each packet for bandwidth efficiency, with elaborated design to accommodate the features of the practical Internet including longest-prefix matching, route aggregation, and asymmetric interdomain routing. Moreover, DOM enables a fast group joining approach to minimize the joining delay perceived by receivers. The scalability and efficiency of DOM are demonstrated with simulation results.

IP--: A Reduced Internet Protocol for Optical Packet Networking

IP− − is proposed as an Internet Protocol suitable for optical packet networking. As optical routers require much faster control than electric ones and lack of optical buffers other than those by fiber delay lines requires fixed time control, Internet Protocols must be at least as simple as IPv4 and much simpler than IPv6. IP− − also addresses issues of IP address space exhaustion and IP routing table explosion.

Expediating IP lookups with reduced power via TBM and SST supernode caching

In this paper, we propose a novel supernode caching scheme to reduce IP lookup latencies and energy consumption in network processors. In stead of using an expensive TCAM based scheme, we implement a set-ssociative SRAM based cache. We use two different algorithms, tree bitmap (TBM) and shape shifting trie (SST), to organize an IP routing table as a supernode tree composed of a group of supernodes. We add a small supernode cache in-between the processor and the low-level memory containing the IP routing table in a tree structure. The supernode cache stores recently visited supernodes of the longest matched prefixes in the IP routing tree. A supernode hitting in the cache reduces the number of accesses to the low-level memory, leading to a fast IP lookup. According to our simulations, up to 72% memory accesses can be avoided by a 128 KB TBM supernode cache for the selected three trace files, and up to 78% memory accesses can be reduced while using a same size of SST supernode cache. Average TBM and SST supernode cache miss ratios are as low as 4% and 7%, respectively. Compared to a TCAM with the same size, the TBM and SST supernode caches can both reduce 77% of energy consumption.

Design of a Scalable Multicast Scheme With an Application-Network Cross-Layer Approach

This paper develops an efficient and scalable multicast scheme for high-quality multimedia distribution. The traditional IP multicast, a pure network-layer solution, is bandwidth efficient in data delivery but not scalable in managing the multicast tree. The more recent overlay multicast establishes the data-dissemination structure at the application layer; however, it induces redundant traffic at the network layer. We propose an application-oriented multicast (AOM) protocol, which exploits the application-network cross-layer design. With AOM, each packet carries explicit destinations information, instead of an implicit group address, to facilitate the multicast data delivery; each router leverages the unicast IP routing table to determine necessary multicast copies and next-hop interfaces. In our design, all the multicast membership and addressing information traversing the network is encoded with bloom filters for low storage and bandwidth overhead. We theoretically prove that the AOM service model is loop-free and incurs no redundant traffic. The false positive performance of the bloom filter implementation is also analyzed. Moreover, we show that the AOM protocol is a generic design, applicable for both intra-domain and inter-domain scenarios with either symmetric or asymmetric routing.

DBCTIA algorithm based on binary object optimization used for load balancing of multiple links

The algorithm DBCTIA(Delay and residual Bandwidth's Covariance Target Iteration Algorithm) based on binary object optimization for load balancing of multiple links was provided based on IP traffic engineering and Delay Target Iteration Algorith(DTIA) for delay balancing of multiple links.DBCTIA algorithm can balance the delay and residual bandwidth of multiple links by the second adjusting of IP routing table's size and amount according to the covariance of links' delay and residual bandwidth.Experimental results show the balancing of multiple links' delay and residual bandwidth is remarkable by DBCTIA and the power value of multiple links after the balancing by DBCTIA is larger than that after the balancing by DTIA.

Efficient IP routing table lookup scheme

One of the pertinent issues in IP router design is the IP routing table lookup. With high-speed multi-gigabit links required in the Internet, the lookup has become a great bottleneck. The authors propose a lookup scheme that can efficiently handle IP route lookup, insertion and deletion inside the routing table. This method is less complex in comparison to other schemes. By using careful memory management design, each of the IP routes are only stored once instead of the range that is used conventionally. Therefore, the required memory is reduced. In addition, a novel skip function is introduced to further decrease the memory size. The proposed scheme, which furnishes approximately 75×106 lookups/s, needs only a small memory size of 0.59 Mbyte. This scheme can be implemented in a pipeline hardware design and thus achieves one route lookup for every memory access. This lookup scheme can also be easily scaled to IPv6 in the future.

High-performance IP routing table lookup

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 packets forwarding, which complicates the IP lookup. Currently, this process is mainly done in software and several schemes have been proposed for hardware implementation. Since the IP lookup performance is a major design issue for the new generation routers, in this article we propose a fast IP address lookup scheme, which significantly reduces the forwarding table to fit into SRAM with very low cost. It can also be implemented in hardware using the pipeline technique. By using our proposed method, the required memory space can be 90–170 Kb less than the previous scheme and three memory accesses for a lookup in the worst case. When implemented in hardware pipeline architecture, our mechanism can achieve one routing lookup per memory access.

IP-address lookup using LC-tries

There has been a notable interest in the organization of routing information to enable fast lookup of IP addresses. The interest is primarily motivated by the goal of building multigigabit routers for the Internet, without having to rely on multilayer switching techniques. We address this problem by using an LC-trie, a trie structure with combined path and level compression. This data structure enables us to build efficient, compact, and easily searchable implementations of an IP-routing table. The structure can store both unicast and multicast addresses with the same average search times. The search depth increases as /spl Theta/(log log n) with the number of entries in the table for a large class of distributions, and it is independent of the length of the addresses. A node in the trie can be coded with four bytes. Only the size of the base vector, which contains the search strings, grows linearly with the length of the addresses when extended from 4 to 16 bytes, as mandated by the shift from IP version 4 to IP version 6. We present the basic structure as well as an adaptive version that roughly doubles the number of lookups/s. More general classifications of packets that are needed for link sharing, quality-of-service provisioning, and multicast and multipath routing are also discussed. Our experimental results compare favorably with those reported previously in the research literature.