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33
Scalable High Speed IP Routing Lookups
, 1997
"... Internet address lookup is a challenging problem because of increasing routing table sizes, increased traffic, higher speed links, and the migration to 128 bit IPv6 addresses. IP routing lookup requires computing the best matching prefix, for which standard solutions like hashing were believed to be ..."
Abstract
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Cited by 202 (13 self)
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Internet address lookup is a challenging problem because of increasing routing table sizes, increased traffic, higher speed links, and the migration to 128 bit IPv6 addresses. IP routing lookup requires computing the best matching prefix, for which standard solutions like hashing were believed to be inapplicable. The best existing solution we know of, BSD radix tries, scales badly as IP moves to 128 bit addresses. Our paper describes a new algorithm for best matching prefix using binary search on hash tables organized by prefix lengths. Our scheme scales very well as address and routing table sizes increase: independent of the table size, it requires a worst case time of log 2 (address bits) hash lookups. Thus only 5 hash lookups are needed for IPv4 and 7 for IPv6. We also introduce Mutating Binary Search and other optimizations that, for a typical IPv4 backbone router with over 33,000 entries, considerably reduce the average number of hashes to less than 2, of which one hash can be si...
Faster IP Lookups using Controlled Prefix Expansion
- ACM Transactions on Computer Systems
, 1998
"... Internet (IP) address lookup is a major bottleneck in high performance routers. IP address lookup is challenging because it requires a longest matching prefix lookup. It is compounded by increasing routing table sizes, increased traffic, higher speed links, and the migration to 128 bit IPv6 addres ..."
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Cited by 126 (4 self)
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Internet (IP) address lookup is a major bottleneck in high performance routers. IP address lookup is challenging because it requires a longest matching prefix lookup. It is compounded by increasing routing table sizes, increased traffic, higher speed links, and the migration to 128 bit IPv6 addresses. We describe how IP lookups can be made faster using a new technique called controlled prefix expansion. Controlled prefix expansion, together with optimization techniques based on dynamic programming, can be used to improve the speed of the best known IP lookup algorithms by at least a factor of two. When applied to trie search, our techniques provide a range of algorithms whose performance can be tuned. For example, with 1 MB of L2 cache, trie search of the MaeEast database with 38,000 prefixes can be done in a worst case search time of 181 nsec, a worst case insert/delete time of 2.5 msec, and an average insert/delete time of 4 usec. Our actual experiments used 512 KB L2 cache ...
Scalable High-Speed Prefix Matching
- ACM TRANSACTIONS ON COMPUTER SYSTEMS
, 2001
"... Finding the longest matching prefix from a database of keywords is an old problem with a number of applications, ranging from dictionary searches to advanced memory management to computational geometry. But perhaps today's most frequent best matching prefix lookups occur in the Internet, when f ..."
Abstract
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Cited by 28 (5 self)
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Finding the longest matching prefix from a database of keywords is an old problem with a number of applications, ranging from dictionary searches to advanced memory management to computational geometry. But perhaps today's most frequent best matching prefix lookups occur in the Internet, when forwarding packets from router to router. Internet traffic volume and link speeds are rapidly increasing; at the same time, an increasing user population is increasing the size of routing tables against which packets must be matched. Both factors make router prefix matching extremely performance critical. In this paper, we introduce a taxonomy for prefix matching technologies, which we use as a basis for describing, categorizing, and comparing existing approaches. We then present in detail a fast scheme using binary search over hash tables, which is especially suited for matching long addresses, such as the 128 bit addresses proposed for use in the next generation Internet Protocol, IPv6. We also present optimizations that exploit the structure of existing databases to further improve access time and reduce storage space.
An axiomatic basis for communication
- In Proceedings of HotNets 2006
, 2007
"... The de-facto service architecture of today’s communication networks lacks a well-defined and coherent theoretical foundation. With layering as the only means for functional abstraction, the diversity of current technologies cannot be expressed consistently and analyzed properly. In this paper, we pr ..."
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Cited by 20 (1 self)
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The de-facto service architecture of today’s communication networks lacks a well-defined and coherent theoretical foundation. With layering as the only means for functional abstraction, the diversity of current technologies cannot be expressed consistently and analyzed properly. In this paper, we present an axiomatic formulation of fundamental mechanisms in communication networks. In particular, we reconcile the existing but somewhat fuzzy concepts of naming and addressing and present a consistent set of primitives that are sufficient to compose communication services. The long-term goal of this exercise is to better document, verify, evaluate, and eventually implement network services. 1
Efficient construction of pipelined multibit-trie Router-Tables
- IEEE Trans. Comput
, 2003
"... Efficient algorithms to construct multibit tries suitable for pipelined router-table applications are developed. We first enhance the 1-phase algorithm of Basu and Narlikar [1] obtaining a 1-phase algorithm that is 2.5 to 3 times as fast. Next we develop 2-phase algorithms that not only guarantee to ..."
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Cited by 18 (2 self)
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Efficient algorithms to construct multibit tries suitable for pipelined router-table applications are developed. We first enhance the 1-phase algorithm of Basu and Narlikar [1] obtaining a 1-phase algorithm that is 2.5 to 3 times as fast. Next we develop 2-phase algorithms that not only guarantee to minimize the maximum per-stage memory but also guarantee to use the least total memory subject to the former constraint. Our 2-phase algorithms not only generate better pipelined trees than generated by the 1-phase algorithm but they also take much less time. A node pullup scheme that guarantees no increase in maximum per-stage memory as well as a partitioning heuristic that generates pipelined multibit tries requiring less maximum per-stage memory than required by the tries obtained using the 1-phase and 2-phase algorithms also are proposed.
Internet traffic load balancing using dynamic hashing with flow volume
- in Internet Performance and Control of Network Systems III at SPIE ITCOM 2002
, 2002
"... Sending IP packets over multiple parallel links is in extensive use in today’s Internet and its use is growing due to its scalability, reliability and cost-effectiveness. To maximize the efficiency of parallel links, load balancing is necessary among the links, but it may cause the problem of packet ..."
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Cited by 10 (1 self)
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Sending IP packets over multiple parallel links is in extensive use in today’s Internet and its use is growing due to its scalability, reliability and cost-effectiveness. To maximize the efficiency of parallel links, load balancing is necessary among the links, but it may cause the problem of packet reordering. Since packet reordering impairs TCP performance, it is important to reduce the amount of reordering. Hashing offers a simple solution to keep the packet order by sending a flow over a unique link, but static hashing does not guarantee an even distribution of the traffic amount among the links, which could lead to packet loss under heavy load. Dynamic hashing offers some degree of load balancing but suffers from load fluctuations and excessive packet reordering. To overcome these shortcomings, we have enhanced the dynamic hashing algorithm to utilize the flow volume information in order to reassign only the appropriate flows. This new method, called dynamic hashing with flow volume (DHFV), eliminates unnecessary flow reassignments of small flows and achieves load balancing very quickly without load fluctuation by accurately predicting the amount of transferred load between the links. In this paper we provide the general framework of DHFV and address the challenges in implementing DHFV. We then introduce two algorithms of DHFV with different flow selection strategies and show their performances through simulation.
o(log n) dynamic router-tables for prefixes and ranges
- IEEE Transactions on Computers
, 2003
"... Two versions of the Internet (IP) router-table problem are considered. In the first, the router table consists of n pairs of tuples of the form (p, a), where p is an address prefix and a is the next-hop information. In this version of the router-table problem, we are to perform the following operati ..."
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Cited by 7 (2 self)
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Two versions of the Internet (IP) router-table problem are considered. In the first, the router table consists of n pairs of tuples of the form (p, a), where p is an address prefix and a is the next-hop information. In this version of the router-table problem, we are to perform the following operations: insert a new tuple, delete an existing tuple, and find the tuple with longest matching-prefix for a given destination address. We show that each of these three operations may be performed in O(log n) time in the worst case using a priority-search tree. In the second version of the router-table problem considered by us, each tuple in the table has the form (r, a), where r is a range of destination addresses matched by the tuple. The set of tuples in the table is conflict free. For this version of the router-table problem, we develop a data structure that employs priority-search trees as well as red-black trees. This data structure permits us to perform each of the operations insert, delete, and find the tuple with most-specific matching-range for a given destination address in O(log n) time each in the worst case. The insert and delete operations preserve the conflict-free property of the set of tuples. Experimental results also are presented.
Adaptive Data Structures for IP Lookups
, 2003
"... The problem of efficient data structures for IP lookups has been well studied in literature. Techniques such as LC tries and Extensible Hashing are commonly used. In this paper, we address the problem of generalizing LC tries and Extensible Hashing, based on traces of past lookups, to provide perfor ..."
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Cited by 7 (1 self)
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The problem of efficient data structures for IP lookups has been well studied in literature. Techniques such as LC tries and Extensible Hashing are commonly used. In this paper, we address the problem of generalizing LC tries and Extensible Hashing, based on traces of past lookups, to provide performance guarantees for memory sub-optimal structures. As a specific example, if a memory-optimal (LC) trie takes 6MB and the total memory at the router is 8MB, how should the trie be modified to make best use of the 2 MB of excess memory? We present a greedy algorithm for this problem and prove that, if for the optimal data structure there are b fewer memory accesses on average for each lookup compared with the original trie, the solution produced by the greedy algorithm will have 22 fewer memory accesses on average (compared to the original trie). An efficient implementation of this algorithm presents significant additional challenges. We describe an implementation with a time complexity of O(#(d)n log n) and a space complexity of O(n), where n is the number of nodes of the trie and d its depth. The depth of a trie is fixed for a given version of the Internet protocol and is typically O(log n).Inthiscase,#(d)=O(log n). We demonstrate experimentally the performance and scalability of the algorithm on actual routing data. We also show that our algorithm significantly outperforms Extensible Hashing for the same amount of memory.
