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25
IPAddress Lookup Using LCTries
, 1998
"... There has recently 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 multiGb/s routers for the Internet, without having to rely on multilayer switching techniques. We address this ..."
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Cited by 100 (0 self)
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There has recently 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 multiGb/s routers for the Internet, without having to rely on multilayer switching techniques. We address this problem by using an LCtrie, 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 \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 version 6. We present the basic structure, as well as an adaptive version that roughly doubles the number of lookups per second. More general classifications of packets that are needed for link sharing, quality of service provisioning and for multicast and multipath routing are also discussed. Our experimental results compare favorably with those reported previously in the research literature.
Fast address lookup for Internet routers
 IEEE Broadband Communications
, 1998
"... We consider the problem of organizing address tables for internet routers to enable fast searching. Our proposal is to to build an efficient, compact and easily searchable implementation of an IP routing table by using an LCtrie, a trie structure with combined path and level compression. The depth ..."
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Cited by 79 (4 self)
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We consider the problem of organizing address tables for internet routers to enable fast searching. Our proposal is to to build an efficient, compact and easily searchable implementation of an IP routing table by using an LCtrie, a trie structure with combined path and level compression. The depth of this structure increases very slowly as function of the number of entries in the table. A node can be coded in only four bytes and the size of the main search structure never exceeds 256 kB for the tables in the US core routers. We present a software implementation that can sustain approximately half a million lookups per second on a 133 MHz Pentium personal computer, and two million lookups per second on a more powerful SUN Sparc Ultra II workstation. 1
Asymptotic Behavior of the LempelZiv Parsing Scheme and Digital Search Trees
 Theoretical Computer Science
, 1995
"... The LempelZiv parsing scheme finds a wide range of applications, most notably in data compression and algorithms on words. It partitions a sequence of length n into variable phrases such that a new phrase is the shortest substring not seen in the past as a phrase. The parameter of interest is the n ..."
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Cited by 64 (30 self)
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The LempelZiv parsing scheme finds a wide range of applications, most notably in data compression and algorithms on words. It partitions a sequence of length n into variable phrases such that a new phrase is the shortest substring not seen in the past as a phrase. The parameter of interest is the number M n of phrases that one can construct from a sequence of length n. In this paper, for the memoryless source with unequal probabilities of symbols generation we derive the limiting distribution of M n which turns out to be normal. This proves a long standing open problem. In fact, to obtain this result we solved another open problem, namely, that of establishing the limiting distribution of the internal path length in a digital search tree. The latter is a consequence of an asymptotic solution of a multiplicative differentialfunctional equation often arising in the analysis of algorithms on words. Interestingly enough, our findings are proved by a combination of probabilistic techniques such as renewal equation and uniform integrability, and analytical techniques such as Mellin transform, differentialfunctional equations, dePoissonization, and so forth. In concluding remarks we indicate a possibility of extending our results to Markovian models.
A Generalized Suffix Tree and Its (Un)Expected Asymptotic Behaviors
 SIAM J. Computing
, 1996
"... Suffix trees find several applications in computer science and telecommunications, most notably in algorithms on strings, data compressions and codes. Despite this, very little is known about their typical behaviors. In a probabilistic framework, we consider a family of suffix trees  further calle ..."
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Cited by 52 (29 self)
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Suffix trees find several applications in computer science and telecommunications, most notably in algorithms on strings, data compressions and codes. Despite this, very little is known about their typical behaviors. In a probabilistic framework, we consider a family of suffix trees  further called bsuffix trees  built from the first n suffixes of a random word. In this family a noncompact suffix tree (i.e., such that every edge is labeled by a single symbol) is represented by b = 1, and a compact suffix tree (i.e., without unary nodes) is asymptotically equivalent to b ! 1 as n ! 1. We study several parameters of bsuffix trees, namely: the depth of a given suffix, the depth of insertion, the height and the shortest feasible path. Some new results concerning typical (i.e., almost sure) behaviors of these parameters are established. These findings are used to obtain several insights into certain algorithms on words, molecular biology and universal data compression schemes. Key Wo...
Burst Tries: A Fast, Efficient Data Structure for String Keys
 ACM Transactions on Information Systems
, 2002
"... Many applications depend on efficient management of large sets of distinct strings in memory. For example, during index construction for text databases a record is held for each distinct word in the text, containing the word itself and information such as counters. We propose a new data structure, t ..."
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Cited by 28 (10 self)
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Many applications depend on efficient management of large sets of distinct strings in memory. For example, during index construction for text databases a record is held for each distinct word in the text, containing the word itself and information such as counters. We propose a new data structure, the burst trie, that has significant advantages over existing options for such applications: it requires no more memory than a binary tree; it is as fast as a trie; and, while not as fast as a hash table, a burst trie maintains the strings in sorted or nearsorted order. In this paper we describe burst tries and explore the parameters that govern their performance. We experimentally determine good choices of parameters, and compare burst tries to other structures used for the same task, with a variety of data sets. These experiments show that the burst trie is particularly effective for the skewed frequency distributions common in text collections, and dramatically outperforms all other data structures for the task of managing strings while maintaining sort order.
On the Distribution for the Duration of a Randomized Leader Election Algorithm
 Ann. Appl. Probab
, 1996
"... We investigate the duration of an elimination process for identifying a winner by coin tossing, or, equivalently, the height of a random incomplete trie. Applications of the process include the election of a leader in a computer network. Using direct probabilistic arguments we obtain exact expressio ..."
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Cited by 28 (10 self)
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We investigate the duration of an elimination process for identifying a winner by coin tossing, or, equivalently, the height of a random incomplete trie. Applications of the process include the election of a leader in a computer network. Using direct probabilistic arguments we obtain exact expressions for the discrete distribution and the moments of the height. Elementary approximation techniques then yield asymptotics for the distribution. We show that no limiting distribution exists, as the asymptotic expressions exhibit periodic fluctuations. In many similar problems associated with digital trees, no such exact expressions can be derived. We therefore outline a powerful general approach, based on the analytic techniques of Mellin transforms, Poissonization, and dePoissonization, from which distributional asymptotics for the height can also be derived. In fact, it was this complex variables approach that led to our original discovery of the exact distribution. Complex analysis metho...
Analysis of an Asymmetric Leader Election Algorithm
 Electronic J. Combin
, 1996
"... We consider a leader election algorithm in which a set of distributed objects (people, computers, etc.) try to identify one object as their leader. The election process is randomized, that is, at every stage of the algorithm those objects that survived so far flip a biased coin, and those who rec ..."
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Cited by 27 (9 self)
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We consider a leader election algorithm in which a set of distributed objects (people, computers, etc.) try to identify one object as their leader. The election process is randomized, that is, at every stage of the algorithm those objects that survived so far flip a biased coin, and those who received, say a tail, survive for the next round. The process continues until only one objects remains. Our interest is in evaluating the limiting distribution and the first two moments of the number of rounds needed to select a leader. We establish precise asymptotics for the first two moments, and show that the asymptotic expression for the duration of the algorithm exhibits some periodic fluctuations and consequently no limiting distribution exists. These results are proved by analytical techniques of the precise analysis of algorithms such as: analytical poissonization and depoissonization, Mellin transform, and complex analysis.
Local limit theorems for finite and infinite urn models
 Ann. Probab
, 2007
"... Local limit theorems are derived for the number of occupied urns in general finite and infinite urn models under the minimum condition that the variance tends to infinity. Our results represent an optimal improvement over previous ones for normal approximation. 1. Introduction. A classical theorem o ..."
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Cited by 17 (2 self)
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Local limit theorems are derived for the number of occupied urns in general finite and infinite urn models under the minimum condition that the variance tends to infinity. Our results represent an optimal improvement over previous ones for normal approximation. 1. Introduction. A classical theorem of Rényi [29] for the number of empty boxes, denoted by μ0(n, M), in a sequence of n random allocations of indistinguishable balls into M boxes with equal probability 1/M, can be stated as follows: If the variance of μ0(n, M) tends to infinity with n, then μ0(n, M) is asymptotically normally distributed. This result, seldom stated in this form in the literature,
Rounding of continuous random variables and oscillatory asymptotics
 Ann. Probab
"... We study the characteristic function and moments of the integervalued random variable ⌊X + α⌋, where X is a continuous random variables. The results can be regarded as exact versions of Sheppard’s correction. Rounded variables of this type often occur as subsequence limits of sequences of integerva ..."
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Cited by 15 (8 self)
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We study the characteristic function and moments of the integervalued random variable ⌊X + α⌋, where X is a continuous random variables. The results can be regarded as exact versions of Sheppard’s correction. Rounded variables of this type often occur as subsequence limits of sequences of integervalued random variables. This leads to oscillatory terms in asymptotics for these variables, something that has often been observed, for example in the analysis of several algorithms. We give some examples, including applications to tries, digital search trees and Patricia tries. 1. Introduction. Let
Laws of large numbers and tail inequalities for random tries and Patricia trees
 Journal of Computational and Applied Mathematics
, 2002
"... Abstract. We consider random tries and random patricia trees constructed from n independent strings of symbols drawn from any distribution on any discrete space. If Hn is the height of this tree, we show that Hn/E{Hn} tends to one in probability. Additional tail inequalities are given for the height ..."
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Cited by 15 (5 self)
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Abstract. We consider random tries and random patricia trees constructed from n independent strings of symbols drawn from any distribution on any discrete space. If Hn is the height of this tree, we show that Hn/E{Hn} tends to one in probability. Additional tail inequalities are given for the height, depth, size, and profile of these trees and ordinary tries that apply without any conditions on the string distributions—they need not even be identically distributed.