IP Lookup by Binary Search on Prefix Length
Waldvogel et al.9 have proposed a collection of hash tables (CHT) organization for an IP router table. Each hash table in the CHT contains prefixes of the same length together with markers for longer-length prefixes. IP lookup can be done with O(log ldist) hash-table searches, where ldist is the number of distinct prefix-lengths (also equal to the number of hash tables in the CHT). Srinivasan and Varghese8 have proposed the use of controlled prefix-expansion to reduce the value of ldist. The details of their algorithm to reduce the number of lengths are given in . The complexity of this algorithm is O(nW2), where n is the number of prefixes, and W is the length of the longest prefix. The algorithm of [7] does not minimize the storage required by the prefixes and markers for the resulting set of prefixes. We develop an algorithm that minimizes storage requirement but takes O(nW3 + kW4) time, where k is the desired number of distinct lengths. Also, we propose improvements to the heuristic of [7].

title: Efficient construction of multibit tries for IP lookup
abstract: Srinivasan and Varghese (1999) have proposed the use of multibit tries to represent routing tables used for Internet (IP) address lookups. They propose dynamic programming algorithms to determine the strides of optimal multibit fixed-stride and variable-stride tries. We improve on these algorithms by providing alternative dynamic programming formulations for both fixed-and variable-stride tries. While the asymptotic complexities of our algorithms are the same as those for the corresponding algorithms of Srinivasan and Varghese, experiments using real IPv4 routing table data indicate that our algorithms run considerably faster. Our fixed-stride trie algorithm is two to four times faster on a SUN workstation and 1.5 to three times faster on a Pentium IV PC. On a SUN workstation, our variable-stride trie algorithm is between two and 17 times faster than the corresponding algorithm of Srinivasan and Varghese; on a Pentium IV PC, our algorithm is between three and 47 times faster. An added feature of our variable-stride trie algorithm is the ability to insert and delete prefixes taking a fraction of the time needed to construct an optimal variable-stride trie "from scratch."

title: Efficient Dynamic Lookup For Bursty Access Patterns
abstract: Internet (IP) packet forwarding is typically done by finding the longest prefix in a router table that matches the packet's destination address. Although significant effort has been devoted to the development of data structures for static and dynamic router-tables for random packet-access-patterns, considerably less effort has been expended in the development of such structures for bursty access-patterns (i.e., streams of packets in which destination addresses repeat frequently within localized windows of packets). In this paper, we first formulate a variant, ACRBT (alternative collection of red-black trees), of the CRBT (collection of red-black trees) data structure proposed earlier for dynamic router-tables. By replacing the red-black trees used in the ACRBT with splay trees, we obtain the CST (collection of splay trees) structure in which search, insert, and delete take O(log n) amortized time per operation, where n is the number of prefixes in the router table. By replacing the front end of the CST with biased skip lists, we obtain the BSLPT (biased skip lists with prefix trees) structure in which search, insert, and delete take O(log n) expected time. The CST and BSLPT structures are designed so as to perform much better when the access pattern is bursty than when it is not. Experimental results using real IPv4 routing databases and synthetically generated search sequences as well as trace sequences are presented. For extremely bursty access patterns, the CST structure is best. Otherwise, the ACRBT is recommended. Our experiments also indicate that a supernode implementation of the ACRBT usually has better search performance than does the traditional one-element-per-node implementation.

title: IP lookup by binary search on prefix length
abstract: Waldvogel et al.  have proposed a collection of hash tables (CHT) organization for an IP router table. IP lookup can be done with O(log l/sub dist/) hash-table searches, where l/sub dist/ is the number of distinct prefix-lengths (also equal to the number of hash tables in the CHT). Srinivasan and Varghese [ACM transactions on Computer Systems, Feb:1-40, 1999] have proposed the use of controlled prefix-expansion to reduce the value of l/sub dist/. The algorithm of [V. Srinivasan, 1999] does not minimize the storage required by the prefixes and markers for the resulting set of prefixes. We develop an algorithm that minimizes storage requirement but takes O(nW/sup 3/ + kW/sup 4/) time, where k is the desired number of distinct lengths, n is the number of prefixes, and W is the length of the longest prefix. Also, we propose improvements to the heuristic of [V. Srinivasan, 1999].

title: Mobility Agent Advertisement Mechanism for Supporting Mobile IP in Ad Hoc Networks
abstract: Mobile IP has been proposed to solve the problem of how a mobile node may roam from its network and still maintain connectivity to the internet. Another emerging wireless architecture, mobile ad hoc networks (MANET), can be flexibly deployed in most environments without the need for infrastructure base stations. Integrating Mobile IP and MANET will facilitate the current trend of moving to an all-IP wireless environment. In this paper we propose an architecture of integrating Mobile IP and MANET based on the on-demand routing protocols. The proposed architecture employs two agent advertisement mechanisms, Mobility Agent Advertisement Mechanism (MAAM) and Aggregation-based Mobility Agent Advertisement Mechanism (AMAAM). In both mechanisms the mobility agent uses periodic beaconing of agent advertisement messages with on-demand routing protocols. Despite its architectural advantage, MAAM has some performance issues to be tackled because it incurs excessive generation of registration request messages of mobile nodes. AMAAM is an enhancement of MAAM for reducing the overhead of the beaconing by aggregating the reply messages of the agent advertisement. The simulation results show that AMAAM can effectively reduce the overhead of periodic agent advertisement and registration process.

title: Efficient distributed simulation of hierarchical DEVS models: transforming model structure into a non-hierarchical one
abstract: The Discrete Event Systems Specification (DEVS) formulism specifies a discrete event system in a hierarchical, modular form. This paper presents a distributed simulation methodology for models specified by the DEVS formalism. The methodology transforms a hierarchical DEVS model into a nonhierarchical one. This transformation can eliminate the overheads incurred during conventional hierarchical simulation, and make ease the synchronization of distributed simulation, thereby increasing the stability of the simulation engine. To show the effectiveness of the proposed methodology, we realize the simulation scheme in Visual C++, and conduct a benchmark simulation for a large-scale logistics system. The performance result shows that the proposed methodology works correctly and performs better than the previous approaches.

title: Performance of Service Location Protocols in MANET Based on Reactive Routing Protocols
abstract: Automatic service discovery, the problem of discovering service providers by specifying desired properties of services, is an important and necessary component for collaboration in the ubiquitous computing environment such as MANET. This paper investigates the effects of the on-demand route discovery on the performance of service location protocols in MANET based on on-demand routing protocols. We first design a service discovery architecture in MANET based on AODV and evaluate both the distributed and centralized versions of the architecture by simulation. For evaluating the performance, we examine such performance metrics as service hit ratio, service discovery time, and control message overheads. The results show that the distributed scheme outperforms the centralized scheme in most simulation scenarios because of the on-demand routing overheads.

title: TCP throughput analysis under transmission error and congestion losses
abstract: This paper analyzes the performance of a large population of long lived TCP flows experiencing random packet losses due to both random transmission errors and congestion created by the sharing of a common tail drop bottleneck router. We propose a natural and simple model for the joint throughput evolution of the set of TCP sessions under such a mix of losses. For the case of Poisson transmission errors, we show that the asymptotic model where the population tends to infinity leads to a well defined and tractable dynamical system. In particular, we get the mean value of the throughput of each session as a function of the transmission error rate and the synchronization rate in the bottleneck router. The large population asymptotic model has two interesting and non-intuitive properties: 1) there exists a positive threshold (given in closed form) on the transmission error rate above which there are no congestion losses at all in steady state; 2) below this threshold, the mean throughput of each flow is an increasing function of the transmission error rate, so that the maximum mean value is in fact achieved when the transmission error rate is equal to this threshold. The finite population model and models based on other classes of point processes are also studied. In particular, a sufficient condition is obtained for the existence of congestion times in the case of arbitrary transmission error point processes.

title: Mapping Cooperating GRID Applications by Affinity for Resource Characteristics
abstract: The Computational Grid, distributed and heterogeneous collections of computers in the Internet, has been considered a promising platform for the deployment of various high-performance computing applications. One of the crucial issues in the Grid is how to discover, select and map possible Grid resources in the Internet for meeting given applications. The general problem of statically mapping tasks to nodes has been shown to be NP-complete. In this paper, we propose a mapping algorithm for cooperating Grid applications by the affinity for the resources, named as MACA. The proposed algorithm utilizes the general affinity of Grid applications for certain resource characteristics such as CPU speeds, network bandwidth, and input/output handling capability. To show the effectiveness of the proposed mapping algorithm, we compare the performance of the algorithm with some previous mapping algorithms by simulation. The simulation results show that the algorithm could effectively utilize the affinity of Grid applications and shows good performance.