Samphel Norden

Algorithms for optimizing leveled commitment contracts

In automated negotiation systems consisting of self-interested agents, contracts have traditionally been binding. Leveled commitment contracts-i.e. contracts where each party can decommit by paying a predetermined penalty were recently shown to improve Pareto efficiency even if agents rationally decommit in Nash equilibrium using inflated thresholds on how good their outside offers must be before they decommit. This paper operationalizes the four leveled commitment contracting protocols by presenting algorithms for using them. Algorithms are presented for computing the Nash equilibrium decommitting thresholds and decommitting probabilities given the contract price and the penalties. Existence and uniqueness of the equilibrium are analyzed. Algorithms are also presented for optimizing the contract itself (price and penalties). Existence and uniqueness of the optimum are analyzed. Using the algorithms we offer a contract optimization service on the web as part of Mediator, our next generation electronic commerce server. Finally, the algorithms are generalized to contracts involving more than two agents.

DRES: network resource management using deferred reservations

We consider the problem of resource reservation for networks. Current approaches for resource reservation in integrated service networks adopt an all-or-nothing approach, where partially acquired resources must be released if resources are not available at all routers on the chosen path. Furthermore, under high load, end-systems must retry requests repeatedly leading to inefficient allocation and increased traffic. We propose a new approach called Deferred REServation (DRES) that substantially improves performance (reduces the overall flow rejection probability and increases link utilization) over the all-or-nothing reservation approach. Flow admissibility is increased by deferring requests at routers for a limited period of time until resources are available. Analytical and simulation results confirm the performance benefits of our approach.

Dynamic planning based protocols for real-time communication in LAN and switched LAN environments

The problem of real-time communication over a multiple access network has been well studied in the recent past. However, there are very few protocols that can bound the worst case channel access time to ensure predictability of message transmission for the LAN environment. In addition, there has been no prior work addressing real-time communication over a switched (extended) local area network (SLAN), where several LAN segments are connected through a switch. In this paper, we propose real-time protocols for the LAN and the SLAN. The proposed protocols are based on CSMA/CD with deterministic collision resolution and belong to the dynamic planning based category, where an admission test is performed for guaranteeing message transmission. The admission test used in the proposed protocols is based on the worst case channel access time that can elapse before a particular node can start transmitting its message. We also compute the worst case buffer requirement at the switch for the proposed SLAN protocols. We study the effectiveness of the proposed protocols through extensive simulation studies.

Performance of Deferred Reservations in Data Networks

This paper studies the performance of deferred resource reservation in data networks. Conventional resource reservation protocols, such as PNNI and RSVP adopt an all-or-nothing approach, where partially acquired resources must be released if resources are not available at all links on the chosen path. During periods of high network load, this leads users to retry requests repeatedly, adding control traffic at exactly the time when the networks capacity to process that control traffic is exhausted. Deferred REServation (DRES) can significantly improve performance by reducing the overall call rejection probability, allowing more traffic to be carried, using the same resources.... Read complete abstract on page 2.

ANMAC: An Architectural Framework for Network Management and Control using Active Networks

In this paper, we propose a new framework called Active Network Management and Control (ANMAC) for the management and control of high speed networks. The software architecture in ANMAC allows routers to execute dynamically loadable kernel plug-in modules which perform diagnostic functions for network management. ANMAC uses mobile probe packets to perform efficient resource reservation (using our novel reservation scheme), facilitate feedback-based congestion control, and to provide “distributed debugging” of complex anomalous network behaviour. ANMAC also provides security measures against IP spoofing, and other security attacks. The network manager has the flexibility to install custom scripts in routers for tracking down anomalous network faults.

DRES: Internet Resource Management using Deferred Reservations

In this proposal, we consider the problem of resource reservation for Integrated Services (IntServ) and Differentiated Services (DiffServ) networks. Current approaches for resource reservation in INtegrated Service Networks adopt an all-or-nothing approach, where partially acquired resources must be released if resources are not available at all routers on the chosen path. Furthermore, under high load, end-systems must retry requests repeatedly leading to inefficient allocation and increased traffic. We propose a new approach called Deferred REServation (DERS) that substantially improves performance (reduces the overall cell rejection probability and increases link utilization) over the all-or-nothing reservation approach. Call admissibility is increased... Read complete abstract on page 2.

Imprecise multicast routing for scalable information distribution

Typically, multicast data distribution uses rendezvous points (PIM, CBT), multicast distribution tree building protocols, and multicast forwarding. Whereas the first two approaches have been extensively studied, scaling multicast forwarding state without increasing forwarding complexity has not been addressed in detail. Having a scalable strategy for aggregation of multicast forwarding state is essential for inter-domain multicast which could have any number of concurrent multicast groups, especially in applications such as event notification and web cache invalidation mechanisms. We first present the essential characteristics of a scalable multicast routing mechanism. We then introduce and analyze, according to these metrics, a scalable aggregation mechanism for multicast-based update and change distribution based on imprecise (too generous) aggregation. Our mechanism is simple to implement, requires no additional information about the groups, and allows important savings in routing table size and routing protocol overhead, at a minimal expense in additional network and end-system traffic.