Journal of High Speed Networks - Volume 8, issue 3

Authors: Mohan, G. | Murthy, C. Siva Ram

Article Type: Research Article

Abstract: In this paper, we consider wavelength rerouting in circuit switched wavelength‐routing Wavelength‐Division Multiplexed (WDM) networks. We address the rerouting issue and propose rerouting algorithms for single‐fiber and multi‐fiber networks with and without wavelength conversion. The wavelength continuity constraint imposed by WDM networks leads to poor blocking performance. The blocking performance can be improved by wavelength rerouting and by providing wavelength conversion capability at the routing nodes. Wavelength rerouting rearranges certain existing lightpaths to accommodate a new connection request. The wavelength continuity constraint is relaxed at the routing nodes having wavelength conversion capability. Since the number of technologically feasible wavelength channels …per fiber is very few (up to 16), multi‐fiber networks have become an attractive alternative which can support increased traffic with improved performance [3]. Recently, in [1], a rerouting scheme called ‘Parallel Move‐To‐Vacant–Wavelength Retuning (MTV–WR)’ with many attractive features such as shorter disruption period and simple switching control, and a rerouting algorithm, for this scheme, to minimize the weighted number of rerouted lightpaths have been proposed. The algorithm runs in polynomial time, but is not time optimal. We present here a time optimal rerouting algorithm to minimize the weighted number of rerouted lightpaths. We also present a rerouting strategy with the same computational complexity for the networks with sparse wavelength conversion. We discuss, how the parallel MTV–WR scheme can be extended to the networks with sparse wavelength conversion for rerouting sub‐lightpaths. We also discuss how this scheme can be modified for multi‐fiber networks, wherein a lightpath can be moved to a vacant wavelength on any vacant fiber in the bundle of fibers, while maintaining the route. We extend the rerouting algorithm for the single‐fiber networks to the multi‐fiber networks with the above modified rerouting scheme. The performance of the proposed algorithms are evaluated through extensive simulation. The results show that the proposed algorithms improve the blocking performance significantly. Show more

Citation: Journal of High Speed Networks, vol. 8, no. 3, pp. 149-171, 1999

Authors: Yau, Victor | Pawlikowski, Krzysztof

Article Type: Research Article

Abstract: Parallel use of multiple channels in WDM star networks requires that either each station is equipped with one receiver per channel or we have to deal with destination conflicts whenever a station is reached by more packets than it is able to receive. Earlier proposed networks resolved destination conflicts either after they occur (applying the detect‐and‐retransmit‐if‐lost principle) or before packets are transmitted (applying the request‐schedule‐then‐transmit principle). This paper introduces networks in which such conflicts are resolved whilst packets are en route to their destinations, using a central arbiter station (CA) located at the star coupler. CA detects destination conflicts, buffers …packets which would otherwise be lost, and forwards them to their destinations as soon as their destinations are free to receive them. Buffer operations at CA are streamlined, allowing either electronic implementation or a simple optical delay‐line implementation. Their performance is evaluated by studying their delay and throughput characteristics, protocol computational complexity, E/O conversion overhead, and hardware demands. Show more

Keywords: Lightwave networks, network architectures, media access control protocols, destination conflicts, photonic switching systems

Citation: Journal of High Speed Networks, vol. 8, no. 3, pp. 173-193, 1999

Authors: Cidon, Israel | Hsiao, Tony | Khamisy, Asad | Parekh, Abhay | Rom, Raphael | Sidi, Moshe

Article Type: Research Article

Abstract: ATM networks are currently moving from the experimental stage of test‐beds to a commercial state where production networks are deployed and operated. The ATM Forum PNNI (Private Network to Network Interface) standard introduces an architecture suited for an internetwork which, in principle, can also be used as an intra‐network nodal interface. However, the current PNNI falls short in providing an acceptable solution due to severe performance limitations in intra‐network operation, limited functionality and the lack of open interfaces for functional extensions and services. OPENET is a common, open and high‐performance network control platform based on performance and functional enhancements …to the PNNI platform. It is designed to address the issues of interoperability (being vendor independent), scalability (in terms of network size and volume of calls), high performance (in terms of call processing latency and throughput) and functionality. OPENET is mainly an intra‐networking extension to current PNNI. It is compatible with PNNI in the internetwork environment where large networks must be partitioned according to natural topological or organizational boundaries. The major novelty of the OPENET architecture (compared to the current PNNI) is its focus on network control performance. A particular emphasis is given to the increase of the overall rate of connection handling, to the reduction of the call establishment latency and to the efficient utilization of the network resources. These performance enhancements are achieved by the use of a native ATM distribution tree for the dissemination of utilization update, light‐weight call setup, take down and modification signaling, the use of fast setup and takedown with the future option to implement them in hardware, and extensive use of caching and pre‐calculation for route computation. OPENET also extends PNNI in terms of functionality. It utilizes a new signaling paradigm that better supports fast reservation and multicast services, a rich control communication infrastructure which enables the development of augmented services leveraging the existing functions, messaging system and information of the network control platform. Show more

Citation: Journal of High Speed Networks, vol. 8, no. 3, pp. 195-210, 1999

Authors: Yoo, Sang‐Jo | Kim, Seong‐Dae

Article Type: Research Article

Abstract: In this paper, we propose a new traffic model and its queueing solution for MPEG‐coded video sequences, which are now widely used for many types of video applications. The MPEG variable bit rate (VBR) video traffic has both very strong short‐range correlations and long‐range dependence. To capture the long‐range dependence, we model the overall scene‐level cell rate flow with a scene‐level state transition diagram. At the same time, we use a frame‐level chain to reflect the short‐range correlation effects between the frames of the same frame type and between the different frame types within a scene state. Thus scene changes …and frame sequences are modeled by a two‐dimensional continuous time Markov chain. We provide an analytic queueing solution in terms of the maximum cell transfer delay and the cell loss ratio. The simulation results show that our analytical model accurately approximates the queueing performance of the original videos. Finally, with an asymptotic approximation, we provide a method for estimating the effective bandwidth for MPEG video sources with a guarantee of the user’s quality of service requirements. Show more

Keywords: MPEG, traffic modeling, QoS

Citation: Journal of High Speed Networks, vol. 8, no. 3, pp. 211-224, 1999

Authors: Maltz, David A. | Bhagwat, Pravin

Article Type: Research Article

Abstract: Application layer proxies already play an important role in today’s networks, serving as firewalls and HTTP caches – and their role is being expanded to include encryption, compression, and mobility support services. Current application layer proxies suffer major performance penalties as they spend most of their time moving data back and forth between connections; context switching and crossing protection boundaries for each chunk of data they handle. We present a technique called TCP Splice that provides kernel support for data relaying operations which runs at near router speeds. In our lab testing, we find SOCKS firewalls using TCP Splice can …sustain a data throughput twice that of normal firewalls, with an average packet forwarding latency 30 times less. Show more

Keywords: TCP, firewalls, SOCKS, application layer proxies, performance

Citation: Journal of High Speed Networks, vol. 8, no. 3, pp. 225-240, 1999