An analytical model is developed in this paper for evaluating the performance of bandwidth allocation algorithms, with or without preemption, when used for Diffserv-aware MPLS traffic engineering. It is shown that, a major difference between various algorithms is their capabilities to provide greater bandwidth sharing versus robust service protection/isolation.
KEYWORDS: Networks, Network architectures, Internet, Control systems, Information operations, Switching, Process control, Signal processing, Statistical multiplexing, Circuit switching
Traffic measurements are collected to gain information about the traffic carried on a network. In this paper, the focus is on those aspects pertaining to network dimensioning and control. Issues related to time scale, read-out period, and traffic classes are discussed. Different measurement types are classified, with each being specified as a meaningful combination of a measurement entity and a measurement basis. To avoid the shortcomings of flow-based measurements, it is proposed that path-based measurements be developed. The use of measurement-based admission control as a means of adaptive resource management is also explored.
Drawing from the experience and work done in ITU-T on traffic engineering, the feasibility of extending telecommunications network dimensioning methods to IP-based networks with MPLS is explored. Further work is required to develop algorithms for the selection of label-switched paths and for the distribution of traffic to the selected paths.
We investigate the impact of scheduling policies on the tail distribution of sojourn times experienced by various unevenly-loaded queues in a two-stage polling system served by a symmetric multiprocessor system running under a Unix- like operating system. The queues are statically divided into groups, with each group being managed by a process. A process can run on any of the available processors. Service to a customer is thus scheduled first at the process level and then at the queue level. Assuming that all customers have the same service requirement, and for Poisson arrivals and exponentially distributed service times and setup times, it is shown by simulation that the earliest-customer policy outperforms both 1-limited and exhaustive policies in the sense of providing equitable service to the queues.
In the hybrid fiber-coax (HFC) architecture, the coax is a shared medium to which the network interface units (NIUs)
of different end-users are attached for accessing a diversity of network services. To analyze the traffic carrying capacities of
the coax, a C-i--i- object-oriented simulation tool has been developed. This paper reports on the use of this tool and analytical
techniques in the investigation of several key traffic issues:
. use of call packing to improve upstream bandwidth efficiency . impact of proximity restriction associated with frequency hopping on blocking
S design of time-slot assignment algorithms . downstream load balancing . effectof call retries
KEYWORDS: Video, Transmitters, Receivers, Systems modeling, Computer simulations, Broadband telecommunications, Clocks, C++, Multiplexing, Process control
This paper provides a high-level overview of an object-oriented simulation tool developed to model the HFC-2000TM broadband access network of AT&T. One objective of this tool is to help estimate the traffic capacity of fiber nodes and to explore various alternatives in architecture and design. Another objective is to provide guidelines for the use of different time slot assignment algorithms and for capacity planning. To achieve these goals, salient operational and serving features of the HFC-2000TM have been incorporated into the tool. Specifically, the tool models the traffic and serving characteristics of an entire fiber node with multiple coaxes, each carrying traffic both upstream and downstream. To facilitate the evaluation of performance under different traffic scenarios, the simulator allows traffic characteristics to be specified on a per-port basis in terms of a large variety of service types. A finite-source quasi-random input process is used to model the call arrivals from the different ports, with each port being considered an independent traffic source. A mixture of lognormal distributions is used for the call holding time distributions of various call types. The traffic from any given port is characterized by a service profile which specifies the probabilities for the different call types to be generated by the port. The traffic loading offered by a given port is specified by the hourly CCS (hundred call seconds) for that port. The tool is built using the object-oriented feature of C++. Different objects are used to implement the various features of the different types of network interface units, upstream and downstream channels, and the various types of call events.
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