Sun Hairong

The flow detection protocol design in multiprotocol over ATM

A key to ATMs success and Internets further success will be the ability to allow for interoperation between the existing network technologies and ATM. The MPOA (multiprotocol over ATM) which is presented and standardized by ATM Forum in July 1997, is an efficient solution to the interoperation between ATM and the existing networks. The goal of MPOA is the efficient transfer of inter-subnet unicast data in a LANE (LAN emulation) environment. The edge-device in the network forwards inter-subnet packets to router through a default path at first. When it recognizes that the flow could benefit from a shortcut that bypasses the routed path, it uses a protocol to establish a shortcut to the destination. If a shortcut is available, the edge-device sets up a shortcut virtual channel, and forwards packets to the destination over the shortcut path. However, the MPOA specification has not defined the protocol of flow detection (switching path from the default one to the shortcut one), it is for further study. Actually, the path switching protocol i.e., how to determine whether the flow will benefit from the shortcut path is a key factor determining the efficiency of the MPOA. We present three kinds of solutions to the flow detection protocol.

Research note: Performance analysis of the constant-bit-rate services in an ATM DQDB MAN

An ATM DQDB MAN can provide integrated services with a pure ATM method which transfers any kind of services in a unified manner. This paper analyzes the performance of the CBR (constant bit rate) services in the ATM DQDB MAN. A four-dimensional Markov chain is used to describe the steady state of a tagged user and the survivor function of the queue length distribution is calculated to design buffer capacity of the tagged user. The analytical method and the results are applied to the prototype we have accomplished. The sojourn time of the CBR services is investigated. The results illustrate that the delay performance of the CBR services is satisfactory in the ATM DQDB MAN if the network is not overloaded seriously. Various priority mechanisms to support integrated services are also compared briefly in the paper.

The influence of burstiness and correlation of traffic on an ATM multiplexer

This paper presents a traffic model for an ATM multiplexer providing video, voice, image, and data services. The traffic model classifies the input traffic into two types: real-time and non-real-time. The input process for real-time traffic is a Markov modulated Bernoulli process (MMBP), while that for non-real-time traffic is a Bernoulli process with batches. The z-transform of the cell interarrival time A/sub MMBP/(z) is obtained. The average traffic load /spl rho//sub MMBP/ and the squared coefficient of variation of the time between success cell C/sup 2//sub MMBP/ are then obtained from the respective derivatives of A/sub MMBP/(z). The autocorrelation coefficient of the cell interarrival time with lag 1 /spl psi/, can be also obtained. This paper presents an iterative algorithm that can be used to calculate the MMBP probability distribution of the cell interarrival time. So far few results about discrete-time finite buffer queues with correlated inputs are known. This paper analyzes the performance of an ATM multiplexer considering the correlation and burst in cell arrivals. For the MMBP-stream, the waiting time distribution and the cell loss probability for MMBP+M/sup [X]//D/1/K finite buffer system are all exactly calculated with the use of a recursive algorithm. Calculations show the influence of burstiness and correlation on both the loss probability and waiting time. The accuracy of the analytical results has been largely validated by means of a simulation approach.

Performance analysis of leaky bucket algorithm with bursty traffic input in ATM networks

A bursty traffic model is introduced in this paper to describe the statistical characteristics of packet video. The performance of leady bucket algorithm with bursty traffic input is analyzed. The influences of various parameters on QOS (Quality of Service) are investigated. The analysis shows that although the loss probability decreases through expanding the buffer capacity, the delay and delay jitter increase, whose effect on QOS will not be negligible.

Sojourn time analysis for constant-bit-rate services in the ATM DQDB MAN

The sojourn time of the constant-bit-rate (CBR) services in the ATM DQDB MAN is studied. The ATM DQDB MAN transfers any kind of services in an unified manner with CBR services obtaining the higher priority level and the variable-bit-rate (VBR) services obtaining the lower priority level. The results display that the delay performance of the CBR services is satisfactory in the ATM DQDB MAN if the network is not seriously overloaded.

Performance analysis of prioritized DQDB MAN for lans interconnection

The sojourn time of the prioritized DQDB MAN with bursty traffic input is studied in this paper. The expressions for the mean sojourn time of the message with two transmission priority are obtained. The conclusions drawn from the paper are that the mean sojourn time of the message, at either higher or lower priority, is a linear function of the mean message length approximately, and the performance improvement by adopting the higher priority level for the user is remarkable, especially when the lower-priority traffic load from the downstream users is heavy.

Sojourn time analysis of DQDB MAN for LANs interconnection

The Distributed Queue Dual Bus(DQDB) Metropolitan Area Network (MAN) is a promising solution for the evolution from current networks to B-ISDN. The performance of the DQDB MAN for Local Area Networks(LANs) interconnection is analyzed. The effects of message length, traffic load of upstream and downstream nodes and the parameters of bandwidth balancing mechanism and network counters on the sojourn time of message in the buffer are investigated, which present a valuable reference for the implementation of the DQDB MAN.