Guven Mercankosk

Multiplexing spacer outputs on cell emissions

In ATM networks, one effective way to provide service guarantees is to shape individual traffic streams at various points in the network. In the paper, the authors present a method for multiplexing a large number of single-stream spacer outputs on cell emissions rather than on cell arrivals. The method not only approximates first come first served (FCFS) multiplexing of such outputs but also better suits bursty arrivals. A number of performance related issues of the proposed method are identified and examined.

A generic flow control protocol for B-ISDN

A generic flow control (GFC) protocol is proposed to regulate multiple terminals within the broadband-ISDN customer premises network. The GFC protocol is based on multipriority distributed queuing preceded by a traffic shaping function, and meets the requirements for flexible allocation of service parameters, control of jitter and guarantee of bandwidth. This GFC protocol provides the necessary flexibility to match the constant bit rate (CBR) jitter performance and variable bit rate (VBR) service requirements to the particular service type. It integrates well with usage parameter control without imposing excessive burstiness on each virtual connection cell stream delivered to the network. By allowing connectionless users to access at the lowest priority, only when no higher priority users are queued, there is no reduction in guaranteed capacity available for other VBR and CBR users.<<ETX>>

Extended distributed queueing for integrated services

A method for supporting time-constrained and nontime-constrained integrated services on a shared dual bus network is presented. The method is an extension of the basic distributed queue protocol defined in the IEEE 802.6 distributed-queue dual-bus (DQDB) MAN standard. The extended distributed queueing protocol differs from the basic protocol in allowing more than one outstanding request in the distributed queue at any one time. Used at the high priority and in conjunction with segment stream shaping and subscribed service limiting, the extended protocol provides bearer services with guaranteed bandwidth and bounded delays. Bearer services with fair but nonguaranteed bandwidth shares, suitable for nontime-constrained applications, are provided by the same protocol and bandwidth balancing operating at the lowest priority. A number of the desirable attributes of the proposed scheme are identified including the optimality of the delay variance introduced by the access protocol. An approximate analysis of the access delay experience by time-constrained streams is presented. >

Establishing a real time VBR connection over an ATM network

The conclusion of this paper flows from the principle of delay constancy. To achieve and maintain the delay constancy in the face of variable transfer delay, a pad-out buffer is used at the destination and the consumption of the first cell is delayed by a determinable amount. We examine the conditions under which the continuity throughout the session is preserved. We also conclude that the transfer of a real variable bit rate application by a deterministic bit rate transfer capability will be indistinguishable from a transfer by a statistical bit rate transfer capability.

Characterization of a CBR connection over a channel with known bounded delay variation

The authors examine how to provide constant bit rate (CBR) service over a channel that can be characterized by a constant transmission delay plus a variable cell access delay. To compensate for the variability in the access delay, buffers are used at the source and the destination ends of the connection. Whenever buffers overflow or underflow the continuity of data flow over the connection breaks down. The minimum size of buffers required at the transmitter and the receiver to provide the connection is determined. The minimum source to sink delay achievable for different buffer initialization strategies and the corresponding buffer prefills are derived.<<ETX>>

Implementing traffic shaping

Traffic shaping is important in ATM networks, especially those that are interconnected or provide service guarantees. We examine what shaping may be considered ideal, and what is attainable under the constraints of transmission systems and cost. We justify the use of FCFS multiplexing of multiple single-stream shaper outputs as a performance reference for multi-stream shapers, but also point out some of its deficiencies. Shaper implementations in which transmissions are scheduled on cell arrivals, emissions, and transmissions are examined and compared both qualitatively and through simulation. We identify the problem of shaping cells that must conform to multiple traffic constraints (e.g. when the rate of a multicast connection must be adapted to suit multiple links) and examine implementations to achieve this. Shaping in which inevitable cell delay variation is intentionally distributed inequitably amongst connections (to assist CDV-intolerant connections) is also examined.<<ETX>>

Internet Transfer Capabilities for Time Critical Communications

Some time-critical communications, e.g. telephony, can frequently be conducted reasonably satisfactorily over the Internet, even when packets are transferred in connectionless mode. However, for any assured service with defined bounds on packet delay and loss, packet transfers need to be connection-oriented and the connections appropriately resourced. A virtual Internet connection with specified switching procedures, traffic capacity, and quality outcomes would, in analogy to transfer capabilities in ATM networks, be a defined Internet transfer capability. With appropriate transfer capabilities, an IP network could work with, or take the place of, traditional STM and ATM networks, as well as exceed them in capability. For instance, IP networking could be superior to STM and ATM in regard to multimedia communications.

Provision of real-time services over ATM using AAL type 2

1. MSTMCT Anew ATRIAdaptation Layer (AAL) type 2 has recentiy been defied in the ~-T to provide both high efficiency transmission of lowrate, shor~ and variable length packets in deky sensitive appfimtions for use in titure ~S/ ~~2000 Radio Access Ne~orks. This paper examines how to provide variable rate voice services over an AAL type 2 channel that can be charactertied by a constant transmission delay plus variable packet mdtiplexing delays and ce~ access dekys. To compensate for the variabfity in the delays, btiers are used at the source and the destination ends of the connection. Whenever a buffer ovefiows or underflow, the continuity of data flow over the AAL connection breaks down. h the papeq we determine the minimum she of btiers required at the source and the destination ends of the connection to provide the service. We ako derive the minimum source to sink delay.

Access delay analysis of a distributed queue based ATM distributor-concentrator network

A distributed queue based ATM distributor-concentrator network may be used to provide a distributed cell multiplexing-demultiplexing function at a broadband user network interface (UNI). The distributor-concentrator network incorporates an asymmetric dual bus architecture and is based on the extended distributed queueing protocol. We analyse the access delay performance of extended distributed queueing in multiplexing the cell streams from delay-sensitive services. In the analysis, we use an N/spl middot/D/D/1 queue model in which the positional priority of requests issued by nodes along the distributor-concentrator changes dynamically. A discussion on the observed performance is also presented.