Bandwidth Allocation Strategies in Wide-Band Integrated Networks

A common digital transmission facility in a wide-band integrated service digital network (ISDN) provides shared access to a community of heterogeneous users. Traffic demands from these users vary in their arrival rate, their service time, and their bit rate. In order for this type of communication system to handle its traffic demands with high efficiency and flexibility, a close control of access to the shared bandwidth is required. We model the system by a general multiserver queueing system where customers demand service from a random number of servers. If no waiting is allowed, this queueing model is readily analyzed, and various server allocation strategies can be studied. If the various access requests are queued for service, then the system calls for efficient strategies for allocating servers to waiting customers. In this case, exact analysis of the underlying queueing model becomes quite difficult. For this case, we present some analytic and simulation results of the performance of the system under several server allocation policies.     

Analysis of Traffic Access Control Strategies in Integrated Service Networks

A common digital transmission facility provides service to a community of heterogeneous users generating traffic with differing intensity, message length, and bit rate. In order for this type of integrated communication system to handle its traffic demands with high efficiency and flexibility, close control of access and switching at the input node is required. We propose, analyze, and compare two different strategies for managing the access of two types of traffic, a blockable wide-band (WB) type of traffic and a queueable narrow-band (NB) type of traffic, sharing the transmission resource dynamically. The first strategy assigns preemptive priority to the WB traffic over the NB traffic, whereas the second strategy employs a wide-band to narrow-band bit rate compression mechanism. Exact analytic models are developed, and solution methods are presented and implemented. It is shown that the best combined performance is obtained when the two strategies are adaptively combined according to the offered load.     

A Channel Access Structure for Wideband ISDN

To be fully integrated, the Integrated Service Digital Network (ISDN) arena is preparing an evolution from its current narrowband structure (at basic and primary access rates) to a futuristic wideband structure where access rates will be capable of supporting services beyond 100 Mbits/s. A wideband channel structure for ISDN, supplementing the narrowband channel standards, is thus needed. This paper presents a channel structure in which the access bandwidth is organized in a hierarchy of channels of increasing speeds. Channels at a given speed level accommodate services with specific bandwidth and holding time requirements. However, to improve performance, the access interface uses a control strategy whereby a service request at a given level can overflow to a lower level for access at lower bit rate. The performance, in terms of access delay and access throughput, of this access scheme is analyzed. Numerical results are provided for the special case of an interface with two levels of channels. These results show that a significant improvement in access performance can be obtained with the overflow mechanism of the access control discipline used.     

Voice and data integration at an ATM DSL access multiplexor

We analyze cell loss and call blocking at an ATM-based DSL access multiplexor which integrates 2 types of calls onto a channel through a common buffer. Type-1 calls have stringent delay, but relaxed cell loss QoS requirement, and are representative of voice. Type-2 calls have stringent cell loss but relaxed delay QoS requirement, and are representative of Internet data. We study an access strategy that allocates separate buffers to the 2 cell types and assigns priority to the voice buffer in accessing the channel. We apply a fluid flow method to analyze both cell loss and call blocking of the two types of calls. These results are then used to size the admission region at the access node under loss and blocking constraints. Numerical results are presented which quantify the interaction between cell loss and call blocking and the utility of the priority scheme compared to the FIFO scheme in handling the two traffic types.