Estimating correct traffic descriptors is an important issue when deploying IP telephony with quality of service guarantees. Usually, a token bucket is used to police a traffic flow. Such a policer checks (and ensures) that the traffic flow fits inside a traffic envelope. For variable bit rate (VBR) sources normally two traffic envelopes are specified: one dealing with the peak rate and one dealing with the sustainable rate with an associated burst size. These parameters have to be specified when making a reservation with either the resource reservation protocol (RSVP) in case of IntServ or may be specified in a service level specification (SLS) when using DiffServ. This paper shows how to choose the traffic descriptors for aggregate voice traffic for both constant bit rate sources and sources that use voice activity detection. Also the influence of variable packet size on the packet discard ratio (PDR) is shown. A traditional policer discards large packets more frequent than smaller ones. To alleviate this, a modification to the token bucket algorithm is proposed.

In this paper, we present a scalable algorithm, capable of finding a single-path traffic-engineered solution for routing traffic in a Differentiated Services network by means of explicit paths. Additional supported features are preemption, fast restoration, with a choice of protection scheme, oversubscription and resource class affinity. The performance of the algorithm is demonstrated by means of statistical simulations on randomly generated network topologies.

We develop a methodology to set the VoIP application parameters (voice packet size and dejittering delay) and the UMTS air interface parameters in such a way that the quality of VoIP calls involving a UMTS party is ensured. We use analytical techniques to determine the delay and packet loss contributions of the various transmission stages crossed by the voice packet flow, and the E-model to predict the perceived quality. Our numerical results show that provided the parameters of the VoIP application and the UMTS air interface are chosen properly, UMTS access and the stringent delay and packet loss requirements of VoIP are reconcilable.

This paper discusses resource allocation and management in Differentia ted Services (DiffServ) networks, particularly in the context of IP telephony. We assume that each node uses Weighted Fair Queuing (WFQ) schedulers in order to provide Quality of Service (QoS) to aggregates of traffic. All voice traffic destined for a certain output interface is aggregated into a single queue. When a voice flow traverses a node, its packets are placed in this queue; which is drained at a certain rate, determined by a weight associated with that queue. This paper shows how to set this weight such that the edge-router-to-edge-router queuing delay in the DiffServ network is statistically bounded. The nodes are modeled as M/G/1 queuing systems and a heuristic formula is used to compute a quantile of the queuing delay. This formula is compared with results derived from simulations. It is also shown how to use this result to allocate the appropriate resources in a DiffServ network and how to update and process RSVP messages at the edge of a DiffServ network in an IntServ over DiffServ scenario.

The throughput optimality of priority management strategies in a single buffer has been studied for a general aggregate arrival law. The tight upper bounds found are useful to understand optimality in utilization of specific priority schemes such as push-out buffer (POB) and partial buffer sharing (PBS). This paper further focuses on the maximum allowable load /spl rho//sub max/ versus the priority mix /spl alpha/ for a PBS and a random push-out buffer (R POB) of size K for a wide variety of arrival processes. The role of priorities in a special type of bursty arrivals, the compound Poisson process with constant burst length and random priority assignment within the burst, is found to be less pronounced than that of 'pure' Poisson arrivals. On the other hand, the results for on-off cell arrivals modeled by a MMPP(2), MMPP(3), and higher order Markov modulated processes closely follow the behaviour of the maximum allowable load in the R POB with Poisson arrivals, however scaled to lower loads. The results indicate that the priority mix distribution within the aggregate arrival flow influences the shape of /spl rho//sub max/(/spl alpha/)-curve more than the aggregate arrival distribution itself.