Session Initiation Protocol (SIP) servers can experience prolonged overload due to high rates of incoming service requests or partial network failures. SIP servers need to be equipped with some form of adaptive overload detection and control, in order to protect against high and unpredictable levels of demand and to keep response times low enough during processing overload to preclude customers abandoning their service requests prematurely. Many SIP servers have internal (local) overload control mechanism, where the overload servers reject enough new INVITE requests to maximize successful completion of admitted sessions. However such mechanisms can only protect the SIP servers against overload to a limited extent, and it cannot prevent congestion collapse. In this paper, we introduce Signal-Based Overload Control, SBOC, which does not require changes in the SIP protocol, as it is implemented at the sending (upstream) servers, consequently it does not impose processing burden on overloaded servers. Extensive simulations show that SBOC maximizes the goodput of the SIP network, and adapts appropriately under realistic overload profile.

We study the delay characteristics of voice packets that share a transmission medium with bursty data traffic. In order to model the data traffic accurately, we used real data traffic traces upon which we superimposed simulated voice sources generating real time traffic at a constant rate. Our simulation environment allows us to easily develop and compare different adaptive algorithms for the play-out delay of voice streams. We motivate and compare the performance of three algorithms based on exponential smoothing techniques. We test the algorithms in the context of a shared 10 Mbps Ethernet LAN, using the CSMA/CD protocol.

The simple data link (SDL) is a new framing protocol for variable/fixed length packets over a general-purpose point-to-point communications channel. SDL extends the HEC-like framing mechanism used in ATM to variable-length data. Its low implementation complexity makes it particularly suitable for high-speed transport links in wavelength channels and dark fiber applications. SDL is a very attractive alternative to conventional solutions such as ATM and PPP-over-SONET (POS) for high data rate environments. SDL has also been designed to facilitate many OAM&P functions needed in next generation multiservice optical packet networks including multiprotocol encapsulation, virtual links, quality-of-service (QoS) differentiation, link management, and control. We describe framing and data link synchronization procedures in SDL, and evaluate its performance over octet and bit synchronous transport facilities.

We provide simple techniques for estimating the end-to-end jitter incurred by a periodic traffic in an asynchronous transfer mode (ATM) network. Our analysis is based on the careful examination of light and heavy traffic behavior of jitter incurred to a tagged renewal stream in a single node. Our results indicate that, in the heavy traffic as the number of nodes increases, the jitter distribution approaches to a limiting distribution which only depends on the behavior of the background traffic. We provide the functional equation satisfying this limit which bounds the moments of the jitter for arbitrary level of traffic. A simple approximation method based on the heavy and light traffic analysis of the jitter process is also provided and the results is supported by extensive simulation.

The authors formulate and analyse the jitter process in an ATM environment. The jitter analysis is presented for a tagged renewal stream. The queueing model consists of the superposition of the tagged renewal stream and background traffic. In the case of periodic tagged stream, the correlated background traffic is also considered. A solution methodology is developed which can be utilized in solving a large class of problems. They investigate the impact of various traffic parameters (e.g. the background traffic load and burstiness, the interarrival time of the renewal stream, etc.) on the jitter of the tagged stream. Numerical examples provide insight into the behavior of the system. They observe that the variance of the jitter behaves (almost) linearly with the variance of the background traffic. Some interesting heavy traffic results are also provided when the background traffic consists of number of identical two state ON-OFF sources.>

The authors provide sample techniques for estimating the end-to-end jitter incurred to a periodic traffic in an ATM network. The analysis is based on carefully examining the light and heavy traffic behavior of jitter incurred to a general tagged renewal stream in a single node. The results indicate that for any number of nodes, the jitter variance is almost proportional to the variance of the background traffic competing for resources with the tagged stream. They also find that in general, as the number of nodes increases, the jitter distribution approaches a limit. In the heavy traffic, they provide the functional equation satisfying this limit which readily gives all the moments of the jitter in closed form for large number of nodes in the network.>