In this article, we present a novel discrete-time Markov chain model of book-ahead bandwidth-sharing mechanisms. We use this analytical model and a simulation model to understand the benefits of book-ahead (BA) bandwidth-sharing when compared to the immediate-request (IR) call-blocking mode of bandwidth-sharing in circuit-switched networks. We study two different BA schemes, BA-all, in which the caller accepts any set of available timeslots, and BA-n, in which the caller specifies n call-initiation time options. Numerical results show that the BA-all achieves 95% utilization with a call-blocking probability of only 1%, while in the IR mode, call blocking probability is 23% even when utilization is only 80%. The BA-n schemes perform as well as the BA-all scheme if the call-initiation time options are restricted to fall on timeslot boundaries separated by the minimum call holding time. The length of the advance reservation horizon, K, is shown to increase linearly with call holding time, H. The ratio K/H is primarily dependent on the link capacity in channels. For example, if the link is divided into 10 channels, to achieve a 2% call blocking probability, the advance-reservation horizon needs to be a factor of 4 times the call holding time. In other words, the extra data storage and processing required to accept and maintain advance reservations is not significant.

Optical networks with book-ahead bandwidth schedulers are being deployed to meet the high-speed and predictable-service networking requirements of applications in the scientific research community. We present an analytical model for a single-link book-ahead bandwidth scheduler, which responds to advance reservation requests with the first-available time interval in which a channel is available. The link is assumed to be divided into m channels, and time is discretized into intervals. Our proposed model is a non-homogeneous continuous-time Markov chain, which has an embedded discrete-time Markov chain. We solve the model for call congestion, mean scheduling delay, and link utilization. This model can be used by network designers to select the size of the reservation window, K, in time-interval units, corresponding to a desired set of values for the output metrics, for a given value of m. For example, when m is 8, increasing the reservation window beyond 4 intervals does not affect the call congestion or system utilization, but causes the mean scheduling delay to increase. We show with comparative simulations that our analytical model can be used as a solution for an M/D/m/p queueing system at moderate-to-high loads.

In this article, we describe our experiences in implementing an experimental wide-area GMPLS network called CHEETAH (circuit-switched end-to-end transport architecture). The key concept is to add a complementary end-to-end circuit based service with dynamic call-by-call bandwidth sharing to the connectionless service already available to end hosts via the Internet. The current CHEETAH experimental network consists of off-the-shelf GMPLS-capable SONET switches (with Ethernet interfaces) deployed at three locations, Research Triangle Park, North Carolina, Atlanta, Georgia, and Oak Ridge, Tennessee. We describe our solutions to various problems relating to control-plane design, IP addressing and control-plane security. We designed and implemented a CHEETAH software package to run on Linux end hosts connected to the CHEETAH network. Among other functions, this software package includes an RSVP-TE module to enable end users and applications to dynamically initiate requests for dedicated end-to-end circuits and receive/respond to requests for circuits. We present measurements for typical end-to-end circuit setup delays across this network. For example, end-to-end circuit setup delay from a Linux end host in NC to a host in Atlanta is 166 ms

In this article, we describe our experiences in implementing an experimental wide-area GMPLS network called CHEETAH (Circuit-Switched End-to-End Transport Architecture). The key concept is to add a complementary end-to-end circuit based service with dynamic call-by-call bandwidth sharing to the connectionless service already available to end hosts via the Internet. The current CHEETAH experimental network consists of off-the-shelf GMPLS-capable SONET switches (with Ethernet interfaces) deployed at three locations, Research Triangle Park, North Carolina, Atlanta, Georgia, and Oak Ridge, Tennessee. We designed and implemented a CHEETAH software package to run on Linux end hosts connected to the CHEETAH network. Among other functions, this software package includes an RSVP-TE client module to enable end users and applications to dynamically initiate requests for dedicated end-to-end circuits and receive/respond to requests for circuits. We present measurements for typical end-to-end circuit setup delays across this network. For example, end-to-end circuit setup delay from a Linux end host in NC to a host in Atlanta is 166ms.