This paper studies the capacity and flow assignment problem arising in the design of self-healing asynchronous transfer mode (ATM) networks using the virtual path concept. The problem is formulated here as a linear programming problem which is solved using standard methods. The objective is to minimize the spare capacity cost for the given restoration requirement. The spare cost depends on the restoration strategies used in the network. We compare several restoration strategies quantitatively in terms of spare cost, notably: global versus failure-oriented reconfiguration, path versus link restoration, and state-dependent versus state-independent restoration. The advantages and disadvantages of various restoration strategies are also highlighted. Such comparisons provide useful guidance for real network design. Further, a new heuristic algorithm based on the minimum cost route concept is developed for the design of large self-healing ATM networks using path restoration. Numerical results illustrate that the heuristic algorithm is efficient and gives near-optimal solutions for the spare capacity allocation and flow assignment for tested examples.

Restoration strategies and spare capacity requirements in self-healing ATM networks

The design of survivable mesh based communication networks has received considerable attention in recent years. One task is to route backup paths and allocate spare capacity in the network to guarantee seamless communications services survivable to a set of failure scenarios. This is a complex multi-constraint optimization problem, called the spare capacity allocation (SCA) problem. This paper unravels the SCA problem structure using a matrix-based model, and develops a fast and efficient approximation algorithm, termed successive survivable routing (SSR). First, per-flow spare capacity sharing is captured by a spare provision matrix (SPM) method. The SPM matrix has a dimension the number of failure scenarios by the number of links. It is used by each demand to route the backup path and share spare capacity with other backup paths. Next, based on a special link metric calculated from SPM, SSR iteratively routes/updates backup paths in order to minimize the cost of total spare capacity. A backup path can be further updated as long as it is not carrying any traffic. Furthermore, the SPM method and SSR algorithm are generalized from protecting all single link failures to any arbitrary link failures such as those generated by Shared Risk Link Groups or all single node failures. Numerical results comparing several SCA algorithms show that SSR has the best trade-off between solution optimality and computation speed.

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Approximating optimal spare capacity allocation by successive survivable routing

For reasons of economy and flexibility, BISDN (Broadband Integrated Services Digital Network) is expected to replace existing application-oriented communication networks. ATM (Asynchronous Transfer Mode) is a high-speed packet-switching technique that has emerged as the most promising technology for BISDN. Since early 1980s, a large number of architectures have been proposed for ATM switching. In this paper, we present a descriptive survey of ATM switch architectures, with emphasis on electronic space-division point-to-point switches.

Survey of ATM switch architectures

Spare capacity allocation (SCA) is an important part of a fault tolerant network design. In the spare capacity allocation problem one seeks to determine where to place spare capacity in the network and how much spare capacity must be allocated to guarantee seamless communications services survivable to a set of failure scenarios (e.g., any single link failure). Formulated as a multi-commodity flow integer programming problem, SCA is known to be NP-hard. We provide a two-pronged attack to approximate the optimal SCA solution: unravel the SCA structure and find an effective algorithm. First, a literature review on the SCA problem and its algorithms is provided. Second, a integer programming model for SCA is provided. Third, a simulated annealing algorithm using the above INP model is introduced. Next, the structure of SCA is modeled by a matrix method. The per-flow based backup path information are aggregated into a square matrix, called the spare provision matrix (SPM). The size of the SPM is the number of links. Using the SPM as the state information, a new adaptive algorithm is then developed to approximate the optimal SCA solution termed successive survivable routing (SSR). SSR routes link-disjoint backup paths for each traffic flow one at a time. Each flow keeps updating its backup path according to the current network state as long as the backup path is not carrying any traffic. In this way, SSR can be implemented by shortest path algorithms using advertised state information with complexity of O( Link/sup 2/). The analysis also shows that SSR is using a necessary condition of the optimal solution. The numerical results show that SSR has near optimal spare capacity allocation with substantial advantages in computation speed.

This paper proposes an optimal design scheme for survivable wavelength-division multiplexing (WDM) transport networks in which fast restoration can be achieved by using predetermined restoration paths that are independent of failure locations and which have one to one correspondence with working paths Integer programming-based design problems are formulated to optimally determine working and their corresponding restoration paths, the number of fibers in each span, and the number of optical cross connects (OXCs) in each node In these optimization problems, total facility cost, which includes not only transmission cost but also cross connection, is minimized This design scheme can handle the dedicated/shared allocation of spare resources and several parameters, such as the maximum available number of wavelengths per fiber /spl Omega/, the matrix size of each OXC, and cross-connection to transmission cost-coefficient ratio /spl gamma/ Total fiber length, the total number of OXCs, etc, are evaluated from obtained design results for these options and parameters Numerical examples show that the dependency of total fiber length and the total number of OXCs on /spl gamma/ is relatively small, and cross-connection to transmission cost ratios (/spl gamma/ times the total number of OXCs divided by total fiber length) in the dedicated and shared cases are almost the same for each combination of /spl gamma/ and /spl Omega/

Optimal design and evaluation of survivable WDM transport networks

This paper studies the capacity and flow assignment problem arising in the design of self-healing ATM networks using the virtual path (VP) concept The problem is formulated as a linear programming problem which is solved using standard methods The objective is to minimize the spare capacity cost for the given restoration requirement The spare cost depends on the restoration strategies used in the network We compare several restoration strategies, notably, global versus failure-oriented reconfiguration, path versus link based restoration and state-dependent versus state-independent restoration, quantitatively in terms of spare cost The advantages and disadvanages of various restoration strategies are also highlighted Such comparisons provide useful guidance for real network design Further, a new heuristic algorithm is developed for the design of large self-healing ATM networks using path based restoration Numerical results illustrate that the heuristic algorithm is efficient and can give near-optimal solutions for spare capacity allocation and flow assignment

Buffer contents and delay for statistical multiplexers with fixed-length packet-train arrivals

An N x N self-routing multistage switching network with bursty and uniform traffic, which is composed of S x 5 switching elements with output queueing and has K = logS N stages, is considered in this paper. The input traffic is modelled by a two-state (active/silent) Markov chain. Each arriving cell selects one of the N outlets as its destination independently and with equal probability I/N. The performance of the switching network is studied by means of a simulation method. An approximate traffic model of a four-state Markov chain is proposed to characterize the cell arrival processes to further stages and its related switching element performance is analyzed. Comparison with the simulation results shows that the proposed traffic model gives a good approximation, which implies that the performance of the switching element mainly depends on the first two moments of the active and silent periods and is not sensitive to the shapes of their distributions. The influence of bursty traffic on the performance of the switching network is discussed and illustrated by some numerical examples. The impact of traffic randomization on the performance of the switching network is also investigated.

Yijun Xiong

Papers

Restoration strategies and spare capacity requirements in self-healing ATM networks

Restoration strategies and spare capacity requirements in self-healing ATM networks

Buffer contents and delay for statistical multiplexers with fixed-length packet-train arrivals

Performance Study of an ATM Self‐Routing Multistage Switch with Bursty Traffic: Simulation and Analytic Approximation

Deriving delay characteristics from queue length statistics in discrete-time queues with multiple servers