Current and evolving telecommunication services will rely on signaling network performance and reliability properties to build competitive call and connection control mechanisms under increasing demands on flexibility without compromising on quality. The dimensions of signaling dependability most often evaluated are the rate of call loss and end-to-end route unavailability. A third dimension of dependability that captures the concern about large or catastrophic failures can be termed network robustness. The paper is concerned with the dependability aspects of the evolving Signaling System No. 7 (SS7) networks and attempts to strike a balance between the probabilistic and deterministic measures that must be evaluated to accomplish a risk-trend assessment to drive architecture decisions. Starting with high-level network dependability objectives and field experience with SS7 in the U.S., potential areas of growing stringency in network element (NE) dependability are identified to improve against current measures of SS7 network quality, as per-call signaling interactions increase. A sensitivity analysis is presented to highlight the impact due to imperfect coverage of duplex network component or element failures (i.e., correlated failures), to assist in the setting of requirements on NE robustness. A benefit analysis, covering several dimensions of dependability, is used to generate the domain of solutions available to the network architect in terms of network and network element fault tolerance that may be specified to meet the desired signaling quality goals.>

A new integrated demand-assignment multiple-access (DAMA) method for multiple-bus local networks (MBLNs) is proposed and evaluated. The performance of this method is shown to be superior to independent token-passing as well as to previously proposed integrated access schemes. V-STIA, a virtual token-passing extension of a modified explicit token-passing scheme called single-token integrated access (STIA), delivers the best overall performance at medium to heavy loads while achieving good light-load performance without collision detection. Consequently, V-STIA makes the fewest possible demands on interface capabilities for DAMA support in MBLNs. Additionally, V-STIA implementation does not require simultaneous transmit capability for correct operation and greatly reduces design complexity. Performance advantages of MBLNs over an equivalent bandwidth single-bus DAMA system are established.>

Multiple-bus local networks (MBLNs) provide an architecturally simple solution to serve high-reliability high-capacity local area networks applications. Access mechanisms for MBLNs possessing stability and favorable delay characteristics are developed. A technique is proposed that uses a single explicit token to achieve demand-assignment multiple access (DAMA) to arbitrate access on all buses in the system. The performance of this algorithm in pure DAMA form and its hybrid, carrier-sense multiple access with collision detection (CSMA-CD), version are discussed. The unique features of the hybrid algorithm are that no backoff policy is needed for colliding messages and the token-passing operation is never suspended, unlike some existing hybrid DAMA approaches.>