1 research outputs found
Distributed Failure Restoration for Asynchronous Transfer Mode (ATM) Tactical Communication Networks
Asynchronous Transfer Mode (A TM) is an attractive choice for future military
communication systems because it can provide high throughput and support multi-service
applications. Furthermore its use is consistent with the 'off the shelf technology
policy that is currently operated by the Defence Engineering Research Agency of Great
Britain. However, A TM has been developed as a civil standard and is designed to
operate in network infrastructures with very low failure rates. In contrast, tactical
networks are much less reliable. Indeed tactical networks operate on the premise that
failures, particularly node failures, are expected. Hence, efficient, automatic failure
restoration schemes are essential if an A TM based tactical network is to remain
operational. The main objective of this research is the proposal and verification of one
or more new restoration algorithms that meet the specific requirements of tactical
networks.
The aspects of ATM networks that influence restoration algorithms' implementation are
discussed. In particular, the features of A TM networks such as the concept of Virtual
Paths Virtual Channels and OAM (Operation And Maintenance) mechanisms that
facilitate implementation of efficient restoration techniques. The unique characteristics
of tactical networks and their impact on restoration are also presented.
A significant part of the research was the study and evaluation of existing approaches to
failure restoration in civil networks. A critical analysis of the suitability of these
approaches to the tactical environment shows no one restoration algorithm fully meets
the requirements of tactical networks. Consequently, two restoration algorithms for
tactical A TM networks, DRA-TN (Dynamic Restoration Algorithm for Tactical
Networks) and PPR-TN (Pre-planned Restoration Algorithm for Tactical Networks), are
proposed and described in detail. Since the primary concern of restoration in tactical
networks is the recovery of high priority connections the proposed algorithms attempt to
restore high-priority connections by disrupting low-priority calls. Also, a number of
additional mechanisms are proposed to reduce the use of bandwidth, which is a scarce
resource in tactical networks.
It is next argued that software simulation is the most appropriate method to prove the
consistency of the proposed algorithms, assess their performance and test them on
different network topologies as well as traffic and failure conditions.
For this reason a simulation software package was designed and built specifically to
model the proposed restoration algorithms. The design of the package is presented in
detail and the most important implementation issues are discussed. The proposed
restoration algorithms are modelled on three network topologies under various traffic
loads, and their performance compared against the performance of known algorithms
proposed for civil networks. It is shown that DRA-TN and PPR-TN provide better
restoration of higher priority traffic. Furthermore, as the traffic load increases the
relative performance of the DRA-TN and PPR-TN algorithms increases. The DRA-TN
and PPR-TN algorithms are also compared and their advantages and disadvantages
noted.
Also, recommendations are given about the applicability of the proposed algorithms,
and some practical implementation issues are discussed. The number of problems that
need further study are briefly described.Defence Engineering Research Agency of Great Britai