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English (United Kingdom)

Delay priorities enhance utilisation of ATM PON access systems

Year: 1997
Type of Publication: Article
Journal: Computer Communications Volume: 20
Number: 11 Pages: 937-949
A dominant factor for the widespread penetration and success of B-ISDN is the access cost for the low traffic customers. For residential and small business customers, the tree Passive Optical Networks (PONs) are a promising solution for the concentration of ATM traffic. Such a solution however requires a method to arbitrate the access to the common Line Termination using the shared slotted system created on the PON tree. The Medium Access Control (MAC) protocol presented in this work employs delay priorities to achieve more efficient multiplexing with better jitter performance in the multi-service B-ISDN environment. It respects the demanding traffic control and enforcement methods of ATM which do not tolerate certain traffic profile distortions. It avoids cell clustering which deteriorates policing efficacy and link utilisation. It shields time-constrained services from the adverse effect on their traffic profile of the contention from bursty services so that they see a very low offered load. The delay insensitive ABR cells are buffered and filled-in when traffic conditions allow on a best-effort basis. This results in a more intelligent multiplexing and smoother traffic stream at the exit. Thus a higher loading is possible for the same performance leading to ‘amortisation’ of the additional complexity due to prioritisation.