After having describing the Paris area telephonic network, the authors examine the appropriate methods of network structuring, to protect from breakdowns due to outs in transmission lines and failures in transit switching centres whereas the disturbance should not affect more than 5% of the traffic and should not hinder priority traffic at all. The setting-up of a last choice network based on a specialized transit centre to deal with traffic overloads in normal conditions and with call routing in case of breakdown is recommended. The network design should provide means for directing the communications towards the above mentioned centre.

J. P. Daoudal

Papers

Traffic securization in «Ile-de-France»