Communications system ingress and egress arrangement
 A communications network is arranged so that an external switching office is connected to the network via multiple ingress/egress nodes such that an originating node which receives a call destined for the external office may route the call through the network to one of the ingress/egress nodes in accordance with a particular class (type) of routing specified in one of a number of routing treatments. Such routing treatments are associated with the external office and at least identify respective ones of the ingress/egress nodes connected to the external office. 
AT&T Bell Laboratories
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Gerald R. Robert A. Jin-Shi
Ash Gerritsen Chen