This International Standard specifies the Path Replacement additional network feature (ANF-PR), which is applicable to
various basic services supported by Private Integrated Services Networks (PISN). Basic services are specified in
ANF-PR is a feature which applies to an established call, allowing that call's connection between Private Integrated Services
Network Exchanges (PINXs) to be replaced by a new connection. If the new connection is required to satisfy certain criteria,
ANF-PR should be used in conjunction with other supplementary services and/or ANFs. Annex A gives examples of the
circumstances under which ANF-PR can be used and criteria which can govern the selection of the new connection.
Additional network feature specifications are produced in three stages, according to the method described in CCITT
Recommendation I.130 for supplementary services. This International Standard contains the stage 1 and stage 2 specifications
of ANF-PR. The stage 1 specification (clause 6) specifies the feature as seen by an entity which initiates path replacement, the
ANF-PR user. The stage 2 specification (clauses 7, 8 and 9) identifies the functional entities involved in the feature and the
information flows between them. Clause 7 contains the stage 2 specification for basic operation of the feature. Clause 8
contains the stage 2 specification for an enhanced mode of working which can be employed when supported by all the
equipment involved. It allows some of the elements of the old connection to be re-used. Clause 9 contains the stage 2
specification for an optional enhancement of the basic operation of the feature. It allows the ANF-PR user to be located in any
PINX in the old connection and to decide the direction of the new connection.