1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G02%#/-%.$!4)/.3G0G0/.G0G04%,%0(/.%37)4#().G0G0!.$G0G03).!,).).4%2.!4)/.!,G0G0!54/-!4)#G0G0!.$3%-)G13!54/-!4)#G0G07/2+)./6%2 this process iscalled overflow. There may also be overflow, at the same exc
2、hange, from a second choice group of circuits to a thirdchoice group of circuits, etc.2 When the group of circuits over which the overflow traffic is routed involves at least one exchange notinvolved in the previous choice route, the process is called alternative routing.3 It should be noted that ov
3、erflow can occur without alternative routing for cases such as, when there are in onerelation two groups of circuits, one group reserved for one-way operation and the other group used for both-wayoperation. In this case, when all one-way circuits are busy, the call can overflow to the both-way circu
4、it group.4 When congestion occurs at a transit exchange, arrangements can be made in some signalling systems, at theoutgoing international exchange on receipt of a busy-flash signal or a congestion signal sent by the transit exchange, toreroute the call automatically from the outgoing international
5、exchange over another route. This process is called re-routing. The use of rerouting is not envisaged in the International Routing Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6、 . . . . . . . . . . . . . . . .5 When a difficulty is encountered in the setting-up of a connection - such as double seizure on both-waycircuits or error detection - arrangements can be provided to make another attempt to set up the connection for that callfrom the point where the first attempt took place. This process is called automatic repeat attempt.An automatic repeat attempt may take place:- on the same circuit; or- on another circuit of the same group of circuits; or- on a circuit in another group of circuits.
