5.17.2. External Rerouting Disabled 
External rerouting by to the public or Foreign networks may want to
be disabled througout the network there by giving the originating system
control
Figure 46. External Rerouting Disabled
When a system wants to decide for itself if it is possible to route
to a foreign network the LDAT attribute NOEXTRTE must be set in each
specified element of the used routes.
In the example in Figure 48
a call is setup from system 1 to sys 4 and encounters congestion between
system 3 and 4.The cot parameter NTBO is set in Public/Private route
to the foreign network and normaly the call would reroute to this route
from system3.
However system 1 wishes to use it's own connection to the external
network (and then only if the route via system 2 is congested)and marks
the outgoing setup message with the attribute No External Rerouting set
by:
ADD-LDAT:LROUTE=xx,LSVC=ALL,TGRP=xx,ODR=xx,LAUTH=xx, LATTR=NOEXTRTE;