This parameter provides operators some alternatives. For example, the problem today
with intercarrier compensation in wireline networks is in identifying the first and
second transit networks prior to a call reaching the destination network. There is no
means of identifying the first transiting network, and if the call transits yet another
network, the destination (or terminating) network is left no choice but to trust and
charge the adjacent carrier for termination.
This header would allow each transiting carrier to place its identity prior to forwarding
the request on to the next network. The home network would then be able to determine
which networks the session request (and ultimately the call itself) transited, and
would be able to then apply the appropriate intercarrier fees.
Use of this header is dependent on intercarrier agreements between the various
carriers, since first, the network identifier must be known to the home network, and
second, the transiting carrier has no obligation to provide this information. It is strictly
voluntary as an optional protocol header.
The network identifier must also be globally unique. That requires some third-party
administrator to prevent duplication of identifiers, much like what is implemented for
the Domain Name Service (DNS).
The VIA header could also provide the same information, but it may be undesirable
because it may require queries to the DNS when the operator inserts its IP address.
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