TELECOM Digest OnLine - Sorted: Re: Caution: Unidentified Callers - VoIP

Re: Caution: Unidentified Callers - VoIP

Thor Lancelot Simon (
Mon, 17 Jul 2006 18:35:32 +0000 (UTC)

In article <>, Rick Merrill
<> wrote:

>> As all the interworking standards make clear, any interworking to a
>> protocol which does not differentiate between customer-provided and
>> network-provided calling party identification must either use the
>> supplied number as a customer provided number only, or replace it with
>> the BTN for the trunk.

> How may SS7 are in use with a VoIP call? As few as zero for PC 2 PC.

Do you _really_ think that what people are up in arms about is forged
calling party ID on PC to PC calls handled by a single carrier? No

The problem is that VOIP carriers are feeding bogus calling party
numbers into the PSTN. These carriers typically connect to the PSTN
via ISDN trunks where the signaling is Q.931; the Q.931<->SS7
interworking standard is very clear that trunks to "customers" should
clear the network-provided bit on all calling party numbers. And, as
far as I'm concerned, if you don't validate the numbers you're sending
up the trunk into the PSTN, you are a "customer"; you are not a
"network", because you are not operating at the level of trust that
would allow other networks to treat calling party numbers supplied by
you as canonical.

The other problem is that the standard for delivery of CLID to analog
sets does not preserve the distinction between customer-provided and
network-provided numbers. In a network environment in which
originating carriers do not validate customer-provided numbers as
being associated with the same BTN as that of the facility on which
they were delivered (which is what they should do; but at present just
about nobody does) the only sane thing to do is _never present
customer-provided numbers over the analog interface_. Either present
"number unavailable" or present the BTN instead -- every call has to
have a BTN, so it's always available for use. This is what the FCC
could require, in order to solve this problem -- along with requiring
carriers to disconnect peers who pass them customer-provided,
unverified numbers as "network provided".

Thor Lancelot Simon

"We cannot usually in social life pursue a single value or a single moral
aim, untroubled by the need to compromise with others." - H.L.A. Hart

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