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Posted by Sam Spade on February 21, 2009, 11:36 am
redacted@invalid.telecom-digest.org
Re: TeleTrap from TelTech Systems [Telecom]
> b: now we get to the magic trick. In reality standard CNID
> is, indeed, sent from the original caller along with the
> call initiation itself. If it isn't "blocked", then it gets
> transmitted to the recipient's phone. If the caller has
> chosen to block it, then the CNID string makes it "all the way"
> to the "central office" (term used a bit loosely) that's
> just before the recipient. That CO, instead of continuing
> to pass the CNID, sends along a "private" or "blocked" message.
>
> Keep in mind, again, that the CNID _is_ making it right to
> that last central office.
Indeed, the CNID is making it to the receiving parties central office
via a SS7 trunk along with a privacy flag if the calling party has
chosen to block.
But, the CNID message with or without a privacy flag does not cross
from the trunk frame through the switch to the receiving partie's
local loop. The privacy flag results in the receiving central office
generating a "private call" message to be sent out yhr receiving
parties local loop.
The analogy is similar with wireless, the receiving party receives no
information all the number contained in the CNID message. The
wireless carrier, just like a wireline carrier, was required to honor
the privacy flag so nothing other than "private call" or a similar
message is sent to the wireless set.
So, there is nothing of an identifying nature that the wireless called
party can send on.
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> is, indeed, sent from the original caller along with the
> call initiation itself. If it isn't "blocked", then it gets
> transmitted to the recipient's phone. If the caller has
> chosen to block it, then the CNID string makes it "all the way"
> to the "central office" (term used a bit loosely) that's
> just before the recipient. That CO, instead of continuing
> to pass the CNID, sends along a "private" or "blocked" message.
>
> Keep in mind, again, that the CNID _is_ making it right to
> that last central office.