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<div class="moz-cite-prefix">On 2024-11-06 13:29, Chris Meilleur
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:YQBPR0101MB469983CE8AB1C5E2E278584EB9532@YQBPR0101MB4699.CANPRD01.PROD.OUTLOOK.COM">Is
SIP to TDM media conversion a possibility? I've had to use that
in a few locations where we are delivering T1 PRI's to customers
for which a SIP expansion of their PBX is required but cost
prohibitive, or not possible on the platform. That said, I
haven't done any SS7 on them. <br>
</blockquote>
<p>Absolutely, yes. But that doesn't help with the SS7/ISUP
problem.</p>
<p>With a typical T1 PRI with a customer, one of the channels is for
signalling call setup.</p>
<p>But if Telco A has a bunch of T1s to Telco B, they wouldn't need
to lose a channel on every T1 for signalling. They could instead,
dedicate just one channel from one of the T1s for signalling, and
the rest are for audio. (For improved redundancy, there should be
two T1s that have a signalling channel on them.) When you have
direct signalling between two carriers like this, it's called an
F-Link.<br>
</p>
<p>But, for some reason, it seems rare for Telco A and Telco B to
have signalling directly between each other. At least in my
experience. The T1s they have between each other are for audio,
and that's it. The signalling between them is instead handled by
one or more third parties, which operate STPs (and probably SCPs,
too). What they are selling you is called A-Links, which gets you
a "default gateway" into the SS7 network. There is a good chance
these STPs are not anywhere geographically near you. Telco A and
Telco B could be just a handful of miles apart, but the signalling
required to setup a call may travel all over the continent. If
your A-Links are down, you won't be able to make calls to the
neighboring telco, even though your T1s with them are up.<br>
</p>
<p>TDM is getting more and more expensive across the board. But
what's happening most recently, is a huge increase in cost from
the above mentioned providers, specifically for the service of
signalling call setup between telcos (ISUP). Other common uses of
the SS7 network include CNAM and LRN lookups, which are not seeing
particularity noteworthy (i.e., fall out of your chair) price
increases.<br>
</p>
<p>-Mike Johnston</p>
<p>[Corrections or improvements to any statements I have made above
are more than welcome!]<br>
</p>
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