[VoiceOps] Large SIGTRAN rate increases

[Mike Johnston]

On 2024-11-06 13:29, Chris Meilleur wrote:
> 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.

Absolutely, yes.  But that doesn't help with the SS7/ISUP problem.

With a typical T1 PRI with a customer, one of the channels is for 
signalling call setup.

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.

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.

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.

-Mike Johnston

[Corrections or improvements to any statements I have made above are 
more than welcome!]
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