You only send calls to point codes you're connected to with ISUP trunks (what 
is a control network without bearer channels?), so you don't really do it that 
way. You would look at your usual LCR/routing table, and the adjacent switch 
you want to pass it to, be it a local end office, feature group D regional ILEC 
tandem, or long distance carrier wholesale circuit, and you would send it to 
the point code of the switch you're connected to that is the appropriate next 
hop for the call.


________________________________
From: VoiceOps <voiceops-boun...@voiceops.org> on behalf of Ross Tajvar 
<r...@tajvar.io>
Sent: Wednesday, September 2, 2020 5:46 PM
To: VoiceOps
Subject: [VoiceOps] Question about SS7 routing

Hi all,

I'm trying to understand how routing works in SS7-land. I am familiar with 
portability, and I know (at least in the US) the first step in routing a call 
is doing an LNP dip to get the LRN.

However, it looks like addresses in MTP3 are "point codes" (PCs) which are 
assigned to switches. Calls are set up with ISDN-UP, which is transported via 
MTP3. So in order for a call to be set up, the destination switch's PC must be 
known. How is the destination PC determined from the destination LRN?

Thanks,
Ross
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