[VoiceOps] Question about SS7 routing

Ross Tajvar ross at tajvar.io
Wed Sep 2 18:10:29 EDT 2020

I see, that makes sense. So then I have two follow-up questions:

   1. If you are connected to multiple carriers, e.g. multiple long
   distance carriers, how do you populate your routing table? (Obviously "it
   depends" but I'd be interested to hear an example.)
   2. If you are setting up equipment for the first time, with a new number
   block, how do you make sure other people include you/your block in their
   routing tables?

On Wed, Sep 2, 2020 at 5:56 PM Paul Timmins <ptimmins at clearrate.com> wrote:

> 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-bounces at voiceops.org> on behalf of Ross Tajvar
> <ross at 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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