[VoiceOps] Question about SS7 routing

Ross Tajvar ross at tajvar.io
Wed Sep 2 17:46:42 EDT 2020

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

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