I'll try to make this as short and sweet as possible even though it's
pretty complicated. Point Codes are the 10 digit addresses for a
particular switch and LRNs are the 10 digit addresses for a particular
connection point that switch is associated with. In the PSTN world, all
connections are dedicated and implemented by LATA / Tandem area for
Local / IntraLATA traffic. When you get your first NPA-NXX for a LATA /
tandem area, you enter it in the LERG (National Routing Database) and
populate the tandems (Local, IntraLATA and FGD) that you are connecting
to. Then you assign a 10 digit phone number from your NXX block to be
your LRN. You add that to both the LERG and NPAC (National Porting
Database).
Once you've published all your switch information in the LERG and NPAC,
then you establish your ISUP trunks with each ILEC you're
interconnecting with. You can set up additional trunks with other
carriers if you want a cheaper option for routing traffic, but the
minimum required is the ILEC. Each carrier's switch will have a distinct
point code associated with it so you'll order ISUP trunks to each switch
(point code route) you need to be connected to. You'll also associate
the distinct LRN for that LATA / carrier tandem area with that trunk
group. Usually there's multiple trunk groups per LATA / tandem area so
you'll program your routing tables with the NPA-NXXs each trunk group
serves. That way when a customer originates a call, your switch can do
the LNP dip to find the LRN and send it over the route that the NPA-NXX
of the LRN is associated with. Routing tables can get complicated
depending on how many carriers you're connected to. Companies that
operate in more than one ILEC area or LATA usually purchase Least Cost
Routing software so they can send their originating traffic out over the
cheapest route.
IXC traffic is routed a little differently because it is routed by CIC
(4 digit code that identifies the IXC) rather than by NPA-NXX. They
connect to all the ILEC carriers just like the CLECs do, but they
populate their routing information in the SMS database instead of the
NPAC database. Once the call is dipped, the traffic is delivered in
pretty much the same way.....by dedicated trunk group / tandem area.
MARY LOU CAREY
BackUP Telecom Consulting
Office: 615-791-9969
Cell: 615-796-1111
On 2020-09-02 04:46 PM, Ross Tajvar wrote:
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
_______________________________________________
VoiceOps mailing list
[email protected]
https://puck.nether.net/mailman/listinfo/voiceops
_______________________________________________
VoiceOps mailing list
[email protected]
https://puck.nether.net/mailman/listinfo/voiceops
