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
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
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
Your number block homing arrangements should be published in the LERG. ? Sent from mobile, with due apologies for brevity and errors.
On Sep 2, 2020, at 6:12 PM, Ross Tajvar <ross at tajvar.io> wrote:
? I see, that makes sense. So then I have two follow-up questions: 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.) 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
VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops
1. You route it to the one that's least expensive, or provides the highest quality, or whatever your target market is. This part's really up to you and it's part of the differentiator of your product. 2. Apply for the blocks with NANPA/National Pooling after getting all the right licensure, interconnection agreements with whoever the local tandems are run by, then make a relationship with an AOCN (NANPA runs one) that can input your blocks into the LERG. 3. Reach out to your local tandem operators before doing this to work out the finer details of routing inbound calls. There are usually the local ILEC, but there are alternative tandem providers such as Inteliquent. 4. Realize that regardless, you may have to connect with many tandems, and several local phone companies to get proper inbound coverage for your numbers. Connecting in the Chicago LATA, this can be something like a minimum of 10-11 T1s to various tandems and trunk groups, in the Upper Penninsula of Michigan this could be two T1s to Marquette, MI, one for local/intralata calling, one for interlata calls. -Paul ________________________________ From: Ross Tajvar <ross at tajvar.io> Sent: Wednesday, September 2, 2020 6:10 PM To: Paul Timmins Cc: VoiceOps Subject: Re: [VoiceOps] Question about SS7 routing 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<mailto: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<mailto:voiceops-bounces at voiceops.org>> on behalf of Ross Tajvar <ross at tajvar.io<mailto: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
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 VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops
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Hi Ross So in your original email you were wondering about the role of MTP, the layer 3 protocol. This keeps tabs on the point codes. If you are troubleshooting down to the SS7 messages (MSU?s), SLTM?s & SLTA?s tell you what point codes those links are reaching. The Global Title Translation uses the SCCP/SS7 protocol when connecting to IXC. Local Number Portability uses AIN/TCAP to dip the database to determine the LRN. But many SS7 operations just troubleshoot this by looking at the ISUP protocol where the original calling Party number (CGN) appears in the Generic Address Part GAP and the LRN in the called party number (CDN) field. Cheers Richard ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? From: VoiceOps <voiceops-bounces at voiceops.org> on behalf of Glen Gerhard <glen at cognexus.net> Date: Tuesday, September 8, 2020 at 11:47 AM To: <voiceops at voiceops.org> Subject: Re: [VoiceOps] Question about SS7 routing Hi Ross, Unless you have an SS7 trunk to an ILEC you don't need to worry much about the Point Code. For SIP traffic you just dip the call and route on the LRN. The Point Code itself is a special format that is assigned to you when you set up your SS7 capable switch. Unless you have one of them you never need to worry about it. ======== ANSI Point Codes ANSI point codes are made up of three groups of digits called the network indicator (NI), network cluster (NC), and network cluster member (NCM). The values for ANSI point codes depends on the value of the pctype parameter of the chg-sid command, either ansi or other. If the pctype parameter is set to ansi, the ANSI rules for the ANSI point code are used to define the point code. The range of values for an ANSI point code with the pctype=ansi parameter are: NI ? 001-255 NC ? 001-255 (if ni = 001-005) or 000-255, * (if ni = 006-255) NCM ? 000-255, * The pctype=other parameter specifies that the ANSI point codes do not meet ANSI standards. The range of values for ANSI point codes with the pctype=other parameter are: NI ? 000-255 NC ? 000-255, * NCM ? 000-255, * The asterisk (*) point code value indicates a single cluster address for a cluster point code (for example, 20-2-*) or a network routing destination (21-*-*). for more information on cluster point codes, see the Cluster Routing and Management Diversity (CRMD) section. For more information on network routing point codes, see the Network Routing section. A double asterisk (**) and triple asterisk (***) can also be used for the NC and NCM fields of the ANSI point code, but for only the rtrv-dstn, rept-stat-dstn, rtrv-rte, and rept-stat-rte commands. A double asterisk in the NCM field of a point code (for example, 20-2-**) produces a summary report that shows all point code destinations or routes residing in the given cluster (20-2). This does not include the cluster point code, if the cluster point code (for example, 20-2-*) is provisioned. The following examples (rtrv-dstn and rtrv-rte) are reports generated using two asterisks in the NCM field of a point code. ======= ~Glen On 9/3/2020 10:55 AM, Mary Lou Carey wrote: 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 VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops _______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops -- Glen Gerhard glen at cognexus.net 858.324.4536 Cognexus, LLC 7891 Avenida Kirjah San Diego, CA 92037 _______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops
participants (6)
-
abalashov＠evaristesys.com -
glen＠cognexus.net -
marylou＠backuptelecom.com -
ptimmins＠clearrate.com -
richard＠teraquant.com -
ross＠tajvar.io