That's really odd for all of your SS7 services to go down because carriers typically connect to 2 A-links which are backed up by 2 D-links. So there are a total of 4 STPs (Signaling Transfer Points) programmed to back each other up. It could be down for one of two reasons. In the SS7 network, each switch is assigned a unique point code (9 digit number that identifies the switch location). In order for the ISUP trunks to work, the SS7 provider has to establish a route between your switch and the other carrier's switch. To make it a little easier to understand let's pretend you have a switch in CA and you are connecting it to 3 of AT&Ts San Francisco tandems. If each switch had the following point code assignments: Your switch's point code: 005-123-456 San Francisco tandem: 222-000-111 Oakland tandem: 222-000-222 Santa Rosa tandem: 222-000-333 Then your SS7 provider would build 3 point code routes: Your switch 005-123-456 to AT&T San Francisco tandem 222-000-111 Your switch 005-123-456 to AT&T Oakland tandem 222-000-222 Your switch 005-123-456 to AT&T Santa Rosa tandem 222-000-333 When your customer makes a call that is served by the Oakland tandem, the call would be routed over the 005-123-456 to 222-000-222 route set. If your links work but the call doesn't complete either your route set failed for some reason, or either AT&T's SS7 links or trunks went down. I'd ask them where the failure occurred. MARY LOU CAREY BackUP Telecom Consulting Office: 615-791-9969 Cell: 615-796-1111 On 2022-01-19 04:13 PM, Mike Hammett wrote:
The links have since come back. This is the second major failure of TNS within 6 months. No RFO yet, but I will certainly be on them for some detail.
My Metaswitch support rep verified that (pardon my lack of using the correct terminology, I'm not that familiar with it) our SS7 links never actually went down, it just lost connectivity beyond that. Sorta like my BGP peer stayed up, but I lost the global routing table behind it.
----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com
Midwest Internet Exchange http://www.midwest-ix.com
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From: "Mike Hammett" <voiceops at ics-il.net> To: "voiceops" <voiceops at voiceops.org> Sent: Wednesday, January 19, 2022 4:05:32 PM Subject: [VoiceOps] TNS SS7 Outage
Does anyone have any information on the TNS SS7 outage going on now? Both of our A-links go to different facilities (Chicago and Ashburn) over different VPNs (which are up).
TNS has acknowledged that it's a carrier issue. That they're investigating.
----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com
Midwest Internet Exchange http://www.midwest-ix.com
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