3 ms·

However, the failure of the two is independent.

Rjevski 9y ago
Not really, most of today's SS7 traffic goes over IP, so if IP is somehow flawed you'll be in trouble in either case. Luckily IP links are pretty reliable so that's not an issue - VoIP also allows for more resiliency, for example my phone has two independent network connections, mobile and Wi-Fi, and my VoIP provider has two servers (advertised via DNS SRV records). So my VoIP app can try each server over each connection to make a call. A conventional landline or mobile on the other hand has a single link to the telco, so if that's down you're in trouble.
- Aloha 9y ago
  IP != Internet Yes, much traffic does traverse on IP now - but its private tightly controlled networks.
  - tatersolid 9y ago
    Not "private" as in "dedicated to voice traffic". Almost all modern telcos route their PSTN as packets on the same MPLS/IP or pure-IP network as internet traffic. This network is usually "privately owned" by the telco in the USA, but is publicly owned or subsidized in many parts of the world. But there is in general no "separate" PSTN other than last-mile copper in most of the world.
thaumasiotes 9y ago
If this is true, you'd want your emergency calls to be going over the more reliable service, not the less reliable one. Independent failures are only relevant if you use both networks redundantly.
- Rjevski 9y ago
  Well my SIP client app manages the loss of Wi-Fi or mobile connectivity pretty well - I loose audio for a second while it renegotiates the path through the other network link but after that it's business as usual. On a conventional call when I loose cell coverage the call is dropped, so SIP is a winner for me. On the server side you can do amazing things with high availability like floating/virtual IPs (the IP of the SIP server is actually shared between multiple machines, and if the primary machine goes down the secondary takes over its IP and as far as the client is concerned nothing happened).

Not really, most of today's SS7 traffic goes over IP, so if IP is somehow flawed you'll be in trouble in either case. Luckily IP links are pretty reliable so that's not an issue - VoIP also allows for more resiliency, for example my phone has two independent network connections, mobile and Wi-Fi, and my VoIP provider has two servers (advertised via DNS SRV records). So my VoIP app can try each server over each connection to make a call. A conventional landline or mobile on the other hand has a single link to the telco, so if that's down you're in trouble.

Aloha 9y ago
IP != Internet Yes, much traffic does traverse on IP now - but its private tightly controlled networks.
- tatersolid 9y ago
  Not "private" as in "dedicated to voice traffic". Almost all modern telcos route their PSTN as packets on the same MPLS/IP or pure-IP network as internet traffic. This network is usually "privately owned" by the telco in the USA, but is publicly owned or subsidized in many parts of the world. But there is in general no "separate" PSTN other than last-mile copper in most of the world.

thaumasiotes 9y ago

If this is true, you'd want your emergency calls to be going over the more reliable service, not the less reliable one. Independent failures are only relevant if you use both networks redundantly.

Rjevski 9y ago
Well my SIP client app manages the loss of Wi-Fi or mobile connectivity pretty well - I loose audio for a second while it renegotiates the path through the other network link but after that it's business as usual. On a conventional call when I loose cell coverage the call is dropped, so SIP is a winner for me. On the server side you can do amazing things with high availability like floating/virtual IPs (the IP of the SIP server is actually shared between multiple machines, and if the primary machine goes down the secondary takes over its IP and as far as the client is concerned nothing happened).