VoLTE and SIP do indeed retail a lot of the concepts of circuit switched. The challenge is that now you have the complexity of (seemingly invariably) a Telco managing a k8s stack on an OS they don't understand, and which has hundreds of CVEs per month they aren't patching. The failure modes of VoLTE/SIP are also a load more complex than CS domain issues - IMS interop issues and XML parsing delights await!

So I guess it's not only about getting off the internet - there is a real shift in complexity in these more modern stacks too.

You are not wrong about the complexity of modern stacks.

However, VoLTE predates k8s adoption in most telcos and the physical network appliance == NF model is still alive and well, so it’s not necessarily a fair comparison. You’re also right about the added complexity of SIP/RTP (let’s agree not to talk about MMS lol).

That’s not true at all. Yes to the k8s but at least at my work we are scanned to death as soon as a new IP comes up on our network. Plus we have golden image updates at least every 30 days. We couldn’t even get SNMP traps out of our virtual firewalls because of “security”.

Containers are 10x better than monitoring and supporting some 30 years old switch in a central office that consumes more power than my cul de sac.