Topic
#sip
2 posts
- What happens when you press 5 on a phone call A key press is two sine waves. On a modern VoIP call it is usually not sound at all, but a small packet that says which key and for how long. A walk from the 1960 Bell Labs design to RFC 4733, with the codec test that drops digits. 9 min read #systems#telephony#voip
- NAT bought us IPv4. It made real-time audio weird. NAT let the internet outgrow its public IPv4 address supply. It also made a connected VoIP call a surprisingly different problem from a working one. 8 min read #nat#voip#sip