A phone call with no phone line
You call a friend on a video app. There is no phone cable. Your voice travels over the internet.
Offices now do the same with desk phones and apps. The old phone line is gone. The question is how a call is set up and carried.
By the end of this lesson
Note
I can explain what VoIP and SIP are and how they work together.
Key words
| Word | What it means |
|---|---|
| Network | computers joined so they can share data |
| Packet | a small piece of data sent over a network |
| Protocol | an agreed set of rules for talking |
| VoIP | Voice over Internet Protocol: calls sent as packets |
| SIP | Session Initiation Protocol: the rules that start, change and end a call |
| Session | one call from start to finish |
| Unified communications | calls, video, chat and meetings in one system |
The cells students fill in are left blank in this preview.
Starter
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
VoIP sends your voice as packets
VoIP means Voice over Internet Protocol. Your voice is turned into digital data. The data is cut into packets and sent over a network.
At the other end the packets are put back in order and played as sound. The network can be the internet or the office network.
SIP sets up and ends the call
SIP is the protocol that handles the call itself. It does not carry your voice.
SIP finds the other person. It makes their phone ring. It agrees how the call will work. When someone hangs up, SIP ends the session.
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3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.