Aan alleen die zijn of zullen zijn, onze groet,
Just a basic question about SIP: I've done all kind of searching on the web and found all kind of documents, manuals, howto's, white-papers about SIP, but I still have a basic question:
I'm looking for a document which explains how a SIP-call is routed, both for the signalling-part and the voice-path itself.
Some practicle questions:1/ Concider a scenario where both clients are registered at two different SIP-providers and I make a call from one to the other.
1a/ Say both clients are directly connected to the internet, I guess the SIP signaling session will go via the registers of the SIP-providers, but the voice call itself will go directly between the two SIP-clients.
Right?1b/ Concider the clients that initiates the call is behind a one-to-many NAT-router (Port Restricted Cone NAT), the kind of routers you find a lot at homes these days.
So, in theory, it should be possible for the client behind the NAT-box to set up the voice-call to the client directly connected to the net; and the traffic will return as "return traffic" on that outgoing UDP-stream. (I'm talking about the voice-traffic itself, not the SIP signaling traffic).
Correct?1c/ Concider the call is initiated by the other side (the one on the internet) and the called party is behind a NAT-box. Again concerning the voice-traffic, what happens?
Is the called party ordered to set up the outgoing UDP-stream to the calling-party? (controlled via the SIP signaling information)?1d/ Concider both clients are behind NAT? What happens then?
Question 2: Port-forwarding:
Concider I have a SIP-box at home and I want to make it "directly reachable" from the internet (so it can be reached via SIP: email@example.com)
If it directly connected on the net, that is not a problem. (I actually have this set up at home), but say I would want to connect it behind a NAT-router and use port-forwarding.
I only have a single SIP-box and it has a fix IP-address on my local LAN. I could set up port-forwarding to forward port 5060 UDP to that box; giving the impression that this directly connected on the net? Correct?
But how do I port-forwarding for voice-traffic? It does not have a reserved range of UDP-ports, has it?
I guess these questions have been asked a number of times before but there seams to be so much information about SIP on the net; that it hard "to see the trees in the wood" (as we say in dutch).
Cheerio! Kr. Bonne.