[libnice] ICE process

[Philip Withnall]

On Tue, 2014-11-04 at 12:55 +0100, fb111 at web.de wrote:
> yes, very helpful! Can you describe what the process is when a node
> wants to stay registerd with a singaling/ rendevouzserver, but does
> not receive a request for a connection?
> As far as I understand, the node first performs the binding request
> with STUN and TURN an THEN forwards the information of the IPs and
> ports to the rendezvousserver, so that other nodes know how to reach
> this node, right?
> Do you need to keep this registration with the rendezvousserver alive,
> to avoid the shutdown of the portmapping on the NAT router by sending
> keep alive STUN signals?

That’s incorrect. The STUN and TURN negotiations are specific to each
remote peer, so must be performed at the point when two nodes need to
connect.

This has to be the case because various NAT configurations can limit
port bindings to packets coming from specific external IP/port
combinations. So if you have node A which has established a port mapping
in its NAT and sent the WAN IP/port for that mapping to the signalling
server, then later node B tries to connect, the packets may be dropped
by the NAT because they’re coming from an external IP/port combination
(node B’s WAN address) which the mapping wasn’t created for.

You may still want to keep each node registered with the signalling
server, for control purposes, but you will need to design your own
protocol for doing that (or use whatever protocol the existing
signalling server you’re using uses). That protocol will be entirely
separate from ICE.

Philip
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