Also can a flow fail temporarily?
For example a broadband router with a NAT timeout of 60 seconds and a UA with a keep-alive interval of 120s. Would the flow succeed for the first 60 seconds after each keep-alive and then fail for 60 seconds until the next keepalive?
Yes. That's a misconfigured ua, isn't it...
Don't think so. It is not easy or common for UAs to discover the NAT timeout. They must make assumptions about what is a reasonable lower bound, unless you are mad enough to expect the user to configure this. On mobile / battery-powered devices it is often not an option to configure a keep-alive interval that low.
But if you want a different example then take an unreliable network connection. My question was more about whether the EP would generate a 430 or a 408/503/504 in this kind of potentially temporary failure case.
The UA will have to make sure to manage connections properly so at least one of the two are always open and working...
Yes AND the proxy has to manage those flows properly so both of the two are always tired when necessary and preferably not after a 32 second timeout trying a flow which it should already know has failed.
Keep in mind the the flows are tried serially, not in parallel.
Outbound is all about pushing responsiblity for the flows to the UA.
Responsibility for initiating them yes. But there is a whole lot for the server to do and that is what we're trying to get to the bottom of.
Well, Outbound is very focused on TCP. It's alive or dead. It doesn't behave like UDP.
So if the network flaps for 60 seconds is a TCP connection dead or alive?
Richard