[reSIProcate] WebSockets, Outbound and Flow tokens

[Scott Godin]

...inline...

On Wed, Apr 3, 2013 at 6:06 PM, Daniel Pocock <daniel at pocock.com.au> wrote:

>
>
> Given that WebSocket clients are largely uncontactable except via the
> original connection, it really appears that there are two ways they must
> work:
>
> a) with outbound (or with the non-outbound flow token hack enabled) -
> this is what the draft proposes
>
> b) talking directly to some kind of B2BUA or SBC that keeps track of the
> WebSocket client
>
>
> I've been able to test case (a) quite well with repro by enabling the
> flow token options in repro.config.
>
> On the other hand, it's not quite clear how we should support case (b),
> as the flow tokens don't really seem appropriate within a B2BUA.  For
> example, we need to be sure that dum or resip will automatically send a
> request such as BYE out to the websocket client when somebody calls
> InviteSession::end().
>
> One way to do this appears to involve making Dialog recognise when it is
> instantiated for a directly connected WS peer, and keep track of the
> flow, calling SipMessage::setForceTarget() when creating any new
> requests that will go back on the wire.  One gotcha is that if the flow
> is lost, the dialog can send no more requests to the peer.  Does this
> seem like the right way to adapt DUM for this purpose, or can anybody
> suggest a more desirable strategy, or should it just be avoided and all
> WS peers go via a proxy?
>

[Scott]  I don't see a need to support b) if we can do a).  a) is also the
better solution.

One additional issue that arises: repro should probably refuse to run
> (and log a helpful error) if somebody enables WS but not flow tokens, or
> the flow tokens should just automatically be enabled for WS peers no
> matter how repro is configured.
>

[Scott]  I think printing an error message at startup is the best way to
go.  You also need to configure the record-route URI if you enable flow
tokens and you can't really do that automatically (at least for transports
binding to IN_ADDRANY).

Scott


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