Re: [hybi] Extensibility mechanisms?

[Mike Belshe <[e-mail]>]

On Mon, Apr 19, 2010 at 2:17 AM, Jamie Lokier <[e-mail]> wrote:

> Adam Barth wrote:
> > On Sun, Apr 18, 2010 at 1:47 PM, Greg Wilkins <[e-mail]> wrote:
> > > Ian Hickson wrote:
> > > Intermediaries can know about websocket framing and so long as
> > > all sub protocols and extensions are restricted to adhere to
> > > websocket framing, then intermediaries can continue to work
> > > regardless of sub protocols.
> >
> > I'm not sure I buy the premise that we want intermediaries to
> > understand and/or interfere with the websocket protocol.  It seems
> > more robust and more secure to establish a point-to-point encrypted
> > tunnel between the user agent and the server.
>
> More secure, but higher latency and slower.
>
> Going by the "each application on each open web page should open its
> own connection" approach, and encrypted tunnels enforcing that, as
> well as enforcing TLS setup latency for each one, *much* slower than
> HTTP.  Not to mention the torrent of idle keepalives with so many
> connections.
>

A few notes:
   - The bulk of the time goes to round trips.
   - WebSockets has a round trip for the upgrade header too.



>
> Less robust - I put together an alternative to Ian's "tic tac toe"
> using long-GET HTTP.  It's a similar amount of code with a similar
> structure, and as far as I can tell fails in all the exact same
> scenarios, except for one: The HTTP version keeps working after a NAT
> or SPI router times out in the middle.  The WebSocket version breaks
> at that point, because it won't detect the broken TCP connection or
> create a new one.
>

The NAT point is a great one.  I don't have any data on how often long-lived
connections are broken by NAT.  We need this.  Unfortunately, I bet may NATs
just drop the connection without notifying the endpoints (e.g. never sends a
RST).   This could become problematic for websockets, I'm not sure.
 Keepalives may help some, but I bet NATs are smart enough to break even
there too.  Data is needed....


> One of the not so obvious strengths of HTTP, which probably wasn't
> deliberate design, is it recovers well from contemporary TCP-breaking
> routers.
>
>
True true true!  Lots of short connections, although less efficient, are
self-healing and robust.

Mike


> -- Jamie
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