Re: [hybi] GET+Upgrade as emended by Greg (was Re: handshake status)

[Zhong Yu <[e-mail]>]

On Wed, Nov 10, 2010 at 10:01 PM, Greg Wilkins <[e-mail]> wrote:
> Zhong,
>
> I think there are always going to be failure modes with any handshake
> were this is going to be a problem.  Even with perfectly good
> intermediaries, networks may still fail and clients can be left with
> the belief that they have a connection when they do not.    There is
> no solution that does not eventually need some form of keep alive to
> check the connection has not silently failed immediately after the
> handshake or at any time after it has been established.

Still, we can contemplate which is relatively better, Client-Server
hello, or Server-Client hello.

If exchange of hellos is not completed within a time window, say 5
second, connection is aborted in either case. However there are still
significant differences.

In the Client-Server case, the client spends 5 seconds waiting for
completion. UI can display a busy icon so the user knows it is trying
to establish a connection. After 5 seconds, the client closes the
connection (in the TCP sense)

The server simply waits for client Hello. It doesn't need to set a
timeout, the client will close the connection after 5 seconds
anyway(assuming TCP FINs are delivered at light speed). If the server
got the client Hello, it will assume that the connection is
established, which is false. The *server* got the wrong impression. It
may even immediately send some app data to client (none of which will
be delivered to client app), then the connection is closed in 5
seconds. Poor Server.

In the Server-Client case, If the client got the server Hello
immediately, it assumes that the connection is established, which is
false. The *user* got the wrong impression. The app seems working at
first, then stops working in 5 seconds. Poor User.

The server isn't deceived though. It never assumed that the connection
is established. It closes the connection after 5 seconds.

Compare the two cases, I think the first one is better from user's
point of view.

The second case is better for servers, but who cares about servers?
Servers have no feelings.

- Zhong