Re: [hybi] Last Call: <draft-ietf-hybi-thewebsocketprotocol-10.txt> (The WebSocket protocol) to Proposed Standard

Willy Tarreau <w@1wt.eu> Sun, 24 July 2011 18:59 UTC

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Date: Sun, 24 Jul 2011 20:59:49 +0200
From: Willy Tarreau <w@1wt.eu>
To: =?iso-8859-1?Q?I=F1aki?= Baz Castillo <ibc@aliax.net>
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Cc: Server-Initiated HTTP <hybi@ietf.org>, IETF-Discussion <ietf@ietf.org>
Subject: Re: [hybi] Last Call: <draft-ietf-hybi-thewebsocketprotocol-10.txt> (The WebSocket protocol) to Proposed Standard
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On Sun, Jul 24, 2011 at 08:30:11PM +0200, Iñaki Baz Castillo wrote:
> 2011/7/24 John Tamplin <jat@google.com>om>:
> >> ~100 ms (if the DNS server is not local and there is no DNS cache for
> >> the given domain). And just during the WS connection, no more. Taking
> >> into account that a WS will be *usually* connected after loading a web
> >> page, such ~100ms in a non-full-realtime protocol is insignificant.
> >
> > Wait, are you really saying that 100ms connect latency is unimportant?
> 
> Open the fastest web page and tell me how long it takes. Probably you
> have performed a DNS A query. I don't think that a xtra DNS query
> would be the bottleneck, never.

On lossy networks such as 3G, they definitely are. A lost UDP packet is
not retransmitted nor signaled as lost, so the browser has to retry. However,
once the connection is established to the server, most losses are more or
less smoothed by TCP extensions such as SACK. So yes, it can take several
seconds to just resolve a host and then only a few hundreds of ms to retrieve
the objects. I've observed it.

Regards,
Willy