W3C home > Mailing lists > Public > ietf-http-wg@w3.org > July to September 2013

Re: Feedback on TCP Fast Open?

From: Adrien de Croy <adrien@qbik.com>
Date: Sun, 04 Aug 2013 00:00:40 +0000
To: "Willy Tarreau" <w@1wt.eu>, "William Chan (?????????)" <willchan@chromium.org>
Cc: "Scharf, Michael (Michael)" <michael.scharf@alcatel-lucent.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>, "tcpm@ietf.org" <tcpm@ietf.org>
Message-Id: <em451aac53-b8da-4533-b586-1fb9460a99aa@bodybag>

we get tech support queries about this as well...

"what are all these connections without a URL showing in activity".

Nice little tech support ticket generator feature.

We figured it was pre-emtive connecting, since eventually a request may 
be made on the connection.

------ Original Message ------
From: "Willy Tarreau" <w@1wt.eu>
To: "William Chan (?????????)" <willchan@chromium.org>
Cc: "Scharf, Michael (Michael)" <michael.scharf@alcatel-lucent.com>; 
"ietf-http-wg@w3.org" <ietf-http-wg@w3.org>; "tcpm@ietf.org" 
Sent: 3/08/2013 2:15:29 a.m.
Subject: Re: Feedback on TCP Fast Open?
>Hi William,
>On Fri, Aug 02, 2013 at 06:51:31AM -0700, William Chan (?????????) 
>>  The short of it is, for vanilla HTTP, it's unclear how beneficial it 
>>  be for us since we already have such gains for browser preconnect 
>>  browser feature that learns from past web browsing to speculatively
>>  establish connections, typically just TCP connections but perhaps 
>>doing a
>>  TLS or other handshakes too as needed).
>That's pretty interesting. Is this already enabled by default ? I'm 
>because I've got several users of haproxy report me that their web site 
>regularly "attacked" by many connections in which no request is sent, 
>that because of this they had to increase the number of concurrent 
>otherwise they can't stand the load. I asked if they thought it could 
>something like a bug in some JS application or something like this as I 
>no aware of the preconnect feature. It's been a bit hard to analyse, 
>they see no request, they can't get any information on the user agent 
>example. The thing is that it does not look like a regular attack since 
>load is more or less constant, and not very high. So till now it was 
>possible to work around this by increasing the connection limits 2-10 
>But now I'm thinking that *if it was a preconnect behaviour*, there 
>possibly be some harm there. I have no idea how many connections a 
>can send to recently visited sites, but for sites which use a short 
>timeout to limit the concurrency, having a significant increase on the 
>of concurrent connections can be a problem.
>Note that I'm talking using a conditional form, as I can't provide 
>for this to be related to a preconnect feature, but your description 
>matches what I observed, and I am really wondering about the risks and
>possibile impacts based on something that could appear related. If the
>increase in connection count may be significant for small sites, then 
>TFO could be a decent alternative (though it will clearly not pass 
>every firewall).
>Best regards,
Received on Sunday, 4 August 2013 00:01:13 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:14:14 UTC