Subject: [hybi] pointers, please?

From: Mark Lentczner <[email-masked]>
Date: Wed, 15 Apr 2009 18:46:46 -0700

> The same-origin security policy.
Can someone point me at a text on this?

Also, while I understand the difficulties that the two connection  
limit imposes on applications doing Comet/AJAX style operations, I  
couldn't seem to find a discussion of why that limit was added to HTTP?

I don't want to incite re-opening of these issues here - I'm just  
looking for pointers....   at least for now :-)

	- Mark

Mark Lentczner
Sr. Systems Architect
Technology Integration
Linden Lab

[email-masked]

Zero Linden
[email-masked]

---

From: "Thomson, Martin" <[email-masked]>
Date: Wed, 15 Apr 2009 21:04:26 -0500

Congestion control was the reason cited at the last meeting.  It’s a good reason.

From: [email-masked] [mailto:[email-masked]] On Behalf Of Mark Lentczner
Sent: Thursday, 16 April 2009 11:47 AM
To: [email-masked]
Subject: [hybi] pointers, please?

Also, while I understand the difficulties that the two connection limit imposes on applications doing Comet/AJAX style operations, I couldn't seem to find a discussion of why that limit was added to HTTP?

I don't want to incite re-opening of these issues here - I'm just looking for pointers....   at least for now :-)

          - Mark

Mark Lentczner

Sr. Systems Architect

Technology Integration

Linden Lab

[email-masked]

Zero Linden

 

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---

From: Jamie Lokier <[email-masked]>
Date: Thu, 16 Apr 2009 06:02:25 +0100

Thomson, Martin wrote:
> Congestion control was the reason cited at the last meeting.Â
> It's a good reason.

(Another reason: additional connections add considerable overhead just
in packets transmitted: 6 for setup and teardown per connection).

Some people have said there is no need to limit the number of
connections made for WebSocket-style things: say 100 sockets from a
single client to a single server are not a problem.

(That's from 10 per window/tab (different app authors on the same page),
times 10 windows/tabs open to the same server).

Does congestion control mean it is important to reduce the number of
connections below that sort of level?

I think so, but I'd like to read other opinions.

-- Jam

---

From: Greg Wilkins <[email-masked]>
Date: Thu, 16 Apr 2009 17:07:15 +1000

Mark Lentczner wrote:
> Also, while I understand the difficulties that the two connection limit 
> imposes on applications doing Comet/AJAX style operations, I couldn't 
> seem to find a discussion of why that limit was added to HTTP?
> 

I don't know if limiting connections on the server was a motivation
for the 2 connection limit, but as a developer of a HTTP server, I
appreciate the limit as every connection to the server consumes some
kernel resources and buffers.

Typically I aim of a server node to handle several 10s of thousands
of simultaneous users.   If each of those users starts using 8 connections
instead of 2, then my FD limit needs to be increased from 40k-ish
to 120,000k-ish and my buffer memory requirements are worst case x 4!
That is possible to do, but I'm not exactly happy that all that extra
memory and server capabilities I now have are being consumed essentially
because client side can't coordinate in order to multiplex.

I'd much rather have a few extra bytes per datagram indicating a
channel id. rather than an extra buffer server side for every connection
created in lieu of channels.

I've also seen people saying that increasing the number of connections
from their browser improves the throughput they receive from the network.
eg http://www.speedguide.net/read_articles.php?id=2448
This may be for a congested network trying to fair share capacity between
many connections - but it will not work if everybody on the network
increases their limit to 8 connections.... then somebody will increase
to 16 and let the arms race commence!

I really love how you see pages like this:
   http://support.microsoft.com/default.aspx?scid=KB;en-us;q183110
which demonstrates that the browser 2 connection limit is well
known, so that modern browsers that violate it are doing so
very knowingly against the RFC recommendations.

cheers