On 05/16/2011 09:42 AM, Kevin Gross wrote:
I would like to try this. Can you suggest specific equipment to look at. Due
to integration and low port count, most of the cheap consumer stuff has
surprisingly good layer-2 performance. I've tested a bunch of Linksys and
other small/medium business 5 to 24 port gigabit switches. Since I measure
latency, I expect I would have noticed if flow control were kicking in.
I think I was using a D-Link DGS2208. (8 port consumer switch).
I then went and looked at the spec sheets of some of the other consumer
kit out there and found they all had the "feature" of 802.3 flow control.
I may have been using iperf to tickle it, rather than ssh.
I was also playing around with an old 100Mbps switch, as documented in
my blog; I don't remember if I saw it there.
- Jim
Kevin Gross
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Jim Gettys
Sent: Monday, May 16, 2011 7:23 AM
To: [email protected]
Subject: Re: [Bloat] Jumbo frames and LAN buffers
On 05/16/2011 09:15 AM, Kevin Gross wrote:
All the stand-alone switches I've looked at recently either do not support
802.3x or support it in the (desireable) manner described in the last
paragraph of the linked blog post. I don't believe Ethernet flow control
is
a factor in current LANs. I'd be interested to know the specifics if
anyone
sees it differently.
Heh. Plug wireshark into current off the shelf cheap consumer switches
intended for the home. You won't like what you see. And you have no
way to manage them. I was quite surprised last fall when doing my home
experiments to see 802.3 frames; I had been blissfully unaware of its
existence, and had to go read up on it as a result.
I don't think any of the enterprise switches are so brain damaged. So i
suspect it's mostly lurking to cause trouble in home and small office
environments, exactly where no-one will know what's going on.
- Jim
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