[Bloat] Jumbo frames and LAN buffers

[Jim Gettys]

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

> My understanding is that 802.1au, "lossless Ethernet", was designed
> primarily to allow Fibre Channel to be carried over 10 GbE so that SAN and
> LAN can share a common infrastructure in datacenters. I don't believe anyone
> intends for it to be enabled for traffic classes carrying TCP.
>
> Kevin Gross
>
> -----Original Message-----
> From: bloat-bounces at lists.bufferbloat.net
> [mailto:bloat-bounces at lists.bufferbloat.net] On Behalf Of Jim Gettys
> Sent: Monday, May 16, 2011 5:24 AM
> To: bloat at lists.bufferbloat.net
> Subject: Re: [Bloat] Jumbo frames and LAN buffers
>
> Not necessarily out of knowledge or desire (since it isn't usually
> controllable in the small switches you buy for home).  It can cause
> trouble even in small environments as your house.
>
> http://virtualthreads.blogspot.com/2006/02/beware-ethernet-flow-control.html
>
> I know I'm at least three consumer switches deep, and it's not by choice.
>                       - Jim
>
>
> _______________________________________________
> Bloat mailing list
> Bloat at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat