From: Rick Jones <rick.jones2@hp.com>
To: Stephen Hemminger <shemminger@vyatta.com>
Cc: David Laight <David.Laight@ACULAB.COM>,
Hagen Paul Pfeifer <hagen@jauu.net>,
Eric Dumazet <eric.dumazet@gmail.com>,
netdev@vger.kernel.org
Subject: Re: [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior
Date: Thu, 01 Dec 2011 10:25:28 -0800 [thread overview]
Message-ID: <4ED7C698.40003@hp.com> (raw)
In-Reply-To: <20111201085701.02f885c5@nehalam.linuxnetplumber.net>
On 12/01/2011 08:57 AM, Stephen Hemminger wrote:
> On Thu, 1 Dec 2011 16:38:51 -0000
> "David Laight"<David.Laight@ACULAB.COM> wrote:
>
>>
>>> One idea to do small delays at higher speed is to insert
>>> dummy pad frames into the device.
>>> It would mean generating garbage, but would allow for
>>> highly accurate fine grain delay.
>>
>> Not a good idea.
>> They would have to be sent to a known MAC address
>> otherwise all the ethernet switches would forward them
>> on all output ports.
>>
>> David
>>
>>
>
> Yes it would have to be a constant destination, not sure if there
> is a discard value in Ethernet protocol spec.
Aren't there special addresses that aren't supposed to be forwarded by
(intelligent) switches? IIRC LLDP uses such things. Though the IEEE
may take a dim view of using it for such a purpose, and knuth only knows
what switch bugs would be uncovered that way...
http://standards.ieee.org/develop/regauth/grpmac/public.html
http://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol
rick jones
next prev parent reply other threads:[~2011-12-01 18:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-30 22:20 [PATCH v3 net-next 1/2] netem: rate extension Hagen Paul Pfeifer
2011-11-30 22:20 ` [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior Hagen Paul Pfeifer
2011-12-01 3:30 ` Eric Dumazet
2011-12-01 8:25 ` Hagen Paul Pfeifer
2011-12-01 9:01 ` Eric Dumazet
2011-12-01 9:32 ` [PATCH net-next] netem: fix build error on 32bit arches Eric Dumazet
2011-12-01 9:46 ` Hagen Paul Pfeifer
2011-12-01 11:04 ` David Laight
2011-12-01 11:19 ` Eric Dumazet
2011-12-01 17:46 ` David Miller
2011-12-01 9:36 ` [PATCH v3 net-next 2/2] netem: add cell concept to simulate special MAC behavior Hagen Paul Pfeifer
2011-12-01 16:24 ` Stephen Hemminger
2011-12-01 16:38 ` David Laight
2011-12-01 16:57 ` Stephen Hemminger
2011-12-01 18:25 ` Rick Jones [this message]
2011-12-01 4:19 ` [PATCH v3 net-next 1/2] netem: rate extension David Miller
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