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Date:      Fri, 21 Jan 2005 11:42:31 +0500
From:      Boris Kovalenko <boris@ntmk.ru>
To:        Brooks Davis <brooks@one-eyed-alien.net>, freebsd-net@freebsd.org
Subject:   Re: [PATCH] 802.1p priority (fixed)
Message-ID:  <41F0A457.5010304@ntmk.ru>
In-Reply-To: <20050121054732.GA30766@odin.ac.hmc.edu>
References:  <41EF9495.5080601@ntmk.ru> <20050120190516.GA12156@odin.ac.hmc.edu> <41F07622.5040102@ntmk.ru> <20050121054732.GA30766@odin.ac.hmc.edu>

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Brooks Davis wrote:
Hello!

>>Yes, the outgoing packets are tagged with specified priority. Then next 
>>device (Cisco Catalyst for example) will assign traffic to different 
>>queues according to 802.1p header information. The only thing (IMHO) 
>>that may be coded for FreeBSD is to allow PF & IPFW assign packets to 
>>ALTQ or DUMMYNET according 802.1p information.

> 
> OK, that makes sense.  Hmm, do we actually want to be using seperate
> interfaces for this?  I'm sure it's very useful in some applications,
> but if the real point is to get packets on the wire with the priority
> tags, won't IPFW, PF, or maybe even the application be the best place
> for this tagging rather then effectivly using the source address to set
> it?  Again, I'm not familiar with the way 802.1p is intended to work, so
> this may be a dumb question.
By the usual way, application does not have access to Layer 2 headers, 
so it can not set 802.1p priority itself. It may only set ToS value, but 
Layer 2 switches can not access Layer 3 information :) Indeed I'm not 
familar with BSD network structure interoperability. Andre Oppermann 
said that there is a way to mark this packets with m_tag from PF/IPFW. 
So, if this is really possible, the best way (IMHO) should be: if 
packet, that going out the vlan iterface has m_tag with 802.1p, we use 
this value, or value provided for vlan instead. This is just the way 
Cisco Catalyst does: trust the received 802.1p inforamtion, or override it.
> 
> -- Brooks
> 


-- 
With respect,
	Boris



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