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RE: [Xen-devel] Is 802.1p surpported by xen?

To: "ANNIE LI" <annie.li@xxxxxxxxxx>
Subject: RE: [Xen-devel] Is 802.1p surpported by xen?
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Wed, 8 Apr 2009 13:28:27 +1000
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Thread-topic: [Xen-devel] Is 802.1p surpported by xen?
>       How are you trying to support this? It should be as simple as telling
> Windows that it is supported and then maintaining different packet queues in
> your driver. I don't think that there is any state information that is shared
> between different adapters.
>       What happens on the backend interface and beyond is pretty much beyond
> your control, but as long as they respect the priority tags it should be fine,
> and even if they don't at least you have transmitted the packets based on the
> priority so you've done your bit.
> It is a requirement for NDIS6.0 driver when testing NDISTest 6.0(priority).
> Only a warning reported for NDIS5.1 driver.
> The server side will send packets with Non-Zero priority, and client side will
> check whether the packets received is with correct priority or not. So if keep
> a different queue in miniport dirver, miniport can not put the priority tag in
> the frame, and receive side still fails to receive the correct priority tag
> packets.
> Following information is i googled:
> The specific NDIS structure is NDIS_NET_BUFFER_LIST_8021Q_INFO
> <http://msdn2.microsoft.com/en-us/library/bb245890.aspx> , which contains
> member variables for both VlanID and UserPriority, and is passed to the NDIS
> miniport driver for implementing both priority tagging (UserPriority) and VLAN
> (VlanId). It is up to the NDIS miniport driver to actually insert the 802.1Q
> tag into the frame based on these values before transmitting on the wire. A
> miniport driver will only insert this tag if the feature is supported and
> enabled in the advanced properties of the NIC driver;
> The miniport drivers must strip the tag when received, and populate the
> NDIS_NET_BUFFER_LIST_8021Q_INFO UserPriority and VlanId fields with the values
> in the tag.
> Details is in http://social.msdn.microsoft.com/forums/en-
> US/networkqosqwave/thread/a774a51c-6c6b-4374-a190-48153b5a74f7/
> Any suggestions?

Just what it says. 802.1P just assigns a vague meaning to the priority field 
bits, it doesn't say what you should do with them in terms if 'sticking them' 
in the packet. 802.1Q (vlan trunking) includes 3 bits to stick the priority 
field into.

http://en.wikipedia.org/wiki/802.1q is a good high level overview of what is 

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