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Message-ID: <20140207161549.GB30416@nicira.com> Date: Fri, 7 Feb 2014 08:15:49 -0800 From: Ben Pfaff <blp@...ira.com> To: Jesse Gross <jesse@...ira.com>, Simon Horman <horms@...ge.net.au> Cc: dev@...nvswitch.org, netdev@...r.kernel.org, Pravin B Shelar <pshelar@...ira.com>, Ravi K <rkerur@...il.com>, Joe Stringer <joe@...d.net.nz> Subject: Re: [PATCH v2.53] datapath: Add basic MPLS support to kernel On Wed, Feb 05, 2014 at 05:54:38PM +0900, Simon Horman wrote: > * Ben has explained to me that there has been a change of direction > at the ONF with regards to MPLS and VLAN tag ordering. As per > his changelog for "Always insert MPLS labels after VLAN tags", > the situation is now as follows: > > * OpenFlow 1.1 and 1.2 always inserted MPLS labels after VLAN tags. > * OpenFlow 1.3 and 1.4 insert MPLS labels before VLAN tags. > * OpenFlow 1.3.4 and 1.5, both in preparation, recognize that the change > in 1.3 was an error and revert it. > > With this in mind only OF1.4 specifies a requirement for inserting MPLS > labels before VLAN tags. This appears to be an abbertation at this > point. > > Ben's suggestion as per his patch "Always insert MPLS labels after VLAN > tags" is that Open vSwtich should only support inserting MPLS labels > after VLAN tags. I agree with this. And to this end I have > updated the MPLS code for the kernel datapath (this patch). I spoke to Jesse briefly about MPLS versus VLANs a few days ago. He expressed a concern about the larger problem of figuring out how all the various forms of tags should interact: VLAN, MPLS, PBB, and others that I can't think of at the moment. It would be more consistent from this higher point of view if "push" and "pop" actions always acted in a predictable place. I agree with that point, but it still stands that I don't know of a well-defined way for VLAN-inside-MPLS to function. So here is my proposal for you and Jesse to consider: - The datapath push_mpls action is well-defined when no VLAN is present. Great. - Declare the behavior of the datapath push_mpls action to be undefined in the presence of a VLAN for now, since we don't really know what should happen. For now, make the datapaths reject any flow that does push_mpls in the presence of a VLAN. Later, we can redefine that case as we please since userspace should not depend on the previous behavior. - Modify userspace to pop_vlan, push_mpls, push_vlan if necessary to avoid the undefined behavior. Jesse, is that reasonable? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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