On 10/17/14, 4:54 PM, Ben Pfaff wrote:
On Fri, Oct 17, 2014 at 01:19:33PM -0400, Dave Benson wrote:
On Fri, Oct 10, 2014 at 6:43 PM, Ben Pfaff<b...@nicira.com> wrote:
...
My first thought is to define a new NXM_NX_VLAN_TPID that matches the
TPID, and for backward compatibility to imply a match on 0x8100 if it
is not given.
I think the assumption in OF is that the vlan-vid match is always on the
outermost tag but the description in the spec is not explicit. The
802.1ad spec requires that the outer TPID must be 0x88a8 so in spite of
some legacy use of 0x9100 or 0x8100 for the outer tpid, I think it is OK
to assume that 0x88a8 is the TPID for the outer tag and 0x8100 is the
TPID for the inner tag.
However, an ambiguity in the OF spec is that the behavior for 802.1q and
802.1ad is implied and not explicitly stated.For example, the entry in
the OF in table 11 (page 57, version 1.4,) the line about vlans should
say that the prerequisite of a VLAN_ID should be a TPID of 0x8100 OR
0x88a8 and the description should be changed to include both 802.1q and
802.1ad and that the match is on on the outer tag.
802.1ah is in a similar situation in this respect. Notice in contrast,
the entry for OXM_OF_PBB_ISID in the same table in the OF spec states
explicitly that 0x88E7 is the prerequisite and that the match is on the
outer ISID.
Your proposal, Ben of adding a match on the TPID to OF is a way to end
the ambiguity but I don't think it absolutely necessary. My opinion is
that it would be sufficient to change in the language in the spec to
explicitly state that the match is on the outer tag.
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Thomas F. Herbert
Network Implementation Engineer
Entry Point LLC
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