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Kevin,  There is a huge difference between (1) a standard explicitly prohibiting feature X, (2) being silent on feature X, or (3) explicitly requiring feature X.  If the feature X is explicitly prohibited, and vendor implements it, that implementation is non-compliant. Standards rarely prohibit anything. It is only done what that feature X breaks something if implemented, or is a safety/security issue.  If a standard is silent on feature X, any vendor may decide to implement it in a proprietary way. Such implementation still remains standards-compliant, even though it goes beyond the standard requirements.  And of course, if a feature X is required, any implementation must have it, and if it doesnâ??t, it is considered non-compliant.  So, here is my position on triple or quadruple tagging: with all existing standards being silent on it, any vendor is free to go ahead and support it in their implementations. Such proprietary support would involve defining proprietary field codes that point to 3rd and 4th tags (or 5th and 6th, if someone wants. The sky is the limit here.)  But explicitly adding this behavior to 1904.2 will require every vendor to support this, whether they need it or not.  -Glen  From: mxhajduczenia@xxxxxxxxx [mailto:mxhajduczenia@xxxxxxxxx]  It is all over the place in 802.1Q, Kevin â?? two tags, not 3, 4, or many more  From: stds-1904-2-tf@xxxxxxxxxxxxxxxxx <stds-1904-2-tf@xxxxxxxxxxxxxxxxx> On Behalf Of Kevin Noll  As I understand 802.1Q, the framework in 802.1Q allows an arbitrary number of tags to be in a frame.  Can you point me to specific text in 802.1Q that prohibits or limits support to 2 tags?  -- Kevin A. Noll  From: Glen Kramer <glen.kramer@xxxxxxxxxxxx>  Kevin,  This was not an arbitrary decision. Both 802.1Q and 1904.1 define frame formats and operations on double-tagged frames. There is no specification defining the format or processing operations for triple- or quadruple-tagged frames.  So, if a user classifies and manipulates the 3rd and 4th tag, what existing standard defines that processing? In 802.1, the ISS interface shows that frames can have just two tags S-TAG and C-TAG (I am not taking about I-tagged frames, which are very different).   -Glen  From: Kevin Noll [mailto:kevin.noll@xxxxxxxxxxxx]  Currently the draft allows classification and manipulation on up to 2 VLAN tags. Recalling the discussion that settled on 2 tags, this was a somewhat arbitrary decision that was made to allow the discussion to move on.  It is common to have more than 2 tags.  How would a user classify on or manipulate a 3rd or 4th tag, or an arbitrary tag depth?  --kan-- -- Kevin A. Noll  To unsubscribe from the STDS-1904-2-TF list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-1904-2-TF&A=1 To unsubscribe from the STDS-1904-2-TF list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-1904-2-TF&A=1 To unsubscribe from the STDS-1904-2-TF list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-1904-2-TF&A=1 |