[rbridge] Consensus Check: C-Tags

[Eric Gray]

James,

	I think there is still something missing in your view;
S-TAGs are defined in 802.1Q, I-TAGs are defined in 802.1ah.

--
Eric Gray
Principal Engineer
Ericsson  

> -----Original Message-----
> From: James Carlson [mailto:james.d.carlson at sun.com] 
> Sent: Tuesday, April 08, 2008 2:03 PM
> To: Eric Gray
> Cc: Eastlake III Donald-LDE008; Dinesh G Dutt; Caitlin 
> Bestler; Rbridge at postel.org
> Subject: RE: [rbridge] Consensus Check: C-Tags
> Importance: High
> 
> Eric Gray writes:
> > 	Hence the subtle issue is that - while I can agree with a
> > statement that use of S-TAGs is out of scope in this version of
> > the protocol specification - I agree with what I believe Dinesh
> > was saying when he indicated that we should not prohibit use of
> > S-TAGs in this specification by including a statement to the 
> > effect that S-TAGs are not used.  Any statement such as "S-TAGs
> > are not used" is innappropriate.  Further, I suggested using a
> > phrase to the effect that while the specification assumes use
> > of C-TAGS, it does not explicitly prohibit the use of S-TAGs.
> > While S-TAG use may be out of scope for this specification, it
> > may or may not require further specification (which means it is 
> > also out-of-scope to make any assertion about whether, or not,
> > additional specification is needed).
> 
> At the level that you're describing S-tags, any equipment that
> understands an ordinary C-tag would perform the right functions,
> leaving the issue essentially moot.
> 
> I read Donald's comments differently.  Equipment that processes what
> are *known* to be S-tags should be dealing with the 'I' bits as well
> and should know about provider-based bridging.  The current RBridges
> specification does not do that.
> 
> So, sure, if you have packets on the wire that happens to look like
> they have C-tags, and you don't tell an RBridge otherwise, then it'll
> just do the right thing with respect to interpreting it as a VLAN.  It
> won't look for the nested headers, though.
> 
> For that reason, I think our current spec leaves S-tags out of scope.
> You're on your own if you use them with RBridges.  If someone cares
> enough about S-tags to do them right, a future document _should_
> discuss how to do that.  It shouldn't be the base document, though,
> and we shouldn't discuss how to use them in that text.
> 
> -- 
> James Carlson, Solaris Networking              
> <james.d.carlson at sun.com>
> Sun Microsystems / 35 Network Drive        71.232W   Vox +1 
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