[rbridge] Use of 802.1ah Encaps

[Eastlake III Donald-LDE008]

Hi Don,

See below at @@@

-----Original Message-----
From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org] On
Behalf Of Don Fedyk
Sent: Wednesday, December 06, 2006 11:15 AM
To: Gray, Eric; Ali Sajassi (sajassi)
Cc: Developing a hybrid router/bridge.
Subject: Re: [rbridge] Use of 802.1ah Encaps

Hi Eric 

> -----Original Message-----
> From: Gray, Eric [mailto:Eric.Gray at marconi.com]
> 
> Ali/Don,
> 
> 	The use of 802.1ah encapsulation does not intuitively suggest
itself 
> in the TRILL problem domain for at least two
> reasons:
> 
> 1)	Provider Back-bone Bridging intuitively seems out of
> 	place in solutions aimed at enterprise networks - and
> 	this would seem to be even more true for solutions 
> 	aimed at "plug-and-play" applicability.

Hmmm Trill spent 1.5 years coming up with a header that looks remarkably
like 802.1ah. A fact many of us have pointed out before.  If you are
using an IEEE 802.1 Ethernet data plane your baseline choices are 802.1Q
or 802.1ah. 

@@@ That might be the baseline in IEEE 802.1 but I don't think it is in
IETF TRILL. I think the TRILL Charter states that our baseline is
draft-perlman-rbridge-03.txt, still available at
http://www.postel.org/rbridge/draft-perlman-rbridge-03.txt, although
that draft is not very specific about the encapsulation format.

@@@ Of course we can and have evolved from that baseline. (For example,
I assess the WG as leaning very strongly to the inclusion of two rbridge
designators.) And if there is an existing encapsulation format that
meets our needs, there is no particular reason to invent one. That is
why we were planning for a while on using an MPLS format. But 802.1ah
does not look much like the Rbridge shim (or Rbridge shim plus following
MAC addresses) to me. Perhaps I am just missing something but have the
"many" people you say have "pointed out" that we should just use the
802.1ah header actually proposed a specific allocation of its fields?
(for current ideas on Rbridge shim fields look at presentations in San
Diego such as
http://www3.ietf.org/proceedings/06nov/slides/trill-2/sld2.htm or
http://www3.ietf.org/proceedings/06nov/slides/trill-3/sld8.htm)

@@@ I would point out that, when we were discussing the MPLS
encapsulation, some who had originally advocated it as a way of re-using
hardware and the like later came to the conclusion that if it had to
have a different Ethertype and/or fields that are differently
interpreted, there was actually very little saving.

@@@ Thanks,
@@@ Donald

...

> > > Regards,
> > > Don