Subject: [rbridge] Use of 802.1ah Encaps

From: sgai at nuovasystems.com (Silvano Gai)
Date: Thu, 7 Dec 2006 17:35:54 -0800

IMO it is technically possible for TRILL to adopt IEEE 802.1ah. 
There are advantages and disadvantages.

The disadvantages are:
1) Lack of Next-Hop addresses. We discussed this at length during the
last meeting and we didn't reach consensus on a way to eliminate them.
2) Lack of a TTL field (it may be added, but it is not there today).
3) Many unneeded fields and therefore larger frame overhead.

The advantages are:
1) Larger addressable market for TRILL

IMO if we stick with the WG charter the disadvantages clearly outweigh
the advantages.

The WG can be re-chartered, but if we consider the Enterprise and Data
Center market, IEEE 802.1ah is an overkill.

-- Silvano

> -----Original Message-----
> From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org]
On
> Behalf Of Don Fedyk
> Sent: Thursday, December 07, 2006 9:21 AM
> To: Gray, Eric; Ali Sajassi (sajassi)
> Cc: Developing a hybrid router/bridge.; Joe Touch
> Subject: Re: [rbridge] Use of 802.1ah Encaps
> 
> Hi Eric
> 
> > -----Original Message-----
> > From: Gray, Eric [mailto:Eric.Gray at marconi.com]
> >
> > Don,
> >
> > 	And yet, someone (Ali Sajassi) asserted (in his message
> > dated Wed 12/6/2006 at 2:16 PM EST) that there were no issues
> > or additional complications with using 802.1ah in enterprises
> > for plug-and-play applicability.
> >
> > 	Perhaps Ali can answer my question then.
> >
> > 	But, to more directly address your earlier comments:
> >
> > 	The TRILL WG has NOT come up with an encapsulation that
> > "looks like" 802.1ah - unless someone squints really hard and
> > tries to pretend that two separate Ethernet encapsulations -
> > separated by a SHIM header - are one single encapsulation.
> 
> To be fair Point to Point header that was discussed without one of the
> shims was very close "functionally" (colloquial looks like) to
802.1ah.
> My opinion is still we don't need several variations of headers doing
> similar things.
> 
> This was the slide that looked a lot like what I posted.
> 
> http://www3.ietf.org/proceedings/06nov/slides/trill-1/sld13.htm
> 
> Regards,
> Don
> >
> > 	That is not to say that the WG has done anything that
> > could be said to disallow the use of 802.1ah encapsulation.
> > It is just not obviously consistent with all of the WG goals
> > to use _only_ 802.1ah encapsulation.
> >
> > --
> > Eric
> >
> 
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