Subject: [rbridge] Use of 802.1ah Encaps

From: sgai at nuovasystems.com (Silvano Gai)
Date: Fri, 8 Dec 2006 07:07:25 -0800

Ali,

Inline:

> -----Original Message-----
> From: Ali Sajassi (sajassi) [mailto:sajassi at cisco.com]
> Sent: Thursday, December 07, 2006 9:23 PM
> To: Silvano Gai; Don Fedyk; Gray, Eric
> Cc: Developing a hybrid router/bridge.; Joe Touch
> Subject: RE: [rbridge] Use of 802.1ah Encaps
> 
> 
> Silvano,
> 
> > -----Original Message-----
> > From: Silvano Gai [mailto:sgai at nuovasystems.com]
> > Sent: Thursday, December 07, 2006 5:36 PM
> > To: Don Fedyk; Gray, Eric; Ali Sajassi (sajassi)
> > Cc: Developing a hybrid router/bridge.; Joe Touch
> > Subject: RE: [rbridge] Use of 802.1ah Encaps
> >
> >
> > 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.
> 
> Can you refresh my memory for why we need a next-hop address when the
> header carries both source and destination PE addresses and when these
> addresses are learned in control plane ?
> 

Radia did in her reply

> > 2) Lack of a TTL field (it may be added, but it is not there today).
> 
> Can probably be accommodated.
> 
> > 3) Many unneeded fields and therefore larger frame overhead.
> >
> 
> Such as ?

The I-tag is not useful in TRILL and in contrast two addresses and the
TTL are missing.

> 
> > 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.
> >
> 
> If by overkill you mean a bit bigger header, then I agree but look at
> all the other advantages that you get from using standard IEEE header
> and shim including:
> 	- security Mgmt:  MACSec/KeySec
> 	- Congestion Mgmt
> 	- Connectivity Fault Mgmt
> 
> Has it been considered how these are going to work with TRILL shim
> header or are these outside of WG charter :-)
> 
> -Ali
> 
> 
> > -- 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
> > > >
> > >
> > > _______________________________________________
> > > rbridge mailing list
> > > rbridge at postel.org
> > > http://mailman.postel.org/mailman/listinfo/rbridge
> >