Subject: [rbridge] Use of 802.1ah Encaps

From: sajassi at cisco.com (Ali Sajassi (sajassi))
Date: Thu, 7 Dec 2006 21:23:26 -0800

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 ?

> 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 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
> > >
> > 
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