[rbridge] Consensus Check: Point to Point links

[Anoop Ghanwani]

I agree with Joe on this point.

Anoop 

> -----Original Message-----
> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org] On Behalf Of Joe Touch
> Sent: Friday, October 05, 2007 12:05 AM
> To: Silvano Gai
> Cc: Rbridge at postel.org; Radia Perlman
> Subject: Re: [rbridge] Consensus Check: Point to Point links
> 
> I do not understand the need to avoid a single entry per 
> link. This is hyperoptimization at the expense of complexity, 
> and isn't useful.
> 
> Joe
> 
> Silvano Gai wrote:
> > I agree with Donald on all points.
> > The saving comes from not having to maintain an adjacency table on 
> > high speed point-to-point links.
> > 
> > -- Silvano
> > 
> >> -----Original Message-----
> >> From: rbridge-bounces at postel.org 
> [mailto:rbridge-bounces at postel.org]
> > On
> >> Behalf Of Eastlake III Donald-LDE008
> >> Sent: Thursday, October 04, 2007 9:24 PM
> >> To: Radia Perlman
> >> Cc: Rbridge at postel.org
> >> Subject: Re: [rbridge] Consensus Check: Point to Point links
> >>
> >> Hi Radia,
> >>
> >> See below at @@@
> >>
> >> -----Original Message-----
> >> From: Radia Perlman [mailto:Radia.Perlman at sun.com]
> >> Sent: Thursday, October 04, 2007 11:51 AM
> >> To: Eastlake III Donald-LDE008
> >> Cc: Rbridge at postel.org
> >> Subject: Re: [rbridge] Consensus Check: Point to Point links
> >>
> >> Personally, I need a reminder of what we are trying to accomplish 
> >> with this before I can have any opinion.
> >>
> >> a) Is omitting the outer VLAN tag to save space?
> >>
> >> @@@ Yes. The outer VLAN tag does nothing for you on a 
> point-to-point 
> >> link.
> >>
> >> b) Why put in anything for destination address other than the MAC 
> >> address of the next hop RBridge, or put in anything into 
> the source 
> >> address other than your
> > own
> >> MAC address?
> >> It won't save space. So what does it gain?
> >>
> >> @@@ While no one has given a really crisp response to that 
> question,
> > it
> >> is my impression that some believe it will make it possible to 
> >> produce simpler, less expensive, or more efficient 
> hardware for this case.
> >>
> >> c) Is there any danger if an RBridge is confused about 
> whether this 
> >> is
> > a
> >> pt-to-pt link or not?
> >>
> >> @@@ I think there might be. And because of this and the extreme 
> >> commonness of the point-to-point case, it may be reasonable to
> > consider
> >> this in designing TRILL. For example, if a fixed MAC address were 
> >> used (such as the unicast version of the All-Rbridges multicast 
> >> address
> > (just
> >> turn off the group bit)), then an interface receiving a frame with
> > that
> >> source address would know there was a sender on the link 
> who believes 
> >> the link was point-to-point. If the receiver knows it is not 
> >> point-to-point or is unwilling to handle such frames, it 
> could take 
> >> appropriate action. Also, Rbridge would know to never bother
> > "learning"
> >> the location of that MAC address.
> >>
> >> @@@ Thanks,
> >> @@@ Donald
> >>
> >> I can see the advantage of omitting the entire outer 
> header if it is 
> >> somehow absolutely known this is a pt-to-pt link, and both ends of 
> >> the link understand this. But that isn't what's being 
> proposed here. 
> >> It seems to be only omitting the VLAN tag, and allowing 
> insertion of 
> >> random addresses into the source and destination fields in 
> the outer 
> >> header, if I'm reading it correctly.
> >>
> >> So anyway, clarification at this point would certainly help me.
> >>
> >>
> >> Eastlake III Donald-LDE008 wrote:
> >>> This is a check via the mailing list to confirm or refute an
> > apparent
> >>> consensus from the minutes of the Chicago meeting for a 
> change from 
> >>> protocol draft -05:
> >>>
> >>>    If it is known that a link is a point to point link between two
> >>>    RBridges, then the outer header, if it is an Ethernet 
> header, can
> >>>    have any source and/or destination addresses, those addresses
> > will
> >>>    be ignored on receipt, and the outer VLAN tag can be omitted.
> >>>
> >>> If no particular controversy arises over this in the next 
> two weeks,
> >> we
> >>> will declare it to be the working group consensus.
> >>>
> >>> Thanks,
> >>> Donald & Erik
> >>>
> >>> _______________________________________________
> >>> rbridge mailing list
> >>> rbridge at postel.org
> >>> http://mailman.postel.org/mailman/listinfo/rbridge
> >>>
> >>
> >> _______________________________________________
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> >> rbridge at postel.org
> >> http://mailman.postel.org/mailman/listinfo/rbridge
> > 
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