[rbridge] a clarification about the core IS-IS instance
Anoop Ghanwani
anoop at brocade.com
Sun Jul 1 13:29:35 PDT 2007
Radia,
I would prefer a separate multicast address.
I think Silvano also said he would prefer it that way.
It makes things a lot simple from a parsing/frame
validation standpoint.
Anoop
> -----Original Message-----
> From: Radia Perlman [mailto:Radia.Perlman at sun.com]
> Sent: Friday, June 29, 2007 10:27 PM
> To: Anoop Ghanwani
> Cc: Silvano Gai; Eastlake III Donald-LDE008; rbridge at postel.org
> Subject: Re: [rbridge] a clarification about the core IS-IS instance
>
> At the time I thought there might be some IS-IS messages sent
> unicast.
> If that were
> true (which it turns out it isn't), then differentiating
> based on multicast addresses would not have worked.
>
> I don't think this is a big deal either way, and I don't
> think anyone had strong opinions about it.
>
> Radia
>
>
>
>
> Anoop Ghanwani wrote:
> > Silvano/Donald/Radia,
> >
> > I would prefer to see a different multicast address used
> for the TRILL
> > IS-IS instances. Was there any consensus on this at the
> time it was
> > discussed. I do remember seeing the discussion, but I
> can't remember
> > how it concluded.
> >
> > Anoop
> >
> >
> >> -----Original Message-----
> >> From: Silvano Gai [mailto:sgai at nuovasystems.com]
> >> Sent: Thursday, June 28, 2007 1:54 PM
> >> To: Eastlake III Donald-LDE008; Anoop Ghanwani
> >> Cc: rbridge at postel.org
> >> Subject: RE: [rbridge] a clarification about the core
> IS-IS instance
> >>
> >>
> >> Donald,
> >>
> >> Radia confirmed that all the ISIS messages are sent to multicast
> >> addresses and therefore we discussed the possibility to
> use separate
> >> multicast addresses instead of the V bit
> >>
> >> -- Silvano
> >>
> >>
> >>> -----Original Message-----
> >>> From: rbridge-bounces at postel.org
> [mailto:rbridge-bounces at postel.org]
> >>>
> >> On
> >>
> >>> Behalf Of Eastlake III Donald-LDE008
> >>> Sent: Thursday, June 28, 2007 8:46 AM
> >>> To: Anoop Ghanwani
> >>> Cc: rbridge at postel.org
> >>> Subject: Re: [rbridge] a clarification about the core
> IS-IS instance
> >>>
> >>> If it were not for the V bit, how would you distinguish an IS-IS
> >>>
> >> routing
> >>
> >>> packet conveying layer 3 routing information being sent
> >>>
> >> inside a TRILL
> >>
> >>> data frame from a layer 2 TRILL per VLAN IS-IS packet being sent
> >>>
> >> inside
> >>
> >>> a TRILL IS-IS frame?
> >>>
> >>> Donald
> >>>
> >>> -----Original Message-----
> >>> From: Anoop Ghanwani [mailto:anoop at brocade.com]
> >>> Sent: Thursday, June 28, 2007 10:34 AM
> >>> To: Eastlake III Donald-LDE008
> >>> Cc: rbridge at postel.org
> >>> Subject: RE: [rbridge] a clarification about the core
> IS-IS instance
> >>>
> >>> Hi Donald,
> >>>
> >>> Thanks again.
> >>>
> >>> What's the function of the V-bit in all of this? What does an
> >>> RBridge gain by looking at this, that it cannot get by looking at
> >>> fields that it already has to?
> >>>
> >>> Anoop
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Eastlake III Donald-LDE008
> >>>> [mailto:Donald.Eastlake at motorola.com]
> >>>> Sent: Thursday, June 28, 2007 7:30 AM
> >>>> To: Anoop Ghanwani
> >>>> Cc: rbridge at postel.org
> >>>> Subject: RE: [rbridge] a clarification about the core
> >>>>
> >> IS-IS instance
> >>
> >>>> Hi Anoop,
> >>>>
> >>>> That looks about right, although you also have to check that the
> >>>> inner length/type field is in the length range. And if you
> >>>> determine that a TRILL IS-IS frame is for a per VLAN
> instance, you
> >>>> still don't know if you should process as well as forwarding it
> >>>> until you check whether you are DRB for a link with an
> end station
> >>>> in that VLAN.
> >>>>
> >>>> Donald
> >>>>
> >>>> -----Original Message-----
> >>>> From: Anoop Ghanwani [mailto:anoop at brocade.com]
> >>>> Sent: Thursday, June 28, 2007 10:00 AM
> >>>> To: Eastlake III Donald-LDE008
> >>>> Cc: rbridge at postel.org
> >>>> Subject: RE: [rbridge] a clarification about the core
> >>>>
> >> IS-IS instance
> >>
> >>>> Hi Donald,
> >>>>
> >>>> Thanks for the clarification. Yes, I do remember the
> discussion on
> >>>> the list. At that time it looked like the Ethertype
> would tell if
> >>>> the frame was IS-IS.
> >>>> It now looks like even the core IS-IS instance will use
> a DSAP/SSAP
> >>>> (for some reason I thought we were going to use a new
> Ethertype for
> >>>> the core IS-IS instance).
> >>>>
> >>>> So, to identify a core IS-IS frame (which all RBridges should be
> >>>> interested in) one would have to check for:
> >>>> outer.etype = trill
> >>>> inner.dsap = xx
> >>>> inner.ssap = xx
> >>>> inner.ctl = yy
> >>>> inner.vlan = not present
> >>>>
> >>>> The V bit doesn't really seem all that useful since both
> the core
> >>>> frames and the per-VLAN instance have it set, so that
> bit doesn't
> >>>> tell one whether or the packet needs to be processed as
> a control
> >>>> packet at a given RBridge. The above fields are necessary and
> >>>> sufficient. Please let me know if I'm missing something
> re the V
> >>>> bit.
> >>>>
> >>>> Thanks,
> >>>> Anoop
> >>>>
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Eastlake III Donald-LDE008
> >>>>> [mailto:Donald.Eastlake at motorola.com]
> >>>>> Sent: Wednesday, June 27, 2007 9:09 PM
> >>>>> To: Anoop Ghanwani
> >>>>> Cc: rbridge at postel.org
> >>>>> Subject: RE: [rbridge] a clarification about the core IS-IS
> >>>>>
> >> instance
> >>
> >>>>> Hi Anoop,
> >>>>>
> >>>>> Yes, that was a change that was extensively discussed on
> >>>>>
> >>>> the mailing
> >>>>
> >>>>> list. There wasn't a formal consensus determination but it
> >>>>>
> >>>> was clear
> >>>>
> >>>>> that the sentiment of the group was to always have a TRILL
> >>>>>
> >>>> Header on
> >>>>
> >>>>> TRILL IS-IS frames and use a formerly reserved bit in the header
> >>>>>
> >> to
> >>
> >>>>> distinguish a TRILL IS-IS frame from a TRILL data frame
> >>>>>
> >>>> whose contents
> >>>>
> >>>>> happens to be a (presumably layer 3) IS-IS message.
> >>>>>
> >>>>> I believe your second point is correct. Checking for the TRILL
> >>>>> Ethertype is the key to deciding whether to process a frame
> >>>>>
> >>>> if you are
> >>>>
> >>>>> not DRB on that port and VLAN. (This ignores the
> >>>>>
> >>>> bridging/media frames
> >>>>
> >>>>> sent to the block of multicast 16 addresses reserved for that
> >>>>> purpose.)
> >>>>>
> >>>>> Thanks,
> >>>>> Donald
> >>>>>
> >>>>> -----Original Message-----
> >>>>> From: rbridge-bounces at postel.org
> >>>>> [mailto:rbridge-bounces at postel.org] On Behalf Of Anoop Ghanwani
> >>>>> Sent: Wednesday, June 27, 2007 9:42 PM
> >>>>> To: rbridge at postel.org
> >>>>> Subject: [rbridge] a clarification about the core IS-IS instance
> >>>>>
> >>>>> From reading the previous version of the draft I got the
> >>>>>
> >> impression
> >>
> >>>>> that frames sent as part of the core IS-IS would not
> >>>>>
> >>>> contain a trill
> >>>>
> >>>>> header or inner header. However, on reading this version, it
> >>>>>
> >> looks
> >>
> >>>>> like the core IS-IS instance would in fact contain a
> >>>>>
> >> trill header.
> >>
> >>>>> Assuming that the above is true, would it be safe to assume that
> >>>>>
> >> an
> >>
> >>>>> RBridge, for a port that is connected to a LAN for which it
> >>>>>
> >>>> is not a
> >>>>
> >>>>> DRB, will drop all frames whose Ethertype does not
> >>>>>
> >> indicate trill?
> >>
> >>>>> Anoop
> >>>>>
> >>>>>
> >>> _______________________________________________
> >>> rbridge mailing list
> >>> rbridge at postel.org
> >>> http://mailman.postel.org/mailman/listinfo/rbridge
> >>>
> >
> > _______________________________________________
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> >
>
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