Thus spake Jesper Skriver (jesper@skriver.dk):
> On Wed, Apr 04, 2001 at 11:01:41AM -0700, Kireeti Kompella wrote:
> > Hi Robert,
> >
> > > The only use of exp-null today would be to pass the QoS info in the EXP
> > > bits to the tailend as otherwise this info is lost at PHP and tail has
> > > no way of knowing how to schedule the packets (of course assuming that
> > > QoS in IP header is different then the one in EXP field - something what
> > > we call QoS transparency :).
> >
> > Ah, so you don't want to touch the IP QoS/ToS bits. Okay, got it.
> >
> > Somewhere in this conversation, there was mention that ciscos had
> > trouble with label 0/label 3 (and ditto junipers). I can speak for
> > the latter; can you comment on the former? If there is no issue with
> > using label 0, should Juniper simply go back to using label 0 always?
> > I'd rather not be putting any more knobs than are really necessary ...
>
> I think it's usefull to, on a per interface basis, be able to choose
> between Explicit and Implicit null.
Can you explain why it would be useful per interface?
I think it makes sense to do on per-LSP basis.
>
> So a knob would be nice to have.
>
> > What if the label stack has depth > 1? PHP in that case? Bit yucky,
> > but doable.
>
> rfc 3032 section 2.1 state
>
> i. A value of 0 represents the "IPv4 Explicit NULL Label".
> This label value is only legal at the bottom of the label
> stack. It indicates that the label stack must be popped,
> and the forwarding of the packet must then be based on the
> IPv4 header.
>
> So yes, for label stacks with a depth > 1 you must use 3 and not 0
I also realize the 3032 recommendation, but would
you not want to maintain the EXP setting state
regardless whether LSP hierarchy is involved or not?
- Serge
>
>
> /Jesper
>
> --
> Jesper Skriver, jesper(at)skriver(dot)dk - CCIE #5456
> Work: Network manager @ AS3292 (Tele Danmark DataNetworks)
> Private: FreeBSD committer @ AS2109 (A much smaller network ;-)
>
> One Unix to rule them all, One Resolver to find them,
> One IP to bring them all and in the zone to bind them.
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