RE: draft of a core protocol spec

Hi Albert,

Your later observation is correct. The setting of the RPR TTL is directly a
funtion of the local ring topology and it does not and should not have any
bearing on the L3 TTL. It would correct to keep the TTL from percolating up
and down the layers. The L3 TTL and the RPR TTL serve two entirely different
purposes and should not have linkage. The L3 TTL avoids infinite looping in
a network whereas, the RPR TTL serves the function of keeping the packet
looping infinitely within a RPR ring.

If one were to choose to use a MPLS label between the layer 2 and layer 3,
then the issue of setting of the MPLS label becomes slightly interesting but
that has nothing to do with RPR.

Vinay

-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of
A.Herrera
Sent: Saturday, November 09, 2002 8:31 AM
To: Anoop Ghanwani; 'Frank Kastenholz'; [email protected];
[email protected]
Subject: Re: [IPORPR] draft of a core protocol spec



----- Original Message -----
From: "Anoop Ghanwani" <[email protected]>
To: "'Frank Kastenholz'" <[email protected]>; <[email protected]>;
<[email protected]>
Sent: Friday, November 08, 2002 11:55 AM
Subject: RE: [IPORPR] draft of a core protocol spec
>
> There used to be a TTL many draft versions ago, so that's
> probably the reason for your recollection :).  It was subsequently
> removed because it was decided that anything above the MAC
> shouldn't need to know about TTL.
>
> -Anoop

Just a quick question for the WG. It could be
outside the scope of the core spec or it might be
a non-issue altogether.

How is L3 TTL reconciled with RPR TTL. Given that
we no longer deal with LANs but rather large
MANs.

Say, a packet from a traditional mesh hits,
traverses, then exits 3 large metro rings (of
over 100 nodes each), does the L3 TTL decrement by
3. And should this packet somehow find an entry back
to the first ring, shouldn't there be a mechanism for
an earlier discard. Or do we treat these rings the
way PWE3 treats their tunnels where the TTLs don't
percolate up nor percolate down.

Albert






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