Dirk - see below for my comments:
> -----Original Message-----
> From: Von-Hugo, Dirk [mailto irk.Hugo
 t-systems.com]
> Sent: Friday, March 03, 2006 2:01 AM
> To: Templin, Fred L; netlmmngnet.it
> Subject: AW: [netlmm] NETLMM and the IPv6 Hop Limit
>
> Hi Fred,
> to my understanding in the tunnelling mode the hop
limit of
> the original header remains untouched.
I agree that the Hop Limit of the original header is
untouched after it enters the tunnel. But before it
is placed into the tunnel the MAP has to forward it
from a receiving interface (e.g., an Ethernet) to the
tunnel interface and would ordinarily decrement the
Hop Limit by 1 in the process.
> The MAP would create a
> new header with new (exterior) hop limit which is
reduced
> until arrival at AR. But the interior HL after
de-capsulation
> at AR should be the same as on arrival at MAP.
>
> However if this would be of interest the AR might
> artificially reduce the interior HL by calculating the
> additional hops on the MAP-AR path, but ... does
anyone see
> a sense in such a procedure?
The tunnel is a single hop from the perspective of the
inner header (layer 3), so it wouldn't make sense to
decrement by the number of layer 2 hops taken.
I'm still seeing two instances of Hop Limit decrementing;
one for the MAP forwarding from the receiving interface
to the tunnel interface and a second for the AR forwarding
from the tunnel interface to the MN on the access network.
This double-decrementing within the same logical IP subnet
is not the way things normally work. Does the design team
plan to address this?
Fred
fred.l.templinboeing.com
> Kind regards
> Dirk v. Hugo
> T-Systems Enterprise Services GmbH
>
>
> -----Ursprüngliche Nachricht-----
> Von: netlmm-adminngnet.it [mailto:netlmm-adminngnet.it]
Im
> Auftrag von Templin, Fred L
> Gesendet: Freitag, 3. März 2006 02:09
> An: netlmmngnet.it
> Betreff: [netlmm] NETLMM and the IPv6 Hop Limit
>
> For the design team, I am wondering what happens with
> the IPv6 Hop Limit due to packet forwarding in the
NETLMM
> scenario when a correspondent node (CN) sends a packet
to
> a mobile node (MN) associated with a localized mobility
> management (LMM) domain.
>
> To my understanding, the CN's packet would be directed
to
> a localized mobility anchor point (LMAP) within the LMM
> domain which would then tunnel the packet to the
correct
> access router (AR) which would then decapsulate the
packet
> and forward it to the MN. But, doesn't this mean that
the
> IPv6 Hop Limit would be decremented twice (once for
> traversing the LMAP->AR tunnel and once for the
AR->MN
> forwarding)?
>
> This would seem strange given that both of these
"hops"
> occur within the same logical IPv6 subnet prefix, i.e.,
> the prefix that is owned by the LMAP and used by the MN
> for address configuration.
>
> Am I understanding this correctly and (if so) is there
a
> way to avoid this double-decrementing of the IPv6 Hop
Limit?
>
> Fred
> fred.l.templinboeing.com
>
>
>
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