Subject: [netlmm] PMIP and Hop Limit

From: Suresh Krishnan <[email-masked]>
Date: Fri, 17 Oct 2008 17:03:49 -0400

Hi Folks,
   Looking at RFC5213, it seems that a packet initiated by an MN towards 
the internet will undergo two Hop Limit decrements before it leaves the 
LMA towards the internet. Is this the expected behavior? I would have 
expected the Hop Limit to be decremented only once.

Cheers
Suresh
_______________________________________________
netlmm mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/netlmm

---

From: Sri Gundavelli <[email-masked]>
Date: Fri, 17 Oct 2008 14:15:23 -0700 (PDT)

Hi Suresh,

On Fri, 17 Oct 2008, Suresh Krishnan wrote:

> Hi Folks,
>  Looking at RFC5213, it seems that a packet initiated by an MN towards the 
> internet will undergo two Hop Limit decrements before it leaves the LMA 
> towards the internet. Is this the expected behavior? I would have expected

IPv6 tunnel appears as a single virtual link in the routed network.
So, the normal tunneling considerations from 2473 apply for PMIP6
tunnels as well.

Where do you see the issue ?

Sri

> the Hop Limit to be decremented only once.
>
> Cheers
> Suresh

---

From: Suresh Krishnan <[email-masked]>
Date: Fri, 17 Oct 2008 17:25:05 -0400

Hi Sri,

Sri Gundavelli wrote:
>> the internet will undergo two Hop Limit decrements before it leaves 
>> the LMA towards the internet. Is this the expected behavior? I would 
>> have expected
> 

The Hop Limit is decremented once by the MAG when it encapsulates the 
packet and once by the LMA when it decapsulates and forwards the packet 
out as required in RFC2473.

Cheers
Suresh

---

From: Sri Gundavelli <[email-masked]>
Date: Fri, 17 Oct 2008 18:11:28 -0700 (PDT)

Hi Suresh,

> The Hop Limit is decremented once by the MAG when it encapsulates the packet 
> and once by the LMA when it decapsulates and forwards the packet out as 
> required in RFC2473.
>

We have two links, MN-AR link and the virtual tunnel link. At the
end of each of link and on the terminating router, the packet hop
limit is decremented. So, a packet from MN to CN, should see a hop
limit decrement twice, once at the MAG and once at the LMA. This is
also the case in a normal routed network of two routers MAG and LMA,
seperated by a single link.

If the MAG is a L2 bridge, I'd expect a hop decrement only once and
at that is at the LMA. But, MAG is a L3 router and the MN-AR link
accounts for one hop.

Sri