Subject: RE: [DNA] RE: Review of link-information from Pekka Savola

From: "Tero Kauppinen (JO/LMF)" <[email-masked]>
Date: Tue, 03 May 2005 08:19:32 +0200

Hi John,

> A Linux machine cannot see the PDP context that has been setup by
> the phone.  If the phone has multiple PDP for applications running
> on the phone, those are not available to a laptop, for example.

True. Actually I meant that if the node is using a GPRS card, which
means that the node runs PPP to the card. If the card has multiple PDP
contexts, are those mapped as several PPP connections or are they still
within the same PPP connection? Because if they are within the same
connection, how does the card know which context to use for an outgoing
packet?

> 
> Phones running the Symbian OS have way of handling these multiple
> PDP contexts; there are a number of other embedded operator systems
> that handle these in a vendor specified manner.
> 
> So, I think we have two cases here:
> 
> 1) Laptop case which uses PPP from the laptop, no open issues here,
>    I think.
> 2) Phone application case: some issues here, I think.
> 
> What I assume we want to do is "detect network attachment" on the
links.  For
> 2G & 3G GPRS, the link is essentially a PDP context.  There are two
types of
> PDP contexts, a Primary PDP Context and a Secondary PDP Context.
Secondary
> PDP contexts get their IP address from the Primary PDP context.

Here I refer to a previous mail of mine where I mentioned the discussion
with Jari. The motivation of DNA can also be seen as a way to find an
answer to the question: "I was previously using this address, can I
still use it on this network too?" On a phone where PDP contexts are not
hidden from the application there should not be any reason to ask that
question because the node gets an address in the PDP context and then
just applies that. If it differs from the previous one, well, then it
does. Hmm ... maybe we have to run MobileIPvX on a phone too :)

Or am I once again completely lost?

Tero

---

From: Bernard Aboba <[email-masked]>
Date: Tue, 03 May 2005 06:29:09 -0700 (PDT)

> Or am I once again completely lost?

I think you are correct.  In the DNAv4 document it explicitly states that
DNAv4 is only for use with media that support ARP, for that reason.