Subject: [DNA] DNA link hints document

From: NJEDJOU Eric RD-RESA-REN <[email-masked]>
Date: Tue, 02 Nov 2004 18:41:48 +0100

Hello dna folks,

There is an issue with respect to the 3GPP section of
draft-ietf-dna-link-information-00.txt i would like to raise up on this
list for discussion in DC. 
In section 2.1 of the document, (GPRS/3GPP) it is said; 

"   Successful establishment of a PDP Context on a GPRS attached MN
signifies the
   availability of IP service to the MT.  Therefore, this link-layer
   event must generate a link up event notification sent to IP-layer.
   The auxiliary information carried along with this notification must
   be the IP address of the MT which is obtained as part of the PDP
   Context."

Actually from an IP layer perspective on an MN, the GPRS link equals to
a ppp connection. Therefore activation of a PDP context is seen by an IP
node as the establishment of a ppp connection (because 3GPP specifies
that an IP node interfaces to the GPRS mobile station via PPP). I guess
the dna process would want to get more information on the real
underlying link than just ppp parameters. Am i wrong?  

If i am, then the question is: do we need to talk about GPRS/UMTS as the
link up event generated to IP when such a link comes up is not specific
to GPRS/UMTS but rather of PPP general type?. 

If i am not, then, we may want to add in the precedent text that
mechanisms (to be defined out of dna scope) are needed to generate a
link up event to IP upon successful establishment of a PDP context. As
of today specification of GPRS/UMTS, such a mechanim does not exist and
PPP(IPCP and LCP) messages are the only available link-layer events. The
problem being that such messages do not identify the underlying link. 

Remark: the PPP link established as a consequence of the activation of a
PDP context brings to the IP layer the  configuration parameters carried
by the PDP context activate accept messsage received on the mobile
station from the GPRS network).

Hooping to hear from the list on this

Eric Njedjou
regards

---

From: Bernard Aboba <[email-masked]>
Date: Tue, 02 Nov 2004 22:34:59 -0800 (PST)

> that an IP node interfaces to the GPRS mobile station via PPP).

Actually, activation will express itself via completion of the PPP NCP
negotiation.  Data may be sent after NCP negotiation is complete, so that
is when the link can be considered "up" for IPv4.  For IPv6, I think that
isn't true; RS/RA also needs to be  completed to enable address
assignment.  Similarly, an LCP-terminate would bring the link "down" for
any network protocol.

> underlying link than just ppp parameters. Am i wrong?

I see no reason why DNA should care about the link technology operating
under PPP.  All that is relevant is the PPP state machine and IPv6 RS/RA
protocol.

> Today specification of GPRS/UMTS, such a mechanim does not exist and

Correct.