Subject: [Pppext] TISPAN proposal for PPP IPCP extension to handle P-CSCF address???

From: <[email-masked]>
Date: Mon, 2 Oct 2006 11:00:55 +0200

Dear members
 
I found on the Internet JUNHYUK SONG draft proposal on PPP IPCP
extensions for SIP server address
(draft-song-pppext-sip-support-02.txt), and I also saw that the proposal
was rejected by IESG
(http://www.ietf.org/IESG/Announcements/rfcno-draft-song-pppext-sip-supp
ort.txt).
 
However I was surprised to read that TISPAN standard ETSI ES 282 004
V1.1.1 (2006-06) is suggesting to use PPP IPCP extensions for
provisioning of P-CSCF IP address (pag 27, section 7.2 "PPP based
authentication", last bullet: "AMF sends the IP address of a TISPAN NGN
Service/Applications Subsystems (e.g. P-CSCF) to UE/CNG within PPP IPCP
configuration option extension.").
 
Isn't it strange? Do you know if TISPAN is actually thinking of
extending the PPP IPCP protocol?
 
Best Regards
 
Alessandro Cotroni 

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From: James Carlson <[email-masked]>
Date: Mon, 2 Oct 2006 07:44:04 -0400

> provisioning of P-CSCF IP address (pag 27, section 7.2 "PPP based

That's really unfortunate.  Their plan won't be interoperable.

> extending the PPP IPCP protocol?

It's not unusual for folks to write their own extensions to
IETF-controlled protocols without bothering with the standardization
process.  We don't have any IETF police out there to stop them.

If they care at all about interoperability, they won't do something
like this.

Thanks for the pointer, though; I'll forward it around to see if we
can't get clarification.

-- 
James Carlson, KISS Network                    <[email-masked]>
Sun Microsystems / 1 Network Drive         71.232W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.496N   Fax +1 781 442 1677

---

From: "Jerome Moisand" <[email-masked]>
Date: Mon, 2 Oct 2006 10:00:04 -0400

Providing a SIP-proxy (P-CSCF) server @ via IPCP does make sense though.

Might be a good idea to address the problem in a constructive manner,
adding a mechanism for vendor-specific (or organization-specific)
parameters that could be conveyed via IPCP. Allowing extensions without
creating interoperability problems, and without the burden of having to
go to IETF for defining such extensions. 

DHCP and many other protocols have such extensibility, why not IPCP?

Was this topic discussed in the past?

-----Original Message-----
From: James Carlson [mailto:[email-masked]] 
Sent: Monday, October 02, 2006 7:44 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: [Pppext] TISPAN proposal for PPP IPCP extension to handle
P-CSCFaddress???

---

From: <[email-masked]>
Date: Mon, 2 Oct 2006 16:11:05 +0200

Yes this topic was already discussed
(http://www.atm.tut.fi/list-archive/pppext-2005/msg00109.html)

The conclusion was that it has no sense to extend PPP IPCP protocol,
because other mechanisms are already in place like for example
DHCPINFORM.

However I was surprised by the fact that TISPAN is suggesting a PPP IPCP
extension, when this ipothesis was already rejected and I was only
wondering if this decision was being revised due to TISPAN work.

Alessandro Cotroni

------------------------------------------------
Alessandro Cotroni
Accenture
Via del Tintoretto 200, Roma
-------------------------------------------------

-----Original Message-----
From: Jerome Moisand [mailto:[email-masked]] 
Sent: 2 ottobre 2006 16.00
To: [email-masked]; Cotroni, Alessandro
Subject: RE: [Pppext] TISPAN proposal for PPP IPCP extension to handle
P-CSCFaddress???

-----Original Message-----
From: James Carlson [mailto:[email-masked]]
Sent: Monday, October 02, 2006 7:44 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: [Pppext] TISPAN proposal for PPP IPCP extension to handle
P-CSCFaddress???

If they care at all about interoperability, they won't do something like
this.

---

From: James Carlson <[email-masked]>
Date: Mon, 2 Oct 2006 10:20:33 -0400

> Providing a SIP-proxy (P-CSCF) server @ via IPCP does make sense though.

Not to me.

> parameters that could be conveyed via IPCP.

See RFC 2153.  We already have a vendor-specific extension mechanism
for PPP.

> Allowing extensions without

Actually, it still does cause interoperability problems, as it forces
everyone else (over time) to implement these unnecessary extensions.

> DHCP and many other protocols have such extensibility, why not IPCP?

IPCP configures the network layer.  IP addresses on the link are
network layer properties, but SIP server addresses are application
properties.

Note that RFC 1877 is a Microsoft-proprietary extension.

> Was this topic discussed in the past?

Many, many times; see the archives for discussions about SIP server
addresses, DNS server addresses, and other bits of application
configuration.  You can use DHCP to handle this application issue, and
it works fine over PPP.  DHCPINFORM seems particularly well-suited to
the job, and it's the long-established consensus of the working group
participants that we don't need IPCP extensions like that.

---

From: Craig Fox <[email-masked]>
Date: Mon, 02 Oct 2006 10:17:41 -0400

> DHCP and many other protocols have such extensibility, why not IPCP?

Do you mean something like RFC 2153, PPP Vendor Extensions?

Craig

---

From: "Jerome Moisand" <[email-masked]>
Date: Mon, 2 Oct 2006 10:29:55 -0400

All right, DHCPINFORM would work, sounds a bit contorted to mix PPP and
DHCP, but why not. This is what 3GPP2 does, I believe. 

Thanks for the historical background.

-----Original Message-----
From: James Carlson [mailto:[email-masked]] 
Sent: Monday, October 02, 2006 10:21 AM
To: Jerome Moisand
Cc: [email-masked]; [email-masked]
Subject: RE: [Pppext] TISPAN proposal for PPP IPCP extension to
handleP-CSCFaddress???

Not to me.

---

From: James Carlson <[email-masked]>
Date: Mon, 2 Oct 2006 10:48:22 -0400

Jerome Moisand writes:
> DHCP, but why not.

It doesn't really sound contorted to me.  In fact, it has a history.
Before PPP was deployed, people used BOOTP over SLIP to handle these
sorts of application configuration issues.  The RFC 1877 feature is
ahistorical because it ignores that practice.

The implication of the bolt-it-onto-IPCP approach is that we must have
an IPCP extension for each defined DHCP option.  Otherwise, we've got
a poor step-child on our hands, as DHCP will always be more capable.
Such an effort seems to me to be quite wasteful, and likely confusing
as well.  (On a multihomed machine, for instance, how do you set
policy for DHCP-like information that may arrive via different
protocols?)

It's not really a question of whether it "would work."  It's a
question of whether the protocols are being used as they're designed
to be used (DHCP is the standard for distributing network-related
configuration options of this sort), and whether the proposed new
feature (IPCP extension) is needed.

In this case, the existing protocols solve the job nicely, and the
newly-proposed feature has no notable benefits over the existing
protocols.

(The sole exception is apparently among the folks who think that it's
easier for them to add a brand-new PPP extension that all other
vendors will eventually be forced to implement, rather than send and
receive a single UDP datagram in an already-defined format that needs
no additional standardization work.  It's that false economy that
causes this sort of proposal to come up time and again.)

(Why not bolt SIP addresses onto ARP?  After all, on non-PPP media,
you'll need an equivalent solution to avoid using DHCP.)

---

From: Ashutosh Dutta <[email-masked]>
Date: Mon, 02 Oct 2006 10:47:43 -0400

Folks, since somebody referred to my earlier posting, let me throw some 
of our experience.

After the discussion in the mailing list in 2005, we ended up using 
DHCPINFORM instead for P-CSCF discovery in our testbed. It works. We had 
some problem in making the DHCPINFORM working over PPP link however, but 
we sorted it out later on.

Thanks
Ashutosh