Re: [pcp] PCP Draft 29 question about PREFER_FAILURE and Suggested External Address field of all zeroes

"Dan Wing" <dwing@cisco.com> Thu, 14 February 2013 22:21 UTC

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From: "Dan Wing" <dwing@cisco.com>
To: "'Norman Sardella'" <sardella@comcast.net>, <pcp@ietf.org>
References: <511D40B5.70104@comcast.net>
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Date: Thu, 14 Feb 2013 14:21:18 -0800
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Subject: Re: [pcp] PCP Draft 29 question about PREFER_FAILURE and Suggested External Address field of all zeroes
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> -----Original Message-----
> From: pcp-bounces@ietf.org [mailto:pcp-bounces@ietf.org] On Behalf Of
> Norman Sardella
> Sent: Thursday, February 14, 2013 11:53 AM
> To: pcp@ietf.org
> Subject: [pcp] PCP Draft 29 question about PREFER_FAILURE and Suggested
> External Address field of all zeroes
> 
> In draft-ietf-pcp-base-29,
>   "Section 13.2.  PREFER_FAILURE Option for MAP Opcode", The draft
> mentions that when PREFER_FAILURE is set,
>    "all-zeros IPv4 or all-zeros IPv6 address in the Suggested External
>     Address field, it is invalid."
> 
> Is this a valid case? Its unclear in a CGNAT/DS-LITE environment where
> the CPE would be running a UPnP to PCP gateway and the CGNAT equipment
> provides an External Address, how the CPE could provide an initial PCP
> MAP request with an External IP Address when the CGNAT device maintains
> them.

The draft says:

   If a PCP request contains the PREFER_FAILURE option and has zero in
   the Suggested External Port field, or has the all-zeros IPv4 or all-
   zeros IPv6 address in the Suggested External Address field, it is
   invalid.

I believe it should say:

   If a PCP request contains the PREFER_FAILURE option and has zero in
   the Suggested External Port field, or has the all-zeros IPv4 or all-
......................................^^
                                     "and"
   zeros IPv6 address in the Suggested External Address field, it is
   invalid.

http://tools.ietf.org/html/draft-ietf-pcp-upnp-igd-interworking is the
canonical document explaining the interworking function, which doesn't
go into that level of detail.

Would that fix the problem?

-d

> On a MAPPING update, I could see providing an Suggested External
> Address
> 
> 
> I understand that UPnP IGDv1 client allows to dictate mapping a specific
> port, but its unclear in a CGNAT/DS-LITE environment how to specify an
> Suggested External IP address.
> 
> 
> On a MAPPING update, I could see providing an Suggested External
> Address, but don't understand how a CPE provide the Suggested External
> Address on an initial MAP request.
> 
> > 13.2.  PREFER_FAILURE Option for MAP Opcode
> ...
> >
> >    If a PCP request contains the PREFER_FAILURE option and has zero in
> >    the Suggested External Port field, or has the all-zeros IPv4 or
> all-
> >    zeros IPv6 address in the Suggested External Address field, it is
> >    invalid.  The PCP server MUST reject such a message with the
> >    MALFORMED_OPTION error code.
> 
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