Subject: [pcp] PCP Server Selection - Address Family Selection

From: Sebastian Kiesel <[email-masked]>
Date: Fri, 25 Apr 2014 16:51:38 +0200

Hi,

draft-ietf-pcp-server-selection-02  says in Section 3:

   1.  If the PCP client can use both address families when
       communicating to a particular PCP server, the PCP client SHOULD
       select the source address of the PCP request to be of the same IP
       address family as its requested PCP mapping (i.e., the address
       family of the Requested External IP Address).

What is the reason for saying it SHOULD use the same familiy as the
requested EXTERNAL IP address?  I think it would make more sense to use
the same familiy as the INTERNAL address (if there is a difference at
all).

Thanks
Sebastian

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From: Simon Perreault <[email-masked]>
Date: Fri, 25 Apr 2014 10:57:44 -0400

> the same familiy as the INTERNAL address (if there is a difference at

+1

I stated this in my review.

Simon
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From: Dan Wing <[email-masked]>
Date: Fri, 25 Apr 2014 18:42:53 -0700

> I stated this in my review.

The intent of the wording is to avoid NAT64 (or NAT46) where NAT44 or no NAT was necessary at all.  If the wording is backwards, let's fix it.  I have now read it three times, and the existing text seems to avoid NAT64.  In any event, yes, there should be an explanation ("To avoid unnecessary IP address family translation, ...").

-d

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From: Sebastian Kiesel <[email-masked]>
Date: Sat, 26 Apr 2014 23:37:57 +0200

On Fri, Apr 25, 2014 at 06:42:53PM -0700, Dan Wing wrote:
> The intent of the wording is to avoid NAT64 (or NAT46) where NAT44 or
> no NAT was necessary at all. 

reasonable goal, but does text about that belong here?

this text is about PCP messages, and I think they should use the
same address family as the actual user data flow on their side of
the NAT.

> If the wording is backwards, let's fix it.  I have now read it three
> times, and the existing text seems to avoid NAT64.  In any event, yes,
> there should be an explanation ("To avoid unnecessary IP address family
> translation, ...").

Thanks
Sebastian

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From: Dan Wing <[email-masked]>
Date: Sun, 27 Apr 2014 17:52:45 -0700

> same address family as the actual user data flow on their side of

If that avoids IP address family translation, sounds good to me.  Or is there some other value or purpose?

-d

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From: Simon Perreault <[email-masked]>
Date: Mon, 28 Apr 2014 08:40:46 -0400

> If that avoids IP address family translation, sounds good to me.  Or is there some other value or purpose?

I understand what you want, but the text doesn't get you what you want.
I want something different, but we can both get what we want with
appropriate text.

First, "sending over IPvX" doesn't imply that the internal address is
IPvX, because of THIRD_PARTY. What you want is: "the client SHOULD pick
an internal address of the same family as that of the mapping's external
address."

Second, what I want is to avoid THIRD_PARTY. So that's why you need to
send the request using the chosen internal address as source for the PCP
request. (This is actually stricter than just using the same address
family, in case you have multiple addresses of that address family.)

Summarizing:

"If a PCP client has access to internal addresses of multiple families,
then it SHOULD choose the mapping's internal address such that it is of
the same family as that of the mapping's external address. This is done
to avoid address family translation when possible.

The PCP client SHOULD use the mapping's internal address as source for
the PCP request. This is done to avoid using the THIRD_PARTY option when
possible."

Simon

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From: "Prashanth Patil (praspati)" <[email-masked]>
Date: Mon, 28 Apr 2014 12:47:43 +0000

We've tried to simplify text around this in the revised draft. Hopefully,
it is more obvious now.

-Prashanth

On 4/28/14 6:10 PM, "Simon Perreault" <[email-masked]> wrote:

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From: Simon Perreault <[email-masked]>
Date: Mon, 28 Apr 2014 08:56:27 -0400

> We've tried to simplify text around this in the revised draft. Hopefully,

I'll do another full review in a new thread.

Simon