Subject: Re: [dhcwg] draft-bpw-softwire-pcp-dhcp-00.txt is a new draft

From: "Bernie Volz (volz)" <[email-masked]>
Date: Sat, 8 May 2010 10:07:26 -0500

Dan:

For DHCPv4, this option structure won't work. In DHCPv4, there is no
concept of multiple instances of options -- if multiple instances are
present, they are concatenated into one (see RFC 3396). I presume that
it would be expected that OPTION_PCP_SERVER with encoding 0 or 1 would
appear with encoding 2 (time wait). Thus, you would have:

+-----+-----+-----+-----+-----+-----+-----+---+---+----------+
         | TBA |  8  |  0  |  a1 |  a2 |  a3 |  a4 | 2 | M | TimeWait |

         +-----+-----+-----+-----+-----+-----+-----+---+---+----------+

Which would not work (as there would be no way for the client to decode
this correctly).

Also, the use of the encoding field isn't very desirable as it
complicates option configuration.

I would recommend that you switch this DHCPv4 option (and perhaps also
the DHCPv6 to be comparable), to use suboptions.

Thus, you would have the OPTION_PCP_SERVER option which contained one
(or more) of 3 suboptions:
	- <Suboption-1><length=4*n><address-1>[<address-2>...]
	- <Subotpion-2><length><fqdn>
	- <Suboption-3><length=3><Method><Timewait>

Note that as RFC 3396 does NOT extend to suboptions, this would allow
you to have multiple FQDN (instances of suboption-2). Not sure if that's
desired, but might come in useful? You could also define suboption-1 to
contain just a single address and allow multiple instances of that
suboption, but I don't think that has any benefits (and just costs an
additional 2 bytes/address).

While for DHCPv6 you could continue to define the 3 options you have, it
may be appropriate to switch to suboptions as well. Note that for DHCPv6
suboptions have 16-bit (2 byte) suboption codes and length fields.

Note: Figure 4, 5, and 6 in your draft also have the incorrect length as
the length of the option MUST include the <enc> byte. However, based on
the above comments, you need to rework this anyway.

- Bernie

---

From: <[email-masked]>
Date: Mon, 10 May 2010 13:20:32 +0200

Dear Bernie,

Thank you for your comments.

An updated version of the draft taking into account your comments has been submitted. 01 version is available at: http://tools.ietf.org/html/draft-bpw-softwire-pcp-dhcp-01 (diff: http://tools.ietf.org/rfcdiff?url2=draft-bpw-softwire-pcp-dhcp-01.txt)

Further comments are more than welcome.

Cheers,
Med

-----Message d'origine-----
De : Bernie Volz (volz) [mailto:[email-masked]] 
Envoyé : samedi 8 mai 2010 17:07
À : Dan Wing (dwing)
Cc : [email-masked]; BOUCADAIR Mohamed NCPI/NAD/TIP; DHC WG
Objet : RE: draft-bpw-softwire-pcp-dhcp-00.txt is a new draft

Dan:

- Bernie

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