Subject: Re: [Softwires] Gen-ART review of draft-ietf-softwire-dslite-deployment-06

From: "Lee, Yiu" <[email-masked]>
Date: Thu, 18 Oct 2012 00:46:24 +0000

Hi David,

Thanks very much for review the draft. Comments inline.

Thanks,
Yiu

On 10/15/12 7:10 PM, "Black, David" <[email-masked]> wrote:

>I am the assigned Gen-ART reviewer for this draft. For background on
>Gen-ART, please see the FAQ at
><http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
>
>Please resolve these comments along with any other Last Call comments
>you may receive.
>
>Document: draft-ietf-softwire-dslite-deployment-06
>Reviewer: David L. Black
>Review Date: October 15, 2012
>IETF LC End Date: October 16, 2012
>IESG Telechat Date: October 25, 2012
>
>Summary:
>
>This draft is on the right track but has open issues, described in the
>review.
>
>This is a generally well-written draft that expands considerably on the
>brief
>deployment considerations for DS-Lite in Appendix A of RFC 6333.  The
>draft
>is clear and reasonably well-written, and a significant improvement on
>that
>RFC 6333 Appendix, although an understanding of RFC 6333 is necessary to
>understand this draft, which seems completely reasonable.
>
>The B4 and AFTR acronyms are clever - kudos to whomever came up with
>those.
>
>I found five open issues, all of which are minor.
>
>Minor Issues:
>
>[1] Ironically, the first issue is that something should be said about
>the relationship of this draft to Appendix A of RFC 6333.  It probably
>suffices to say that this draft expands on the material in that Appendix,
>as I see no need to specify that this draft updates RFC 6333 solely to
>change non-normative material in an Appendix.

[YL] In "Overview", we will add:

"This document expands Appendix A of RFC6333 and discusses various
DS-Lite deployment considerations for operators."

>
>[2] The MTU increase technique in Section 2.2 is a "may", which is
>consistent with Section 5.3 of RFC 6333.  OTOH, Section 2.2 of this
>draft should also discuss the AFTR resource exhaustion concern that
>described in Section 6.3 of RFC 6333, as that is a potential
>operational reason for an ISP to increase MTU size (e.g., if customer
>sourcing of large IPv4 packets is not sufficiently rare).

[YL] In 2.2, we will add:

"Note that reassembly at Tunnel Exit-Point is resource
	intensive. A large number of B4 may terminate on the same AFTR. If many B4
	fragment the packets, it would increase sufficient load to the AFTR for
	reassembly. We recommend the operator should increase the MTU size of the
IPv6
	network between B4 and AFTR to avoid fragmentation."

>
>[3] Section 2.7 refers to "the AFTR's internal interface".  There may be
>two internal interfaces, the physical IPv6 interface (outer header) and
>the tunnel's IPv4 interface (inner header).  The text should be clarified
>to indicate which interface is involved - it appears that the AFTR's
>physical IPv6 interface is intended in this section.

[YL] We replace "internal" to "IPv6"

>
>[4] Section 2.7 cites RFC 6333 for use of DHCPv6 with DS-Lite.  RFC 6334
>should be cited - either in addition to or instead of RFC 6333.

[YL] Fixed

>
>[5] Section 2.8 discusses IPv4 accounting at the AFTR, but notes that
>"the AFTR does not have detailed customer identity information."  Does
>that create a theft of service possibility?  If so, that possibility
>should be mentioned as a security consideration.  Also, Section 2.8
>ought to be expanded with a sentence or two explaining why the AFTR
>does not have that identity information, and in particular to explain
>whether and why it is unreasonable in some or all cases to expect
>that customer identity information be provided to the AFTR as part
>of provisioning each customer's softwire.

[YL] Good catch. Actually I believe AFTR "does" have both IPv4 and IPv6 to
identify the customer. I suggest we remove

"but it will potentially introduce some additional complexity because
   the AFTR does not have detailed customer identity information."

>
>Nits:
>
>Section 2.3 on MTU Considerations could usefully mention MTU discovery
>techniques, as possibilities for customer IPv4 traffic to adapt to a
>smaller IPv4 MTU.  If this is done, it would be useful to mention
>RFC 4821 in addition to the mention of RFC 1191 in RFC 6333.

[YL] We would consider RFC 4821. However, the challenge is I don't have
information how many current OS support RFC 4821. Since DS-lite is a
transition technology, it would be unreasonable to ask the OS company to
implement RFC 4821 for DS-lite.

>
>Section 2.4 should define "lawful intercept".  It would be helpful to
>cite a reference for this concept if something appropriate can be found.

[YL] We will find whether there is any reference to this concept. If we
can't find any, we would add an explanation in the draft.

>
>Section 2.5:
>- Are one or both types of logging recommended?

[YL] We tempted to recommend source-specific log. However, some regulators
require to use both and the regulations vary country from country, this is
why we left it open and let the operators to decide.

>- Last paragraph on p.4, "timestamped log" is not a good verb phrase.
>	"maintain a timestamped log of" would be a better replacement.

[YL] Fixed

>- Last paragraph in section, where is the batch file sent?

[YL] We will add:

"The files may be compressed before transferring to a repository server
	to better utilize bandwidth and storage."

>
>In Section 2.7, I'm having a hard time understanding which traffic is
>intended to be subject to the Outgoing Policies and the Incoming Policies.
>Expanding each of those two bullets to explain what traffic is subject
>to each class of policies would help.

[YL] Does this help?

Outgoing Policies apply to packets originating from B4 to IPv4 network.
Incoming Policies apply to packets originating from IPv4 network to B4.

>
>Section 3.2.2.2 uses 192.0.0.2/32 as an example IP address for the
>B4.  That section should also cross-reference Section 5.7 on RFC 6333
>on IP address assignment to B4s, as other IP addresses may be used.

[YL] Added the cite.

>
>idnits 2.12.13 found a tiny nit - draft-ietf-pcp-base is now at
>version 28.

[YL] Fixed.

>
>Thanks,
>--David
>----------------------------------------------------
>David L. Black, Distinguished Engineer
>EMC Corporation, 176 South St., Hopkinton, MA  01748
>+1 (508) 293-7953             FAX: +1 (508) 293-7786
>[email-masked]        Mobile: +1 (978) 394-7754
>----------------------------------------------------
>
>

---

From: "Lee, Yiu" <[email-masked]>
Date: Thu, 18 Oct 2012 12:29:09 +0000

Thanks David! I will apply your changes to the next version.

On 10/17/12 9:11 PM, "Black, David" <[email-masked]> wrote:

>Yiu,
>
>Thank you for your responses - most of them look fine, and in
>particular anything that I don't comment on here is acceptable to me.
>
>> 	reassembly. We recommend the operator should increase the MTU size of
>>the IPv6
>I would change "is" to "may be" in the first line.
>
>That's definitely an easy way to address that issue, and it's fine with
>me.
>
>That's ok - this was a nit.
>
>Please add a version of your explanation to the draft.
>
>Yes, that's clearer, although the B4 is not the network endpoint for any
>of that traffic.  I suggest:
>
>Outgoing Policies apply to packets originating from behind the B4 with
>a destination on the IPv4 network.
>
>Incoming Policies apply to packets originating from the IPv4 network to
>a destination behind the B4.
>
>Thanks,
>--David
>
>
>> -----Original Message-----
>> From: Lee, Yiu [mailto:[email-masked]]
>> Sent: Wednesday, October 17, 2012 8:46 PM
>> To: Black, David; [email-masked];
>>[email-masked];
>> [email-masked]; [email-masked];
>>[email-masked]
>> Cc: [email-masked]; [email-masked]; Ralph Droms
>> Subject: Re: Gen-ART review of draft-ietf-softwire-dslite-deployment-06
>> 
>> Hi David,
>> 
>> >This is a generally well-written draft that expands considerably on
>>the brief
>> 	reassembly. We recommend the operator should increase the MTU size of
>>the IPv6