Re: [dhcwg] Eric Rescorla's No Objection on draft-ietf-dhc-rfc3315bis-10: (with COMMENT)
Eric Rescorla <ekr@rtfm.com> Tue, 23 January 2018 00:26 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 22 Jan 2018 16:25:15 -0800
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To: Tomek Mrugalski <tomasz.mrugalski@gmail.com>
Cc: The IESG <iesg@ietf.org>, draft-ietf-dhc-rfc3315bis@ietf.org, Ralph Droms <rdroms.ietf@gmail.com>, dhc-chairs@ietf.org, dhcwg@ietf.org
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Subject: Re: [dhcwg] Eric Rescorla's No Objection on draft-ietf-dhc-rfc3315bis-10: (with COMMENT)
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On Mon, Jan 22, 2018 at 4:14 PM, Tomek Mrugalski <tomasz.mrugalski@gmail.com > wrote: > On 01/21/18 20:26, Eric Rescorla wrote: > > Eric Rescorla has entered the following ballot position for > > draft-ietf-dhc-rfc3315bis-10: No Objection > Hi Eric, > > Thank you for your review and your favourable ballot. See my answers below. > > > ---------------------------------------------------------------------- > > COMMENT: > > ---------------------------------------------------------------------- > > > > Document: draft-ietf-dhc-rfc3315bis-10.txt > > > > This document was quite clear and well written. A few small comments > > below. > > > > It would have been easier for me to have a bit of intro about why > > both the 4-message and 2-message rapid commit exchanges exist > > and maybe some guidance about when to use each one. > How about this text being added early to Section 5.1: > "It is sometimes desired to expedite the configuration process from > typical four messages down to two. This may be desired for couple > reasons. The first one is when there is only one server available > on link and there is no expectation that a second server would become > available. The second is when completing of the configuration process > as quickly as possible is a priority." > Yes, that helps. > I am finding the guidance on DUIDs a bit confusing. Rather than > > having a bunch of constructions that produce variable length > > things that are intended to be unique, why not just take all > > those values and feed them into a hash function and then you > > could just have UUIDs? > I was not participating in the original discussion that led to this > decision back around 2002, but I can imagine there was a need to > generate unique identifiers by devices with various capabilities (thus > with/without timestamp variants). This concept predates usage of UUIDs > in IETF, which as far as I can tell was first mentioned in RFC4122. > > Anyway, this part of the spec hasn't changed in bis. It would be > extremely difficult to make any changes as there are millions of devices > that already use those DUID types. > Well, we could encourage people to move to a UUID type for sending, no? > I'm a little sad that the transaction ID is so short. This doesn't > > seem like really enough to provide uniqueness against guessing > > attacks. > This was never meant as protection, simply as a way to differentiate > between separate transactions that could be happening at the same time. > Even if the transaction was much larger, it is sent by the client to a > multicast address. > Fair enough. > We're trying to discourage HMAC-MD5. Do you have any way to > > transition to something stronger? > Am afraid not at this time. The whole WG seriously tried very hard, but > the draft-ietf-dhc-sedhcpv6 was abandoned at revision -21. > Yeah, that's what I expected. > > The description of how to actually do replay detection seems pretty > > thin. Do you think more detail would be helpful here. > It would. How about this text added to the end of Section 20.3: > > "The client that receives a message with RDM field set to 0x00 MUST > compare its replay detection field with the previous value sent by > the same server. If this is the first time a client sees Authentication > option sent by the server, it MUST record the replay detection value, > but otherwise skip the replay detection check. > > The servers that support reconfigure mechanism MUST ensure the replay > detection value is retained after restarts. Failing to do that will > cause the clients to refuse reconfigure messages sent by the server, > effectively rendering the reconfigure mechanism useless." > This seems like it scales badly as you need to keep an infinite replay list. What happens if you falsely declare something a replay? > > > S 1. > > DHCPv6 can also provide only other configuration options (i.e., no > > addresses or prefixes). That implies that the server does not have > > > > Perhaps "DHCP can also be used just to provide..." > Sounds good. > > > S 2. > > Nit: do you want to cite 8174. > Yes. > > > S 4.2. > > When acronyms are used ahead of their definition, it would be good to > > expand them. > Ok, will do that. > > > S 21.22. > > What is the part of the IPv6-prefix after prefix-length filled with? > > Does it matter? > Should be filled with zeros by sender and ignored by the receiver. Will > add a text that clarifies that. > thanks -Ekr > > Tomek >
- [dhcwg] Eric Rescorla's No Objection on draft-iet… Eric Rescorla
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Tomek Mrugalski
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Eric Rescorla
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Tomek Mrugalski
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Eric Rescorla
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Bernie Volz (volz)
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Eric Rescorla
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Ted Lemon
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Eric Rescorla
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Ted Lemon
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Eric Rescorla
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Ted Lemon
- Re: [dhcwg] Eric Rescorla's No Objection on draft… Michael Richardson