If you're going to have multiple DHCP servers, such as failover pairs, doing the DNS updates, you need to have those servers agree on how they will identify the clients. This is not JUST for DNS updates. Failover partners need to use the same identifiers for clients. So, this is really not an issue. The rules are pretty clearly described in the RFC: For DHCPv4: 1. Use the DUID if the client identifier option is provided by the client and it is a DUID and the server supports it. This is a new RFC that is in the RFC-editor queue so no clients and servers yet support this. 2. Otherwise, use the client identifier option if provided by the client, 3. Otherwise, use htype and chaddr. For DHCPv6: 1. Use the DUID of the client. There really is no mystery here. - Bernie > -----Original Message----- > From: Jeffrey Hutzelman [mailto:jhutz@xxxxxxx] > Sent: Sunday, December 04, 2005 11:43 PM > To: Bernie Volz (volz); Sam Hartman; Mark Stapp (mjs) > Cc: namedroppers@xxxxxxxxxxxx; ietf@xxxxxxxx; Pekka Savola; > Ted Lemon; iesg@xxxxxxxx; dhcwg@xxxxxxxx; Steven M. Bellovin; > Jeffrey Hutzelman > Subject: RE: [dhcwg] Re: DHCID and the use of MD5 [Re: Last > Call:'Resolution of FQDN Conflicts among DHCP Clients' to > Proposed Standard] > > > > On Thursday, December 01, 2005 08:48:10 AM -0500 "Bernie Volz (volz)" > <volz@xxxxxxxxx> wrote: > > > How about we address issue 1 by expanding the DHCID RR type code. We > > have 16-bits and we're just using 4 values presently. > There's plenty of > > room for future expansion *SHOULD* someone come along and > demand a new > > algorithm in the future. I can't see why this would EVER occur since > > this really isn't about strong cryptographic protection (we're just > > trying to make it non-trivial to find a client's identity > by not storing > > it in clear text). > > I think that's a good start; in fact, I was going to propose > something very > similar. This solves half the problem; particularly, it > makes it possible > to indicate that some other hash is in use. It does bind the > hash to the > type, rather than allowing them to be specified orthogonally, > but I don't > think that's a major problem. If it ever becomes an issue, > there should be > no problem defining a type where the next 16 bits indicate a > subtype and > the 16 bits after that indicate a hash. > > However, it doesn't solve the other half of the problem, > which is present > even without considering changing hash algorithms. The > problem is that for > any given fqdn and DHCP client, there are multiple possible > DHCID RR's; in > particular, one for each type. In order the update mechanism to work > without requiring either an advance query or multiple update > attempts, all > possible updaters must agree in advance on the type in use. > This lack of > negotiation seems problematic to me, even in the absence of > multiple hash > algorithms. > > -- Jeffrey T. Hutzelman (N3NHS) <jhutz+@xxxxxxx> > Sr. Research Systems Programmer > School of Computer Science - Research Computing Facility > Carnegie Mellon University - Pittsburgh, PA > _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf
