Re: [dhcwg] Last Call: <draft-ietf-dhc-option-guidelines-14.txt> (Guidelines for Creating New DHCPv6 Options) to Best Current Practice

Ted Lemon <ted.lemon@nominum.com> Wed, 09 October 2013 15:48 UTC

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From: Ted Lemon <ted.lemon@nominum.com>
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Date: Wed, 9 Oct 2013 11:47:51 -0400
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To: "Cullen Jennings (fluffy)" <fluffy@cisco.com>
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Subject: Re: [dhcwg] Last Call: <draft-ietf-dhc-option-guidelines-14.txt> (Guidelines for Creating New DHCPv6 Options) to Best Current Practice
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On Oct 9, 2013, at 11:26 AM, Cullen Jennings (fluffy) <fluffy@cisco.com> wrote:
> Help educate me on this a bit - I don't see all the things that get requested of DHCP. What are some examples of things where people are request FQDN where IP would be better. I think having some real examples that have come up would make it easier to see what advice is needed.

DNS server IP address.   NTP server IP address.   Router IP address (not in DHCPv6, of course).   AFTR IP address.   Basically, network infrastructure IP addresses.

Bear in mind that the set of services configured by DHCP ought to be pretty small—just things that really are local network infrastructure services, not things that are specific to the host and not to the network.   It's not even clear to me that NTP ought to be configured by DHCP, and indeed in most cases it is not, despite there being an RFC describing how to do it.

Considering the case of SIP, when you configure SIP I think that's probably a configuration that shouldn't change as the phone moves from network to network.   So it shouldn't be configured by DHCP.   In the case where the phone happens not to be likely to move from network to network, you could _get away_ with using DHCP.   But a solution that would work for phones that _do_ move from network to network would also work for phones that do not, and that solution would therefore be preferable, particularly as an MTI solution, since it addresses all use cases.

As I mentioned in the IESG discussion, it is a shame that aggsrv didn't become a working group, since it was intended to address this specific problem, at least as I understood it.