Re: [ntpwg] [dhcwg] Re: Network Time Protocol (NTP) Options for DHCPv6

Brad Knowles <brad@shub-internet.org> Wed, 28 November 2007 13:55 UTC

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Date: Tue, 27 Nov 2007 01:32:42 -0600
To: Mark Stapp <mjs@cisco.com>
From: Brad Knowles <brad@shub-internet.org>
Subject: Re: [ntpwg] [dhcwg] Re: Network Time Protocol (NTP) Options for DHCPv6
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On 11/21/07, Mark Stapp wrote:

>  there seems to be a concern that delivering addresses via DHCP somehow
>  makes them difficult to update over time. just to reiterate: it's often
>  the case that the information at the DHCP server is updated. the updated
>  information flows out to clients as they renew.

But in the case of NTP clients, that assumes that they know that 
there is a renewal, and that they need to update their configuration. 
Which seems to imply that there would need to be something in the NTP 
protocol standard that says something like:

	If you got your other-protocol-specific configuration via DHCP,
	then you need to make sure that you're fully DHCP-aware and
	that you pick up all changes when the DHCP client renews the lease.

>                                                  if the lease timers were
>  very long, a client who got NTP addresses and found itself having
>  trouble with them all could also use the INFORMATION-REQUEST message to
>  check whether the addresses were still valid, outside of the normal
>  renewal timers.

Which implies that the NTP client now needs to become fully DHCP aware.


NTP is a weird beast.  It's not like a mail or news server, which can 
pretty much always continue to use the same upstream server as 
defined in the configuration file, and never needs to worry about 
watching for DHCP lease renewals.

NTP is one of those layer 2.5 things that doesn't have the name Cisco 
branded on the side, and doesn't look like a router, switch, or hub, 
and therefore your traditional network admins may not understand it. 
It also doesn't have the name Microsoft or Sun stamped on the side, 
and therefore your traditional host administrators aren't necessarily 
going to know anything about it.

This is a piece of network systems infrastructure which acts as glue 
at the interface between the network itself and the hosts on the 
network, and since it's an edge case on both sides of the equation, 
we need to be careful in how we handle it.

-- 
Brad Knowles <brad@shub-internet.org>
LinkedIn Profile: <http://tinyurl.com/y8kpxu>

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