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Re: [dhcwg] What sorts of services does DHCP configure?

"Reinaldo Penno (repenno)" <repenno@cisco.com> Tue, 15 October 2013 14:45 UTC

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From: "Reinaldo Penno (repenno)" <repenno@cisco.com>
To: Ted Lemon <mellon@fugue.com>
Thread-Topic: [dhcwg] What sorts of services does DHCP configure?
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Date: Tue, 15 Oct 2013 14:44:58 +0000
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Cc: "dhcwg@ietf.org WG" <dhcwg@ietf.org>
Subject: Re: [dhcwg] What sorts of services does DHCP configure?
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On 10/15/13 7:14 AM, "Ted Lemon" <mellon@fugue.com> wrote:

>On Oct 15, 2013, at 9:41 AM, Reinaldo Penno (repenno) <repenno@cisco.com>
>wrote:
>> Would it make sense to determine which DHCP options are used today in
>>wild
>> and reasoning behind them?
>> 
>> I have done a few captures before and noticed that DHCP options vary
>> between home, Hotel, Hotspot, Airport, etc.
>
>It can't hurt to ask this question, but I'm not convinced that it's
>necessary.   DHCP clients don't use options they don't request, so it
>doesn't matter if the server sends them.   So it's probably not necessary
>to survey DHCP servers‹just survey DHCP clients and see what options they
>request.

Right, DHCP clients.

certain OSs allows applications to ask for certain DHCP options.

http://msdn.microsoft.com/en-us/library/windows/desktop/aa363298%28v=vs.85%
29.aspx

>
>> As far as your SIP example below, I see SIP server through DHCP just as
>>a
>> discovery step. Your SIP client should apply whatever security policies
>>to
>> accept or not that SIP Server.
>
>Right, but going a little farther into your example, this only works for
>clients that 


"Clients" here can be an application as above, not necessarily a DHCP
client that triggers everything.

>(a) request the SIP option and (b) have some way of validating the
>response they get back.   So we can have a very clear discussion about
>this security model, and also possibly ask whether existing clients
>actually do this, and whether this is a good idea, or just the best we
>could do with what services are available.
>
>And then this question can be asked about lots of other services as well.
> E.g., does it make sense to configure NTP this way, given that NTP
>provides replay protection for security protocols (that's a complicated
>question)?   Does it make sense to configure SMTP this way, given that
>SMTP servers are no longer really interchangeable as they were in the
>early days of the Internet?   POP?   IMAP?   Etc.
>

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