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Re: [dhcwg] Ben Campbell's Discuss on draft-ietf-dhc-relay-port-08: (with DISCUSS and COMMENT)

"Naiming Shen (naiming)" <naiming@cisco.com> Thu, 30 November 2017 05:36 UTC

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From: "Naiming Shen (naiming)" <naiming@cisco.com>
To: Ben Campbell <ben@nostrum.com>
CC: Ted Lemon <mellon@fugue.com>, The IESG <iesg@ietf.org>, "draft-ietf-dhc-relay-port@ietf.org" <draft-ietf-dhc-relay-port@ietf.org>, dhcwg <dhcwg@ietf.org>, "dhc-chairs@ietf.org" <dhc-chairs@ietf.org>
Thread-Topic: [dhcwg] Ben Campbell's Discuss on draft-ietf-dhc-relay-port-08: (with DISCUSS and COMMENT)
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Date: Thu, 30 Nov 2017 05:36:44 +0000
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Subject: Re: [dhcwg] Ben Campbell's Discuss on draft-ietf-dhc-relay-port-08: (with DISCUSS and COMMENT)
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Ha, I missed that. This paragraph I took from AD review suggested text, and
it just means the implementation can have configuration knob to either enable
this feature by specifying a non-DHCP port number or disable that and leave
the port number to be at default:-)

I’ll modify the text so that is more readable. thanks.

- Naiming

On Nov 29, 2017, at 8:02 PM, Ben Campbell <ben@nostrum.com<mailto:ben@nostrum.com>> wrote:



On Nov 29, 2017, at 9:00 PM, Naiming Shen (naiming) <naiming@cisco.com<mailto:naiming@cisco.com>> wrote:


Hi Ben,


On Nov 29, 2017, at 6:30 PM, Ben Campbell <ben@nostrum.com<mailto:ben@nostrum.com>> wrote:

Thanks for the updates.

In 5.4, you added advice to the first paragraph that one shouldn’t turn this on unless the upstream devices support it. That’s good. But I still wonder about the intent of the second paragraph. Is the intent that the relay listens for messages on _both_ ports? Or that it could be configure to listen on either? If a message arrives on the standard port in as a result of one from a non-standard port, is it valid?

I think it's up to implementation. It is possible to listen on both ports, especially in ipv4 DHCP,
it has to listen on port 67 for client DHCP messages. For an implementation, if it configures
the relay-port feature and but receives the server relay-reply message on port 67, should it
drop or should it just log an error and keep handling this? either way is fine I think.

But from the large scale relay box implementation case, say there are three relay processes handling
the DHCP relay on the same box, there can be a default/central DHCP process just to receive on the
port 67, then dispatch the work to one of the relay-agents in round-robin fashion. In such a setup, if the
server does not support this feature, and it sends back on port 67, this central DHCP process may not
have information on which relay-agent to give it to. If it does, then that defeats the purpose of multiple
relay-agents on this box.

So to your question, it depends on the implementation and operational needs.

Thanks, and that seems reasonable. But I’m still unclear on the intent of that paragraph. Can you elaborate?

Ben.

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