Subject: [dhcwg] draft-zi-dhc-agent-request-multi-pool-00.txt

From: zikang <[email-masked]>
Date: Thu, 20 Oct 2005 10:52:29 +0800

Dear all,
I have submitted a new internet draft to the dhc working group.
This draft introduces new option used by relay agent to tell the DHCP Server
to allocation address from more than one address pool.
Abstract of the draft are at the bottom of this email.
I would appreciate any feedback and comments.

Sincerely,
Zi Kang
-----------
Abstract

   This document modifies the Subnet selection option and defines a new
   sub-option of the relay-agent-information option. Each of these
   options is used by the relay agent to tell the DHCP Server to
   allocation address from more than one address pool.

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From: Ted Lemon <[email-masked]>
Date: Wed, 19 Oct 2005 12:45:13 -0700

There are a couple of problems with this draft.

First, it changes the meaning of the subnet selection option.   This is easy 
to deal with - just use a different option code.

Second, though, and more serious, it doesn't explain what it's trying to do.   
What is the server supposed to do?   It sounds like you want the server to 
allocate two or more IP addresses, but you don't explain how the server will 
return these IP addresses to the client.   If you want to allocate more than 
one IP address, the only way that I think you can really do it is to either 
use a different protocol (that is, not DHCP), or do more than one DHCP packet 
exchange, using a different client identifier for each desired IP address.   

While this is not explicitly allowed in RFC2131/2132, a conforming DHCP server 
will treat a client that identifies itself with two separate IP addresses as 
two separate clients, and as a result a DHCP client that wants more than one 
IP address can, in practice, use two DHCP client identifiers and thereby get 
two IP addresses.

If what you want isn't for the client to get two IP addresses, then you need 
to explain what you do want.

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From: Andre Kostur <[email-masked]>
Date: Wed, 19 Oct 2005 21:49:57 -0700

> exchange, using a different client identifier for each desired IP address.   
I got the impression that the draft is trying to address the issue where 
the Relay agent is unable to determine which of a multitude of subnets a 
client is originating from.
> IP address can, in practice, use two DHCP client identifiers and thereby get 
Note that this is specifically used in the CableHome specifications.  
The CableHome device has multiple "personalities" each distinguished by 
a different ClientID.
> to explain what you do want.

However, having said that, DHCP Servers today can deal with this issue 
by some mechanism of grouping together various subnets at the DHCP 
server, offhand this draft seems to be a solution in search of a problem....