RE: [dhcwg] Changes to remove "client-link-local-address" from th e DHCPv6 header

Yeah, in thinking some more about this, perhaps it is better that the relay
doesn't know about prefix lengths (it doesn't really need to) - though it
likely will anyway (because of Router Advertisements, etc).

It also is one more thing that could get misconfigured in some way between
the relay and server, so perhaps best to just let the server deal with it.

Therefore, I would suggest it can either be the prefix (with 0's in the interface
id) or just an address. Since the server knows the prefix lengths, it can find
the appropriate "network" by doing the checks only against the prefix-length
bits. Essentially, only the prefix bits are significant and the remaining bits
are don't care. But, I have no major issue if we want to force it to be just
the prefix (with 0's in the other bits).

- Bernie

-----Original Message-----
From: Ralph Droms [mailto:rdroms@cisco.com]
Sent: Thursday, August 30, 2001 2:05 PM
To: dhcwg@ietf.org
Subject: RE: [dhcwg] Changes to remove "client-link-local-address" from
the DHCPv6 header 

Bernie opined:

>Just to be clear, there are three pieces of information: 
>
>1. The address used to communicate with the relay. 
>2. The link on which the client's packet was received. 
>3. The prefix to be used for address assignment for the client. 
>
>I think 1 is easy and it should just be the IPv6 source address of the Relay-Forw. 
>
>In many cases 2 and 3 are the same but they need not be. I would suggest we solve 
>this by doing the following: 
>
>For 3, the relay should send a prefix and prefix-length. 

For 3, we can either do a variable length length+prefix field or send
a prefix with 0's in the interface-id or just send an address
from the appropriate link and let the server deduce the
prefix (which is what we do in DHCPv4, right?).  I've written up
the third alternative, which is as easy as any.  I'll rewrite
it as soon as someone expresses a preference for one of the
other alternatives or comes up with a different plan.

- Ralph

=====
9.1. Relay-forward message

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    msg-type   |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                          link-prefix                          |
     |                                                               |
     |                                                               |
     |               |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
     +-+-+-+-+-+-+-+-+                                               |
     |                                                               |
     |                     client-return-address                     |
     |                                                               |
     |               |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
     +-+-+-+-+-+-+-+-+                                               |
     .                                                               .
     .            options (variable number and length)   ....        .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      msg-type                    RELAY-FORW

      link-prefix                 An address with a prefix that is
                                  assigned to the link from
                                  which the client should be assigned
                                  an address.

      client-return-address       The source address from the IP
                                  datagram in which the message from the
                                  client was received by the relay agent

      options                     MUST include a "Client message
                                  option"; see section 18.7.  The relay
                                  MUST include a "circuit-ID option" if
                                  it needs to explicitly identify the
                                  link on which the client message should
                                  be forwarded to the client

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