Re: [dhcwg] Changes to remove "client-link-local-address" from the DHCPv6 header

[Ralph Droms <[e-mail]>]

Here's the final text on this issue (extracted from the revved draft):

9. Relay messages

   Relay agents exchange messages with servers to forward messages
between clients and servers that are not connected to the same link.


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.


9.2. Relay-reply 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-REPL

      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 "Server message option"; see
                      section 18.8.


16. Relay Behavior

   For this discussion, the Relay may be configured to use a list of
server destination addresses, which may include unicast addresses,
the All DHCP Servers multicast address, or other multicast addresses
selected by the network administrator.  If the Relay has not been
explicitly configured, it MUST use the All DHCP Servers multicast
address as the default.


16.1. Relaying of client messages

   When a Relay receives a valid client message, it constructs a
Relay-forward message.  The relay places an address with a prefix
assigned to the link on which the client should be assigned an address
in the link-prefix field.  This address will be used by the server to
determine the link from which the client should be assigned an address
and other configuration information.

   If the relay cannot use the address in the link-prefix field
to identify the interface through which the response to the client
will be forwarded, the relay MUST include a circuit-id option (see
section TBD)in the Relay-forward message.  The server will include the
circuit-id option in its Relay-reply message.

   The relay copies the source address from the IP datagram in which
the message was received from the client into the client-return-address
field in the Relay-forward message.

   The relay constructs a "client-message" option 18.7 that contains the
entire message from the client in the data field of the option.  The
relay places the "relay-message" option along with any "relay-specific"
options in the options field of the Relay-forward message.  The Relay
then sends the Relay-forward message to the list of server destination
addresses that it has been configured with.


16.2. Relaying of server messages

   When the relay receives a Relay-reply message, it extracts the server
message from the "server-message" option.  If the Relay-reply message
includes a circuit-id option, the relay forwards the message from the
server to the client on the link identified by the circuit-id option.
Otherwise, the relay forwards the message on the link identified by the
link-prefix option.  In either case, the relay forwards the message
to the address in the client-return-address field in the Relay-reply
message.



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