usage of secs field [draft-ietf-dhc-protocol-07]

[Akihiro Tominaga <[e-mail]>]

I have some suggestions and questions about retransmission of DHCP
messages.  Firstly, question about retransmission of DHCPDISCOVER.

When retransmit DHCPDISCOVER message, does the client have to add some
number ?  If the client follows the "bootp clarification and
extensions (draft-ietf-dhc-bootp-02)", the client must add seconds
since first DHCPDISCOVER.  Then in the draft-ietf-dhc-protocol-07,

>    DHCPREQUEST message must use the same value in the DHCP message
>    header's 'secs' field and be sent to the same IP broadcast address as
>    the original DHCPDISCOVER message.

the client must use the same 'secs' value as DHCPDISCOVER 'secs'.
But, how can the client choose which 'secs' between the previous
DHCPDISCOVER messages ?

So, in the table 3:

>  Field_________DHCPOFFER____________DHCPACK_____________DHCPNAK______________
>  'op'          BOOTREPLY            BOOTREPLY           BOOTREPLY
>  'xid'         'xid' from client    'xid' from client   'xid' from client
>                DHCPDISCOVER         DHCPREQUEST         DHCPREQUEST
>                message              message             message
>  'secs'        0                    0                   0
                 ^^                   ^^                  ^^

Is it better to change them to " 'secs' from client DHCP**** " ?
So, the client can use appropriate 'secs'.


Secondly, question about retransmission of DHCPREQUEST, especailly
when the client reacquiring the previously allocated IP address.

When T1 has expired, the client unicast DHCPREQUEST to the server.  In
that case, the client must reset 'secs' field ? ('reset' means 'set
0'.) So, when retransmit the DHCPREQUEST, set seconds elapsed from
first (reacquiring) DHCPREQUEST ?

When T2 has expired, 'secs' are seconds from the first (reacquiring
unicast) DHCPREQUEST ? Or, from the first broadcast DHCPREQUEST ?


If server returns 'secs' from client DHCP message, the client can compute
lease expiration time as follows:

	lease = local_time + lease_duration + secs

then, the client can use reacquiring lease without loss time which
comes from retransmission.

--
Keio Univ.
WIDE Project.
Akihiro Tominaga			[e-mail]