Ralph Droms wrote:
The only reference to fragmentation in RFC 951 is:
3. Packet Format
[...] For
simplicity it is assumed that the BOOTP packet is never fragmented.
There are no references to fragmentation in RFC 213[12] or RFC 3315.
In my opinion, this reference is to simplicity in the IP layer, not in
the BOOTP layer. The IP layer handles any fragmentation and the
BOOTP/DHCP layers are unaware of that fragmentation. Therefore, any
addresses included in the DHCP messages are irrelevant to BOOTP/DHCP
message reassembly.
The issue with some (most?) client implementations, at least on UNIX, is
that they use methods like raw sockets to be able to send and receive
UDP without having an IP address. This means that the DHCP client would
need to take care of fragmentation and reassembly, and I believe they
generally don't.
Note that I haven't studied the source code of that many
implementations, but I believe this is common.
Stig
On the other hand, as I wrote in a previous message, all bets are off
regarding L2 (or other) devices that snoop the DHCP messages without
performing IP reassembly.
And, as a practical matter, I suspect all extant DHCP clients and
servers have a DHCP message MTU less than 1500 octets.
- Ralph
[...]
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