Re: [dhcwg] recommendation on DHCP6 source port numbers

[Ole Trøan <[e-mail]>]

Guess we haven’t departed too far from bootp. 
Which seems to make a case for the client using the reserved port number also as the source port. 

Rfc951:
  The UDP header contains source and destination port numbers.  The
   BOOTP protocol uses two reserved port numbers, 'BOOTP client' (68)
   and 'BOOTP server' (67).  The client sends requests using 'BOOTP
   server' as the destination port; this is usually a broadcast.  The
   server sends replies using 'BOOTP client' as the destination port;
   depending on the kernel or driver facilities in the server, this may
   or may not be a broadcast (this is explained further in the section
   titled 'Chicken/Egg issues' below).  The reason TWO reserved ports
   are used, is to avoid 'waking up' and scheduling the BOOTP server
   daemons, when a bootreply must be broadcast to a client.  Since the
   server and other hosts won't be listening on the 'BOOTP client' port,
   any such incoming broadcasts will be filtered out at the kernel
   level.  We could not simply allow the client to pick a 'random' port
   number for the UDP source port field; since the server reply may be
   broadcast, a randomly chosen port number could confuse other hosts
   that happened to be listening on that port.

O.