"Bad bgp identifier"

[Joe Maimon]

4271 specifies that bgp identifier must be a valid unicast ip address
So what is the larget 32 bit value expressed as a dotted quad that meets 
this requirement?

Is it the last address in class c? class e? Can 255.x.x.x be used?

Do all vendors implement this?

I understand that  draft-ietf-idr-bgp-identifier-06.txt does away with 
the above requirements. Is this something I should ask vendors if they 
will support it?

Thanks,

Joe