CIDR question

Milo S. Medin (NASA ARC NSI Office) medin at
Thu Jul 29 05:12:11 UTC 1993

Well, I stand corrected!  In many ways, the mask and match approach is a very
natural way to think about things, but many of us who were raised on BSD
unix had class drilled into the way we used those systems as routers and hosts.
I think it's sort of like learning BASIC as your first computer language.  
You're hobbled for life! :-)

You raise a good point about NIC's handing out such addresses.  This will
be problemmatic, but straightforward engineering.  Enough to employ some
database types for awhile.  The biggest problem I don't think is with the 
routers either.  I think it's with the way the kludge in the
DNS will deal with address allocation on non-8bit boundaries.  This is a mess.
Automation can help, but that's going to be ugly.  We should try and allocate
chunks of address space on 8 bit boundaries until we can field a more flexible

Most of the major router vendor's CURRENT releases support classless IP
forwarding operations, I think mostly as a consequence of Variable Length
Subnet Mask support required in OSPF.  Since OSPF is pretty much considered
a must-have in the router game, people had to invest in the labor to fix
this up.  It took awhile, but by and large we are there, though many of
the Unix vendors who use these systems as routers still haven't taken the
code from CSRG and LBL that would make this work for them.  But I think
the OSPF push for VLSM will make life a lot easier on the BGP4 folks,
since they won't have to coerce the vendors for classless forwarding support.


PS You also made me think that we should probably try and get the InterNIC
folks to start working on making their address allocation and database
stuff support "classless" allocation.  I'll bring this up with NSF next
time I'm in DC...

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