[ppml] Follow on to 2003-4, and suggested change.

Michael.Dillon at radianz.com Michael.Dillon at radianz.com
Mon Oct 27 11:33:53 EST 2003

>A large aspect of our business is running data centers.  Typically
>we drop off a 100Mbps FE, or 1000Mbps GE link to a customer who
>plugs in a number of layer 2 switches and installs many servers.

>As far as I can tell the best thing to do with these customers is
>assign a /64.  A shorter prefix would be a waste, as they own no
>layer 3 gear, so they would have no way to break it into separate
>lans anyway.  I suspect anyone who runs data centers will generally
>be assigning /64's in the data centers to customers.

I don't think this is consistent with IPv6 policy. Specifically, the 
policy says:

    Assignments are to be made in accordance with the existing guidelines 
    [RFC3177,RIRs-on-48], which are summarized here as:

    - /48 in the general case, except for very large subscribers

    - /64 when it is known that one and only one subnet is needed by 

I don't think you can say that one and only one subnet is needed by design 
because it is your
customer's network and not yours. If a customer asks you for an IPv6 
assignment then you would
have to ask the customer to agree to not *EVER* install a router or a 
firewall or a NAT
device otherwise you don't have a design rule to justify the /64.

The prudent thing to do here would be to assign a /48 because this is an 
endsite network
outside of your management control. They may assign a separate subnet with 
separate addresses
for managing their devices. They may set up a separate subnet with 
separate physical interfaces for
doing backups of their servers. They may deploy a firewall that needs a 
DMZ subnet.

There is no waste of addresses by doing this. Remember that IPv6 gives us 
340 undecillion, 282 decillion, 366 nonillion, 920 octillion,
938 septillion, 463 sextillion, 463 quintillion, 374 quadrillion,
607 trillion, 431 billion, 768 million, 211 thousand, 456 addresses
to use. That is an awful lot of room, unimaginably huge. The people
who have thought these things through carefully, think that it's ok
to use up an entire /48 for any network that might grow and change
in topology. For now, we should accept that and work with it. Save the
/64 allocations for cell-phones and PDAs were there is unlikely to be 
more than one subnet on the device. If there is any network infrastructure
beyond your demarc, including a layer 2 switch, then you probably cannot
predict whether or not they will someday need to subnet. Therefore, /48.

--Michael Dillon 

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