[e2e] Mystery

Steve Deering deering at cisco.com
Sun Apr 29 14:10:10 PDT 2001

At 4:24 AM -0400 4/29/01, J. Noel Chiappa wrote:
>    > From: David.Eckhardt at cs.cmu.edu
>    > one of the myriad forms of IPv6 address is some constant prefixed to
>    > a 48-bit MAC address, which can somehow be parleyed into a globally
>    > routable address.
>I gather IPv6 stateless configuration can do do this (the host gets the
>topologically significant high-order part of its globally-significant IPv6
>address from the network) - but I gather that the use of MAC addresses has
>recently been deprecated because of privacy concerns. In other words, you
>pick some random bits for the low order part, and proceed as above.


The IPv6 temporary addresses (with randomly-generated lowest-order
field) do not deprecate the ones generated from MAC addresses, but
rather augment them.  I expect many IPv6 nodes to use both kinds of

  - To accept communication initiated by others (e.g., when providing
    the server side of a client-server style application, or accepting
    incoming IP telephone calls, or participating in a peer-to-peer
    style application), one wants a stable, globally-unique address,
    usually with a corresponding entry in the DNS.  The MAC-address-
    derived IPv6 addresses are good candidates for that.

  - When initiating communication to others (e.g., when acting as a
    client in a client-server style app like the web), one may prefer
    a less-long-lived address for privacy reasons.  The IPv6 temporary
    addresses are intended for that purpose.

A single IPv6 node may of course play multiple roles, and therefore
obtain both kinds of addresses (just like I want a stable phone number
for my phone so people can call me, but also the ability to hide that
number -- by suppressing caller-ID -- when I call others).


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