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Re: IPv6CP - rfc 2472 --- why only IID, why not prefix too



Hi Rajan,

Rajan Srivastava wrote:
Hi,

In rfc 2472, it is provisioned that PPP server will negotiate
interface identifier with PPP client, server will not pass on network prefix;
and prefix delegation is left for DHCPv6 etc.


What is rationale behind this strategy?

IP(v4)CP believes that the peer PPP device can only have one address.

In IPv6, there's a lot more flexibility regarding prefix utilization
on a host or network.

IPv6 Link-Local addresses have a fixed 64 bit upper portion, and so
the 64 bit token used for IP6CP may be usable to generate a valid
Link-Local address.

Such an address can then be used in DHCP, or Neighbour Discovery.

Since Router Discovery (part of Neighbour Discovery) can provide
multiple prefixes to a host, any one or more of these prefixes
may be used to autoconfigure an address.

As you mentioned, prefix delegation caters to another set of devices:
those requiring networks/prefixes of addresses.

Each fills its own requirement, and it doesn't necessarily make sense
to define another way to do this in IP6CP, since the assumptions
are different to IPv4.


Yours Sincerely,

Greg Daley


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