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Re: Networking design proposal


From: Olivier Péningault
Subject: Re: Networking design proposal
Date: 26 Oct 2002 22:52:31 +0200

le sam 26-10-2002 à 20:13, Niels Möller a écrit :

I have one remark, and some questions about your proposal.

> Layer 3 (IPv4 and IPv6), part 1
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

>   Tells the interface that we're interested in packets with the given
>   ip-address. Can be a unicast or multicast address. It's not clear
>   whether or not the same layer 3 component should handle both ipv4
>   and ipv6. One way might be to use ipv6 exclusively, and represent
>   ipv4 addresses as ipv6 mapped addresses.
I don't know where you saw this use of IPv6 address that automagically
include IPv4 addresses.

In RFC-2373, a mechanism for transition between IP4 and IP6 addresses is
explained. The addresses like :
|                80 bits               | 16 |      32 bits        |
+--------------------------------------+--------------------------+
|0000..............................0000|????|    IPv4 address     |
+--------------------------------------+----+---------------------+
define a compatible IP4 addressing, with the 16 bits all set to 0 for
dynamic tunnels, and all bits to 1 for hosts that don't implement IP6.
The uses of these addresses are to route IP6 packets on IP4 networks.

There is also local link addresses :
|   10     |
|  bits    |        54 bits          |          64 bits           |
+----------+-------------------------+----------------------------+
|1111111010|           0             |       interface ID         |
+----------+-------------------------+----------------------------+

and site local addresses :
|   10     |
|  bits    |   38 bits   |  16 bits  |         64 bits            |
+----------+-------------+-----------+----------------------------+
|1111111011|    0        | subnet ID |       interface ID         |
+----------+-------------+-----------+----------------------------+

In RFC-2374 is defined a :
|  n  |      24-n bits     |   16   |    64 bits      |
+-----+--------------------+--------+-----------------+
|NLA1 |      Site ID       | SLA ID | Interface ID    |
+-----+--------------------+--------+-----------------+

and the concept of "interface ID" (see above) is defined in chapter 3.6
as the data link layer address, represented on 64 bits (the address is
"on the right side" of the 64 bits, and if the address length is less
than 64 bits, all remaining bits "on the left" are set to 0).

And I think that listening IP4 with IP6 addresses would be an issue. IP6
addresses are 2^96 more times numerous as IP4 addresses, no mapping is
possible, and not any /32 IP6 address pool has been reserved for that.


Some questions :

How dhcp will work ?
What about sockets ? Who cares about them, how do they work (we bind on
a per-interface basis, or on all interfaces ?) ?


My work is still in progress (I read RFCs... :).

olivier






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