During w.g. last call, I suggested a change of wording in the
definition of IPv4-mapped addresses (mail attached below). I
see the suggestion was not incorporated in addr-arch-v3-01.
Let me offer an example of what motivated my suggestion.
Suppose we have 2 IPv6/IPv4 nodes: Node A has IPv6 address A::A
and IPv4 address 1.2.3.4. Node B has IPv6 address B::B and IPv4
address 5.6.7.8. Node A is running a server which is listening
for both IPv4 and IPv6 connections on an AF_INET6 socket. A client
on node B connects to node A's IPv4 address (1.2.3.4), with packets
sourced from B's IPv4 address (5.6.7.8). (Why does the client use
A's IPv4 address? Perhaps it is an AF_INET application that has
not yet been upgraded, or perhaps the user entered 1.2.3.4.) The
server on node A accepts the connection, and because it is using
AF_INET6 sockets, accept() returns B's IPv4 address as ::FFFF:5.6.7.8.
In this example, an IPv4-mapped address (::FFFF:5.6.7.8) is used
to represent the address of an IPv6/IPv4 node (B).
Is this correct usage of IPv4-mapped addresses? Or is it a violation
of the architecture?
- Jack
------------------------------------------------------------
>From [EMAIL PROTECTED] Thu Mar 30 13:22:09 2000
Date: Thu, 30 Mar 2000 13:16:21 -0500 (EST)
From: Jack McCann <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: W.G. Last Call on "IP Version 6 Addressing Architecture"
IPv4-mapped addresses are defined as:
A second type of IPv6 address which holds an embedded IPv4 address is
also defined. This address is used to represent the addresses of
IPv4-only nodes (those that *do not* support IPv6) as IPv6 addresses.
This type of address is termed an "IPv4-mapped IPv6 address"...
IPv4-mapped addresses are not limited to IPv4-only nodes. They can
also be used to represent the IPv4 address of an IPv6/IPv4 node, or
more generally, to represent any IPv4 address in an IPv6 address format.
I suggest replacing this sentence:
This address is used to represent the addresses of
IPv4-only nodes (those that *do not* support IPv6) as IPv6 addresses.
with something like this:
This address is used to represent an IPv4 address
(for example, the IPv4 address of an IPv4-only or IPv6/IPv4 node)
in an IPv6 address format.
- Jack
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