Re: IPv6 Address Architecture update question

[Bob Hinden <[e-mail]>]

Hi,

In response to my question about keeping the "IPv6 Addresses with Embedded 
IPv4 Addresses" (e.g., compatible and mapped) I heard the following:

"I think that at least all the BSD's and most Linuxes are using this.
They allow binding on :: (IPv6 any) and also accept IPv4 connections on
the same socket, which are then represented in netstat etc
as ::ffff:1.2.3.4.", "IMO the section can be removed and programmers need 
to be learned the correct thing for which I always very inclined to point 
people to Eva's excellent document at 
http://gsyc.escet.urjc.es/~eva/IPv6-web/ipv6.html and/or 
draft-ietf-v6ops-application-transition-02.txt"

"They should not be removed. Implementations already support it, removing 
would just create confusion. I don't see any harm in keeping it in."

"helps with porting applications" and "dropping this section will create 
confusion and chaos for the already ported applications"

"Among other things, this would break the just published full
Standard for URIs (RFC 3986).", "I suspect some people have used the 
::10.1.2.3 format to carry IPv4 addresses in an IPv6 container, simply for 
convenience. I think this is very convenient and should be available.",
" otoh the ::FFFF:10.1.2.3 format seems useless to me."

"IPv4-mapped addresses facilitate an important interoperability mechanism
in the socket API (RFC 3493, section 3.7).", "the API still needs
a way to represent IPv4 addresses in a way that preserves compatibility
between IPv6 and IPv4 hosts.  Removal just makes transition all the more
time-consuming and difficult for software developers.

"rather see clarification of the use of embedded addresses in the
document rather than complete removal.  Ie. add a statement to the effect
of 'Embedded addresses are intended for internal representation only'."

"It is clear that the mapped addresses are widely used and useful, and a 
lot of people have raised their concerns about removing that.", "I suggest 
just simply removing compatibles."

"Removal and formal deprecation would simplify life for software 
developers.", "We might as well rid developers of the burden of having to 
cope with mapped-address sockets as well.", "Anyway, in summary, removal 
would in my opinion actually make transition much easier for software 
developers, not harder. Don't let the superficial ease of the 
mapped-address API fool you :)"

My take of this is that they should remain in the IPv6 address 
architecture.  There is current usage and removing them would break other 
specifications.

Thanks,
Bob




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