Subject: (IPng 7133) Link layers we dont have yet...

From: Ignatios Souvatzis <[email-masked]>
Date: Fri, 29 Jan 1999 16:32:27 +0100

Hello,

there are two protocols that come into my mind, with no IPv6 specification
I am aware of: AX25 layer 2 (amateur packet radio) and Appletalk.

Is there any work in progress?

	-is
-- 
 * Progress (n.): The process through which Usenet has evolved from
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   smart terminals.  -- [email-masked] (obscurity)
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From: Bob Fink <[email-masked]>
Date: Fri, 29 Jan 1999 08:30:33 -0800

>Is there any work in progress?

I believe these two are in distinctly different categories. The first might
indeed be a candidate for a "v6-over" spec. 

AppleTalk is a full protocol suite that can have its network layer replaced
by IPv4 (and in one early test demo, IPv6 as well).  Though one could, in
theory, attempt to push AppleTalk's network level down to a media level for
IPv6, I can't see why it would be useful (just my opinion).

Bob

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From: Ignatios Souvatzis <[email-masked]>
Date: Fri, 29 Jan 1999 17:42:51 +0100

> IPv6, I can't see why it would be useful (just my opinion).

Uhm, yes, but there's AppleTalks original link level protocol (how is it
called officially?), that 220 kbit HDLC over RS422....

I thought (but might be wrong) that IPv4 was defined over that.

	-is

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From: Bob Hinden <[email-masked]>
Date: Fri, 29 Jan 1999 09:20:30 -0800

Ignatios,

>I thought (but might be wrong) that IPv4 was defined over that.

I think we usually call this "localtalk".  Bob is correct, Appletalk is a
complete protocol suite (e.g., appletalk over ethernet, appletalk over
localtalk, etc.).  There is a IPv4 over Localtalk specification.  We should
consider doing an IPv6 version.

The question I would ask is there any need for IPv6 over Localtalk?  My
guess is that any Apple machines that will be capable of running a new
version of MacOS that includes IPv6 will have Ethernet and will not have
LocalTalk (e.g., the iMac).

Bob

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From: Steve Deering <[email-masked]>
Date: Fri, 29 Jan 1999 09:49:16 -0800

At 9:20 AM -0800 1/29/99, Bob Hinden wrote:
> localtalk, etc.).  There is a IPv4 over Localtalk specification.

It is my understanding that the common practice is IP-over-AppleTalk,
*not* IP-over-LocalTalk.  I.e., IP is "tunneled" through the AppleTalk
internet protocol to reach LocalTalk-attached devices.

Steve

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From: Steve Deering <[email-masked]>
Date: Fri, 29 Jan 1999 10:14:25 -0800

> internet protocol to reach LocalTalk-attached devices.

One more thing: the maximum payload size of AppleTalk is less than the
1280-byte minumum IPv6 link MTU, so any IPv6-over-AppleTalk spec will
need to include a mechanism for fragmenting and reassembling IPv6
packets across the AppleTalk "hop".  One possible solution is to use
IPv4 as the local fragmentation protocol, since that's already
implemented in the devices of interest.  However, that would impose
a greater header cost than a new fragmenting protocol defined
specifically for this purpose.

By the way, I agree with Bob that the importance of specifying a means
of transmitting IPv6 over LocalTalk is debatable.

Steve