Subject: (IPng 6633) W.G. Last Call on "A Method for the Transmission of IPv6 Packets over ARCnet Networks"

From: Bob Hinden <[email-masked]>
Date: Tue, 13 Oct 1998 12:15:12 -0700

This is a IPng working group last call for comments on advancing the
following document as a Proposed Standard:

	Title		: A Method for the Transmission of IPv6 Packets 
                          over ARCnet Networks.
	Author(s)	: I. Souvatzis
	Filename	: draft-souvatzis-ipv6-arcnet-04.txt
	Pages		: 6
	Date		: 28-Sep-98

Please send substantive comments to the ipng mailing list, and minor
editorial comments to the author.  This last call period will end two
week from today on October 27, 1998.

Bob Hinden / Steve Deering

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From: Ignatios Souvatzis <[email-masked]>
Date: Fri, 16 Oct 1998 14:58:46 +0200

Hello,

I was just re-reading the ARCnet, and then the Ethernet and FDDI paper, and
stumbled over this passage [Ethernet paper; similar words used by the
FDDI and ARCnet papers]:

    The default MTU size for IPv6 [IPV6] packets on an Ethernet is 1500
    octets.  This size may be reduced by a Router Advertisement [DISC]
    containing an MTU option which specifies a smaller MTU, or by manual
    configuration of each node. 

Until here, ok.

				If a Router Advertisement received on
    an Ethernet interface has an MTU option specifying an MTU larger  
    than 1500, or larger than a manually configured value, that MTU
    option may be logged to system management but must be otherwise
    ignored.

What happens if two Router Advertisements come in, one with a small
MTU, one with a bigger one? Does the driver code or protocol stack need
to keep two MTU values per interface, one for the latest "manual"
(which includes DHCP) value, and one for the active value (initialized
to the manually configured one, and changed when receiving router
advertisements with a MTU smaller than the manual value?

Regards,
	-is

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From: Ignatios Souvatzis <[email-masked]>
Date: Fri, 16 Oct 1998 15:13:27 +0200

Comparing it to the IPv6 over Ethernet and FDDI specifications, I found that
this sentence is missing at the end of the MTU discussion:

    For purposes of this document, information received from DHCP is
    considered "manually configured".

I didn't take part in the discussion leading to this, "back then", so I don't 
know the rationale, but ARCnet should certainly be handled in the same way as
the other two protocols.

Regards,
	-is

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From: Thomas Narten <[email-masked]>
Date: Fri, 16 Oct 1998 10:44:42 -0400

> advertisements with a MTU smaller than the manual value?

You process them in order, and when you get an update, you toss out
the old value and use the new. If as a consequence you oscillate
between multiple values, so be it.

At the time, it was felt that the benefits of trying to specify
something more complex wasn't worth the benefit. After all, this is a
config error on the routers. If this causes a problem in practice, the
sys admin (presumably) has an easy fix. :-)

Thomas

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From: Ignatios Souvatzis <[email-masked]>
Date: Fri, 16 Oct 1998 16:56:54 +0200

> sys admin (presumably) has an easy fix. :-)

In case this wasn't clear: My concern is not oscillating per se, but limiting
the received MTU as specified. After I first lowered it, I dont have the old
limit anymore, if I use the traditional "1-MTU" approach, right?

Regards,
	-is

---

From: Ignatios Souvatzis <[email-masked]>
Date: Tue, 20 Oct 1998 21:02:51 +0200

> week from today on October 27, 1998.

Whats the procedure to do updates to the paper suggested during the last call
period?

	-is