Subject: Re: Draft on Advice for Internet Subnetwork Designers

From: Joe Touch <[email-masked]>
Date: Tue, 29 Feb 2000 10:19:49 -0800 (PST)

> From [email-masked]  Mon Feb 28 08:05:06 2000
> Date: Mon, 28 Feb 2000 15:06:57 +0100
> From: Dr G Fairhurst <[email-masked]>
> CC: "[email-masked]'" <[email-masked]>,
>         "Phil Karn (E-mail)" <[email-masked]>
> Subject: Re: Draft on Advice for Internet Subnetwork Designers
> 
> Here are some comments on Link Level Issues:
> 
> "Falk, Aaron" wrote:
> 
> > Folks--
> >
> > A very important piece of work for PILC is the LINK draft that Phil Karn is
> > editing.
> > http://www.ietf.org/internet-drafts/draft-ietf-pilc-link-design-01.txt
> 
> PAGE 4: MTU Size
> 
> It may be useful to note that using IPSEC in tunnel mode can increase
> the size of a packet as it travels across the network.  This can result
> in a smaller MTU.

Doesn't IPSEC in any mode do this? (tunnel or transport?)

(provided it's added after the source - and, in the case
of overlay networks, [paradoxically] transport may be
more useful)

> The IPv4 packet header contains a header checksum that verifies the integrity
> of the header. This checksum was originally design to protect from router
> software errors, however this function is no longer necessary.

Not so much necessary, as not worth the cost.

> IPv6 does
> not therefore implement a network level integrity checksum. The role of the
> IP checksum has therefore been subsumed into the TCP and UDP
> checksums.

More into IPSEC than into TCP and UDP, no?

Joe