On Wed, 11 Oct 2006, Joe Touch wrote:
IMO, it won't make fragmentation less likely. Tunneling will drive
fragmentation up, i.e.
Certainly
there is still fragmentation in IPv6 world (see below), but I guess the
main issue with respect to this draft is whether it can be classified
"Very Harmful"?
It's true that the tunnel encap/decap points may need to fragment and
reassemble the encapsulating packet in certain cases (see Section 7 of
RFC2473), but still there is 16 bits more of ID space, which is
significant improvement -- not enough for "Very Harmful" in my book.
The 16 bits of ID space there can be _more_ limiting, not less. The
protocol type is constant (IP inside), so the 16 bits is for all
tunneled traffic. And tunnels can be aggregation points, which means
that multiple IP sources sent over a tunnel use the same tunnel endpoint
addresses. The only thing left is the IP ID field; all other fields are
identical for tunneled traffic, which makes things worse, not better.
All I was saying was that IPv4 has 16 ID bits, IPv6 has 32. Even for
tunneled traffic, because ICMPv6 errors are required to contain full
payload up to 1280 bytes, with IPv6 you _can_ propagate the ICMP
errors received from the outside to the inside if you wish to. With
ICMPv4 you don't necessarily have enough payload information to do so.
I.e., there's only one corner case of using around 1280 byte MTUs and
packet sizes where you fragmentation is _required_. I'd say this
situation is much better with IPv6 than with IPv4.
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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