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generic v6 tunneling
- Subject: generic v6 tunneling
- From: IPSix Developer" <[email protected] (IPSix Developer)
- Date: 6 Feb 2002 10:50:11 -0000
The looping i'm refering to section 7.1(a) of RFC 2473,
occurs when the ipv6 packet size is checked against the
min. link MTU always- which is always 1280 (or PathMTU ???)
I'm not refering to errors on errors loop.
On Wed, 06 Feb 2002 Francis Dupont wrote :
> In your previous mail you wrote:
> 1)With ref to section 3.3 of RFC 2473 :
> "The tunnel exit-point node, which decapsulates the
> tunnel packets,
> and the destination node, which receives the
> resulting original
> packets can be the same node".
> Does it mean tunnel exit-point IPv6 address and
> original packets
> destination IPv6 address are same?
> => "can be" but usually they are configured to be
> different because:
> - this can too easily mess the routing system
> - there is no reason to encapsulate such packets (they
> can be sent
> If they are same, how do we configure the route for
> the destination
> V6 address at the tunnel entry point?
> => there is already a route to the exit-point, not
> using the tunnel.
> If you try to misconfigure a tunnel with a route to the
> through the tunnel, good systems will detect the error
> and won't crash
> trying infinite encapsulation. But this is harder if
> the loop is distributed
> between different nodes so section 4 describes this
> kind of problems
> and some solutions (note that 4.1.2 check detects your
> 2)With ref to section 7.1(a) of RFC 2473:
> When the IPv6 packet size is larger than IPv6 min
> link MTU, the
> ICMPv6 pkt too big msg is sent with MTU as
> max(tunnel MTU, IPv6 min
> link MTU) .
> If the furthur received packets' size is larger than
> IPv6 min link
> MTU, again TOO BIG message will be sent
> => yes, ICMPv6 are sent on errors but are rate limited.
> and a looping will occur?
> => I believe your loop is errors on errors. There are
> two counter-measures:
> (draft-ietf-ipngwg-icmp-v3-02.txt section 2.4)
> - (c) Every ICMPv6 er
IPv6 offending (invoking) packet (the packet that
> caused the
> error) as will fit without making the error message
> exceed the minimum IPv6 MTU.
> - (e.1) An ICMPv6 error message MUST NOT be sent as a
> result of
> receiving an ICMPv6 error message.
> (don't forget (f) aka rate limitation too).
> how to avoid this?
> => understand and implement carefully the specs (:-)!
> [email protected]