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 > directly). > > 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 > exit-point > 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 > problem). > > 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 > packet > 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 (:-)! > > Regards > > [EMAIL PROTECTED] -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
