Vishwas, It's not a question of what's optional or not. Erik gave a clear example of an operational issue which is if a host sends a packet with size equal to MTU of the link and if such a packet arrives at a router1 in such a network and router1 slaps its RH on the packet, the packet size grows larger than the max MTU. Now router1 forwards the packet to router2 who issues an ICMPv6 Too Big error to the host. The host stands totally confused because the host did not exceed the link MTU.
Also, tunneling used by transition mechanisms is orthogonal to this operational issue discussion. For tunneling with no use of RH, there is well-defined behavior for not exceeding the MTU in RFC 2473. Hemant -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Vishwas Manral Sent: Monday, May 31, 2010 2:03 PM To: Erik Nordmark Cc: [email protected]; culler Culler Subject: Re: Fwd: I-D Action:draft-hui-6man-rpl-routing-header-00.txt Hi Erik, The first thing is IPv6 MTU discovery is optional and the only requirement is that the Minimum MTU is satisfied. Also in cases like LLN the Routing paths may change so even after discovery the Packet too big may come anyway. Besides PMTU issues you mention are no different than a lot of cases such as tunnelling and transition mechanisms. For MTU discovery in cases when padding is done, the right MTU will be found as the data packets will undergo the same behavior as the PMTU discovery message. Thanks, Vishwas -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
