Re: [Softwires] map-t to proposed standard rather than experimental

[Ted Lemon <[e-mail]>]

On Nov 14, 2014, at 12:49 AM, Rémi Després <[e-mail]> wrote:
> - Only MAP-T lacks transparency to the IPv4 DF bit. 

So your concern is that if fragmentation at the translator results in an IPv6 packet that is larger than the MTU of the IPv6 path between the 4->6 translator and the 6->4 translator, fragmentation will not occur?   This would result in a packet too big ICMP message being sent back to the translator, which would then use a lower MTU in making its fragmentation decision on the next packet.

So I guess your concern is that the problem is that in this case the specific packet that was dropped due to IPv6 PMTU discovery on the path between the two translators would _not_ result in an ICMP Packet Too Big message being sent to the IPv4 host.   Instead that host would see this as a dropped packet.

Can you explain why this is bad?   I mean, I can see that there is possibly a small advantage to the DF transparency you are talking about, but it doesn't amount to an interop problem, and clearly the right thing will happen.   So why is this a blocking issue?