Hi Yiu,

Thanks for your clarification.

Do you consider another method that let the IPv4 packet inside the
tunnel do fragmentation at a lower MTU (link-MTU - 40), so that the
packet won't exceed the MTU after IPv6 header encapsulation. Then
there is no need of IPv6 encapsulation and assembly.  I believe this
is more cost efficient than IPv6 fragmentation and assembly.

Thanks and regards,
Zhen

On Mon, Aug 17, 2009 at 12:34 AM, Lee, Yiu<[email protected]> wrote:
> Hi Zhen,
>
> In general, the Tunnel-Entry Point and Tunnel-Exist Point should fragment
> and reassemble the oversize datagram. This mechanism is transport protocol
> agnostic and work for both UDP and TCP.
>
> For TCP, we “could” potentially avoid fragmentation by modify MSS option.
> However, we were required by the Chairs to remove this optimization from the
> draft in next update.
>
> Thanks,
> Yiu
>
>
> On 8/16/09 3:56 AM, "Zhen Cao" <[email protected]> wrote:
>
> Hi Alain and All,
>
> I have a question on MTU issue in ipv4-in-ipv6 softwire. I notice
> Sec.10.2 of DS-Lite draft has discussed the MTU problem. The draft
> introduces one possible way of using TCP MSS option to avoid IP layer
> fragmentation and reassembly. It is a good idea but how about the case
> for UDP sockets? I suppose there should be a general way to handle the
> MTU issue? Thanks for any explanation.
>
> Thanks and regards,
> Zhen
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>
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