We have many discussions in the IETF-75 meeting about optimizing fragmentation. In the end, the group agreed that this draft isn¹t the best place to discuss the optimization. For fragmentation problem shares among all the tunneling protocols, this is not unique to ds-lite technology. The chairs suggested we should produce another draft which only discusses fragmentation strategy for tunnel protocols.
On 8/17/09 9:48 AM, "Zhen Cao" <[email protected]> wrote: > Hi Yiu, > > Thanks for your message. In this sense, any methods except > fragmentation and assembly are optimization and up to implementation. > But it is not a bad idea to introduce some suggestion for > implementation in the draft, so keeping the text for TSS option and > others is also reasonable. > > Best regards, > Zhen > > On Mon, Aug 17, 2009 at 10:29 AM, Lee, Yiu<[email protected]> wrote: >> > This is *not* recommended because it will require the v4 host to know about >> > ds-lite. This won¹t work for home router model where the hosts behind the >> > ds-lite home router won¹t know about ds-lite. Besides, the v4 packet isn¹t >> > over-sized, it is the v6 encapsulation caused the oversized issue. So the >> > tunnel points are responsible to handle the fragmentation. >> > >> > In the hosted model, the host is aware of ds-lite. The host can in fact >> > reduce the v4 packet size to avoid fragmentation. This optimization is up >> to >> > the implementation rather than mandated in the draft. >> > >> > >> > On 8/16/09 9:42 PM, "Zhen Cao" <[email protected]> wrote: >> > >> > 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 ³could² 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 >>> >> _______________________________________________ >>> >> Softwires mailing list >>> >> [email protected] >>> >> https://www.ietf.org/mailman/listinfo/softwires >>> >> >>> >> >> > >> > >> > >
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