Re: [tcmtf] TCM-TF: Path MTU

["Reinaldo Penno (repenno)" <[e-mail]>]

On 9/27/13 6:56 AM, "Jose Saldana" <[e-mail]> wrote:

>Just my opinion about the MTU problem when TCM-optimizing:
>
>
>(Š) 
>>>>>3) Path MTU discovery issues
> 
>>>>[RP] Very important issue. There are some gaming consoles  that  just
>>>>by
>putting their packets in a lightweight UDP tunnel you get a message
>>>>saying you have MTU issues and everything stops. Debugging is up to the
>user.  
> 
>>>[Jose] Which game genre are you talking about? Perhaps this only happens
>when the console is sending MTU packets. Real-time games usually send
>>> very small ones, but this is a very interesting topic we have to study.
>
>>[RP2] The console itself (not a game) does MTU probing. If there is a MTU
>problem you get a network error.
>
> (Š)
>
>[Jose] TCM is deployed inside the network (within a network segment), and
>the end machines do not know that it is being deployed.
>
>TCM only makes sense for small-packet flows.

[RP] Yes, but how TCM would know that before hand about the flow ? Is that
a run time decision based on packet size inspection?

>Obviously, a TCM optimizer will
>not multiplex packets if they are big. Those packets will travel in their
>native form, and the tunnel is not required. So if a console does that
>test,
>a good TCM implementation should not do anything.

[RP] If you have a mix of large packets (close to MTU, no tunneling) and
small packets, that would cause reordering, no?

>
>There is another question: we are talking about multiplexing based on a
>time
>period. However, the MTU is another limitation. I mean, if the period has
>not expired yet, but you are near the MTU, you'd better send the packet
>and
>begin a new period.

[RP] Agree.

>
>What do you think?
>
>Jose
>