Henning,

I agree.  My recollection is that TSV wasn't too fond of this idea the
last time it came up at an area meeting, so I wouldn't expect it to
happen quickly, but maybe I'm wrong.  Would certainly be an easy
drop-in if it were available.

Bruce


On Mon, Mar 16, 2009 at 5:32 PM, Henning Schulzrinne
<[email protected]> wrote:
> Another related option: Use TCP-tunneled-over-UDP for those cases where
> "native" TCP fails. There are plenty of UDP tunneling protocols around to
> choose from, so the amount of stuff to be invented or standardized may be
> relatively small.
>
> On Mar 16, 2009, at 3:36 PM, Salman Abdul Baset wrote:
>
>> I have tried to summarize the solution space for addressing fragmentation,
>> congestion control and reliability issues when using an unreliable
>> transport. This includes the proposal by Bruce. I think that the WG needs to
>> contrast their complexity with the use of a reliable transport (TCP), and
>> consider whether to specify these mechanisms in a separate document or the
>> base document.
>>
>>
>>
>> Fragmentation
>> -------------
>>
>> *Hop-by-hop fragmentation, hop-by-hop complete reassembly
>>
>> *Hop-by-hop fragmentation and end-to-end reassembly
>>  -When RELOAD header exceeds MTU --> do IP fragmentation
>>  -When RELOAD header does not exceed MTU --> do RELOAD fragmentation
>>
>>
>> Congestion control and hop-by-hop reliability of a message fragment
>> ------------------
>>
>> *Stop-and-wait
>> -send a packet and wait for a response before transmitting next packet.
>> -retransmit lost packets at RTO.
>> -introduce gap of 10ms btw packet transmissions.
>>
>> *AIMD-like
>> -transmit packets as permitted by a congestion window.
>> -No slow start, fast retransmit, or recovery.
>> -always in congestion avoidance, at every loss, reduce window by half.
>> -retransmit at RTO if permitted by congestion window.
>>
>> *TFRC
>> -TFRC for congestion control
>> -retransmission at RTO intervals
>> -needs careful consideration whether TFRC can be implemented using
>>  existing message parameters.
>>
>> (The above methods require RTO estimation with some caveats. See Bruce's
>> email:
>> http://www.ietf.org/mail-archive/web/p2psip/current/msg04697.html)
>>
>> *Use TCP
>> -use TCP if expecting fragmentation, otherwise use UDP
>> -issue: TCP may not work behind some NATs for setting up
>>  direct connections, however:
>>  --UDP may also be blocked by firewalls--
>>  --and nodes behind restrictive NATs can act as clients.
>>
>>
>> -salman
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