[p2p-hackers] UDP file transfer link speed identification

[Paul Campbell]

On Sat, Jul 23, 2005 at 11:27:02PM -0700, Michael Parker wrote:
> David,
> 
> Because TCP data can take different paths between a single source and 
> destination, TCP packets may arrive out-of-order at the destination. Now 
> TCP usually maintains a timer for each packet sent (usually set to the 
> RTO); if it has not received an ACK for that packet's sequence number by 
> the time this timer expires, it retransmits the packet. But in reality, 
> this is naive, and causes too long a delay for lost packets. Say the 

Fortunately, out-of-order conditions are so exceedingly rare that more
recent protocols are essentially assuming that they don't happen. The amount
of losses/overhead incurred by NOT assuming out-of-order=packet loss is less
than 1%. I would have to dig up the report on this to show it, but the
empirical information is out there. So under that scenario, any time that
you are missing an ACK (out of order or not), it's a loss.