Coded TCP

Masataka Ohta mohta at
Wed Oct 24 06:35:41 UTC 2012

(2012/10/24 12:29), Rodrick Brown wrote:
> "With coded TCP, blocks of packets are clumped together and then
> transformed into algebraic equations that describe the packets. If
> part of the message is lost, the receiver can solve the equation to
> derive the missing data.

Don't do that.

> MIT found that campus WiFi (2%
> packet loss) jumped from 1Mbps to 16Mbps. On a fast-moving train (5%
> packet loss), the connection speed jumped from 0.5Mbps to 13.5Mbps."

If everyone start using TCP with FEC to tolerate 20% of packet
loss with 30% FEC overhead, it will make congestion more severe
that more than 20% of packets will be dropped and effective speed
share of each TCP will be decreased by 30%.

The proper approach against lossy liks is to have link local
retransmissions or FEC.

							Masataka Ohta

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