17-09-2016, 01:05 PM
1455126066-tcpvariations.05f.ppt (Size: 7.24 MB / Downloads: 5)
What Are TCP Variations?
Implementations of TCP that use different algorithms to achieve end-to-end congestion control.
Tahoe
Reno
NewReno
Vegas
SACK
Rome
Paris
How Did TCP Cause Congestion? (Original Recipe TCP)
Poor Efficiency
In telnet-like applications, TCP sends 1 byte of data with 4000% overhead.
Sending too much, too soon
Unnecessary retransmits
Sending window too large
Very little change in behavior due to congestion
TCP Variation: TCP Tahoe
1st improvement was TCP Tahoe (1988)
Adjusts sending window as congestion increases or decreases (AIMD congestion avoidance & slow-start)
Improved retransmission policy (Fast Retransmit)
Nagle’s algorithm
Improved RTO calculation and back-off (Karn’s algorithm)
TCP Tahoe Window Control
TCP sender maintains two new variables:
cwnd – congestion window
cwnd is inferred from the level of congestion in the network.
ssthresh – slow-start threshold
ssthresh can be thought of as an estimate of the level below which congestion is not expected.
send_win = min (rwin, cwnd)