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TCP Fast Transmit and Recovery pdf
TCP Slow Start and Congestion Avoidance lower the data throughput
drastically when segment loss is detected. Fast Retransmit and Fast
Recovery have been designed to speed up the recovery of the connection,
without compromising its congestion avoidance characteristics. Fast
Retransmit and Recovery detect a segment loss via duplicate
acknowledgements. When a segment is lost, TCP at the receiver will keep
sending ack segments indicating the next expected sequence number. This
sequence number would correspond to the lost segment. If only one
segment is lost, TCP will keep generating acks for the following
segments. This will result in the transmitter getting duplicate acks
(i.e. acks with the same ack sequence number)
TCP Congestion Avoidance pdf
We have already seen that TCP connection starts up in slow start
mode, geometrically increasing the congestion window (cwnd) until it
crosses the slow start threshold (ssthresh). Once cwnd is greater that
ssthresh, TCP enters the congestion avoidance mode of operation. In this
mode, the primary objective is to maintain high throughput without
causing congestion. If TCP detects segment loss, it assumes that
congestion has been detected over the internet. As a corrective action,
TCP reduces its data flow rate by reducing cwnd. After reducing cwnd,
TCP goes back to slow start.
TCP Slow Start pdf
TCP is an end to end protocol which operates over the heterogeneous
Internet. TCP has no advance knowledge of the network characteristics,
thus it has to adjust its behavior according to the current state of the
network. TCP has built in support for congestion control. Congestion
control ensures that TCP does not pump data at a rate higher than what
the network can handle. In this sequence diagram we will analyse "Slow
start", an important part of the congestion control mechanisms built
right into TCP. As the name suggests, "Slow Start" starts slowly,
increasing its window size as it gains confidence about the networks
throughput.
TCP - Transmission Control Protocol pdf
TCP (Transmission Control Protocol) provides a reliable end to end
service that delivers packets over the Internet. Packets are delivered
in sequence without loss or duplication.
System Reliability and Availability
We have already discussed
reliability and availability basics in a previous article. This
article will focus on techniques for calculating system availability
from the availability information for its components. The following
topics are discussed:
- Calculating Availability in Series
- Calculating Availability in Parallel
- Calculating System Availability
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