Thursday, March 17, 2011

Transmission Control Protocol (TCP)

The TCP provides reliable transmission of data in an IP environment. TCP corresponds to the
transport layer (Layer 4) of the OSI reference model. Among the services TCP provides are stream
data transfer, reliability, efficient flow control, full-duplex operation, and multiplexing.
With stream data transfer , TCP delivers an unstructured stream of bytes identified by sequence
numbers. This service benefits applications because they do not have to chop data into blocks before
handing it off to TCP. Instead, TCP groups bytes into segments and passes them to IP for delivery
TCP offers reliability by providing connection-oriented, end-to-end reliable packet delivery through
an internetwork. It does this by sequencing bytes with a forwarding acknowledgment number that
indicates to the destination the next byte the source expects to receive. Bytes not acknowledged
within a specified time period are retransmitted. The reliability mechanism of TCP allows devices
to deal with lost, delayed, duplicate, or misread packets. A time-out mechanism allows devices to
detect lost packets and request retransmission.
TCP offers efficient flow control, which means that, when sending acknowledgments back to the
source, the receiving TCP process indicates the highest sequence number it can receive without
overflowing its internal buffers.
Full-duplex operation means that TCP processes can both send and receive at the same time.
Finally, TCP’s multiplexing means that numerous simultaneous upper-layer conversations can be
multiplexed over a single connection.

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