For example, here is an IPv6 address:
2001:DB8::2F3B:2AA:FF:FE28:9C5A
TCP
The Transmission Control Protocol operates at the Transport layer, which handles connections.
Its purpose is to assure the reliable delivery of information to a specific destination.
TCP is a connection-oriented service, in contrast with IP, which is connectionless.
TCP makes the connection with the final destination and maintains contact with the
destination to make sure that the information is correctly received. Once a connection is
established, though, TCP depends on IP to handle the actual transfer. And because IP is
connectionless, IP depends on TCP to assure delivery.
The sending and receiving TCPs (the protocols running in each machine) maintain
an ongoing, full-duplex (both can be talking at the same time) dialog throughout a transmission
to assure a reliable delivery. This begins with the sending TCP making sure that
the destination is ready to receive information. Once an affirmative answer is received,
the sending TCP packages a data message into a segment containing a header with control
information and the first part of the data. This is then sent to IP, and TCP creates the
remaining segments while watching for an acknowledgment that the segments have
been received. If an acknowledgment is not received for a particular segment, it is re-created
and handed off. This process continues until the final segment is sent and acknowledged,
at which point the sender tells the receiver that it??™s done.
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