User`s guide

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TCP/IP Network Basics
TCP/IP Protocols
Example: Using ping for Echo Request
For example, you could use the Ping utility to send ICMP echo request
packets to the destination host and request the destination host return these
packets. If the packets are returned, you can assume the connection is
good. If the packets are not returned, a connectivity problem exists. This
figure shows an example return from pinging a computer at IP address
156.140.72.1.
The Transport Layer
The Transport Layer of the TCP/IP model contains the protocols responsible
for addressing and routing of packets. The Transport Layer determines if the
sender and receiver will establish a connection before communicating and
how often acknowledgements of the connection are sent. The protocols at
the Transport Layer deliver data to and receive data from the Transport
Layer protocols of other hosts. Hosts can be on the same local network or on
a remote network. The Transport Layer has two protocols:
! Transmission Control Protocol (TCP)
! User Datagram Protocol (UDP)
Transmission
Control Protocol
(TCP)
Transmission Control Protocol (TCP) is the protocol that connects the
sending host and the receiving host to each other. TCP provides the
connection as packets are moved between hosts having the conversation.
Every packet has a TCP header that includes
sequence numbers,
acknowledgement numbers, address information, and other information.
If packets get out of order enroute from the source to the destination, the
sequence number allows the packets to be reassembled in the correct order.