Tcp - Novell NETWARE 6-DOCUMENTATION Manual

Figure 3 A UDP datagram encapsulated in an IP datagram which, in turn, is encapsulated in an Ethernet
frame
Header
Frame
Header

TCP

Source
Port
IP
Ethernet Frame
In this example, the IP address transmits the IP datagram to the node. At that
destination, the IP software extracts the UDP datagram and delivers it to the
UDP-layer software. The UDP-layer software delivers the UDP data through
the destination port to the receiving application. The process at that port uses
the data in the UDP datagram. The UDP datagram also contains a source port
to ensure that the destination process can reply correctly.
For applications that must send or receive large volumes of data, unreliable
datagram delivery can become burdensome. Application programmers might
have to develop extensive error handling and status information modules to
track the progress and state of data transfer for every application. The TCP/IP
suite of protocols avoids this problem by using TCP, a reliable byte-stream
delivery protocol. TCP establishes a connection between two applications and
sends a stream of bytes to a destination in exactly the same order that they left
the source. Before transmission begins, the applications at both ends of
transmission obtain a TCP port from their respective operating systems. These
are analogous to the ports used by UDP. The application initiating the transfer,
known as the client side, generally obtains a port dynamically. The application
UDP
Header
Destination
Port
UDP Datagram
IP Datagram
UDP
Data
UDP
Data
Ethernet
CRC
Understanding
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