Basics of network communication

This section looks at network communication from a very high level and defines some terms used throughout the information. For more detailed information on z/OS® network communication and TCP/IP sockets, see z/OS Communications Server: IP Configuration Guide and z/OS Communications Server: IP Programmer's Guide and Reference. For more detailed information on IPv6 network communication and AF_INET6 sockets, see z/OS Communications Server: IPv6 Network and Appl Design Guide.

Network communication, or internetworking, defines a set of protocols (that is, rules and standards) that allow application programs to talk with each other without regard to the hardware and operating systems where they are run. Internetworking allows application programs to communicate independently of their physical network connections.

The internetworking technology called TCP/IP is named after its two main protocols: Transmission Control Protocol (TCP) and Internet Protocol (IP). To understand TCP/IP, you should be familiar with the following terms:

client: A process that requests services on the network.
server: A process that responds to a request for service from a client.
datagram: The basic unit of information, consisting of one or more data packets, which are passed across an Internet at the transport level.
packet: The unit or block of a data transaction between a computer and its network. A packet usually contains a network header, at least one high-level protocol header, and data blocks. Generally, the format of data blocks does not affect how packets are handled. Packets are the exchange medium used at the Internetwork layer to send data through the network.