TCP/IP protocols
TCP/IP is a family of communication protocols used to connect computer systems in a network. It is named after two of the protocols in the family: Transmission Control Protocol (TCP) and Internet Protocol (IP). Hypertext Transfer Protocol (HTTP) is a member of the TCP/IP family.
The protocols in the TCP/IP family correspond, in many cases, to the layers of the Open Systems Interconnection (OSI) model. Table 1 shows HTTP and the underlying layers of the TCP/IP family in terms of the OSI model. The Systems Network Architecture (SNA) layers, which approximately match the OSI layers, are also shown.
| Layer | OSI | SNA | TCP/IP |
|---|---|---|---|
| 7 | Application | Application | HTTP |
| 6 | Presentation | Presentation | (empty) |
| 5 | Session | Data flow | (empty) |
| 4 | Transport | Transmission | TCP |
| 3 | Network | Path control | IP |
| 2 | Data link | Data link | Subnetwork |
| 1 | Physical | Physical | Subnetwork |
- Internet Protocol (IP)
- IP is a network-layer protocol that provides a connectionless data transmission service that is used by TCP. Data is transmitted link by link; an end-to-end connection is never set up during the call. The unit of data transmission is the datagram.
- Transmission Control Protocol (TCP)
- TCP is a transport-layer protocol that provides a reliable, full duplex, connection-oriented data transmission service. Most Internet applications use TCP.
- Hypertext Transfer Protocol (HTTP)
- HTTP is an application-layer protocol that is used for distributed, collaborative, hypermedia information systems. HTTP is the protocol used between web clients and web servers.
Many TCP/IP implementations provide an application programming interface to the TCP protocol; that is, to the transport layer. This interface is commonly known as the Sockets interface. The TCP/IP Sockets interface for CICS is the z/OS® Communications Server IP CICS Sockets interface. It is supplied with z/OS Communications Server and is an integral part of z/OS. It is not part of CICS web support and does not use the CICS SO domain. z/OS Communications Server: IP CICS Sockets Guide, SC31-8807, describes the CICS Sockets interface.