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 |
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.