CICS® Web
support now supports HTTP/1.1.
Releases of CICS before CICS Transaction Server for z/OS®, Version 3 Release 1 supported
HTTP/1.0. CICS Web
support is now enhanced to handle and provide features of the HTTP/1.1 specification,
including chunked transfer-coding, pipelining, and persistent connections.
CICS Web
support is conditionally compliant with the HTTP/1.1 specification, as described
in the Internet Society and IETF (Internet Engineering Task Force) Request
for Comments document RFC 2616, Hypertext Transfer Protocol - HTTP/1.1
(http://www.ietf.org/rfc/rfc2616.txt).
Conditional compliance with the HTTP/1.1 specification means that CICS satisfies
all the "MUST" level requirements, but not all the "SHOULD" level requirements,
that are detailed in the HTTP/1.1 specification, where these requirements
are relevant to the functions actually provided by CICS itself. An implementation that satisfies
all the MUST or REQUIRED level and all the SHOULD level requirements for its
protocols is said to be unconditionally compliant. An implementation is not
compliant if it fails to satisfy one or more of the MUST or REQUIRED level
requirements for the protocols it implements.
There are three aspects to CICS Web support compliance with the HTTP/1.1
specification.
- CICS Web
support performs actions that are required from an HTTP server. For example, CICS Web
support receives inbound requests, maintains persistent connections, writes
certain HTTP headers, and transmits responses. The behavior of CICS Web support
during these actions is conditionally compliant with the HTTP/1.1 specification.
Where necessary, this represents a change in behavior from earlier releases
of CICS. CICS Web support behavior in compliance with HTTP/1.1 describes
how the behavior of CICS Web support complies with HTTP/1.1, and where this
differs from releases of CICS before CICS Transaction Server for z/OS, Version 3 Release 1.
- Some parts of the HTTP/1.1 specification are not relevant to CICS Web support.
For example, CICS Web
support does not act as a proxy server or provide a caching facility. HTTP functions not supported by CICS Web support notes these areas,
so that you know the areas in which HTTP/1.1 compliance is not a concern for CICS Web
support and for your user application program.
- Web-aware user application programs in CICS can be used to create application-generated
HTTP responses and instruct CICS Web support how to serve the responses. If you
want your CICS Web
support implementation to be compliant with the HTTP protocol specifications,
in particular HTTP/1.1, your user application programs share the responsibility
for compliance in the actions that they perform. Some basic guidance information
is provided in this documentation, but it is important to check the HTTP specification
to which you are working for more detailed information. Writing Web-aware application programs for CICS as an HTTP server describes the
process for writing a user application program for CICS Web support.
In practical terms,
the different levels of requirement in the HTTP/1.1 specification (MUST, SHOULD,
or MAY) should be handled by your application program as follows:
- MUST level requirements must be implemented to maintain compliance. CICS Web
support is designed to handle, or to assist you to comply with, all the MUST
level requirements that apply to straightforward activities. Some additional
MUST level requirements might apply if you choose to fulfil an optional requirement
that CICS Web
support does not already handle. Also, some MUST level requirements relate
to actions that your application must not perform in certain circumstances.
- SHOULD level requirements are not necessary for conditional compliance
with the HTTP specifications. CICS does not comply with all the SHOULD
level requirements in the HTTP/1.1 specification. However, if your application
can comply with a SHOULD level requirement without inconvenience, it is advisable
to do so.
- MAY actions are optional for any HTTP implementation, whatever its level
of compliance. They should be treated as suggestions or recommendations.