General The concept of Profiles for OSI, and the structure of the International Standardized Profiles that document them, are defined in ISO/IEC TR 10000-1. Such Profiles are divided into a number of different classes and sub-classes. Two of these classes contain sub-classes comprising functions of the Virtual Terminal Basic Class Service and Protocol specified in the base standards ISO 9040 and ISO 9041. These are the Application Profiles (A-Profiles) and the Interchange Format and Representation Profiles (F-Profiles). The relationship between A-Profiles and F-Profiles is described in 7.3.2 of ISO/IEC TR 10000-1 and is as follows. Application Layer base standards require, implicitly or explicitly, the structure of information carried or referenced by them to be specified for each instance of communication. It is the purpose of F-Profiles to specify such information structures. Particular functional requirements may then be met by the combination of an A-Profile with one or more F-Profiles.
Establishment of a VT-association involves the selection by negotiation of a particular Virtual Terminal Environment profile (VTE-profile), and of particular values for any arguments of that VTE-profile. The VTE-profile specification, and possibly also the values of certain VTE-profile arguments, may in turn reference the definitions of VT control object types and assignment types. These VTE-profiles, control object types and assignment types are thus information structures that require explicit reference within the VT protocol. Particular instances of these structures are fully defined within the base standards, but the base standards also provide for further instances to be defined by registration. Each registered instance constitutes an F-Profile within the framework of ISO/IEC TR 10000. The Virtual Terminal Basic Class Service and Protocol may be used to realize a wide range of distinct functions. Particular functions may be realized through the selection of appropriate VT functional units, F-Profiles and other VTE-profile argument values. The specification of the selection required to realize a particular function and to promote interoperability constitutes a Virtual Terminal A-Profile within the framework of ISO/IEC TR 10000.
The three International Registers of VT information structures and the specifications of VT Application Profiles are each published as a separate multi-part ISP as follows:
- ISO/IEC ISP 11184 is the Register of VTE-profiles;
- ISO/IEC ISP 11185 is the Register of control object type definitions;
- ISO/IEC ISP 11186 is the Register of assignment-type definitions;
- ISO/IEC ISP 11187 contains the specifications of VT Application Profiles.
This part of ISO/IEC ISP 11185 contains the definition of control object types that are used for the transfer of TELNET signals and negotiation of TELNET options.
Position within the Taxonomy The taxonomy of International Standardized Profiles for OSI is laid down in ISO/IEC TR 10000-2:1994. Within the classification scheme of this taxonomy, the OSI Profiles specified in this International Standardized Profile are in the Virtual Terminal Registered Object sub-class of the class of Interchange Format and Representation Profiles. A Profile within this subclass has a Profile identifier of the form FVTabc, where abc is a structured numerical identifier that identifies the position of the Profile within each of the three levels of subdivision of the subclass. The values of a and b are single digits but c is an integer that is not necessarily a single digit. In principle the ISO Virtual Terminal model allows for multiple classes of operation, although at the time of publication of this International Standardized Profile only the Basic Class has been defined.
The value of the identifier component a distinguishes between distinct types of information object as follows:
a = 1 for Basic Class VTE-profiles;
a = 2 for Basic Class Control Objects;
a = 3 for Basic Class Assignment Types.
Values of a greater than 3 are reserved for future developments. This International Standardized Profile ISO/IEC ISP 11185 contains the specifications of the Profiles with identifiers of the form FVT2bc.
For this form of identifier, the component b distinguishes between the five major classifications of Basic Class Control Objects as follows:
b = 1 for Miscellaneous Control Objects;
b = 2 for Field Entry Instruction Control Objects;
b = 3 for Field Entry Pilot Control Objects;
b = 4 for Reference Information Objects;
b = 5 for Termination Conditions Control Objects.
Each of these classifications corresponds to a sub-register under the procedures of ISO/IEC 9834-5. Values of b greater than 5 are reserved for new classifications of Basic Class Control Objects that may be defined in future amendments to ISO 9040. The identifier component c is the serial number of the control object type in the appropriate sub-register. This part of ISO/IEC ISP 11185 contains the definitions of the Miscellaneous Control Object types with the Profile identifiers:
FVT2116 Generalized Telnet Synch Control Object;
FVT2117 Generalized Telnet Signal Control Object;
FVT2118 Generalized Telnet Negotiation Control Object;
FVT2119 Generalized Telnet Subnegotiation Control Object.