Data terminal equipment and data transmission control method

A data transmission control method adapted to a data terminal equipment which uses a hierarchical protocol and has, as a transmission function on an information channel, a first transmission procedure in conformity to ISO standard ISO8208 and a second transmission procedure in conformity to CCITT recommendation T.70, the method comprising the steps of:

• receiving a procedure signal related to supplied from a calling terminal when an information channel related to said network layer is established, said procedure signal having a network layer header preceding procedure information on the network layer;
• extracting said network layer header from said received procedure signal;
• discriminating a transmission function on the information channel available in said calling terminal by referring to said extracted network layer header;
• and
• selecting one of said first and second transmission procedures from the discrimination result.

A data transmission control method adapted to a data terminal equipment which uses a hierarchical protocol and has, as a transmission function on an information channel, a first transmission procedure in conformity to ISO standard ISO8208 and a second transmission procedure in conformity to CCITT recommendation T.70, wherein said data terminal equipment further has a memory which registers information on a transmission function available in each of other terminals, the method comprising the steps of:

• determining whether information on a destination terminal with which said data terminal equipment serving as a calling terminal wants to communicate has been registered in said memory;
• reading out said information related to said destination terminal stored in said memory when it is found that information on said destination terminal has been registered;
• determining whether said read-out information shows the first transmission procedure in conformity to the ISO standard ISO8208 or the second transmission procedure in conformity to the CCITT recommendation T.70;
• selecting one of said first and second transmission procedures so as to coincide with that of the destination terminal on the basis of the determined result;
• and
• setting up a call to said destination terminal on the basis of the selected one of the first and second transmission procedures.

A data terminal equipment which is coupled to an integrated services digital network through an access line and uses a hierarchical protocol in conformity to an OSI reference standard model, comprising:

• protocol control means for providing a plurality of protocols for a data link layer and a network layer of said hierarchical protocol;
• protocol storage means for storing information on a protocol which is related to each of said data link layer and said network layer and which is available in a second data terminal equipment with which said data terminal equipment wants to communicate;
• protocol learning means for discriminating a transmission procedure in said second data terminal equipment for each of said data link layer and said network layer by referring to a procedure signal transferred between said data terminal equipment and said second data terminal equipment at the time of setting up a call and for storing said discriminated transmission procedure in said protocol storage means;
• and
• protocol setting means for setting one of said plurality of protocols for at least each of said data link layer and said network layer in said protocol control means by referring to said information stored in said protocol storage means.