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THINK  Cyclades

A Technical History of the CYCLADES -
A Technical Tour

 

Application Layer:

The Application Layer instantiates the End to End protocols for the Cyclades Network. Two examples of these End to End Protocols are the Virtual Terminal Protocol and the File Transfer Protocol which are described below.  

Virtual Terminal Protocol:

The Virtual Terminal Protocol is a set of conventions which define a logical model for each class of terminals (called a Virtual Terminal) and a specification about how to drive this virtual terminal. A Virtual Terminal is a logical model in the sense that it defines an abstract model of a terminal in terms of logical functions that different real terminals can interpret.

The virtual terminal layer  resides on top of the transport box. It provides additional functions required for terminal oriented  communications, for example between a human user at a terminal and an application program in the host computer. Virtual terminals have several implementations: an intelligent terminal which directly handles the virtual terminal protocol; a terminal with the additional logic in a concentrator required to handle the VTP; or an access method providing application programs in a host with some kind of virtual terminal access method. 

Figure:  Virtual Terminal Layer [Pouzin 1982]

The virtual terminal protocol covers several classes of terminals with different functional capabilities corresponding to different classes of applications:

  1. Scroll-mode virtual terminal class - simple sequential terminals such as teleprinters, displays in scroll mode, card readers and punches, and line printers.

  2. Page-mode virtual terminal class - simple terminals which offer direct addressing within the pages.

  3. Data entry virtual terminal class - terminals with field and attribute capability

  4. Overlap class - terminals with elementary compatibility between classes

 

File Transfer Protocol

This entry is currently just a placeholder, in Chris's Cyclades Document's folder I found a reference to a Cyclades' File Transfer Protocol (not RFC-959 FTP). There should be more documentation about this protocol in the digital archive.

 

 


 
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Written by the THINK Protocols team, CS Dept, UT Austin
Please direct comments to Chris Edmondson-Yurkanan.

This document was last modified on Tuesday, 11-Jun-2002 10:17:59 CDT.