University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 1984 Development of a file transfer protocol and associated programs for the Bridge CS/1 system Murali Veeramoney The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Veeramoney, Murali, "Development of a file transfer protocol and associated programs for the Bridge CS/1 system" (1984). Graduate Student Theses, Dissertations, & Professional Papers. 5531. https://scholarworks.umt.edu/etd/5531 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. COPYRIGHT ACT OF 1976 Th i s is a n unpublished m a n u s c r i p t in w h i c h c o p y r i g h t s u b ­ s i s t s . An y f u r t h e r r e p r i n t i n g o f its c o n t e n t s m u s t b e a p p r o v e d BY THE AUTHOR. Mansfield Library Un iversity of Montana Date : _____II Q R 4 _______ Development of a File Transfer Protocol and Associated Programs for the Bridge CS/1 System by Murali Veeramoney M.S., University of Bombay, 1983 Presented in partial fulfillment of the Requirements for the degree of Master of Science UNIVERSITY OF MONTANA 1984 Chairman, Board of Examiners Dean, Graduate School Date UMI Number: EP40995 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. OfeMWtation Pub) UMI EP40995 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under,Title 17, United States Code ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Veeramoney, Murali, M.S., August 10, 1984 Computer Science Development of a File Transfer Protocol and Associated Pro­ grams for Bridge Communications CS/1 System (112 pp.) Advisor: Dr. John R. Barr An important feature of computers connected to networks is the availability of standardized protocols for communicating across the network. The International Standard Organization proposes various protocols for different levels of communi­ cation and the File Transfer Protocol is one of them. With the decreasing cost of computer systems it is possible to dedicate a computer as a communications server in a network. Its sole responsibility is to provide its host with the capability of communication with any other host by hiding the details of the communication. In this project a File Transfer Protocol as specified by the International Stan­ dards Organization is developed on a communications server CS/1 system manufactured by Bridge Communications, Inc. The author's purpose for undertaking this project was to explore current network technology while making use of software engineering techniques. After a detailed analysis and specifications the parts of the system were identified. The system consists of a File Transfer Utility on the host (connected to the CS/1) that allows a user to request the services on the CS/1, a host to CS/1 interface on the host and a CS/1 to host interface on the CS/1 that drive the hardware between the host and the CS/1 and is responsible for a logical connection between the communicating process on the host and the CS/1, a host agent on the CS/1 which accesses the File Transfer services on behalf of the host, and finally the File Transfer service that is to be built on top of the existing Virtual Terminal Connection Service. The design of these parts is discussed, and a possible implementation outlined. TABLE OF CONTENTS A b s t r a c t .................. ii List of illustrations ..... v 1 Background ..... 1 1.1 Local Area Networks ............ 1 1.2 ISO Standards ........... 4 1.2.1 The OSI Reference Model ........... 5 1.3 The OSI File Transfer Protocol ............... 8 1.4 The OSI File Service ..................... 15 1.5 The Multi-Vendor Demonstration Protocol ........ 18 1.6 Communication Servers ............................. 18 2 The Bridge CS/1 System ................................ 20 2.1 Overview of the CS/1 ............................. 20 2.2 System Architecture .......... 21 2.3 CS/1 Facilities ............... 26 2.4 The Virtual Connection Service ............... 27 2.4.1 The Program Interface ......... 30 3 Project Formulation ............... 34 3.1 Project Background ................................. 34 3.2 Scope of the project .......................... 36 3.3 Software Engineering Techniques ......... 38 3.4 Analysis ........................ 39 3.5 Design ................... 40 3.6 Mode of development ................................ 41 4 The Analysis and specification of the system ....... 44 4.1 Analysis ............................................ 44 4.2 Specifications....... 50 4.2.1 Specification of the modules on the host ........................ 50 4.2.2 Specification of the Host to CS/1 protocol ................................... 51 4.2.3 Specification of the modules on the CS/1 ........................................................ 52 5 The Design of the system ............................. 54 5.1 Structure of the file transfer system ........... 54 5.2 The Host to CS/1 protocol ....................... 56 5.2.1 Overview of the protocol .................... 58 5.2.2 Initial connection ........ 63 5.2.3 Transfer syntax ............................... 64 iii 5.2.4 Termination ..................................... 67 5.3 Design of the File Transfer Utility .............. 68 5.3.1 The user interface ...................... 69 5.3.2 The file transfer functions ................... 71 5.4 Design of the Host Agent .......................... 72 5.5 Design of the interfaces ..................... 77 5.5.1 Building the Transfer Identities ............. 82 5.5.2 Functions of the interface ............. 83 5.6 Design of the File Transfer Service ........... 85 5.6.1 Initialization ......... 85 5.6.2 Alternative structure for the file service ........................................................ 87 5.6.3 Program Interface ........... 90 5.6.4 Connection Establishment ...................... 90 6 Discussion ............................................. 96 6.1 Implementation............ 96 6.1.1 Structure of UNIX processes ......... 100 6.1.2 Unix system interfaces ................ 100 6.2 Conclusion ............. 106 References ................................................ Ill iv LIST OF ILLUSTRATIONS 1-1. OSI model for network architecture ........... 6 1-2. Relation between regimes and phases ........... 17 2-1. Basic Functional Modules of the CS/1 .......... 22 2-2. Hardware Architecture of the CS/1 ............. 24 2-3. Software Architecture of the CS/1 ............. 25 2-4. Virtual Terminal Connection Service .......... 29 2-5. Communication between Client and VT Process .. 30 2-6a. Initiator State Diagram - VT Connection ...... 32 2-6b. Responder State Diagram - VT Connection ...... 33 4-1. Host to Host connection using CS/1 ........... 47 4-2. Data flow diagram of the system ............... 49 5-1. Relationship of parts of the system ........... 57 5-2a. Initiator state diagram - Initial Host to CS/1 protocol ................... 59 5-2b. Responder state diagram - Initial Host to CS/1 protocol .................... 60 5-3. CRQ, DRQ and CCN packets ....................... 65 5-4. RRQ/WRQ p a c k e t ...... 65 5-5. DAT Packet ..................................... 65 5-6. ACK packet ....................................... 65 5-7. ERR packet ....................................... 65 5-8a. State diagram while receiving a file - initiator ...... 73 5-8b. State diagram while sending a file - initiator .................. 74 5-9a. State diagram while receiving a file - Responder ........................................... 78 5-9b. State diagram while sending a file - Responder ........................................... 79 5-10. Routing table for interfaces .......... 81 5-11. Building of transfer identities................ 86 5-12. Structure of the File Transfer Service ....... 88 5-13. Alternative for the File Transfer Service .... 89 5-14. Connection Establishment, Step One ........... 92 5-15. Connection Establishment, Step Two ............ 94 5-16. Connection Establishment, Step Three .......... 95 6-1. Simulated processes on UNIX ................... 99 6-2. Structure of File Transfer Client ............ 101 v Structure of the interfaces Structure of Host Agent server Chapter 1 Background 1.1. Local Area Networks The decrease in cost of computer systems and the economic benefits of sharing expensive peripheral dev­ ices are the primary causes of the growing interest in local area networks. Local area networks allow diverse computer systems, terminals and other peripherals to exchange information at high speeds over short dis­ tances, thus permitting a single printer, plotter, tape . drive, etc. to serve several computers. A local area network may span distances of up to three kilometers, but they are usually contained within