【国外标准】 Standard Guide for Digital Communication Protocols for Computerized Systems

4.1 This guide is intended to provide an understanding of the wide range of communication protocols standards, allowing the user to understand better their applicability to shipboard networks and marine platform computerized systems. For computerized networks and systems, communication protocols are necessary for integrating various system devices, providing functionality between dissimilar subnetworks, or for enabling remote connections, either pier side or through geophysical communication technologies.4.2 The wide variety and scope of digital communication protocol standards adds greatly to the complex decision process for specifying compatible protocols for system applications and related devices for the myriad of potential shipboard systems. However, the user must identify the initial networking requirements, so once the network protocols under evaluation are well understood, the decision process should determine the appropriate network protocols. Therefore, this guide is intended to reduce the complexity involved with protocol selection and implementation.4.3 Network protocols define an agreed, quantifiable entity, or set of rules, by which user computers, system networks, and internetworking devices communicate and exchange information. Communication protocols specify essential networking guidelines, such as physical interface connections, or data format and control operations between two communicating computers. Ship and marine digital communication protocol requirements are no different than their land-based networked counterparts. Both require standardized protocol selection, in various protocol categories, including LAN standards, WAN protocols, LAN/WAN protocols, network management, wiring hub configurations/operations, hardware platforms, operating systems, and network applications.1.1 The principal content of this guide provides a road map to implement a communication network applicable to ship and marine computer systems by:1.1.1 Examining the relationship of digital communication protocols as a network technological infrastructure,1.1.2 Outlining the basic building blocks of network topologies and transmission techniques associated with the implementation of transmission media in a network environment; and,1.1.3 Identifying operating system and environments.1.2 Using the Open System Interconnection (OSI) model, which provides a layered approach to network functionality and evaluation, common network communications protocols are identified and characterized in this guide according to lower and upper layer protocols corresponding to their degree and type of functionality.1.3 Although it is desirable that network users, designers, and administrators recognize and understand every possible networking protocol, it is not possible to know the intimate details of every protocol specification. Accordingly, this guide is not intended to address fully every hardware and software protocol ever developed for commercial use, which spans a period of about 25 years. Instead, the user of this guide will be introduced to a brief overview of the majority of past and present protocols which may comprise a ship or marine internetwork, to include Local Area Networks (LANs), Wide Area Networks (WANs), and related hardware and software that provide such network interoperability and data transfer.1.4 While this guide provides an understanding of the wide range of communication protocols, the user is recommended to consult the reference material for acquiring a more comprehensive understanding of individual communication protocols. However, by examining the basic functions of protocols and reviewing the protocol characterization criteria identified in this guide, the user will be more apt to understanding other protocols not mentioned or addressed herein.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.