Network standards Layered Architectures Chapter 2 Updated january 2009 XU Zhengchuan Fudan University
Network Standards Layered Architectures Chapter 2 Updated January 2009 XU Zhengchuan Fudan University
Message Standards (Protocols)
1. Message Standards (Protocols)
Figure 2-1: Standards Govern the Exchange of Messages Standards Rules of operation that allow two hardware or software processes to work together Even if they are from different vendors Standards govern the exchange of messages Messages must be governed by strict rules Because computers are not intelligent Message
2-3 Figure 2-1: Standards Govern the Exchange of Messages • Standards – Rules of operation that allow two hardware or software processes to work together – Even if they are from different vendors • Standards Govern the Exchange of Messages – Messages must be governed by strict rules – Because computers are not intelligent Message
Figure 2-1: Standards Govern the Exchange of Messages(Continued Standards govern Syntax Syntax the organization of the message Human example: Susan thanked Tom This sentence has a subject-verb-object syntax Standards Govern Semantics Semantics: The meaning of the message Human example:“ Susan thanked tom” Humans understand the meaning of this easily
2-4 Figure 2-1: Standards Govern the Exchange of Messages (Continued) • Standards Govern Syntax – Syntax: the organization of the message – Human example: “Susan thanked Tom” – This sentence has a subject-verb-object syntax • Standards Govern Semantics – Semantics: The meaning of the message – Human example: “Susan thanked Tom” – Humans understand the meaning of this easily
FIgure2-2:HypertextTransferProtocol(http) Interactions Http Request Message Asking for a File Browser Webserver Application。 Client Pc Webserver Http Response mEssage delivering the File or gIvIng an error message Semantics in Http Which governs the Web 2-5
2-5 Figure 2-2: Hypertext Transfer Protocol (HTTP) Interactions Client PC Webserver Browser Webserver Application 1. HTTP Request Message Asking for a File 2. HTTP Response Message delivering the File or giving an error message Semantics in HTTP, which governs the Web