第一章 Introduction And Overview
1The Telnet protocol provides incredible flexibility because it only defines interactive communication and not the details of the service accessed. Telnet can be used as the communication mechanism for many interactive services besides remote login.
2 Provideing concurrent access to application services is important and difficult; many chapters of this text explain and discuss concurrent implementations of application protocol software
第二章The Client Server Model And Software Design
1 Because TCP/IP does not provide any mechanism that automatically create running programs when a message arrives, a program must be waiting to accept communication before any requests arrive.
2 Servers must contain code that handles the issues of :
authentication-verifying the identity of the cient
Authorization- determining whether a giben client is permitted to access the servive the server supplies.
Data security- guaranteeing that the data is not unintentionally revealed or compromised
privacy- keeping information about an individual from unauthorized access
Protection - guaranteering that network applicaion cannot abuse sysytem resourses.
3 When designing client applicaion software, include parameters that allow the user to fully specify the destination machine and destination protocol port number.
4 When designing client-server applicaitons,beginners arestrongly advised to use RCP because it provides reliable, connection-oriented communication. Programs only use UDP if the applicaion protocol handles reliability, the application requires hardware breadcast or multicast, or the application cannot tolerate virtual circuit overhead.
5In an ideal world, where networks deliver all messages reliably and computers nerver crash, having a server maintain a small amount of state information for each ongoing interaction can make messages smaller and processing simpler.
6 In a real internet, where machines crash and reboot, and messages can be lost, delayed, duplicated, or delivered out of order, stateful designlead to complex application protocols that are difficult to design,understand, and program correctly.