Summary
In this chapter, you learned about reliable and unreliable network services, connectionless and connection-oriented services, and frame formats for various LAN and WAN protocols/technologies. LAN and WAN protocol frame formats have been laid out in some detail. The work you do for the remainder of this course, with the exception of SDLC and ATM, will allow you to hone your expertise in using the information learned in this chapter to troubleshoot networks. At this point you should have a solid foundation in the general theory of network protocols. The remainder of this curriculum will focus on building troubleshooting expertise one technology at a time. 

It's interesting to speculate where the various LAN and WAN technologies explored in this chapter will be in 10 years - it may be that Terabit Ethernet, SONET/SDH, and DWDM will be the primary technologies at that time. However, for now Frame Relay, ATM, ISDN, DSL, SNA/SDLC, PPP, Ethernet, and Token Ring are the predominant WAN and LAN technologies of the day. What can be expected is that a much greater percentage of the world population will be connected to the Internet and that rich Web-based multimedia applications will become even more commonplace, realistic, and reliable.