Welcome to Networks and Network Security!

1. Welcome to Networks and Network Security! Brett Tjaden 216 ISAT/CS Building Department of Computer Science James Madison University Harrisonburg, VA 22807 Email: tjadenbc@jmu.edu Phone: 540-568-2771 Webpage: https://users.cs.jmu.edu/tjadenbc/Web

2. Introduction • “[Internetworking] has become a fundamental part of life.” • Internetworking is two things: • Idea: Many heterogeneous networks can be interconnected to function as a coordinated unit • Implementation: A set of open communication conventions (or protocols) have been developed (i.e. TCP/IP)

3. Network Protocols • Protocol = syntactic and semantic rules for communication • Open = protocol specifications are publicly available • Anyone can implement them • Run on lots of different operating systems • Designed to accommodate: • Lots of different networking technologies • Lots of different applications

4. Internet Services • Many popular and widespread application-level Internet services (used by users): • World Wide Web • Electronic mail • File transfer • Remote login • Etc.

5. Internet Services (cont) • The Internet’s primary network-level services (used by network programmers): • Connectionless packet delivery • Break messages up into small chunks (called packets) • Route each packet separately through the network • Reassemble message when all packets reach destination • Reliable stream transport • Handle problems that can occur such as: • Lost or corrupted packets • Other network errors

6. Distinguishing Features of TCP/IP • Many vendors offer proprietary network technologies that offer: • Connectionless packet delivery service • Reliable stream transport service • TCP/IP also offers: • Network technology independence • Universal interconnection • End-to-end acknowledgements • Application protocol standards

7. Internetworking – How It Works

8. Protocol Layering Sender Receiver Layer N Layer N . . . . . . Layer 2 Layer 2 Layer 1 Layer 1 Physical Network

9. Physical Networks • An internetwork is typically comprised of many physical networks over which data travels • There are many different types of physical networks: • Circuit-switched vs. packet-switched networks • Local Area Networks (LAN) vs. Wide Area Networks (WAN)

10. Circuit-Switched Networks • Forms a dedicated connection (circuit) between the two endpoints • Examples • Advantages • Disadvantages

11. Packet-Switched Network • Data is divided into packets and each packet is routed through the network separately • Examples • Advantages • Disadvantages

12. Wide Area Networks (WANs) • Provide communication over large distances • Example • Advantages • Disadvantages

13. Local Area Networks (LANs) • Only spans short distances • Examples • Advantages • Disadvantages

14. Ethernet • A popular packet-switched LAN technology invented at Xerox PARC in the 1970’s • Components: • The ether • Transceivers • Attachment Unit Interface (AUI) cable • Host Interface

15. Ethernet (cont)

16. Ethernet (cont) • Advantages • Disadvantages

17. Thinnet • A thinner, less expensive, and more flexible alternative to Ethernet • Components: • The ether • Computers with transceivers and host interface built in

18. Thinnet (cont)

19. Twisted Pair • Very thin, very cheap, very flexible alternative to Ethernet and Thinnet • Components: • A hub • Computers with host interface built in

20. Twisted Pair (cont)

21. Summary • Internetworking enables many heterogeneous networks can be interconnected to function as a coordinated whole • An internetwork is typically comprised of many physical networks over which data travels • A popular physical network technology is Ethernet