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Welcome to Networks and Network Security! Brett Tjaden 216 ISAT/CS Building Department of Computer Science James Madison University Harrisonburg, VA 22807 Email: [email protected] Phone: 540-568-2771 Webpage: https://users.cs.jmu.edu/tjadenbc/Web 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) 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 Internet Services • Many popular and widespread applicationlevel Internet services (used by users): – – – – – World Wide Web Electronic mail File transfer Remote login Etc. 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 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 Internetworking – How It Works Protocol Layering Sender Receiver Layer N Layer N ... ... Layer 2 Layer 1 Layer 2 Layer 1 Physical Network 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) Circuit-Switched Networks • Forms a dedicated connection (circuit) between the two endpoints • Examples • Advantages • Disadvantages Packet-Switched Network • Data is divided into packets and each packet is routed through the network separately • Examples • Advantages • Disadvantages Wide Area Networks (WANs) • • • • Provide communication over large distances Example Advantages Disadvantages Local Area Networks (LANs) • • • • Only spans short distances Examples Advantages Disadvantages 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 Ethernet (cont) Ethernet (cont) • Advantages • Disadvantages Thinnet • A thinner, less expensive, and more flexible alternative to Ethernet • Components: – The ether – Computers with transceivers and host interface built in Thinnet (cont) Twisted Pair • Very thin, very cheap, very flexible alternative to Ethernet and Thinnet • Components: – A hub – Computers with host interface built in Twisted Pair (cont) 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