Welcome to Networking and 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

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 application-level 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

Physical Network

Layer 1

Layer 2

Layer N

Layer 1

Layer 2

Layer N

. . .. . .

Sender Receiver

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