Transcript Welcome to CS 444/544!

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):
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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:
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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)
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Provide communication over large distances
Example
Advantages
Disadvantages
Local Area Networks (LANs)
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Only spans short distances
Examples
Advantages
Disadvantages
Ethernet
• A popular packet-switched LAN technology
invented at Xerox PARC in the 1970’s
• Components:
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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