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CTC 228 – Computer Networks
Fall 2015Instructor: Robert Spengler
OSI Model
Picture Credit: blog.butchevans.com
Picture Credit: ieee.org
Chapter 1: The Fundamentals
● Network components– Computer with Network Interface Card (NIC)– Network Medium– Interconnecting Device (maybe)
Chapter 1: IP and MAC address
● IP address is a logical address● MAC address is a physical address● Commonly used tools:
– ipconfig– ping– arp -a
Chap 1: LAN, WAN, PAN...
● Local Area Network● Wide Area Network● Personal Area Network● Internetwork● Metropolitan Area Network● Wireless Local Area Network
Chap 1: Encapsulation
Chap 1: Clients and Servers
● Client is accessing resources● Server is providing resources● This is not always a clear distinction
Group Work
Case Project 1-2● Page 59● Bonus questions:
– 1. Why would you use the 'ping' command? – 2.Why would you use the 'ipconfig' command?– 3. Is it possible that your network settings could be
correct but the ping command could report an error? If yes, how? If no, why not?
Chapter 2
● Repeaters● Hubs● Switches● Wireless Access Point ● Routers (will be discussed later)
Chap 2: Connecting to the LAN
● Need a NIC if you're plugging in● Need a Wireless NIC if you're going to WiFi in● These are frequently built-in.
Chap 2: Routers● Used to interconnect LANs to each other● May directly connect or connect through
intermediate routers
Chap 2: A Hub
Chap 2: A Switch
Chap 2: Old Wireless Access Point
Chap 2: So what is this thing?
Chap 2: But what about the back?
Chap 2: Tables and Gateways
● Hosts use a Default Gateway to get out ● Switches do their magic with MAC tables● Routers do their magic with Routing tables
● These entries can be STATIC or DYNAMIC– Special route: Default Route
Chap 2 Group Project
● Project 2-8 ● Page 99● Bonus Questions: A computer has a standard
NIC and a USB wireless adapter that are both connected to the same network.– 1. How many MAC addresses will it have? Why?– 2. How many IP address will it have? Why?
● Turn in before you leave.
Chapter 3
Topologies and CablesEthernetWifiInternet Access
Chapter 3
● Topologies– Bus, Physical Star, Ring, Point-to-Point, Mesh
● Cables– UTP, Fiber Optic, Coaxial
Chap 3: Unshielded Twisted Pair
Chap 3: Coax
Chap 3: Fiber Optic
Multimode vs Single-Mode
Chapter 3
Topologies and CablesEthernetWifiInternet Access
Chap 3: Ethernet
● Invented in the 1970s but has been updated● Uses Carrier Sense Multiple Access with
Collision Detection (CSMA/CD)● Uses Media Access Control (MAC) addresses
– 12 Hexadecimal digits● One Ethernet protocol data unit is called a
frame– Contains source and destination MAC addresses
Chap 3: Ethernet Frame
Chap 3: About Collisions and Errors
● If two devices in the same collision domain send frames at the same time, a collision might occur.– Unlikely with switches but common with hubs.
● Frames could get mangled on the wire, but since Ethernet is best effort, there is no acknowledgment or verification from receiver.– Errors are detected with a Cyclic Redundancy
Check (CRC) added to the end of a frame.
Chapter 3
Topologies and CablesEthernetWifiInternet Access
Chap 3: WiFi
● Two modes: infrastructure and ad-hoc● Uses Carrier Sense Multiple Access Collision
with Avoidance (CSMA/CA)● Different standards and speeds:
– 802.11a 54Mbps but poor reception– 802.11b/g/n 11/54/600Mbps and better reception – 802.11ac up to 6.7 Gbps
Chap 3: Wifi Standards
Chap 3: Wifi Channels
Chap 3: WiFi Security
● Traffic can be intercepted relatively easily● Encryption protocols
– Wired Equivalent Privacy (WEP)– Wi-Fi Protected Access (WPA)– WPA2
Chapter 3
Topologies and CablesEthernetWifiInternet Access
Chap 3: Internet Access Technology
● Cable Modem● Dial-up● DSL● Satellite ● Ethernet
Chap 3 Group Project
● EMAIL TO RSPENGLER@CSUDH.EDU● Case Project 3-1● Page 159● Bonus Question: If five users are
simultaneously participating in a Wi-Fi network operating in ad-hoc mode, what is the network topology? Why?
Chapter 4
● PVC is used as the jacket of UTP cables and is toxic when it burns
● UTP Cable types– CM, CMR (Riser), CMP (Plenum)– Also called Cat-5, Cat-5e, Cat-6
Chap 4: RJ45
Chap 4: Terms
● Crossover vs Straight-Through (patch)● Horizontal wiring vs Vertical wiring● Entrance facility and “point of demarcation”
Chap 4: Fiber Optic
● Tons of connector types● Termination is a little difficult● Can go great distances with great speed● Multi mode and Single Mode
Chap 5: Protocol Stacks
● TCP/IP Stack actually has a lot more stuff than just TCP and IP.
Chap 5: In depth with the layers
Chap 5: IP address
Two forms: IPv4 and IPv6
Going into detail on IPv4
Subnet Masks
Classful and Classless
Chap 5: IPv4 Packet
Chap 5: Transport Layer
Transmission Control Protocol
Reliable and connection-oriented
User Datagram Protocol
Unreliable and connectionless
Both work with segments, use source and destination ports, and use checksums
Chap 5: TCP and UDP
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