1. Hardware Concepts
Chapter 4

2. Contents Explain the different types of network topology
Describe the different types of network cabling
Describe and distinguish between the 802.2, 802.3, 802.5, and IEEE networking standards

3. Topology

4. Topology
A topology describes how computers connect to each other

5. Types of Topologies Bus Ring Star Mesh
All computers connect via a main line, called a bus cable
Ring
All computers attach to a central ring of cable
Star
All computers connect to a central wiring point, usually a hub
Mesh
Each computer has a dedicated line to every other computer
Exam Tip
Make sure you know your topologies.

6. Types of Topologies Tech Tip
A mesh topology is very robust but not practical
For just 10 computers, it would take 45 cables for every PC to connect to every other PC
With a wireless network radio waves are used instead of actual cables
A true mesh topology may be used

7. Network Technologies
A network technology is a practical application of a topology to get data from one computer or network to another
Ethernet
Token Ring
FDDI-(Fiber Distributed Data Interface) is a standard for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km
Tech Tip
Logical vs. Physical Topology
The physical topology describes how the cables are actually connected to the devices on the network
The logical topology describes how data actually flows in the network

8. Bus Topology
Ethernet was the first network technology that used the bus topology
Each computer on the network is connected to the single cable

9. Bus Topology
If there is a break in the cable, the entire network would stop functioning
It has no fault tolerance to survive a problem
Fault tolerance refers to a system’s capability to continue functioning even when some part of the system has failed. When bad things happen, a robust or fault tolerant system continues to operate, at least to some degree.

10. Star Topology
Each computer is connected to a central device such as a hub
If a cable breaks only the one computer is affected
A good way to separate logical from physical is to think about an electronic schematic. The schematic shows how everything connects, but does not represent the way the piece of electronics will actually physically appear.

11. Star Bus Topology A star bus topology is a hybrid topology
Uses a physical star topology
Uses a logical bus topology
Most common topology used today

12. Token Ring Topology Token ring uses a star ring topology
Uses a physical star topology
Uses a logical ring topology
Declining in popularity

13. Cabling

14. Coax
Coaxial cable (or coax) contains a central conductor wire, surrounded by an insulating material, which in turn is surrounded by a braided metal shield
The braided metal shield lessens electro-magnetic interference (EMI). EMI will corrupt the signal flowing through the cable causing interference. EMI is caused by things like lights, fans, copy machines, and refrigerators.

15. EMI
Electro-magnetic interference (EMI) is caused by lights, fans, copy machines, and other devices
EMI corrupts the signal flowing through the cable
The braided shield helps to reduce the effects of EMI

16. Types of Coax Cable
The Ohm rating is a measure of resistance in the cable and differentiates different types of coaxial cable
RG-8, RG-62, and RG-58 are used in computer networks
Exam Tip
Know the Ohm ratings.
Tech Tip
Ohm Rating and Why It Matters
The Ohm rating of a particular piece of cable describes the impedance of that cable. Impedance describes a set of characteristics of that define how much a cable resists the flow of electricity. It’s not simple resistance, though, but also factors in things like how long it takes the wire to get a full charge—the wire’s capacitance—and other things.
The most important aspect of Ohms ratings for network technicians is to use the same-rated cables within a network, otherwise you’ll run into data corruption and data loss.

17. RG-8 RG-8 cable is also called Thick Ethernet
Oldest type of coax still in use
Rated at 50 ohms
Yellow or orange/brown color

18. RG-62 RG-62 cable is never installed in networks today
Was used with ARCnet

19. RG-58
RG-58 is also called Thin Ethernet
Still in widespread use today

20. Twisted Pair
Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP) are the most common types of cabling used today
Composed of multiple pairs of wires twisted together to reduce interference from adjacent wires, called crosstalk

21. Shielded Twisted Pair (STP)
Twisted pairs of wires surrounded by shielding to protect them from EMI
Only used in older Token Ring networks

22. Unshielded Twisted Pair (UTP)
Most common type of cabling used in networks
Twisted pairs of wires surrounded by a plastic jacket
Inexpensive and flexible

23. CAT Ratings
Twisted pair cabling varies by things like the number of twists per foot
Cables are rated in categories or CAT ratings (or levels)
Tech Tip
Throughput and Bandwidth
UTP cables are rated to handle a certain bandwidth, such as 10 MHz or 100 MHz, which originally translated as the maximum throughput for a cable. On a one-for-one basis, for example, a 10 million cycle per second (10 MHz) cable could accommodate 10 million bits per second (10 Mbps)—1 bit per cycle. Through the use of bandwidth efficient encoding schemes, such as MLT-3, manufacturers can squeeze more bits into the same signal as long as the cable can handle it. Thus the CAT 5e cable can handle throughput of up to 1000 Mbps even though it’s rated to handle a bandwidth of only up to 100 MHz.

24. CAT Ratings CAT Rating Bandwidth Typical Throughput in Networks CAT 1
<1 MHz
Analog phone lines – not data
CAT 2
4 MHz
Speeds up to 4 Mbps
CAT 3
16 MHz
Speeds up to 16 Mbps
CAT 4
20 MHz
Speeds up to 20 Mbps
CAT 5
100 MHz
Speeds up to 100 Mbps
CAT 5e
Speeds up to 1000 Mbps
CAT 6
MHz
Speeds up to Mbps
Tech Tip
When network engineers talk about cable, they refer to them using terminology such as CAT-5 or CAT-6.
CAT 5e is an enhanced version of CAT 5 that supports higher speeds.

25. CAT Usage
Most new installations use CAT 5e cable since it is cheaper than CAT 6 cable
CAT level
CAT level

26. Fiber Optic
Fiber optic cabling transmits light rather than electricity
Immune to EMI
Very long distances
Consists of the fiber, cladding, and insulating jacket
Defined by fiber and cladding measurements
Most common is 62.5/125 µm
Fiber generally requires two cables
Note: The symbol µ stands for micro, or 1/1000th.

27. Light Sources Fiber optic cables use two possible light sources
Light Emitting Diodes (LEDs) – called multimode
Lasers – called single-mode
Supports faster speeds and longer lengths
Exam Tip
Concentrate on UTP—that’s where the hardest Network+ questions lie. Don’t forget to give STP and fiber a quick pass as well to understand why you would pick one type of cabling over another. Even though Network+ doesn’t test too hard on cabling, this is important information that you will use in the real networking world.

28. Networking Industry Standards

29. IEEE
Institute of Electrical and Electronic Engineers (IEEE) defines industry-wide standards
Organized the 802 committee in February of 1980 to define networking standards
Split up into smaller subcommittees

30. IEEE Subcommittees IEEE 802 LAN/MAN Overview & Architecture IEEE 802.2
Logical Link Control (LLC)
IEEE 802.3
CSMA/CD access method (Ethernet)
IEEE 802.3ae
10 Gigabit Ethernet
IEEE 802.5
Token Ring access method and Physical layer specifications
IEEE 802.8
Fiber Optic
IEEE
Wireless LAN Medium Access Control (MAC) and Physical layer specifications
Exam Tip
Memorize the 802.2, 802.3, 802.5, and standards. Ignore the rest.
There are more subcommittees than listed in this table.