1. Network Media Types COMPUTER NETWORKS 4TH Edition Chapter3
BY Andrew s. Tanenbaum
Chapter3
Network Media Types

2. Topics Types of Media Cable (conducted media) Wireless Media
Coaxial
Twisted pair (UTP)
Shielded twisted pair (STP)
Fiber optic
Wireless Media
Wireless Authentication
Wireless Transmission

3. Media Selection Criteria
Cost
For actual media and connecting devices such as NICs hubs etc
Installation
Difficulty to work with media
Special tools, training

4. Media Selection Criteria
Capacity
The amount of information that can be transmitted in a giving period of time
Measured as
Bits per second bps (preferred)
Baud (discrete signals per second)
Bandwidth (range of frequencies)

5. Cable Specifications
Cables have different specifications and expectations pertaining to performance:
What speeds for data transmission can be achieved using a particular type of cable?
What kind of transmission is being considered?
3.1.6

6. Cable Specifications
Some examples of Ethernet specifications which relate to cable type include:
10BASE-T
10BASE5
10BASE2
10BASE-T refers to the speed of transmission at 10 Mbps.
The type of transmission is baseband, or digitally interpreted.
The T stands for twisted pair.
3.1.6

7. Cable Media Shielded Twisted Pair STP Unshielded Twisted Pair UTP
Coaxial
Fiber optic

8. Shielded Twisted Pair (STP)
Shielded twisted-pair cable (STP) combines the techniques of shielding, cancellation, and twisting of wires.
Each pair of wires is wrapped in metallic foil.
The four pairs of wires are wrapped in an overall metallic braid or foil.
STP affords greater protection from all types of external interference, but is more expensive and difficult to install than UTP.
The metallic shielding materials in STP need to be grounded at both ends.

9. Shielded Twisted Pair (STP)

10. Unshielded Twisted Pair (UTP)
Unshielded twisted-pair cable (UTP) is a four-pair wire medium used in a variety of networks.
Each of the 8 individual copper wires in the UTP cable is covered by insulating material.
In addition, each pair of wires is twisted around each other.

11. Unshielded Twisted Pair (UTP)
Categories
categories 1 and 2
voice grade
low data rates up to 4 Mbps
category 3
suitable for most LANs
up to 16 Mbps
category 4
up to 20 Mbps
Data grade UTP cable usually consists of either 4 or 8 wires, two or four pair
Uses RJ-45 telephone connector

12. Coaxial Cable
Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements.
One of these elements, located in the center of the cable, is a copper conductor.
Surrounding the copper conductor is a layer of flexible insulation.
Over this insulating material is a woven copper braid or metallic foil that acts as the second wire in the circuit and as a shield for the inner conductor.
3.1.7

13. Coaxial Cable
3.1.7

14. Coaxial Cable Advantages:
For LANs, coaxial cable offers several advantages.
It can be run longer distances than shielded twisted pair STP, and unshielded twisted pair UTP, cable without the need for repeaters.
Coaxial cable is less expensive than fiber-optic cable, and the technology is well known.

15. Fiber Optic Cable
Thin strand(s) of glass or plastic protected by a plastic sheath and strength wires or gel
Transmits laser (single mode) or LED (multi mode)
Single mode more expensive but can handle longer distances

16. A fiber optic ring with active repeaters.
Fiber Optic Networks
A fiber optic ring with active repeaters.

17. Wireless Networks
When a source node sends a frame, the receiving node returns a positive acknowledgment (ACK).
This can cause consumption of 50% of the available bandwidth.
This overhead when combined with the collision avoidance protocol overhead reduces the actual data throughput to a maximum of 5.0 to 5.5 Mbps on an b wireless LAN rated at 11 Mbps.
3.3.3

18. Wireless Media Uses the earth’s atmosphere as a conducting media
Main types
radio wave
microwave (including satellite)
infrared

19. Wireless Authentication
Authentication and Association types:
Unauthenticated and unassociated - The node is disconnected from the network and not associated to an access point.
Authenticated and unassociated - The node has been authenticated on the network but has not yet associated with the access point.
Authenticated and associated - The node is connected to the network and able to transmit and receive data through the access point.

20. Wireless Transmission
There are three basic ways in which a radio carrier signal can be modulated.
Amplitude Modulated (AM) radio stations modulate the height (amplitude) of the carrier signal.
Frequency Modulated (FM) radio stations modulate the frequency of the carrier signal as determined by the electrical signal from the microphone.
In WLANs, a third type of modulation called phase modulation is used to superimpose the data signal onto the carrier signal that is broadcast by the transmitter.