DCN286 INTRODUCTION TO DATA COMMUNICATION TECHNOLOGY

Network Media, Connectors and Standards

OSI Model

OSI Layers

OSI Layers

•Provides connectivity and path selection between two host

•Provides Logical address

•No error correction, best effort delivery.

OSI Layers

OSI Layers

OSI Layers

OSI Layers

OSI Layers

Names for Data at Each Layer

Digital Signal Transmission

1. By varying an electrical signal when it passes over a wire that is typically made of copper.

2. By varying the power of light as sent over a glass optical fiber.

3. By varying the radio waves sent through space, which is commonly referred to as wireless communications.

Main Types of Electrical Materials

Material Definition Examples

Insulator Difficult for electrical current to flow

Plastic, paper, rubber, dry wood, air, pure water, glass

Semi-conductor

Electrical flow easily controlled

Carbon, germanium, gallium arsenide, silicon

Conductor Easy for electrical current to flow

Metals such as Copper, gold, silver, solder, water with ions, human body

Popular Copper Media Standards

TIA (Telecommunications Industry Association) and EIA (Electronic Industries Alliance) work together to publish commercial building telecommunications cabling standards TIA/EIA-568-B which defines how to use the pins on the connectors on the ends of the cables.

IEEE (Institute of Electrical and Electronic Engineers) publishes LAN standards such as IEEE802.3 which will define cable requirement.

Coaxial cable

Gradually outdated from LANCan run for longer distances than either

STP or UTPLess expensive than fiber-optic cable

though it is expensive than STP or UTPStill popular for TV and home internet

service

STP (Shielded Twisted Pair) cable

Shielding provides better electrical signals by reducing noise and attenuation.

Shielding makes the cable more expensive, heavier and hard to bend.

STP - 3 insulations

Total 3 insulations:1.Each thin wire is covered

in color-coded plastic insulation

2.Each pair of wires is twisted with a insulator called a pair shield around them

3.All the wires in the cable (usually 4 pairs) are covered by a shield called the overall shield.

ScTP (Screened Twisted Pair)

ScTP is also called FTP (Foil Twisted Pair)

ScTP does not have pair shield. Thus, it has only two insulations: wire insulation and overall shield.

Cheaper than STP

UTP (Unshielded Twisted Pair)

Flexible and easy installOffer the same data speedsInexpensiveRJ45 connector (RJ11 is for phone cable).

UTP cable categories

UTP cable category

Purpose Comments

Category 1 Telephone Not suitable for data

Category 2 Token Ring 4Mbps Token Ring

Category 3 Telephone and 10BASE-T

10Mbps

Category 4 Token Ring 16Mbps Token Ring

Category 5 Ethernet 10BASE-T and 100BASE-T

Category 5e Ethernet Same cable and connector. Support gigabit

Category 6 Ethernet Support 1Gbps. May support 10Gbps

TIA/EIA568-A and B pin outs

Pin # Function 568A wire color 568 B wire color

1 TD+ White/Green White/Orange

2 TD- Green Orange

3 RD+ White/Orange White/Green

4 Unused Blue Blue

5 Unused White/Blue White/Blue

6 RD- Orange Green

7 Unused White/Brown White/Brown

8 Unused Brown Brown

Straight through cable

Can be used to connect PC and other network equipments to LAN hub/switch

Wire 1 and 2 are used to transmit dataWire 3 and 6 are used to receive data

Cross-over cable

It is used to connect two same equipments such as PC-to-PC.

Both ends need to send data on pin 1 and 2; receive data on pin 3 and 6.

In 568B, one end has white/orange and orange on pin 1 and 2; another has white/orange and orange on pin 3 and 6.

In 568B, one end has white/green and green on pin 3 and 6; another end has them on pin 1 and 2.

Rollover cable

Usually used as console cable.Change the sequence on another end. Most commonly used to connect a

computer terminal to a router’s console port.

This cable is typically flat to help distinguish it from other types of network cabling.

It gets the name rollover because the point-outs on one end are reversed from the other end.

Connector and Adapter

The 8 Position 8 Contact (8P8C) (often called RJ45) connector

Cross over adapter

Gigabit crossover

All four pairs crossed

Optic media

Fiber-optic cable has the strongest ability to resist EMI (electromagnetic interference), RFI (Radio Frequency Interference)

Fiber’s bandwidth is much higher than any other media.

Fiber is highly secure and it is easy to detect intrusion.

Fiber uses light signal transmission and its attenuation is much less than electrical signals. Its length could be very long

Duplex

A duplex communication system is a system composed of two connected parties or devices which can communicate with one another in both directions. (The term duplex is not used when describing communication between more than two parties or devices.)

Half duplex cannot send/receive in same time.

Optical fiber cable components

Core: usually made by silicon dioxide (from sand)

Cladding: coated on the core to reflect light and seal it inside

Buffer: physical protect cladding and core

Jacket: prevent damage from abrasion, solvents and other contaminants

Multimode fiber

Fiber with large (greater than 10 μm) core diameter may allow light coming in with different angles. (It must be in limit of acceptance cone)

Single mode fiber

Fiber with a core diameter less than about ten times the wavelength of the propagating light and it can only allow light coming in from one direction.

Some thumbnail rules

Inexpensive LED transmitter is usually used with inexpensive multimode cable

Expensive laser transmitter is usually used with expensive single mode cable

Single mode cable with laser transmitter can support longer cable distance than multimode cable with LED transmitter.

Optical Fiber Connector (Optional)

LC/PC connector and SC/PC connectors have caps covering the ferrules

Other connectors are ST, SC, MT, MT-RJ, MU, etc, etc

Wireless tech introduction

InfraredBluetoothMicrowaveRadioWi-Fi

In general, wireless network is secondary because of two concerns: speed and security. But, it does offer mobility and convenience.

Main wireless components

Access point: linking wireless network to the wired world.

Wireless NIC on each hosts in the networkWireless hub, switch and router:

functioning as same as regular wire connected equipments

WLAN standards organizations

IEEE published the WLAN standard.FCC (Federal Communication

Commission) will specify restriction on power and radio frequencies in US.

Industry Canada is taking care of radio frequency usage in Canada.

Frequency use/approval may be different in various areas, regions and countries.

WLAN standards: IEEE802.11

Question

Any question?

If you do not have question, please search internet and collect more information of those cables, connectors and standards.

1. Please be comfortable to draw the shape of popular connectors.

2. Please be familiar with those organizations’ full name and main responsibilities.