CCNA1: Network Basics v3.0 CISCO NETWORKING ACADEMY PROGRAM CCNA1: Networking Media Copper and Fiber Based Media, Wireless Networking

CCNA1: Network Basics v3.0

CISCO NETWORKING ACADEMY PROGRAM

CCNA1: Networking Media

Copper and Fiber Based Media, Wireless Networking

CCNA1: Networking Basics v3.0


Chapter 3 – Networking Media

Copper-based Media Vocabulary

• Voltage• Electromotive force• Resistance• Current• Attenuation• Electromagnetic Interference




What Causes Electricity?• Electricity is caused when

electrons “flow” from one atom to a neighboring atom (current)

• The electromotive force (what compels the electrons to move) is pressure caused by a separation in charges. This is known as voltage (v)

• Voltage causes current

-

-

+ +N

N




Electrical Circuits

• Electricity flows in closed loops called circuits

• Every circuit has three components– A source of energy– A conductor (path) for the

energy– A load (work the energy is

used for)

SourceSource

LoadLoad

ConductorConductor

-




Two Types of Circuits

• Direct Current– Electricity flows in only one

direction– Easy to precisely regulate

• used in computers and networks

• Alternating Current– Direction of flow changes

constantly• Continuous wave of

variable voltage

– Not very precise

V

V

-

-




Resistance

• For every force in the universe, there is an opposing force

• The opposite of current is resistance – the opposition to the flow of electrons

• All materials have some degree of resistance

• Resistance is measured in ohms (Ω)

- - -

current

resistance




Attenuation• In order to overcome

resistance, some of the energy of the signal is lost to its surroundings. This is known as attenuation

• At a certain point, not enough energy is left to overcome any further resistance

• Attenuation limits the distance a signal can travel over cable

- - -

current

resistance-




Noise

• All EM signals are subject to outside interference by electromagnetic and radio frequency sources

• EMI limits signal distances




Coaxial Media




Coaxial Pros and Cons

• Shielding allows signal to travel 500m unrepeated

• Relatively inexpensive• Medium difficulty to install

• Limited to 10Mbps• Relatively unreliable• Only usable in bus

topologies• Not the easiest to install• Not the least expensive

medium




Screened Twisted Pair




Shielded Twisted Pair




Unshielded Twisted Pair




UTP Pros and Cons

• Inexpensive media• Supports speeds up to 1

Gbps• Easiest medium to install• Most widely used for

workstation connections, telephone, etc.

• Signal can only travel 100m because of no shielding (50m if used for Gigabit Ethernet)

• Highly susceptible to outside interference




Fiber Optic Vocabulary

• Core• Cladding• Buffer• Refraction• Laser• Laser emitting diode• Bend radius• Pulling strength




Laser Safety

• Laser energy in the infrared or near-infrared range (used in networking) can cause thermal damage to the human eye

• NEVER look into the end of an optical fiber that is connected to equipment or directly into equipment that generates laser light




Fiber Optics

• Two kinds of optical fibers are used:– Multimode – carries multiple frequencies of light. Not

very precise, but designed for lower cost LAN use. Fibers may be glass, but typically optical-grade plastic is used.

– Single-mode – carries a single light frequency. More expensive, but signals can travel further. Generally used for high-performance networks or long-haul carriers. Almost always glass fibers.




Fiber Optic Cable




Common Fiber Connectors




Fiber Optics Pros & Cons

• Not subject to EMI, RFI or resistance

• Theoretically unlimited speed potential

• Easily adaptable to new technologies

• Expensive to purchase cable

• Expensive connectors• Most difficult medium to

install




Wireless LANs




Wireless Networking

• Increasingly important as computing devices become smaller and more mobile– Laptops– Handhelds– Cell phones

• Important Concerns– Bandwidth– Security– Interoperability




Wireless LAN Standards802.11 General Standards Number

802.11b 11 Mbps WEP Security: 64-bit or 128-bit encryption

Uses same frequency range as some cordless phones (2.4 Ghz)

802.11a 54 Mbps Not interoperable with other standards – uses higher frequency range (5 GHz)

802.11g 54 Mbps Interoperable with 802.11b because it uses the same frequency range




Wireless Network Adapters




Wireless Access Point (WAP)




Wireless Access Point

WAP




Wireless Range

As range from WAP increases, negotiated speed is reduced toensure data integrity.

Typical Range is300-500 feet.




Authentication & Association

• Who has access to your network and where?• WLAN Authentication occurs at Layer 2 and identifies the DEVICE

not the USER• Authentication keys must match on the WAP and the Wireless NIC• ASSOCIATION means that your wNIC communicates through a

particular WAP. This assignment can be changed manually, or automatically as he user moves through the WLAN. Association can also be restricted based on MAC address.




WLAN Communications Process

• Client probes, finds a WAP • Client transmits authentication key• WAP accepts/rejects key, notifies client of result• Client is associated with the WAP• All other network processes begin (i.e. dynamic

IP address assignment, network login, etc.)




Two Types of WLANs: Ad-Hoc

• Ad-hoc system– Also known as an Independent Basic Service Set

(IBSS) or Wireless Peer-to-Peer network– All clients communicate directly with one another via

their wireless adapters– No WAP is used, and there is no access to a wired

network infrastructure




Two Types of WLANS: Infrastructure

• Uses a WAP to provide access to a wired network– Technical Term: Basic Service Set (BSS)

• Multiple WAPs can be used to form microcells with overlapping coverage areas– Technical Term: Extended Service Set (ESS)– Allows the user to roam




Roaming and WAPsAs client moves closer to another WAP, it re-authenticates and re-associates.

This process occurs in the background and is transparent to the user.




WLAN Roaming

• Network Admin configures multiple WAPs with overlapping coverage, each one set to a different radio channel

• When client probes, it chooses a WAP based on signal strength and error rates

• If signal strength weakens, client will search for another WAP and re-tune to a new frequency, then authenticate and associate with the new WAP




What Affects Range?

• Indoor/Outdoor Use– Building structure (internal)– WAP vs. wireless LAN relay

• Antenna type– Most consumer wireless products equipped with an

Omnidirectional antenna– Other antenna types shape the signal and can extend

distance in certain directions




Antennae

Unidirectional- emits signalin one direction only.

Omnidirectional- emits signalequally in all directions.

Documents

CCNA1: Network Basics v3.0 CISCO NETWORKING ACADEMY PROGRAM CCNA1: Networking Media Copper and Fiber Based Media, Wireless Networking