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CCNA1: Network Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
CCNA1: Networking Media
Copper and Fiber Based Media, Wireless Networking
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Copper-based Media Vocabulary
• Voltage• Electromotive force• Resistance• Current• Attenuation• Electromagnetic Interference
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
-
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
-
-
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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-
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Noise
• All EM signals are subject to outside interference by electromagnetic and radio frequency sources
• EMI limits signal distances
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Coaxial Media
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking 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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Screened Twisted Pair
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Shielded Twisted Pair
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Unshielded Twisted Pair
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Fiber Optic Vocabulary
• Core• Cladding• Buffer• Refraction• Laser• Laser emitting diode• Bend radius• Pulling strength
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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.
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Fiber Optic Cable
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Common Fiber Connectors
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Wireless LANs
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Wireless Networking
• Increasingly important as computing devices become smaller and more mobile– Laptops– Handhelds– Cell phones
• Important Concerns– Bandwidth– Security– Interoperability
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Wireless Network Adapters
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Wireless Access Point (WAP)
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Wireless Access Point
WAP
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Wireless Range
As range from WAP increases, negotiated speed is reduced toensure data integrity.
Typical Range is300-500 feet.
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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.
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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.)
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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.
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
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
CCNA1: Networking Basics v3.0
CISCO NETWORKING ACADEMY PROGRAM
Chapter 3 – Networking Media
Antennae
Unidirectional- emits signalin one direction only.
Omnidirectional- emits signalequally in all directions.
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