---
title: 'Topic 02 Network Media'
disqus: hackmd
---

:::info
ST1010 Network Fundamentals
:::

Topic 02 Network Media
===

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## Table of Contents

[TOC]

Wired Networking
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- uses tangible physical media called cables
- 2 broad categories of cables
- copper wire
- fiber optic
- main diff between them
- composition of signals (electicity & light)
- speed of signals
- distance signal can travel

### Criteria for Choosing Network Media
- bandwidth rating - num of bits per sec that can be transmitted across medium
- factor determining bandwidth is how bit signals represented on medium (called __encoding__)
- 
- when possible choose cabling cat that's compatible with the standard you want to implement now but will support growth & faster speeds
- max segment length - max cable length between 2 network devices
- ea cable type can transport data only so far before its signals begin to weaken beyond what can be read by a receiving device (__attenuation__)
- intermediate passive devices (Eg. wall jacks) are part of total segment length
- interference & eavesdroppping susceptibility
- interference to electrical signals on copper media comes in form of __electromagnetic interference (EMI)__ & __radio frequency interference (RFI)__
- motors, transformers, fluorescent lights or other sources of intense electrical activity can emit both EMI & RFI
- RFI can also affect wireless networks if freq in same range
- __Crosstalk__ - inteference 1 wire generates on another when in bundle
- copper wires susceptible to electronic eavesdropping
- fiber-optic carry light signals so not susceptible to interference or eavesdropping
- cable grade
- building & fire codes include specific cabling requirements
- cables ran between false ceiling
- true ceiling (plenum) must be plenum-rated
- UTP cabling marked as __communication cable riser (CMR)__ or __comm cable plenum (CMP)__
- CMR can only be used for building risers/cable trays
- CMP suitable for use in plenum spaces
- connection hardware
- every type of cable has connectors that influence kinds of hardware cable can connect to
- must make sure media selected can support network device

__Other Considerations__
- ease of installation
- media's minimum bend radius
- limits angle cable can be bent to run around corners
- cost & time to terminate medium
- phy environment - types of walls, ceilings, EMI or RFI
- testability - network that "works" might be crippled by excessive errors
- important to certify whether cable meets requirements for its cat
- total cost
- cabling, connectors, termination panels, wall jacks, termination tools, testing eq, time etc.

Cables
---
### Coaxial Cable
- AKA coax
- once was predominant form of network cabling
- started to phase out in early 1990's
- inexpensive & easy to install
- still used primarily in connecting cable modem to wall outlet your cable TV/internet provider installs

### Twisted-Pair Cable
- 2 types
- unshielded
- shielded
- consists of 1 or more pairs of insulated strands of copper wires twisted around 1 another & housed in outer jacket
- twists necessary to improve resistance to crosstalk from wires & EMI from outside sources
- more twists per unit length, better resistance to EMI & crosstalk
- more expensive TP wisted more than less expensive
- provides better pathway for higher bandwidth networks
- tbh you won't bother, just make sure its cat is high

### Unshielded Twisted-Pair Cable
- most networks use unshielded twisted pair (UTP)
- consists of 4 pairs of insulated wires
- rated accordingly to cats devised by __Telecommunications Industry Assocation (TIA)__ & __Electronic Industries Alliance (EIA)__ & __American National Standards Institutes (ANSI)__
- cat 1 to 6a accepted in US
- 2 additional cat aren't yet TIA/EIA standards & might never be in US
- Europe has accepted cat 7 & 7a, which specify that ea wire pair is shielded
- cat 5e & 6 UTP cabling characteristics
- most popular types of UTP cabling today

### Shielded Twisted-Pair Cable
- includes shielding to reduce crosstalk & interference
- has wire braid inside sheath material/foil wrap
- best to use in electrically noisy environments/very high-bandwidth apps

__Twisted-Pair Cable Plant Components__
- __RJ-45 connectors__ - STP & UTP uses registered jack 45
- most commonly used in patch cables
- used to connect computers to hubs, switches & RJ-45 wall jacks
- Rj-45 jacks - what you plug an RJ-45 connector into when computer not near a switch/hub
- usually placed behind wall plates when cables run inside walls
- patch cable
- short cable for connecting computer to RJ-45 wall jack or connecting a patch-panel port to switch/hub
- can be made with inexpensive tols, 2 RJ-45 plugs & length of TP cable
- patch panels
- used to terminate long runs of cable from where computers are to wiring closet (where switches & hubs are)
- distribution racks
- hold network equipment
- Eg. routers, switches, patch panels, rack-mounted servers etc.
- AKA 19" racks as upright rails are 19" apart

### Medium Dependent Interface
- network devices that connect using RJ-45 plugs over twisted-pair cabling classified as __medium dependent interface (MDI)__ or __MDI crossed (MDI-X) devices__
- Eg. PC, NICs & routers
- MDI devices receive on pins 1 & 2 and transmit on pins 3 & 6
- Eg. hubs & switches
- when 2 switches etc. need to be connected, use crossover cable so that transmit & receive wires get crossed

__why 2 transmit & 2 receive wires?__
- 1 wire pair used for transmit (labeled transmit+/transmit-) and 1 pair for receive (labeled receive+/receive-)
- plus & minus symbols indicate that wires carry positive & negative signal
- this __differential signal__ mitigates effect of crosstalk & noise on cable

### Fiber-Optic Cable
- bits transmitted as pulses of light instead of electricity
- immune to electrical interference
- highly secure
- electronic eavesdropping eliminated
- composition
- slender cylinder glass fiber called core surrounded by concentric layer of glass called __cladding__
- fiber jacketed in thin transparent plastic material called __buffer__
- ea fiber-optic strand carries data in only 1 dir
- network connections consist of 2 or more strands
- fiber-optic cable used as backbone cabling often comes in bundles of 12 or more fiber strands
- even only using 2 in backbone, running more is good idea so ready for future expansion
- some testing shown that glass fibers can carry several terabits (1000 gigabits) per second
- fiber-optic may 1 day replace copper for all types of network connections

__Fiber-Optic Connectors__
- types
- straight tip (ST)
- straight connection (SC)
- locking connection (LC)
- mechanical transfer registered jack (MT-RJ)
- fiber channel or ferrule connector (FC)
- medium interface connector (MIC)
- subminiature type A (SMA)

__Fiber-Optic Installation__
- more difficult & time consuming than copper media installation
- however advances in connector tech closing gap
- connectors & test eq required for termination still more expensive than copper
- many methods for terminating fiber-optic cables due to many connectors & cable types available
- installation details beyond scope of this book

__Fiber-Optic Cable Types__
- single-mode fiber (SMF)
- includes single, small-diameter fiber at core
- 8 microns
- generally works with laser-based emitters
- longest dist
- used in higher-bandwidth apps
- multimode fiber (MMF)
- larger diameter fiber at core
- 50 & 62.5 microns
- cheaper than SMF
- works with lower-power light emitting diodes (LEDs)
- shorter dist

Structured Cabling
---
### Managing & Installing UTP Cable Plant
- structured cabling
- specifies how cabling should be organised, regardless of media type or network architecture
- large networks typically use most/all of these
- work area
- horizontal wiring
- telecommunications closets
- equipment rooms
- backbone or vertical wiring
- entrance facilities
- work area
- where workstations & other user devices located
- faceplates & wall jacks installed in work area
- patch cable connect computers & printers to wall jacks
- horizontal wiring
- runs from work area's wall jack to telecomm closet
- wiring from wall jack to patch panel should be no longer than 90 meters (plus 10m for patch cables)
- telecommunications closet
- TC provides connectivity to computer equipment in nearby work area
- typical eq includes
- patch panels to terminate horizontal wiring runs
- hubs
- switches
- TC that hosues cabling & devices for work area computers referred as __intermediate distribution frame (IDF)__
- equipment room
- houses servers, routers, switches & other major network equipment
- serves as connection point for backbone cabling
- eq room that's connection point between IDFs called __main distribution frame (MDF)__
- MDF can be main cross-connect for entire network or serve as connecting point for backbone cabling between buildings
- ea building has own MDF
- backbone cabling
- interconnects IDFs & MDFs
- runs between floors/wings of building & between buildings
- frequently fiber-optic cable but can also be UTP if dist between TC is < 90m
- entrance facility
- location of cabling & equipment that connects a corporate network to 3rd party telecomm provider
- can also serve as eq room & main cross-connect for all backbone cabling
- where WAN conection made
- __demarcation point__ - point where corporate LAN eq ends & 3rd party provider's equipment & cabling begins

__Installing UTP Cabling__
- cable termination - putting RJ-45 plugs on ends of cable/punching down wires into terminal blocks on jack/patch panel
- tools needed
- wire cutters
- crimping tool
- cable tester
- punchdown tool
- cable stripper
- RJ-45 plugs/jacks
- when making cable/terminating cable at a jack or patch panel
- important to get colored wires arranged in correct order
- 2 standards: 568A & 568B

__Straight-Through VS Crossover Cable__
- standard patch cables called __straight-through cables__
- same wiring standard on both ends
- __crossover cables__ - use 568A standard on 1 side & 568B on other
- crosses transmit & receives wires so that transmit on 1 end connects to receive on other
- this type of cable often needed when you connect 2 devices of same type to 1 another
- for 1000BaseT crossover cable, have to cross blue & brown pins as used in 1000BaseT

Cable-Testing Equipment
---
- common tools for testing & troubleshotting wired networks
- cable certifier
- basic cable tester
- tone generator
- time domain reflectometer (TDR)
- multimeter
- optical power meter (OPM)

Wireless Networking
---
- demand increased considerably
- many home users turn to wireless networks
- often used with wired to interconnect geographically dispersed LANs or groups of mobile users with wired servers & resources on wired LAN
- AKA hybrid networks
- AP or router usually connects to internet via wired connection to cable modem though clients through wireless

### Wireless Benefits
- create temp connections to wired networks
- establishes backup/contingency connectivity for existing wired networks
- extends network's span beyond reach of wire-based or fiber-optic cabling
- especially in older buildings where rewiring might be too ex
- allows businesses to provide customers with wireless networking easily, offering service that gets customers in & keeps them
- enables users to roam around a corporate/college campus with their machines

### Types of Wireless Networks
- __local area networks (LAN)__
- usually provides connectivity for mobile users or across areas that couldn't otherwise be networked
- __extended LANs__
- usually used to increase LAN's span beyond normal dist limitations
- __internet service__
- used to bring internet access to homes & businesses
- __mobile computing__
- users communicate by using wireless networking medium that enable them to move while remaining connected

### Wireless LAN Components
- network interface attaches to antenna & emitter instead of cable
- transceiver/access point (AP) - transmitter /receiver device must be installed to translate between wired & wireless networks
- includes antenna & transmitter to send & receive wireless traffic but also connects to wired side of network
- shuttles traffic back & forth between network's wired & wireless sides

### Wireless LAN Transmission
- signals take form of waves in electromagnetic (EM) spectrum
- frequency of wave forms used for comm measured in cycles per second __(hertz HZ)__
- lower-frequency transmissions can carry less data more slowly over longer distances
- higher-freq transmissions can carry more data faster over short dist
- high freq radio waves has higher signaling rate
- common frequencies for wireless data comm
- radio - 10Khz to 300Mhz
- microwave - 300Mhz to 300Ghz
- infrared - 300Ghz to 400Thz (terahertz)
- wireless LANs use 4 primary tech for transmitting & receiving data
- infrared
- laser
- narrowband (single-freq) radio
- spread-spectrum radio

Wireless LAN Technologies
---

### Infrared LAN Tech
- use infrared light beams to send signals between devices
- works well for LAN apps due to high bandwidth
- 4 main kinds
- __line-of-sight networks__ - require unobstructed view between transmitter & receiver
- __reflective wireless networks__ - broadcast signals from optical transceivers near devices to central hub
- __scatter infrared networks__ - bounce transmissions offwalls & ceilings to deliver signals
- __broadband optical telepoint networks__ - provide broadband services

### Laser-Based LAN Tech
- also need clear line of sight between sender & receiver
- subject to many same limitatons as infrared
- aren't as susceptible to interference from visible light sources as infrared

### Narrowband Radio LAN Tech
- use low-powered, 2 way radio comm
- receiver & transmitter must be tuned to same freq to handle incoming/outgoing data
- need no line of sight between sender & receiver as long as both stay within broadcast range
- 70m or 230 feet
- depending on freq, walls or solid barriers can block signals
- interference from other radio sources possible

### Spread-Spectrum LAN Tech
- uses multiple freq simultaneously, improving reliability & reducing susceptibility to interference
- also makes eavesdropping more difficult
- 2 main kinds
- freq-hopping - switches data between multiple freq at regular intervals
- direct-sequence modulation - breaks data into fixed-size segments called __chips__
- transmits data on several diff freq at once

LAN Media Selection Criteria
---
- 3 main media choices: UTP, fiber-optic & wireless
- when choosing consider
- bandwidth - higher = more expensive & higher installation costs
- if >40gbps, fiber-optic only choice
- budget
- typical UTP cable installation costs $100 to $200 per cable run
- fiber-optic costs twice
- wireless has no phy installation costs but need to install access points & verify connectivity
- environmental considerations
- how electrically noisy?
- how important is data security?
- more weight factor has, more likely fiber-optic/secured wireless is right choice
- span
- what dist must network span?
- longer spans need fiber-optic or wireless to use between buildings
- strategic placement of small switches/hubs give UTP surprising reach
- existing cable plant
- for upgrade, existing cable plant must be considered

Chapter Summary
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###### tags: `NETF` `DISM` `School` `Notes`