CompTIA Network+ N10-006 - 1.4

Question 1

Synchronous optical networking (SONET)

Answer 1

• Multiplex digital signals over optical cable
– All circuits are synchronized to an atomic clock

• SONET
– Synchronous Optical NETworking
– American National Standards Institute (ANSI) standard
– Used in United States and Canada

• SDH
– Synchronous Digital Hierarchy
–International Telecommunications Union (ITU) Standard
– Used everywhere else

• Both are effectively identical

Question 2

SONET/SDH speeds

Answer 2

• SONET / Synchronous Transport Signals (STS)

* SDH / Synchronous Transport Modules (STM)

Question 3

Wavelength-Division Multiplexing (WDM)

Answer 3

• Wavelength-Division Multiplexing
– end multiple carriers over a single fiber

• Use different wavelengths for each carrier
– Different “colors”

• CWDM (Coarse Wavelength-Division Multiplexing)
– 10BASE-LX4 uses four 3.125 Gbps/sec carriers at four different wavelengths

• DWDM (Dense Wavelength-Division Multiplexing)
– Multiplex multiple OC carriers into a single fiber
– Add 160 signals, increase to 1.6 Tbit/s

Question 4

ATM

Answer 4

• Asynchronous Transfer Mode
– A common protocol transported over SONET

• 53-byte “cells” spaced evenly apart
– 480byte for data, 5 byte routing header

• High throughput, real-time, low latency
– Data, voice, and video

• Max speeds of OC-192
– Limits based on segmentation and reassembly (SAR)

Question 5

Frame relay

Answer 5

• One of the first cost0effective WAN types
– Departure from circuit-switches T1s

• LAN traffic is encapsulated into frame relay frames

• Frames are passed into the “cloud”
– Magically pop out the other side

• Usually 64 Kbits/s through DS3 speeds
• Replaced by MPLS (Multiprotocol Label Switching)

Question 6

Multiprotocol Label Switching

Answer 6

• Learning from ATM and Frame Relay
–Keep the advantages, ditch the disadvantages

• Packets through the WAN have a label
– Routing decisions are easy

• Any transport medium, any protocol inside
–IP packets, ATM cells, Ethernet frames
–OSI layer 2.5 (!)

• Increasingly command WAN technology
–Ready-to-network

Question 7

MPLS pushing and popping

Answer 7

• Labels are “pushed” onto packets as they enter the MPLS cloud
• Labels are “popped” off on the way out

Question 8

Satellite networking

Answer 8

• Communication to a satellite
–Non-terrestrial communication

• High cost relative to terrestrial networking
–15 Mbit/s down, 2 Mbit/s up
– Remote sites, difficult-to-network sites

• High latency
– 250 ms up, 250 ms down

• High frequencies - 2 GHz
– Suffer from line of sight, rain fade

Question 9

ISDN (Integrated Services Digital Network)

Answer 9

• BRI - Basic Rate Interface (2B+D)
– Two 64 kbit/s bearer (B) channels
– One 16 kbit/s signaling (D) channel

• PRI – Primary Rate Interface
 –Delivered over a T1 or E1
    • T1 –23B + D
    • E1 – 30B + D + alarm channel
 –Commonly used as a connectivity from the PSTN to large phone systems (PBX)

Question 10

DSL (Digital Subscriber Line)

Answer 10

• ADSL (Asymmetric Digital Subscriber Line)
– Uses telephone lines
– Download speed is faster than the upload speed (asymmetric)
–~10,000 foot limitation from the central office
–24 Mbit/s downstream / 3.3 Mbit/s upstream

VDSL (Very-high-bit-rate DSL)
– 3 Mbit/s through 100 Mbit/s

Question 11

PPPoE (Point to Point Protocol over Ethernet)

Answer 11

• Encapsulate point-to-point protocol over Ethernet
– The past with the present

• Common on DSL networks
– Telephone providers know PPP

• Easy to implement
– Support in most operating systems
– no routing required
– Similar to existing dialup architecture

•Allows competition
–Once connected, data is switched to the appropriate ISP

Question 12

Cable modem

Answer 12

• Data on the “cable” network
– DOCSIS (Data Over Cable Service Interface Specification)

• High-speed networking
–4 Mbit/s through 250 Mbits/s

• Múltiple services
–Data, voice

Question 13

Dialup

Answer 13

• Network with voice telephone lines
–Analog lines with limited frequency response

• 56 kbit/s modems
–Compression up to 320 kbit/s

• Relatively slow throughput
–Difficult to scale

• Legacy systems, network utility
–May be difficult to find a modem

Question 14

Point-to-point protocol

Answer 14

• Create a network connection between two devices
–OSI layer 2 / data link protocol
–Communicate using many different protocols

• Works almost anywhere
– Dial-up connections, serial links, mobile phone, DSL (PPPoE)

• Provides additional data link functionality
 – Authentication
 – Compression
 –Error detection
 –Multilink

Question 15

Multilink PPP

Answer 15

• Aggregate traffic across multiple point-to-point links
–Why use a single connection when you can use two?

• Scale up your throughput
–Use multiple links simultaneously
–Requires additional hardware and network

• MPPP adds numbers to the data fragments
–Fixes out-of-order frames

Question 16

Cellular networks

Answer 16

• Mobile devices
–”Cell” phones

•Separate land into “cells”
–Antenna coverages a cell with certain frequencies

• 2G networks
–GSM - Global System for Mobile Communications
–CDMA - Code Division Multiple Access

• Poor data support
–Originally uses circuit-switching
–Minor upgrades for some packet-switching

Question 17

LTE (Long Term Evolution) and HSPA+

Answer 17

• Long Term Evolution (LTE)
–Based on GSM/EDGE
– Download rates of 300 Mbit/s, upload 75 Mbit/s
– A “4G” technology

• Evolved High Speed Packet Access (HSPA+)
– Based on CDMA
–Download rates of 84 Mbit/s, upload 22 Mbit/s

•The 3rd Generation Partnership Project (3GPP)
–Collaboration between telecommunications organizations

Question 18

WiMAX (Worldwide Interoperability for Microwave Access)

Answer 18

• WiMAX (Worldwide Interoperability for Microwave Access)
– Wireless high-speed Internet access

• 30 mile signal radius
–”Wi-Fi on steroids”

• Fixed WiMAX
–IEEE 802.16
–37 Mbit/s download, 17 Mbit/s upload

•Mobile WiMAX
–IEEE 802.16e-2005
–Theoretical throughput of 1 Gbit/s for fixed stations
– Mobile station throughput of 100 Mbit/s (“4G”)

Question 19

T1 / E1

Answer 19

•T-Carrier Level 1
 –Time-division multiplexing
 –North America, Japan, South Korea
 –24 channels 
    •64 kbit/s per channel
    • 1.544 Mbit/s line rate

• E-Carrier Level 1 
 –E is for Europe
    •32 channels
    • 64 kbit/s per channel
    • 2.048 Mbit/s line rate

Question 20

T3 / DS3 / E3

Answer 20

• T-Carrier Level 3
–Delivered on cox (BNC connectors)
–DS3 is the data carried on a T3

• T3
–Twenty-eight T1 circuits
–44.736 Mbit/s

• E3
–Sixteen E1 circuits
– 34.368 Mbit/s

Question 21

Circuit switching

Answer 21

• Circuit is established between endpoints before data passes
– Like a phone call

• Nobody else can use the circuit when it’s idle
–Inefficient use of resources

• Connect is always there
– It’s mine, You can’t use it.

Question 22

Circuit switching

Answer 22

• POT (plain old telephone server) and PSTN (public switched telephone network)
• T1 / E1 / T3 / E3
• ISDN

Question 23

Packet switching

Answer 23

• Data is grouped into packets
–Voice, data , video, etc.
–Like a network

• The media is usually shared
–Someone else can use it, even when you don’t.

• One connection may have more bandwidth allocated than another
–How much money would you like to spend?

• SONET, ATM
• DSL
• Frame relay
• MPLS
• Cable modem
• Satellite
• Wireless

Question 24

RJ11 connector

Answer 24

• 6 position, 2 conductor (6P2C)
–RJ14 uses 6P4C for dual-line use

• Telephone connection

Question 25

RJ45 connector

Answer 25

• 8 position, 8 conductor (8P8C)
–Modular connector

•Similar in shape to an RJ48C
–8P4C, used in T1/WAN data lines

Question 26

DB-9 (RS-232)

Answer 26

• Recommended standard 232
– An industry standard since 1969

• Serial communications standard
–Built for modem communication
• Used for modems, printers, mice, networking

Question 27

Couplers

Answer 27

•Connect cables together
– Lengthen the cable run

• Very specific use cases
– Signal loss for each coupler

•Useful for temporary or one-time use
–Permanent links are generally home runs

Question 28

BNC connector

Answer 28

•Bayonet Neil-Concelman
–Paul Neil (Bell Labs) and Carl Concelman (Amphenol)

•Coaxial cable connector
– RG-58 used in 10BASE2, DS3 WAN links

• Rigid and bulky
–Can be difficult to work with

Question 29

F-connector

Answer 29

• Cable television
– Cable modem

• RG-6
– Threaded connector

Question 30

66 block

Answer 30

• A patch panel for analog voice
– And some digital links

• Left Sid is patched to the right
–Easy to follow the path

• Wire and a punch-down tool
–No additional connectors required

Question 31

110 block

Answer 31

• Wire-to-wire patch panel
– No intermediate interface required

• Replaces the 66 block
–Patch category 5 and Category 6 cables

•Wires are “punched” into the block
– Connecting block is on top

•Additional wires punched into connecting block
– Patch the top to the bottom