2.5 Compare and contrast WAN technologies.

Question 1

ISDN - Integrated Services Digital Network

Answer 1

• BRI – Basic Rate Interface (2B+D)• Two 64 kbit/s bearer (B) channels

• One 16 kbit/s signaling (D) channel
• Delivered over a T1 or E1

Question 2

T1 / E1

Answer 2

• T-Carrier Level 1
• Time-division multiplexing
• 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 3

T3 / DS3 / E3

Answer 3

• T-Carrier Level 3
• Delivered on coax (BNC connectors)
• DS3 is the data carried on a T3
• Twenty-eight T1 circuits - 44.736 Mbit/s
• E3 • Sixteen E1 circuits - 34.368 Mbit/s

Question 4

OC (Optical Carrier)

Answer 4

• SONET (Synchronous Optical Networking)

* Commonly implemented by carriers on SONET rings

Question 5

OC-3

Answer 5

155.52 Mbit/sec

Question 6

OC-12

Answer 6

622.08 Mbit/sec

Question 7

OC-48

Answer 7

2.49 Gbit/sec

Question 8

OC-192

Answer 8

9.95 Gbit/sec

Question 9

DSL

Answer 9

• ADSL (Asymmetric Digital Subscriber Line)
• Uses telephone lines
• Download speed is faster than the upload speed
• ~10,000 foot limitation from the central office (CO)
• 52 Mbit/s downstream / 16 Mbit/s upstream are
• Faster speeds may be possible if closer to the CO

Question 10

Metro Ethernet

Answer 10

• Metropolitan-area network
• A contained regional area
• The Ethernet is usually running over a different topology
• Pure Ethernet
• Ethernet over SDH, MPLS, or DWDM

Question 11

Cable broadband

Answer 11

• Transmission across multiple frequencies
• Data on the “cable” network
• High-speed networking
• Multiple services - Data, voice

Question 12

Dialup

Answer 12

• Network with voice telephone lines
• 56 kbit/s modems - Compression up to 320 kbit/s
• Relatively slow throughput - Difficult to scale

Question 13

Satellite networking

Answer 13

• Communication to a satellite
• High cost relative to terrestrial networking
• High latency - 250 ms up, 250 ms down

Question 14

Copper

Answer 14

• Extensive installations
• Limited bandwidth availability
• Wide area networks
• Often combined with fiber

Question 15

Fiber

Answer 15

• High speed data communication - Frequencies of light
• Higher installation cost than copper
• Large installation in the WAN core
• SONET, wavelength division multiplexing

Question 16

• SONET, wavelength division multiplexing

Answer 16

• Use the cellular network - Wireless WAN
• Intermittent communication
• Roaming communication
• Limited by coverage and speed

Question 17

MPLS

Answer 17

• Learning from ATM and Frame Relay
• Packets through the WAN have a label
• Any transport medium, any protocol inside
• IP packets, ATM cells, Ethernet frames

Question 18

MPLS pushing and popping

Answer 18

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

Question 19

ATM

Answer 19

• Asynchronous Transfer Mode
• High throughput, real-time, low latency
• 53-byte “cells” spaced evenly apart

Question 20

Frame relay

Answer 20

• One of the first cost-effective WAN types
• LAN traffic is encapsulated into frame relay frames
• Frames are passed into the “cloud”
• Effectively replaced by MPLS

Question 21

PPP (Point-to-point protocol)

Answer 21

• Create a network connection between two devices

* Works almost anywhere

Question 22

• Provides additional data link functionality

Answer 22

• Authentication
Compression
• Error detection
Multilink

Question 23

PPPoE

Answer 23

• Encapsulate point-to-point protocol over Ethernet
• Common on DSL networks• Easy to implement
• Allows competition

Question 24

DMVPN

Answer 24

• Dynamic Multipoint VPN
• Your VPN builds itself
• Tunnels are built dynamically, on-demand

Question 25

SIP trunking

Answer 25

• Session Initiation Protocol
• Traditional PBX connectivity uses T1/ISDN
• Use SIP/VoIP to communicate to an IP-PBX provider
• More efficient use of bandwidth

Question 26

Demarcation point

Answer 26

• The point where you connect with the outside world

Question 27

CSU/DSU - Channel Service Unit / Data Service Unit

Answer 27

• CSU - Connects to the network provider
• DSU - Connects to the data terminal equipment (DTE)
• Physical device - Or built-in to the router

Question 28

CSU/DSU connectivity

Answer 28

• From the demarc
• RJ-48c wiring
• To the router
• Serial connection, v.35, RS-232• May also include monitor jacks

Question 29

Smartjack

Answer 29

• Network interface unit (NIU)
• The device that determines the demarc
• More than just a simple interface
• Built-in diagnostics
• Alarm indicators