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Dion (N10-008) > WANs > Flashcards

WANs Flashcards

1
Q

Circuit-Switched Connection

A

Connection is brought up only when needed, like making a phone call

On-demand bandwidth can provide cost savings for customers who only need periodic connectivity to a remote site

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2
Q

Packet-Switched Connection

A

Always on like a dedicated leased line, but multiple customers share the bandwidth

SLAs used to guarantee a certain quality
(5Mbps at least 80% of the time)

Virtual circuits are represented as dashed lines

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3
Q

WAN Physical Media

A

UTP/STP (analog/digital)
Ex: T1, DSL, Dial-up, ISDN

Coaxial (RG-6)
Ex: cable modems

Fiber Optic Cable
High bandwidth, long distance, no EMI

Electric Power Lines
BPL (Broadband over Power Lines)
Up to 2.7Mbps

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4
Q

WAN Wireless Media

A

Cellular (See other flash cards)

WiMAX (Worldwide Interoperability for Microwave Access)
Alternative to DSL/Cellular
Wireless fixed location service
802.16

Satellite
HughesNet Gen5
VSAT (Very Small Aperture Terminal)
Used for remote areas (expensive too)
Starlink (Smaller coverage area, more satellites, faster)

High-Frequency Radio

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5
Q

Dedicated Leased Line

A

Logical connection that connects two sites through a service provider’s facility or telephone company’s central office

More expensive than other WAN tech because customer doesn’t share bandwidth

Point-to-point connection between two sites
(All bandwidth online is available at all times)

Digital circuits are measured in 64kbps channels called DS0 (Digital Signal 0)

CSU/DSU (Channel Service Unit/Data Service Unit)
Terminates the digital signals at customer location

Common circuits:
T1, E1, T3, E3

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6
Q

Metro Ethernet

A

Service providers are beginning to offer Ethernet interfaces to their customers

Less expensive & more common than specialized serial ports used in CSU/DSU

Tech used by service provider is hidden from customer
Only need to connect their network’s router to Smart Jack

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7
Q

PPP

A

Point-to-Point Protocol
Commonly used Layer 2 protocol on dedicated leased lines to simultaneously transmit multiple Layer 3 protocols (IP, IPX)

Each layer 3 control protocol runs an instance of PPP’s LCP (Link Control Protocol)

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8
Q

PPP: LCP

A

Link Control Protocol (Used in PPP)

Multilink interface
Allows multiple physical connections to be bonded together into a logical interface
(Can combine multiple T1s, T3s, etc) - Similar to link aggregation

Looped link detection
Layer 2 loop can be detected & prevented

Error detection
Frames containing errors can be detected & discarded

Authentication
Device on another end can authenticate the link

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9
Q

PPP Authentication: PAP

A

Password Authentication Protocol
Performs one-way authentication between client/server

Credentials sent in clear text (not secure)

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10
Q

PPP Authentication: CHAP

A

Challenge-Handshake Authentication Protocol
Performs one-way authentication using a three-way handshake

Credentials are hashed before transmission

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11
Q

PPP Authentication: MS-CHAP

A

Microsoft Challenge-Handshake Authentication Protocol

Microsoft-enhanced version of CHAP, includes two-way authentication

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12
Q

PPPoE

A

PPP over Ethernet
Commonly used with DSL modems

Encapsulates PPP frames within Ethernet frames
Allows for authentication over ethernet

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13
Q

ADSL

A

Asymmetric Digital Subscriber Line
Max distance to DSLAM: 18,000 ft
Voice & data on same line
Downstream: up to 8 Mbps
Upstream: up to 1.544 Mbps

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14
Q

SDSL

A

Symmetric Digital Subscriber Line
Max distance to DSLAM: 12,000 ft
NO simultaneous voice & data on same line
Downstream: 1.168 Mbps
Upstream: 1.168 Mbps

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15
Q

VDSL

A

Very High-Bit Rate DSL
Max distance to DSLAM: 4,000 ft
Downstream: up to 52 Mbps
Upstream: up to 12 Mbps

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16
Q

Cable Modems

A

HFC (Hybrid Fiber-Coax) distribution network is a cable TV infrastructure containing both fiber/coax

Specific frequency ranges used for upstream/downstream data transmission
Determined by DOCSIS (Data-over-cable service interface specification)

17
Q

Satellite Modems

A

Used in remote/rural locations where other connections are unavailable

Provides relatively fast speeds like DSL, but low bandwidth usage limits & high cost (especially when over limit)

Issues: Weather conditions can cause loss of connectivity
Delays (time to satellite & back = > 0.25 sec)

18
Q

POTS

A

Plain Old Telephone Service
PSTN (Public Switched Telephone Network) consists of telephone carriers around the world

Analog connections (voice and/or data) using PSTN are POTS connections

53.3 Kbps max bandwidth
(Can only access one 64 Kbps channel at a time)

19
Q

ISDN (2 Channels)

A

Integrated Services Digital Network
Supports multiple Bearer (B) channels - 64 Kbps
Older tech used to carry voice/video/data

Delta (D) channel existed for 64Kbps signaling data

BRI (Basic Rate Interface)
Two 64Kbps B channels with 16Kbps D channel

PRI (Primary Rate Interface)
1.472Mbps data pather over 23 B channels
64Kbps D channel

20
Q

Frame Relay

A

Losing market share due to cable & DSL
Frame relay sites connected to virtual circuits
VCs = point-to-point or point-to-multipoint

Low cost, widely available
Always-on or On-demand

Layer 2 tech

21
Q

SONET

A

Synchronous Optical Network
Layer 1 tech using fiber as media
Transports layer 2 encapsulation (like ATM)
High data rates (155Mbps to 10Gbps)
Covers large distances (20km to 250km)
Physical topology = bus or ring

22
Q

ATM (& cell size [header/payload])

A

Asynchronous Transfer Mode (Fiber & SONET networks!)
Layer 2 WAN tech operating using PVCs & SVCs (Permanent Virtual Circuits & Switched Virtual Circuits)

Similar to frame relay, except all frames are transferred as fixed-length “cells” as its PDU (protocol data unit)

Fixed-length cells of 53-bytes used to increase speed of transmissions
(5-byte header & 48-byte payload)

23
Q

ATM Virtual Circuits

A

UNI (User-Network Interface)
Used to connect ATM switches & endpoints

NNI (Network-Node Interface)
Used to connect ATM switches together

24
Q

MPLS

A

Multiprotocol Label Switching
Supports multiple protocols on the same network (used by ISPs, not end-users)

Support both frame relay & ATM on same backbone

Allows traffic to be dynamically routed based on load conditions & path availability

Label switching is more efficient than Layer 3 IP routing

25
Q

DMVPN

A

Dynamic Multipoint Virtual Private Network
Allow internet to be used as WAN connection for secure site-to-site communication

VPN tunnel has authentication & encryption so users on an unsecure network cannot read or decrypt the traffic without proper keys

Can connect remote locations with low cost (instead of dedicated or leased-line access)

26
Q

WAN Data Rates

A

ATM & SONET measured by optical carrier
OC levels bassed on OC1 (51.84Mbps)
All others are multiples (OC-3 = 155.52Mbps)

Frame Relay = 56Kbps to 1.544Mbps
T1 = 1.544 Mbps
T3 = 44.736 Mbps
E1 = 2.048 Mbps
E3 = 34.4 Mbps
ATM = 155 to 622 Mbps
SONET = 51.84 Mbps (OC-1) to 159.25 Gbps (OC-3072)

27
Q

Cellular: 1G

A

30KHz frequency communication
2Kbps Bandwidth

28
Q

Cellular: 2G

A

Communicated over GSM network; 1800MHz frequency band

14.4-64Kbps

EDGE (Enhanced Data Rates)
Brought speed up to 1Mbps

Multiplexing

First to have SMS/texts & international roaming

29
Q

Cellular: 3G

A

144Kbps bandwidth
1.6GHz - 2GHz frequency band range

WCDMA (Wideband Code Division Multiple Access)
Up to 2Mbps (slowest of 3G)

HSPA (High Speed Packet Access) 3.5G
Up to 14.4Mbps

HSPA+ (High Speed Packet Access Evolution) - 3.75G
Up to 50Mbps

30
Q

Cellular: 4G

A

Introduction of MIMO
Covers 2-8GHz frequency band

Up to 100Mbps while driving
Up to 1Gbps (fixed cellular stationary modem w/antenna)

AKA: 4G LTE (Long Term Evolution)

Improved to become LTE-A (Advanced)

31
Q

Cellular: 5G

A

Up to 10Gbps using high-band 5G frequencies

3 Frequency Bands:
Low-Band (600-850MHz) - Up to 30-250Mbps
Mid-Band (2.5-3.7GHz) - Up to 100-900Mbps

High-Band (25-39GHz) - Extremely high (Gbps range)
Tower range is much smaller; easily blocked

32
Q

GSM

A

Global System for Mobile Communications:
A cellular technology that takes your voice during a call & converts it to digital data

A SIM card is used to identify yourself to the network

Uses WCDMA (Wideband CDMA)

Widely supported across the globe

33
Q

CDMA

A

Code-Division Multiple Access:
A cellular technology that uses code division to split up the channel

For every call made, data is encoded with a unique key & then all data streams can be transmitted at once in a single channel

34
Q

Microwave (WiMAX)

A

Uses a beam of radio waves in the microwave frequency range to transmit info between two fixed locations

UHF (Ultra-High Frequency)
SHF (Super-High Frequency)
EHF (Extremely-High Frequency)

Up to 1Gbps depending on monthly rate
Antennas must maintain line-of-sight
About 40miles/64km distance limitation

35
Q

SDWAN

A

Software-Defined WAN:
Virtual WAN architecture
Allows enterprises to leverage any combo of transport services to securely connect users to their apps

Centralized control function
Securely/intelligently redirect traffic across WAN
Cloud-first enterprises

Allows WAN to be more dynamic/efficient

Reduces bottlenecks caused by traditional, centralized WAN architecture

36
Q

mGRE

A

Multipoint Generic Routing Encapsulation:
A protocol that can be used to enable one node to communicate with many other nodes

Point-to-multipoint link

Usually combined with DMVPN for security

Dion (N10-008) (27 decks)

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