WANs Flashcards
Circuit-Switched Connection
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
Packet-Switched Connection
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
WAN Physical Media
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
WAN Wireless Media
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
Dedicated Leased Line
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
Metro Ethernet
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
PPP
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)
PPP: LCP
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
PPP Authentication: PAP
Password Authentication Protocol
Performs one-way authentication between client/server
Credentials sent in clear text (not secure)
PPP Authentication: CHAP
Challenge-Handshake Authentication Protocol
Performs one-way authentication using a three-way handshake
Credentials are hashed before transmission
PPP Authentication: MS-CHAP
Microsoft Challenge-Handshake Authentication Protocol
Microsoft-enhanced version of CHAP, includes two-way authentication
PPPoE
PPP over Ethernet
Commonly used with DSL modems
Encapsulates PPP frames within Ethernet frames
Allows for authentication over ethernet
ADSL
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
SDSL
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
VDSL
Very High-Bit Rate DSL
Max distance to DSLAM: 4,000 ft
Downstream: up to 52 Mbps
Upstream: up to 12 Mbps
Cable Modems
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)
Satellite Modems
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)
POTS
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)
ISDN (2 Channels)
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
Frame Relay
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
SONET
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
ATM (& cell size [header/payload])
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)
ATM Virtual Circuits
UNI (User-Network Interface)
Used to connect ATM switches & endpoints
NNI (Network-Node Interface)
Used to connect ATM switches together
MPLS
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
DMVPN
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)
WAN Data Rates
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)
Cellular: 1G
30KHz frequency communication
2Kbps Bandwidth
Cellular: 2G
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
Cellular: 3G
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
Cellular: 4G
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)
Cellular: 5G
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
GSM
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
CDMA
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
Microwave (WiMAX)
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
SDWAN
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
mGRE
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
