1.4 Explain the characteristics and benefits of various WAN technologies - Paiet/Tech-Journal-for-Everything GitHub Wiki

1.4 Explain the characteristics and benefits of various WAN technologies

Fiber
- SONET
  - Synchronous Optical Network (U.S./ANSI)
  - Synchronous Digital Hierarchy (Europe/ITU)
  - Developed as a synchronous data transfer standard so that telcos from different areas could use different equipment vendors
  - Optical Carrier (OC)
    - Specifications for using fiber optic cable
    - Used for transmitting over long distances
    - Standards
      - OC-N N x 51.84 (Mbps)
      - OC-1 51.84
      - OC-3 155.52
      - OC-9 466.56
      - OC-12 622.08
      - OC-18 933.15
      - OC-24 1244.16
      - OC-36 1866.24
      - OC-48 2488.32
      - OC-192 9953.28
      - OC-768 39813.12
  - Synchronous Transfer/Transport Signal (STS)
    - Specification for using electric signals over copper
    - Used for transmitting over very short distances
      - Usually within the site or from rack to rack
    - Standards
      - STS-N N x 51.84 (Mbps)
      - STS-1 51.84
      - STS-3 155.52
      - STS-9 466.56
      - STS-12 622.08
      - STS-18 933.15
      - STS-24 1244.16
      - STS-36 1866.24
      - STS-48 2488.32
      - STS-192 9953.28
      - STS-768 39813.12
  - Dual Fiber Ring topology
    - Adds reliability with redundancy
    - Self correcting ring
      - If one ring is severed, an alternate or standby ring automatically takes over
  - Network Architecture
    - 3 tiers
      - Local Collector Ring
        
        This is the point at which the end user connects to SONET services
        
        A SONET multiplexer called a Digital Cross-Connect Switch (DCS) connects the end user to the SONET ring.
        
        Can be connected to by ATM, T1, T3, IDSN, or DSL voice
      - Regional Networks
        
        Combines multiple Local Collector Rings
        
        Add/Drop Multiplexers (ADMs)
        
        Gives Local Collector Rings access to Regional Networks
      - Broadband Backbone Networks
        
        High-speed, high bandwidth reliable transport over long distances
        
        Connects Regional Networks
  - Typically employed as a high-speed backbone for other systems because of its high bandwidths and high speeds
    - ATM, Frame Relay, Metro Ethernet
  - Time Division Multiplexing (TDM)
    - Each signal is given a time slot
    - The time slot is dedicated to that particular signal
      - Signal retains its time slot whether it sends traffic or not
  - OSI Layer 1 (Physical Layer)
    - Single-mode/multi-mode fiber cable
    - Transmission media technology
    - Data must be framed by a Data-Link layer protocol (Layer 2) before being ready for transmission by SONET media
Wavelength Division Multiplexing
- DWDM
  - Dense Wavelength Division Multiplexing
  - Used as a SONET alternative
  - Transmits and carries data from multiple sources over multiple wavelengths
    - Separate light beams sources use different frequencies/colors to transmit their data
    - Allowing for simultaneous data transfers
  - Multiplexes up to 80 separate data channels
  - Can handle multiple protocols simultaneously
- CWDM
  - Coarse Wavelength Division Multiplexing
  - Multiplexes the same way DWDM does, but is less efficient in the way it spaces light signals
  - Because of the limitations of CWDM, it is less expensive
Frame relay
- OSI Layers 1 and 2
- Packet switched
- Successor to X.25
  - More reliable due to variable length packets, simplified headers, little overhead, and no error correction
- Speeds from 56kbps to 1.544Mbps
- Virtual Circuits
  - Permanent Virtual Circuits (PVC)
    - Established by the service provider
    - Always-on connection
    - Works like a leased line for all necessary connections but only needs one connection to the frame relay network instead of
- Committed Information Rate (CIR)
  - Minimum guaranteed bandwidth
  - CIR can be exceeded when network allocation is low
  - If network allocation is high, traffic that exceeds the CIR will be marked as "discard eligible" and then dropped
  - Zero CIR
    - aka CIR 0
    - Lowest priority traffic
    - Will always be dropped first
    - Economical way to employ frame relay
- DTE/DCE
  - Data Terminal Equipment (DTE)
    - Terminal here meaning the computer terminal, usually the end user's router
  - Data Communication Equipment (DCE)
    - aka Data Circuit-Terminating Equipment
    - Frame Relay Switch
    - Used to establish, maintain, and terminate network communications between DTEs through the Frame Relay cloud
      - Frame Relay Bearer Service (FRBS)
    - DCEs provide clocking (used for sychronization)
  - DTE device connects to DCE (CSU/DSU for a T1/E1)
- DLCI
  - Data Link Connection Identifier
  - Layer 2 addressing
  - Basically a label for each frame relay connection
Satellite
- Made up of two distinct segments
  - Space and Ground
    - Space
      - Consists of constellation of satellites
      - Satellites are in geo-synchronous orbit for delivering services wirelessly to users on the ground
    - Ground
      - Ground terminals for accessing the satellite network
        
        Fixed terminals which are stationary
        
        Transportable terminals which are portable, but are stationary during transmission
        
        Mobile terminals which are able to transmit and receive while in motion
- Satellite services
  - Internet
    - Usually found in areas where no other type of high-speed internet is available
    - Some require secondary connection for upload
      - At one time required a phone line
    - Suffers from an inherent latency
      - Data has to be sent to and from the satellites in orbit
        
        This takes time, causing a delay
  - Telephone
    - Provides telephone service for user that are in an area that has no access to POTS or Cellular
    - Sat-phone to Sat-phone calls are directly connected directly
    - Sat-phone to Landline or cellular phone
      - Satellite routes the call through a "gateway"
        
        Gateway is a Earth based telephone system with access to the satellite system and handles call routing between them
    - Works great in open areas, not so great in closed areas
  - Television
    - Direct Broadcast center sends the channels to the satellites
    - Satellites then transmit the signals to Earth
    - Subscribers aim a dish at the DB's satellite and pick up the signal and send it to the receiver (aka set-top box)
  - Global Positioning System (GPS)
    - Used for geographical navigation by using a group of 27 satellites
      - 24 active sats with an additional 3 in standby mode
    - Pinpoints the receiving device by calculating the time and distance signals from at least 4 sats
  - Very Small Aperture Terminal (VSAT)
    - Uses a dish antenna to send and receive signals
      - Usually antenna is 1.2 to 2.4 meters in diameter
    - Can transmit video, voice, and data
    - Antenna is connected to a MODEM which handles the conversions of sending and/or received data, voice, or video information
    - Point to Point, Star, or Mesh topologies
- Line of Sight (LoS)
  - Obstructions can cause signal degradation or total loss
    - Solid obstacles like trees, buildings, animals
    - Atmospheric conditions
      - Rain
      - Snow
      - Heavy overcast
      - Wind (moves the receiving dish off alignment)
- Setup is difficult
  - It can take a lot of work to align the receiving dish with the satellite in orbit
- Download speeds
  - Slow (256 Kbps - 1.5 Mbps typical)
    - Providers are now promising speeds of up to 15 Mbps
Broadband cable
- Internet connection delivered over coaxial cable
- Service provider is a cable TV company
  - Cable modem necessary
- Shared connection
  - The more users occupying the segment the lower the available bandwidth
  - Slow downs are common during certain times
    - After work
    - Evening
    - Weekends
- Download speeds fluctuate
  - 768 Kbps is typically guaranteed
  - 3-7 Mbps is common
  - 20+ Mbps is possible
    - Starting to become the norm
DSL/ADSL
- Digital Subscriber Line
- Works on OSI Layers 1 and 2
- Uses ATM
  - DSL is a method of access to an ATM network
  - Implements Point-to-Point Protocol over Ethernet (PPPoE)
    - This provides authentication, encryption, and compression for the end user
    - Allows the provider to regulate and monitor bandwidth utilization
- High-speed internet over pre-existing telephone lines
  - DSL modem required
    - Converts digital signal into analogue for transmission over phone line
  - DSL Line Filter
    - Phone calls and data can coexist on the same line
    - Plugs into the phone jack splitting it into 2 jacks
      - One for the phone line and the other for the DSL
    - Acts as a line conditioner filtering out "noise"
- Cost effective high-speed internet access
  - Great for homes and small businesses
- Download speeds
  - 1.5-7 Mbps typical
  - Bandwidth can be affected by
    - Line quality
    - Distance from Central Switching Office (CSO)
    - Local electronic interference
- ADSL (Asymmetrical DSL)
  - Download and upload speeds differ (hence asymmetrical)
    - Download speeds are usually faster than upload speeds
  - 26.075 - 137.825 kHz range for upstream communications
  - 138 - 1104 kHz range for downstream communications
  - Download speeds
    - 1.5-24 Mbps depending on your ADSL version
      - ADSL, ADSL2, ADSL2+
    - Average speeds depend on many factors, but typical speeds are 6-12 Mbps
      - ADSL maxes out at 8Mbps
    - ["ADSL Speed vs. Distance" graph][2]
  - Upload speeds
    - 0.5-3.5 Mbps depending on your ADSL version
    - 1 Mbps is typical
  - Dedicated bandwidth with ADSL
  - Tends to be a very reliable service
  - Hard to get in rural areas because of distance from the CSO is limited to 18000ft
  - Homes with older, low quality wiring can limit speeds
  - The farther away from the Switch, the slower speeds
ISDN
- Integrated Services Digital Network
- ISDN uses existing telephone infrastructure for both voice and data but requires a digital loop.
- Operates on OSI Layers 1,2,& 3
  - Utilizes "identifiers"
    - Telephone number of the circuit
    - Service Profile Identifier (SPID)
    - 3 Dynamic Identifiers that are generated during usage
      - TEI (Terminal Endpoint Identifier)
      - BC (Bearer Code)
      - SAPI (Service Access Point Identifier)
  - Requires the use of...
    - Terminal Equipment (TE)
    - Terminal Adapter (TA)
      - Used to connect the computer terminal to the ISDN network
      - Signal is not converted to analog, but stays digital
    - Network Termination (NT)
      - Connects the ISDN customer to the telephone local loop
      - Separate device or built-in to the TA
  - Download speeds
  - 2 Mbps
  - 128 Kbps average
- Channels
  - B Channel (Bearer Channel)
    - Carries Data
    - 64 Kbps
  - D Channel (Signal Channel)
    - Call setup and link management
    - 16 Kbps
      - Channels, and their bandwidth, are aggregated together
        
        Create one large pipe from many smaller pipes
- BRI and PRI ISDN
  - BRI (Basic Rate Interface)
    - Comprised of 2 B channels and 1 D channel
      - (64 x 2) + 16 = 144 Kbps
    - Relatively inexpensive
      - $20-$40 per month
    - Good for home or small business although rare to find anymore since DSL and Cable
  - PRI (Primary Rate Interface)
    - Comprised of 23 B channels and 1 D channel
      - (23 x 64) + 64 = 1536 Kbps
    - Expensive
      - $200-$300 per month
    - Good for business use

Explain the characteristics and benefits of various WAN technologies Pt2

ATM
- Asynchronous Transfer Mode
  - Versatile
    - Able to carry any kind of data
      - Voice, video, audio, email, files
  - High bandwidth availability
    - Bandwidth limited by the transmission media connected to it
    - Usually a fiber backbone
      - Can hit the 10Gbps levels when on OC-192 connection (at least, theoretically)
  - OSI Layers 1 and 2
  - ATM uses Layer 2 frames called "Cells"
    - Cells are fixed at 53 bytes in size
      - 5 byte header and 48 byte payload
      - This makes for better bandwidth management
    - Cells are passed through the ATM network by ATM switches
      - ATM Switches are usually
  - QoS
    - Connection oriented, end-to-end Quality of Service
  - ATM ARP
    - ATM's version of Address Resolution Protocol
    - Maps layer 3 addresses to layer 2 address
  - ATM Network Interfaces
    - User-to-Network Interface (UNI)
      - End-user ATM border device
      - Connects one ATM network to another ATM network or a LAN
    - Network-to-Network Interface (NNI)
      - ATM switch inside an ATM network
  - Virtual Channels (VCs)
    - Individual connections
    - Virtual Channel Identifier (VCI)
      - 16 bit ID in Cell header
  - Virtual Paths (VPs)
    - Virtual Path Identifier (VPI)
      - 8-12 bit ID in Cell header
      - Made up of VCs with the same path
PPP/Multilink PPP
- Point-to-Point Protocol
  - Remote access/networking protocol that provides compression, encryption (for passwords), and authentication
  - Layer 2 protocol
  - Sends IP data over point-to-point serial connections
  - Synchronous and Asynchronous connections
  - PPP Flavors
    - PPPoE
      - PPP over Ethernet
      - Allows the use of PPP with DSL
      - Discovers MAC addresses on client before creating a connection
        
        PPPoA
        
        PPP over ATM
    - EAP
      - Extensible Authentication Protocol
      - Extends PPP authentication capabilities
      - Adds support for the use of
        
        Tokens
        
        Smart Cards
        
        Certificates
    - PEAP
      - Protected Extensible Authentication Protocol
      - Secures EAP by using TLS encryption between the client and server
      - Add more security by also using MS-CHAPv2
        
        Microsoft Challenge Authentication Protocol version 2
    - Multilink PPP
      - Distributes traffic throughout multiple PPP connections
      - Aggregates 2 PPP ports to create a single port
        
        Increases bandwidth
      - Home user combining 2 56kbps modems
      - Business combining 2 leased lines
MPLS
- Multi-Protocol Label Switching
  - Successor to Frame Relay and ATM
  - Layer "2.5"
  - Label-Switching
    - Traditional routing gets requests for transmission, looks up the next router in the routing table, and sends the data along to that router. The process repeats until the data reaches its destination.
    - Label-switching creates a label with a pre-configured route path and sends the data along that path to its intended destination router
      - The routers don't need to look at the Layer 3 headers, only the label
      - The destination router then removes the label and delivers the traffic normally
  - Supports QoS, VPN, and Ethernet Virtual LAN
  - Very scalable
    - Small or large networks that have thousands of site locations that span any distance
      - MPLS is usually found connecting WAN sites, while smaller sites usually utilize VPN for cost-benefit reasons
  - Very reliable
    - 99.9 - 99.99% uptime
  - ["MPLS for Dummies"][1]
GSM/CDMA
- Global System for Mobile Communications and Code Division Multiple Access
  - Protocols for 2G cellular networks
  - Use RF for transmitting and receiving voice and data
  - Both have ports to 3G
    - GSM uses * Universal Mobile Telecommunications System * (UMTS)
    - CDMA uses CDMA2000
- LTE/4G
  - Provides broadband speeds for mobile/cellular networks
  - Long Term Evolution (LTE)
    - Uses an IP network
    - Peak download speeds of 1Gbps
    - Peak upload speeds of 500Mbps
- HSPA+
- High Speed Packet Access
- Based on 3GPPr5
- High speed data service over mobile networks
  - Download speed up to 14Mbps
  - Upload speed up to 5.8Mbps
- Uses multiple carriers in the 5MHz range with large data channels
  - Decreasing latency
  - Increased capacity for web traffic
- 3G
  - Mobile/cellular network that supports speeds of at least 200Kbps
- EDGE
  - Enhanced Data-rates for GSM Evolution
  - 3G standard based on GMS
  - Speed is 3xGSM
    - Approximately 384Kbps
Dialup
- Internet connectivity using the PSTN or Public Switched Telephone Network
  - AKA Plain Old Telephone Service or POTS
- Computer is connected to existing telephone service via a phone cable with an RJ11 connector from the MODEM to the phone jack
- Bandwidth is limited
  - Top speed of 56 Kbps (FCC limits to 53Kbps)
- To connect to network
  - Computer dials up a RAS (Remote Access Server)
  - User authenticates with a username and password
  - Connection is then established
- Still around even though it isn't as robust as other internet connections
  - Only phone service and a MODEM is required
  - Cheap!
  - Easy!
  - Reliable! (even when power goes out, POTS is still working)
WiMAX
- World Wide Interoperability for Microwave Access
- Implements the 802.16 wireless standards for Metropolitan Area Networks
- Range of around 50 km with fixed stations and 5-16 km for mobile stations
- Operates in the 2 Ghz - 11 Ghz range
- Download speeds
  - About 70 Mbps
  - Line-of-Sight (LoS)
    - Direct, unobstructed path from transmitter to receiver
  - Non-Line-of-Site (NLoS)
    - Partially obstructed path from transmitter to receiver
Metro-Ethernet
- Metropolitan Area Network (MAN) that uses Ethernet
  - Can connect LANs to a WAN or to the Internet
  - Connects remote offices to HQ that are spread out in a large city
- Works at OSI Layer 2
- Can be provided over Ethernet, SONET, MPLS...
- Topology can be Star, Ring, Mesh (full or partial)
- Capable of speeds of...
  - 1Gbps over fiber at a distance of 100Km
  - 100Gbps over fiber at a distance of 10Km
  - Future speeds predicted at Terabit level
- Can connect to Metro-Ethernet using
  - Layer 2 switch
  - Layer 3 router
- Supports 802.1q VLAN tagging
  - Allows users to extend their VLANs across multiple sites
- Being used mostly as core backbone for data replication between sites
Leased lines
- Dedicated bandwidth that is always on
  - End user pays a fixed rate fee for access to a line with a guaranteed amount of bandwidth
- Bandwidth varies with line availability
  - Usually falls somewhere between 56kbps and 2Mbps
- T-1 - 1.544 Mbps
- T-3 - 44.736 Mbps
- E-1 - 2.048 Mbps
- E-3 - 34.368 Mbps
- OC3 - 155.52 Mbps
- OC12 - 622.08 Mbps
Circuit switch vs packet switch
- Circuit switched
  - A single path connection from one end to another
  - "Circuit" = connection path
  - The circuit is established, bandwidth is dedicated to the path for transmission, data is transmitted, connection is terminated
  - If another data transmission is needed, the process repeats although not necessarily through the exact same path
  - PSTN and ISDN are examples of circuit switching
- Packet switched
  - Sends data in small chunks called packets
    - Data is broken up into packets which are organized by sequence numbers
  - Each packet has all the necessary routing info for getting to the desired destination and takes the best available route at the time of transmission
    - Each packet determines the best route as it travels, making necessary route adjustments on the fly
      - Route adjustments my be necessary due to broken links or network congestion
  - Once packets are delivered, they are reassembled into the the correct sequence
    - Since packets take multiple routes, they can arrive out of order and need re-orerding at the end point.
    - Because of this, packet switching isn't the best option for live voice and/or video data
      - Live voice/video data packets can arrive out of order causing jitter or delays
        
        Stream can drop entirely