Internet & The Cloud—NETWORKING ESSENTIALS—CompTIA A+ (220-1001) A-PLUS Certification Prep Course Notes

Internet & The Cloud

The Internet

• Beyond the LAN
  • Local Area Network (LAN) computers share the same network ID.
  • A wide area network (WAN) is two or more LANs interconnected by one or more routers
  • A metropolitan area network (MAN) is a WAN that spans a city.
  • A personal area network (PAN) is a point-to-point connection used only in Bluetooth connections
  • LAN—computers hooked together to one switch (All share identical Network ID)
  • WAN—bunch of LANs interconnected with routers. Each LAN has a unique network ID.
  • CAN—Campus Area Network
  • MAN—Metropolitan Area Network
  • WLAN—Wireless Local Area Network
  • Intranet—private network

• Internet Tiers
  • The Internet is composed of many organizations that connect to each other
  • Tier 1 are providers that do not pay anyone (peering)
  • Tier 2 are providers that pay some Tier 1s but also peer with Tier 1 and Tier 2s
  • Tier 3 providers pay Tier 1 or Tier 2 providers
  • Peering agreements
  • NOCs (Network Operation Centers)

• Dial-Up Connections
  • Dial-up also goes by the name ‘plain old telephone service’ (POTS)
  • Dial-up plugs RJ-11 connectors to the phone system
  • Modems converts analog POTS to digital COM port connections.
  • Modems connect to other modems using a phone number
  • POTS is aka PSTN (Public Switched Telephone Network)
  • Comport
  • Dial-Up 56 kbps Max speed
  • ISDN (Integrated Services Digital Network)—set of communication standards that uses digital transmission to make phone calls, video calls, transmit data and other network services over the circuits of the traditional PSTN (Public Switched Telephone Network); Still used by some “cottage industries” like voice-over actors!)

• Broadband Connections
  • Broadband are high-speed, always on connections
  • Digital Subscriber Line (DSL) runs on top of telephone service
  • Data Over Cable Service Interface Specification (DOCSIS) uses cable connections
  • Satellites are handy for more remote locations
  • Many metro areas provide native Ethernet for an ISP
  • ”Modem” has become a generic ’catch-all’ phrase even when technically not a modem
  • ADSL—(Asymmetric DSL)-upload speed slower than download speed
  • SDSL—(Symmetric DSL)-upload & download speeds the same
    • Speeds—up (768k – 3Mbps), down (1.5-7Mbps)
  • Fiber (speed up to GB both ways)
    • Fiber is really DSL (marketing term)
  • PPPoE (Point-to-Point Protocol Over Ethernet) DSL may sometimes require PPPoE
  • Cable uses DOCSIS
    • Speeds—1.5/10 Mbps, today 50/100 Mbps or better
  • Satellite—rural or remote areas
    • Speeds—3 Mbps/ 25 or higher
  • 802.11 service providers also exist (more in rural areas)

• Firewalls & Servers
  • All internet connections require a client & a server
  • One of the primary functions of firewalls is to block ports
  • Client and server networks use firewalls
  • Firewalls block ports on an incoming vs. outgoing concept
  • Servers must not block incoming ports on the ports to which they listen

• FTP
  • File Transfer Protocol (FTP) is used to transfer files from one system to another
  • You need an FTP client; almost all web browsers are also FTP clients!
  • FTP uses TCP port 21 in passive mode & TCP ports 20 and 21 in active mode.
  • Active mode FTP requires the router to use port triggering to allow port 20 incoming

• E-Mail
  • Email uses Simple Mail Transfer Protocol (SMTP) to send email from a client to an e-mail server
  • Use Post Office Protocol v3 (POP3) or Internet Message Access Protocol (IMAP) to pull email down from the email server
  • SMTP uses TCP port 25; POP3 uses TCP port 110; IMAP uses port 143.
  • Setting up an email account requires knowledge of the IP addresses or DNS name for the different servers
  • Know these port numbers for the exam, but also be aware that in the real world sometimes private ports are used with completely different numbers.

• Proxy Servers
  • A proxy server acts as a go between (a proxy) between a client and a server.
  • Proxy servers are application specific (e.g., a Web proxy for HTTP and HTTPS)
  • Proxy servers provide firewalling, check for malware, ban bad URLs.
  • Applications must know the address of the proxy server

• Virtual Private Networks (VPNs)
  • VPNs use the Internet to create a private connection to a remote network.
  • We need a VPN client program that connects to a VPN server at the remote network.
  • The VPN client needs to know the IP address of the VPN server to make the connection.

• Internet of Things (IoT)
  • IoT (Internet of Things) means giving Internet capability to devices not traditionally associated with the Internet
  • The most common IoT connections are 802.11, Zigbee, & Z-Wave.
  • IoT requires a hub to link to the IoT devices.
  • Google Home, Amazon Alexa, and Apple Siri add voice capabilities to IoT.