What Technology Does a Wide Area Network Use?

What is a Wide Area Network?

A wide area network also known as a WAN, is going to allow us to connect multiple LANs together across a geographical area. The internet is the largest WAN in the world.

What is the Difference between Circuit and Packet Switching Connection?

Either a dedicated “on when we need it” service or an “always on shared” service.

• Circuit Switching
  • Connect as needed.
  • Dedicated
  • ISDN/Phone Lines
  • No buffer
• Packet Switching
  • Shared bandwidth
  • Always On
  • Have buffering as you may need to wait for the shared resource

Wide Area Network Transmission Media

Medium that carries the data

• Cable Types
  • Phone Lines
  • Cable Lines
  • Fiber Optics
• Wireless
  • Radiowaves/Infrared
  • Satellite
  • Cellular

Types of Circuit Switched Lines

Dedicated Leased Lines

• Offer point to point connectivity and provides Layer 2 connectivity.
• Used as backbone infrastructure to handle large amounts of data
• Dedicated to the customers use.
• Allows for the use of multiplexing, a Layer 2 technology, that allows for the sending of multiple streams of data simultaneously.
• Made from coaxial or fiber cabling.
• 2 sending and 2 receiving cables for each line.

Leased Lines Specifications

T and E are on the same level, T lines are an American standard, E is a European standard

If we want dedicated point to point connectivity, but can’t get a dedicated leased line, we have a couple of options that Allow us to use backbone lines not as dedicated lease lines, but as virtual lease lines.  The ISP can use which ever path it wants between the two points.

Frame Relay

• A layer 2 technology.
• Uses virtual circuits.
  • Permanent virtual circuit:  Always on.
  • Switched virtual circuit: On as needed.
• Send data over T and E lines without having an actual lease over them.
• Maximum transmission based on lines.
• Agreement between ISP and company stating an SLA.
• The ISP can use which ever path it wants.
• Variable length frame.

Asynchronous Transfer Mode

Asynchronous Transfer Mode (ATM), similar to Frame Relay, is a telecommunications standard defined by ANSI and ITU for digital transmission of multiple types of traffic in one network without using separate overlay networks.
Uses virtual circuits
Use cells, which are fixed length packets of 53 bytes

• 5 byte headers
• 48 byte payload

User Network Interface (UNI)

Connection between ATM switch and the endpoint

Network Node Interface (NNI)

Connection between ATM switches

Telephone Lines

• POTS/PSTN – Dial up
  • Plain old telephone system/public switched telephone network.
  • The major reason to use this system is that it provides excellent infrastructure for coverage (Saves costs)
  • 56Kbps
  • Data or phone & modem
    • Modems change digital signals to analog signals as well as vice versa.
  • An analog system
• ISDN – Integrated Services Digital Network
  • Telephone lines & terminal adaptor
    • Allowed to use the phone and internet at the same time.
  • 128Kbs (2 data channel * 64 kbps)
  • PRI – Primary Rate Interface
    • 23 data channels and 1 control channel
    • Large organizations
• DSL – Digital Subscriber Line
  • One of the most common connection
  • Uses phone lines, but sends at higher frequencies (more data, less interference)
  • SDSL: Symmetrical DSL
    • 1.6 Mbps up/down
  • ADSL – Asymmetric DSL
    •  8Mbps Down/1.544 Mbps up
  • VDSL: Very High Bit Rate DSL
    • 52 Mbps Down/ 12 Mbps up

Cable TV

• Data down cable TV lines;
• Different frequencies are used for Internet data and TV data;
• Transceiver – The cable version of a telephone modem;
• 10 Mbps down and 2 Mbps.
• A bit faster that POTS based systems

Fiber Technologies

Faster than cable and telephone as they do not use electrical signals but rather use light signals over glass rods; Light also carries more data so bandwidth increases with the use of optical fiber.   This is why optical fiber is used for backbone cables.

Having said that, there can be many different fiber optic connection types (see the diagram below):

Fiber to the neighbour:  Could mean anywhere within a few miles of your house with the balance of the distance covered by Coaxial/TPs.

Fiber to the curb: Within a mile of the termination point with the balance of the distance covered by Coaxial/TPs.

Fiber to the premises:  Terminates at the site, with coaxial cable through the building.

Fiber to the desktop:  Fiber terminates at the end device with no metal cabling.  Requires you to be in the right location and a fiber router.

Sonet

Synchronous Optical Network
Other protocols run on top of Sonet
Synchronous Digital Hierarchy (SDH)- European version of Sonet
Divided in to different optical carrier levels (like the T’s and E’s) based on speed.

Dense Wavelength Division Multiplexing

• DWDM
• Multiple signals over the same cable as each signal is assigned its own wavelength.
• Increase fiber carrying capacity.

Passive Optical Network

• PON
• Point to multipoint technology (from ISP to homes)
• Uses one wavelength up and one down
• Made up of 3 components
  • OLT – Optical Line Terminal
    • At ISP office and destination if there is fiber there.
  • ONU – Optical Network Unit
    • Near endpoint terminal, like a fiber box.
  • Splitters
    • Powerless non-switching device to split fiber

Wireless Technologies

Satellite

• Need a satellite dish installed at the site.
• May have wide streams.
• Slow, high latency.  Not good for streaming.

WiMax

• World Wide Interoperability Microwave Access
• IEEE 802.16 standard
• Broadband Metropolitan Wireless
• Up to 31 Miles
• 70 Mbps

Cellular

• Internet to cellphone
• Mobile hotspot
• 3G: up to 14.4 Mbps
• HSPA – High speed Packet Access – 168 Mbps
• 4G: Up to Mbps
• The above are standards set by telecom agencies at the government level
• Companies often misrepresent standards.