WAN Concepts
WAN Technologies
with speeds
WAN Services
Internet Connectivity
Remote Access
100

Central office (CO)

A switching facility connected to the WAN. It is the nearest point of presence for the WAN provider. It provides WAN cloud entry and exit points.

100

(POTS)

Plain Old Telephone Service (POTS) 

POTS characteristics include:

  • Existing wires use only one twisted pair.
  • Analog signals are used through the local loop.
  • 56 Kbps
100

Public switched telephone network (PSTN)

The PSTN is the network used to place local and long distance phone calls.

  • The PSTN is a circuit-switched network. A dedicated circuit is established when the call is placed and remains in place throughout the call.
  • The local loop uses analog signals over POTS (through regular telephone cable wires). The long distance network typically uses digital signaling over fiber optic.
  • End-to-end speeds are limited to 56 Kbps, a restriction imposed by POTS in the local loop at each end.
  • A modem is required to convert digital signals to analog.
  • Remote access clients use the PSTN as a way to access the network or as a temporary or backup connection between sites.
100

Leased Lines

A leased line refers to a dedicated communication line rented from a telecommunications provider. It provides point-to-point connectivity between two locations and typically offers high reliability and consistent performance. Leased lines are commonly used for connecting remote offices, data centers, or connecting to the internet. They are leased for a fixed monthly or yearly fee, hence the term "leased line."

100

Authentication

The process of proving identity where logon credentials are exchanged and logon is allowed or denied.

200

Local loop

The cable that extends from the central office to the customer location. The local loop is owned and maintained by the WAN service provider.

200

T1

1.544 MbpsT-carrier is a digital standard widely deployed in North America.

  • T1 lines usually run over two pairs of shielded twisted pair (STP) cabling. They can also run over other media like coaxial, fiber optic, or satellite.
  • A T1 line has 24 channels that each run at 64 Kbps.
200

Integrated Services Digital Network (ISDN)

ISDN is a WAN technology that provides increased bandwidth within the local loop. These are two forms of ISDN:

  • ISDN basic rate interface (BRI) uses digital signals over POTS. The traditional phone line is divided into separate channels: two 64 Kbps bearer (B) channels and one 16 Kbps control (D) channel. ISDN BRI is often called 2B + 1D.
  • ISDN primary rate interface (PRI) uses digital signals.
    • In North America it uses a T1 line with 23 64 Kbps B channels and one 64 Kbps D channel (up to 1.544 Mbps).
    • In Europe it uses an E1 line with 30 64 Kbps B channels and one 64 Kbps D channel in (up to 2.048 Mbps).
    • ISDN PRI is often referred to as 23B + 1D.
200

Digital Subscriber Line
(DSL)

A high-speed digital bandwidth connection from a phone wall jack on an existing telephone network. With DSL, data and voice are both sent on the same copper wire with data using one frequency and voice using another.

200

Authorization

The process of identifying the resources that a user can access over the remote access connection.

300

WAN cloud

The collection of equipment that makes up the WAN network. The WAN cloud is owned and maintained by telecommunications companies. 

300

T3

  • T3 lines usually run over fiber optic cable.

    • A T3 line has 672 channels that each run at 64 Kbps.
  • A T1/T3 connection requires a channel service unit (CSU) and a data service unit (DSU).
    • A CSU manages the digital channel.
    • A DSU reads and writes synchronous digital signals.
  • To connect routers by using their CSU/DSU interfaces, you can use a T1 crossover cable.
  • T3 is also known as a Digital Signal 3 (DS3).

44.736 Mbps

300

Multiprotocol Label Switching (MPLS)

A WAN data classification and data-carrying mechanism.

  • MPLS is a packet switching technology that supports variable-length frames.
  • MPLS adds a label to packets between the existing Network and Data Link layer formats. Labels are added when the packet enters the MPLS network and are removed when the packet exits the network.
  • Information in the label is used to switch the packet through the MPLS network to the destination.
  • MPLS labels can identify the route or even the network type to use. MPLS labels are often used to provide different classes of service for data streams.
  • MPLS is a connection-oriented protocol.
300

Cellular networking

A digital mobile network that can provide internet access. It is commonly used by phones, tablets, laptops, and mobile hot spots.

300

Accounting

An activity that tracks or logs the use of the remote access connection.

400

Wavelength-division multiplexing

A WAN technology that allows multiple signals to be carried along a single fiberoptic cable in both directions using different wavelengths of light for each signal. WDM types include coarse and dense. Both coarse and dense WDM can be single- or bi-directional.

400

E3

  • An E1 line has 32 channels that run at 64 Kbps.
  • An E3 line transmits 16 E1 signals at the same time.
  • E1/E3 connections require a CSU/DSU.


34.368 Mbps

400

Distributed switching

Distributed switching is an architecture in which multiple processor-controlled switching units are distributed. There is often a hierarchy of switching elements with a centralized host switch and remote switches located close to concentrations of users. Distributed switching:

  • Is often used in telephone networks, though it is often called host-remote switching.
  • Is used in rural areas, where population centers tend to be too small to economically deploy a full-featured dedicated telephone exchange. The distances between these centers make the transmission costs relatively high.
  • Can use many data-centric telecommunications platforms, such as routers and Ethernet switches, utilize distributed switching on separate cards within an equipment chassis.
400

Cable

Internet access provided by companies that offer cable TV service using the same lines.

400

AAA Server

A server used to centralize authentication, authorization, and accounting for multiple remote access servers. Connection requests from remote clients are received by the remote access server and are forwarded to the AAA server to be approved or denied. Policies defined on the AAA server apply to all clients connected to all remote access servers. 


500

Distributed switching

An architecture in which multiple processor-controlled switching units are distributed. There is often a hierarchy of switching elements with a centralized host switch and remote switches located close to concentrations of users.

500

OC-1

Optical carriers use wavelength division multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

  • Each OC level is a multiple of the base rate (OC-1).

51.84 Mbps

500

Multiprotocol Label Switching (MPLS)

A WAN data classification and data-carrying mechanism.

  • MPLS is a packet switching technology that supports variable-length frames.
  • MPLS adds a label to packets between the existing Network and Data Link layer formats. Labels are added when the packet enters the MPLS network and are removed when the packet exits the network.
  • Information in the label is used to switch the packet through the MPLS network to the destination.
  • MPLS labels can identify the route or even the network type to use. MPLS labels are often used to provide different classes of service for data streams.
  • MPLS is a connection-oriented protocol.
500

Satellite

Internet access by using signals transmitted to and received from orbiting satellites.

500

Password Authentication Protocol (PAP)

The username and password are sent in clear text to the remote server, which either accepts or rejects them. While this is the most simple form of authentication, for security concerns, it is no longer used.

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