NET-125-1D1 CHAPTER 12

LTE (Long-Term Evolution)

A 4G cellular network technology that, in its latest version (called LTE-Advanced), can theoretically offer 1 Gbps throughput, although actual speeds are significantly less.

DSL (digital subscriber line)

A WAN connection technology that operates over the PSTN and can support multiple data and voice channels over a single line.

DIA (dedicated Internet access)

A WAN service where the cable or a portion of its available bandwidth is dedicated to a single customer and comes with an SLA-defined guarantee of minimum uptime percentages and maximum recovery times if the service goes down. The cable itself or a portion of its available bandwidth is dedicated to a single customer; this is more common for business customers and comes with an SLA-defined (service-level agreement) guarantee of minimum uptime percentages and maximum recovery times if the service goes down. Bandwidth is symmetrical or synchronous, meaning download and upload speeds are the same. This is especially important for businesses that back up large amounts of data online. The subscription will also often include a number of static IP addresses.

ATM (Asynchronous Transfer Mode)

A WAN technology functioning primarily at Layer 2 that delivers data using fixed-size packets, called cells.

Metro (Metropolitan) Ethernet

A WAN technology that sends Ethernet traffic across MAN connections.

broadband

A WAN technology where the cables and available bandwidth are shared between multiple customers. Especially well-suited for residential customers, the cables (whether telephone, copper, or fiber) and available bandwidth are shared between multiple customers. The ISP makes a "best effort" attempt to provide up to the advertised bandwidth, and actual performance varies considerably during busy usage. Bandwidth is also asymmetrical or asynchronous, meaning download speeds (data traveling from the carrier's switching facility to the customer) are faster than upload speeds (data traveling from the customer to the carrier's switching facility). For a higher premium, businesses can get faster broadband speeds and possibly a static IP address included in the package. However, uptime, service, and bandwidth are still not guaranteed.

dedicated line

A cable or other telecommunications path that has continuously available communications channels and is not shared with other users.

CDMA (Code Division Multiple Access)

A cellular standard that uses spread-spectrum technology, in which a signal is spread over a wide bandwidth so that multiple users can occupy the same channel.

virtual circuit

A connection between network nodes that, although based on potentially disparate physical links, logically appears to be a direct, dedicated link between those nodes.

OC-12

SONET throughput service that provides a maximum 622.08 Mbps. Used by ISPs for WAN connections and by some large enterprises. Consists of four OC-3s.

T-carrier

Standards that specify a method of signaling using TDM (time division multiplexing) over two wire pairs to divide a single channel into multiple channels, which enables digital data to be transmitted at high speeds over the PSTN.

Switching

The determination of how connections are created between nodes on a network.

HSPA+ (High Speed Packet Access Plus)

A 3G mobile wireless technology released in 2008 that uses MIMO and sophisticated encoding techniques to achieve a maximum 168-Mbps downlink throughput and 22-Mbps uplink throughput in its current release.

CSU/DSU

A device that serves as the connection point for a T1 line at the customer's site.

T3

A digital carrier standard used in North America and most of Asia that can carry the equivalent of 672 channels for voice, data, video, or audio, with a maximum data throughput of 44.736 Mbps.

T1

A digital carrier standard used in North America and most of Asia that provides 1.544-Mbps throughput and 24 channels for voice, data, video, or audio signals.

Frame relay

A group of Layer 2 WAN protocols that separate data into variable-length frames, which are then relayed from one node to another without any verification or processing.

SONET (Synchronous Optical Network)

A high-bandwidth WAN signaling technique that specifies framing and multiplexing techniques at the Physical layer of the OSI model.

SVC (switched virtual circuit)

A logical, point-to-point connection that is established when parties need to transmit, then terminated after the transmission is complete.

TDMA (time division multiple access)

A method of multiplexing in which signals from several sources on a channel are separated by timeslots.

PVC (permanent virtual circuit)

A point-to-point connection over which data may follow any number of different paths. Connections that are established before data needs to be transmitted and are maintained after the transmission is complete. Note that in a PVC, the connection is established only between the two points (the sender and receiver); the connection does not specify the exact route the data will travel.

circuit-switched

A type of switching in which a connection is established between two network nodes before they begin transmitting data. Bandwidth is dedicated to this connection and remains available until users terminate the communication between the two nodes.

packet-switched

A type of switching in which data is broken into packets before being transported. Data is broken into packets before it's transported. Packets can travel any path to their destination because, as you already know, each packet contains the destination address and sequencing information. Consequently, packets can attempt to find the fastest circuit available at any instant. When packets reach their destination node, the node reassembles them based on control information included in the packets. The greatest advantage to packet switching lies in the fact that it does not waste bandwidth by holding a connection open until a message reaches its destination, as circuit switching does. Ethernet networks and the Internet are the most common examples of packet-switched networks.

MPLS (multiprotocol label switching)

A type of switching that enables multiple types of Layer 3 protocols to travel over any one of several connection-oriented Layer 2 protocols.

SDSL (symmetric DSL)

A variation of DSL that provides equal throughput both upstream and downstream between the customer and the carrier. has equal download and upload speeds maxing out around 2 Mbps. Symmetrical transmission is suited to users who both upload and download significant amounts of data—for example, a bank's branch office that sends large volumes of account information to the central server at the bank's headquarters and, in turn, receives large amounts of account information from the central server at the bank's headquarters. SDSL cannot use the same wire pair that is used for voice signals. Instead, this type of DSL uses the extra pair of wires contained in a telephone cable (which are otherwise typically unused). REALLY BAD IMO

VDSL (very high bit rate DSL or variable DSL)

A variety of DSL that provides higher throughput than its predecessor, ADSL. is faster than ADSL and is also asymmetric, with faster download speeds than upload speeds. A VDSL line that carries 50-60 Mbps in one direction and 5-10 Mbps in the opposite direction can extend only a maximum of 1.6 km before dropping to speeds similar to ADSL2+. VDSL2 offers throughput speeds nearing 100 Mbps in both directions but drops off quickly at even shorter distances. These limitations might suit businesses located close to a telephone company's CO (for example, in the middle of a metropolitan area), but it won't work for most individuals.

CET (Carrier-Ethernet Transport)

An Ethernet-based transport solution designed to overcome the inherent weaknesses of implementing Ethernet outside of a LAN environment.

smart jack

An intelligent type of NIU located at the customer's demarc that can provide diagnostic information about the interface.

GSM (Global System for Mobile Communications)

An open standard for cellular networks that uses digital communication of data separated by time slots on a channel.

line driver

Essentially a repeater, a line driver can be installed either on copper lines (in which case, it is called a copper line driver) or fiber lines (in which case, it is called a fiber line driver) to boost the signal across greater distances. The device might be placed on either side of the demarc and, if located on the customer's side, might be owned by either party.

ADSL (asymmetric DSL)

The most popular variation of DSL and offers faster download speeds than upload speeds. 24 Mbps downstream and a maximum of 3.3 Mbps upstream slow

PSTN (Public Switched Telephone Network)

The network of lines and carrier equipment that provides wired telephone service to most homes and businesses.

NIU (network interface unit)

The point at which the ISP's local loop connects to the customer's network The NIU, or NID (network interface device), at the demarc connects the ISP's local loop to the customer's network.