CompTIA Network+ N10-005 Chapter 7: Vocabulary
Definition of Key Terms: Chapter 7 Introducing Wide-Area Networks
Terms in this set (35)
dedicated leased line
dedicated leased line A logical connection interconnecting two sites. This logical connection might physically connect through a service provider's facility or a telephone company's central office. The expense of this line is typically higher than other WAN technologies offering similar data rates, because with this line, a customer does not have to share bandwidth with other customers.
A connection that is brought up on an as-needed basis. This connection is analogous to phone call, where you pick up a phone, dial a number, and a connection is established based on the number you dial.
Similar to a dedicated leased line, because this is an always on network. However, unlike a dedicated leased line, this connection allows multiple customers to share a service provider's bandwidth.
(optical carrier) Optical networks often use OC levels to indicate bandwidth. As a base reference point, the speed of an OC-1 link is 51.84 Mbps. Other OC levels are multiples of an OC-1. For example, an OC-3 link has three times the bandwidth of an OC-1 link (that is, 3 * 51.84 Mbps = 155.52 Mbps).
This circuit were originally used in telephony networks, with the intent of one voice conversation being carried in a single channel (that is, a single DS0). This circuit is comprised of 24 DS0s, and the bandwidth of this circuit type is 1.544 Mbps.
This circuit contains 32 channels, in contrast to the 24 channels on a T1
circuit. Only 30 of those 32 channels, however, can transmit data (or voice or video).Specifically, the first of those 32 channels is reserved for framing and synchronization, and the 17th channel is reserved for signaling (that is, to set up, maintain, and tear down a session).
(channel service unit/data service unit) Acts as a digital modem,
which terminates a digital circuit (for example, a T1 or an E1 circuit).
In the same T-carrier family of standards as a T1, a T3 circuit offers an
increased bandwidth capacity. Although a T1 circuit combines 24 DS0s into a single physical connection to offer 1.544 Mbps of bandwidth, a T3 circuit combines 672 DS0s into a single physical connection, with a resulting bandwidth capacity of 44.7 Mbps.
A digital circuit in the same E-carrier family of standards as an E1. An E3
circuit's available bandwidth is 34.4 Mbps.
(Point-to-Point Protocol) ) A common Layer 2 protocol offering features
such as multilink interface, looped link detection, error detection, and authentication.
(Password Authentication Protocol) Performs one-way authentication
(that is, a client authenticates with a server). However, a significant drawback to PPP, other than its unidirectional authentication, is its clear-text transmission of credentials, which could permit an eavesdropper to learn authentication credentials.
(Challenge-Handshake Authentication Protocol) Like PAP, CHAP
performs one-way authentication. However, authentication is performed through a three-way handshake (challenge, response, and acceptance messages) between a server and a client. The three-way handshake allows a client to be authenticated without sending credential information across a network.
(Microsoft Challenge-Handshake Authentication Protocol) A Microsoft-enhanced version of CHAP, offering a collection of additional features not present with PAP or CHAP, including two-way authentication.
(Point-to-Point Protocol over Ethernet) Commonly used between a
DSL modem in a home (or business) and a service provider. Specifically, PPPoE encapsulates PPP frames within Ethernet frames. PPP is used to leverage its features, such as authentication.
(Microsoft Routing and Remote Access Server) A Microsoft Windows
Server ® feature that allows Microsoft Windows ® clients to remotely access a Microsoft Windows network.
(digital subscriber line) A group of technologies that provide high-speed
data transmission over existing telephone wiring. DSL has several variants, which vary in data rates and distance limitations. Three of the more popular DSL variants include asymmetric DSL (ADSL), symmetric DSL (DSL), and very high bit-rate DSL (VDSL).
Attaches to the same coaxial cable (typically in a residence) that
provides television programming. A cable modem can use predetermined frequency ranges to transmit and receive data over that coaxial cable.
(Synchronous Optical Network) A Layer 1 technology that uses fiber-optic cabling as its media. Because SONET is a Layer 1 technology, it an be used to transport various Layer 2 encapsulation types, such as TM. Also, because SONET uses fiber-optic cabling, it offers high data rates, typically in the 155 Mbps-10 Gbps range, and long-distance limitations, typically in the 20 km-250 km range.
satellite (WAN technology)
Provides WAN access to sites where terrestrial WAN solutions are unavailable. Satellite WAN connections can suffer from long round-trip delay (which can be unacceptable for latency-sensitive applications) and are susceptible to poor weather conditions.
(public switched telephone network) The worldwide telephony network
comprised of multiple telephone carriers.
(plain old telephone service) A POTS connection connects a customer
device (such as a telephone) to the public switched telephone network (PSTN).
A telephone company. Some countries have government-maintained telcos, while other countries have multiple telcos that compete with one another.
A connection between a customer premise and a local telephone
company's central office.
(central office) A building containing a telephone company's telephone switching equipment is referred to as a central office (CO). COs are categorized into five hierarchical classes. A Class 1 CO is a long-distance office serving a regional area. A Class 2 CO is a second-level long-distance office (that is, it is subordinate to a Class 1 office). A Class 3 CO is a third-level long-distance office. A Class 4 CO is a fourth-level long-distance office, which provides telephone subscribers access to a live operator. A Class 5 CO is at the bottom of the five-layer hierarchy and physically connects to customer devices in a local area.
tip and ring
The red and green wires found in an RJ-11 wall jacks, which carry voice, ringing voltage, and signaling information between an analog device (for example, a phone or a modem) and an RJ-11 wall jack.
Also known as demarcation point or a demarc extension , this is the point in a telephone network where the maintenance responsibility passes from a telephone company to a subscriber (unless the subscriber purchased an inside wiring plan). This demarc is typically a box mounted to the outside of a customer's building (for example, a residence).
(Integrated Services Digital Network) A digital telephony technology
that supports multiple 64-kbps channels (known as bearer channels or B channels ) on a single connection. ISDN was popular back in the 1980s for connecting PBXs, which are telephone switches owned and operated by a company, to a telephone company's central office. ISDN has the ability to carry voice, video, or data over its B channels. ISDN also offers a robust set of signaling protocols: Q.921 for Layer 2 signaling and Q.931 for Layer 3 signaling. These signaling protocols run on a separate channel in an ISDN circuit (known as the delta channel , data channel , or D channel ).
(Basic Rate Interface) A BRI circuit contains two 64-kbps B channels and
one 16-kbps D channel. Although such a circuit can carry two simultaneous voice conversations, the two B channels can be logically bonded together into a single virtual circuit (by using PPP's multilink interface feature) to offer a 128-kbps data path.
(primary rate interface) A PRI circuit is an ISDN circuit built on a T1 or E1
circuit. Recall that a T1 circuit has 24 channels. Therefore, if a PRI circuit is built on aT1 circuit, the ISDN circuit has 23 B channels and a one 64 kbps D channel. The24th channel in the T1 circuit is used as the ISDN D channel (that is, the channel used to carry the Q.921 and Q.931 signaling protocols, which are used to set up, maintain, and tear down connections).
A Layer 2 WAN technology that interconnects sites using virtual
circuits. These virtual circuits are identified by locally significant data-link connection identifiers (DLCI).
(Asynchronous Transfer Mode) A Layer 2 WAN technology that interconnects sites using virtual circuits. These virtual circuits are identified by a pair of numbers, called the VPI/VCI pair. A virtual path identifier (VPI) identifies a logical path, which can contain multiple virtual circuits. A virtual circuit identifier (VCI) identifies the unique logical circuit within a virtual path.
(Multiprotocol Label Switching) A WAN technology popular among
service providers. MPLS performs labels switching to forward traffic within an MPLS cloud by inserting a 32-bit header (which contains a 20-bit label) between a frame's Layer 2 and Layer 3 headers and making forwarding decisions based on the label within an MPLS header.
(customer premise equipment) This device resides at a customer site. A
router, as an example, can be a CPE that connects a customer with an MPLS service provider.
(edge label switch router) Resides at the edge of an MPLS service
provider's cloud and interconnects a service provider to one or more customers.
(label switch router) Resides inside a service provider's MPLS cloud and
makes frame forwarding decisions based on labels applied to frames.