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Ch7 Wide Area Networks
N/A
115
Computer Networking
06/02/2013

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Term
What is the transmission speed of a SONET OC-1 line?
A. 155.52 Mbps
B. 1244.16 Mbps
C. 51.84 Mbps
D. 622.08 Mbps
Definition
C. 51.84 Mbps
Term
Suppose you work for a bank and are leasing a frame relay connection to link an automatic teller machine located in a rural grocery store with your bank's headquarters. Which of the following circuits would be the best option, given the type of use this automatic teller machine will experience?
A. DLC
B. PVC
C. SVC
D. HLC
Definition
C. SVC
Term
T3 lines run at a speed of:
A. 64 Kbps
B. 1.544 Mbps
C. 2.048 Mbps
D. 44.736 Mbps
Definition
D. 44.736 Mbps
Term
Which of the following refers to the throughput offered by a single ISDN bearer (B) channel?
A. 64 Kbps
B. 1.544 Mbps
C. 128 Kbps
D. 256 Kbps
Definition
A. 64 Kbps
Term
A _____ converts digital signals into analog signals for use with ISDN phones and other analog devices.
A. smart jack
B. terminator
C. DSLAM
D. terminal adapter
Definition
D. terminal adapter
Term
What is the purpose of ISDN's D channel?
A. To carry call session information
B. To carry error checking information
C. To enable time division multiplexing
D. To carry data
Definition
A. To carry call session information
Term
The science museum where you work determines that it needs an Internet connection capable of transmitting and receiving data at 12 Mbps at any time. Which of the following T-carrier solutions would you advise?
A. A T1
B. Ten T3s
C. A T3
D. Ten T1s
Definition
D. Ten T1s
Term
At the customer's demarcation point, either inside or outside the building, RJ-48 connectors terminate in a _____.
A. switch
B. smart jack
C. CSU/DSU
D. terminal adapter
Definition
B. smart jack
Term
What is the size of an Asynchronous Transfer Mode (ATM) cell?
A. 48 bits
B. 53 bytes
C. 1500 bytes
D. 64 Kb
Definition
B. 53 bytes
Term
The individual geographic locations connected by a WAN are known as _____.
A. WAN sites
B. central offices
C. WAN access points
D. network service providers
Definition
A. WAN sites
Term
What is the throughput of the ISDN Basic Rate Interface (BRI)?
A. 1.544 Mbps
B. 128 Kbps
C. 2.048 Mbps
D. 256 Kbps
Definition
B. 128 Kbps
Term
Which of the following matches the speed of a single ISDN B channel?
A. DS2
B. DS1
C. DS3
D. DS0
Definition
D. DS0
Term
The data rate of a particular SONET ring is indicated by its _____, a rating that is internationally recognized by networking professionals and standards organizations.
A. OC (Optical Carrier) level
B. BRI (Basic Rate Interface)
C. DS0 (digital signal, level 0)
D. CIR (committed information rate)
Definition
A. OC (Optical Carrier) level
Term
What technique does T1 technology use to transmit multiple signals over a single telephone line?
A. Time division multiplexing
B. Wave division multiplexing
C. Frequency modulation
D. Amplitude modulation
Definition
A. Time division multiplexing
Term
T1 lines run at the speed of:
A. 1.544 Mbps
B. 2.048 Mbps
C. 44.736 Mbps
D. 64 Kbps
Definition
A. 1.544 Mbps
Term
_____ means that a telephone company connects residential users to its network with fiber-optic cable.
A. OLT
B. PON
C. FITL
D. FTTH
Definition
D. FTTH
Term
Your company has decided to order ADSL from its local telecommunications carrier. You call the carrier and find out that your office is located 17,000 feet from the nearest CO. Given ADSL's potential throughput and your distance from the CO, what is the maximum downstream throughput you can realistically expect to achieve through this connection?
A. 16 Mbps
B. 200 Kbps
C. 2 Mbps
D. 8 Mbps
Definition
C. 2 Mbps
Term
Public Switched Telephone Network (PSTN) is also commonly referred to as :
A. POTS
B. DSL
C. UART
D. NIST
Definition
A. POTS
Term
You work for a regional common carrier and have been asked to design a passive optical network that will bring high speed Internet access to a new neighborhood in a nearby suburb. The area served by the network will bring fiber-optic cable to as many as 45 households. At least how many ports on the carrier's OLT should you expect to configure?
A. 2
B. 3
C. 4
D. 1
Definition
A. 2
Term
In ISDN standards, the channel responsible for carrying data (voice, video, user data) is labeled as:
A. channel A
B. channel D
C. channel C
D. channel B
Definition
D. channel B
Term
In ISDN standards, the signalling channel responsible for managing calls is labeled as:
A. channel C
B. channel D
C. channel B
D. channel A
Definition
B. channel D
Term
In a process called _____, two 64 Kbps ISDN B channels can be combined to achieve an effective throughput of 128 Kbps.
A. bonding
B. linking
C. slicing
D. merging
Definition
A. bonding
Term
The portion of the PSTN that connects any residence or business to the nearest CO is known as the _____.
A. local loop
B. central office
C. NIU (Network Interface Unit)
D. demarcation point
Definition
A. local loop
Term
How does ATM differ from every other WAN technology described in this chapter?
A. It uses fixed-sized cells to carry data.
B. It does not use packet switching.
C. It does not provide error detection or correction.
D. It requires fiber-optic media.
Definition
A. It uses fixed-sized cells to carry data.
Term
The speed of a T-carrier depends on its ______ level.
A. hierarchy
B. signal
C. channel
D. traffice
Definition
B. signal
Term
You offer your networking expertise to a small nonprofit corporation. The three employees each have a desktop computer and want to share the single broadband cable Internet connection that comes to their office. You donate a router you have sitting around to make this sharing possible. Where on your network should you install the router?
A. Attached to one of the end workstations
B. Between the cable modem and the workstations
C. Between the cable modem and the cable drop
D. Attached to a server that's connected to the cable drop
Definition
B. Between the cable modem and the workstations
Term
Channel Service Unit/Data Service Unit (CSU/DSU): (select 2)
A. is a LAN-specific device and can be used only within a LAN
B. is a hardware device that can be used as an interface for connecting a router to a T-carrier line
C. operates at Layer 3 of the OSI model
D. operates at the Physical Layer of the OSI model
Definition
B. is a hardware device that can be used as an interface for connecting a router to a T-carrier line
D. operates at the Physical Layer of the OSI model
Term
What part of a SONET network allows it to be self-healing?
A. Its use of fiber-optic cable
B. Its double-ring topology
C. Its use of error correction protocols
D. Its independence from local carriers' switching facilities
Definition
B. Its double-ring topology
Term
In which physical network topology does every node have a direct connection to every other node?
A. star
B. ring
C. partial mesh
D. full mesh
Definition
D. full mesh
Term
Which of the following provides an ISP with a troubleshooting tool for testing connection at the customer site without the need of sending a technician to that site?
A. smart jack
B. multimeter
C. demarc extension
D. demarc
Definition
A. smart jack
Term
Which of the following elements of the PSTN is most likely capable of transmitting only analog signals?
A. Central office
B. Local loop
C. CSU/DSU
D. Remote switching facility
Definition
B. Local loop
Term
Which of the following WAN topologies comes with the highest availability and the greatest cost?
A. Bus
B. Tiered
C. Partial mesh
D. Full mesh
Definition
D. Full mesh
Term
A customer calls your ISP's technical support line, complaining that his connection to the Internet usually goes as fast as 128 Kbps, but today it is only reaching 64 Kbps. He adds that he has tried dialing up three different times with the same result. What type of connection does this customer have?
A. PSTN dial-up
B. DSL
C. ISDN
D. T1
Definition
C. ISDN
Term
On an ISDN connection, what device separates the voice signal from the data signals at the customer premises?
A. Network termination
B. Terminal equipment
C. Multiplexer
D. Terminal adapter
Definition
D. Terminal adapter
Term
Which of the following WAN technologies operates at Layer 3 of the OSI model?
A. ATM
B. DSL
C. SONET
D. None of the above
Definition
D. None of the above
Term
You work for an Internet service provider that wants to lease a T3 over a SONET ring. What is the minimum Optical Carrier level that the SONET ring must have to support the bandwidth of a T3?
A. OC1
B. OC3
C. OC12
D. OC24
Definition
A. OC1
Term
Which two of the following are asymmetrical versions of DSL?
A. SDSL
B. ADSL
C. HDSL
D. VDSL
E. FDSL
Definition
B. ADSL
D. VDSL
Term
Where on the PSTN would you most likely find a DSLAM?
A. In a remote switching facility
B. At the demarc
C. In a border router
D. In a CSU/DSU
Definition
A. In a remote switching facility
Term
Your're troubleshooting a problem with a T1 connection between your business and the service provider's facility. The T1 connection intermittently goes down. When you call the service provider for assistance, they say they will only engage one of their service technicians after you have verified that all of your customer premises equipment is in working order. Given that requirement, which of the following do you not examine for faults?
A. The CSU/DSU interface card where the T1 terminates
B. The router that contains the CSU/DSU interface card
C. The RJ-48 connectors in your smart jack
D. The cable that enters the smart jack from outside your building
Definition
D. The cable that enters the smart jack from outside your building
Term
Which of the following may limit a DSL connection's capacity?
A. The number of nodes connected to the incoming DSL line
B. The distance from the carrier's switching facility to the ISP
C. The existence of more than one copper wire phone line at the customer's location
D. The distance from the customer to the carrier's switching facility
Definition
D. The distance from the customer to the carrier's switching facility
Term
You have just started working for a regional network service provider. The company provides several T1s to businesses around your city. In addition, your company supplies Internet service to three ISPs, using multiple T1s. Two T3s connect your employer's data center with two even larger service providers. You notice a router in the data center that handles the multiple T1s and T3s. Which of the following routing protocols is this router almost certainly running to exchange route information with routers on the other service providers' networks?
A. OSPF
B. RIP
C. BGP
D. EIGRP
Definition
C. BGP
Term
ADSL (Asymmetric DSL)
Definition
A variation of DSL that offers more throughput when data travel downstream, downloading from a local carriers's switching facility to the customer, than when data travel upstream, uploading from the customer to the local carrier's switching facility.
Term
asymmetrical
Definition
The characteristic of a transmission technology that affords greater bandwidth in one direction (either from the customer to the carrier, or vice versa) than in the other direction.
Term
asynchronous
Definition
A transmission method in which data being transmitted and received by nodes do not have to conform to any timing scheme. In asynchronous communications, a node can transmit at any time and the destination node must accept the transmission as it comes.
Term
ATM(Asynchronous Transfer Mode)
Definition
A Data Link layer technology originally conceived in the early 1980s at Bell Labs and standardized by the ITU in the mid-1990s. ATM relies on fixed packets, called cells, that each consist of 48 bytes of data plus a 5-byte header. ATM relies on virtual circuits and establishes a connection before sending data. The reliable connection ensured by ATM allows network managers to specify QoS levels for certain types of traffic.
Term
B channel
Definition
In ISDN, the "bearer" channel, so named because it bears traffic from point to point.
Term
bonding
Definition
The process of combining more than one bearer channel of an ISDN line to increase throughput. For example, BRI's two 64-Kbps B channels are bonded to create an effective throughput of 128 Kbps.
Term
BPL (broadband over powerline)
Definition
High-speed Internet access delivered over the electrical grid.
Term
BRI (Basic Rate Interface)
Definition
A variety of ISDN that uses two 64-Kbps bearer channels and one 16-Kbps data channel, as summarized by the notation 2B+D. BRI is the most common form of ISDN employed by home users.
Term
broadband cable
Definition
A method of connecting to the Internet over a cable network. In broadband cable, computers are connected to a cable modem that modulates and demodulates signals to and from the cable company's head-end.
Term
bus topology WAN
Definition
A WAN in which each location is connected to no more than two other locations in a serial fashion.
Term
cable drop
Definition
The fiber-optic or coaxial cable that connects a neighborhood cable node to a customer's house.
Term
cable modem
Definition
A device that modulates and demodulates signals for transmission and reception via cable wiring.
Term
cell
Definition
A packet of a fixed size. In ATM technology, a cell consists of 48 bytes of data plus a 5-byte header.
Term
CIR (committed information rate)
Definition
The guaranteed minimum amount of bandwidth selected when leasing a frame relay circuit. Frame relay costs are partially based on CIR.
Term
CO (central office)
Definition
The location where a local or long-distance telephone service provider terminates and interconnects customer lines.
Term
CSU (channel service unit)
Definition
A device used with T-carrier technology that provides termination for the digital signal and ensures connection integrity through error correction and line monitoring. Typically, a CSU is combined with a DSU in a single device, a CSU/DSU.
Term
CSU/DSU
Definition
A combination of a CSU (channel service unit) and a DSU (data service unit) that serves as the connection point for a T1 line at the customer's site. Most modern CSU/DSUs also contain a multiplexer. A CSU/DSU may be a separate device or an expansion card in another device, such as a router.
Term
D channel
Definition
In ISDN, the "data" channel is used to carry information about the call, such as session initiation and termination signals, caller identity, call forwarding, and conference calling signals.
Term
dedicated
Definition
A continuously available link or service that is leased through another carrier. Examples of dedicated lines include ADSL, T1, and T3.
Term
dial-up
Definition
A type of connection in which a user connects to a distant network from a computer and stays connected for a finite period of time. Most of the time, the term dial-up refers to a connection that uses a PSTN line.
Term
downstream
Definition
A term used to describe data traffic that flows from a carriers's facility to the customer. In asymmetrical communications, downstream throughput is usually much higher than upstream throughput. In symmetrical communications, downstream and upstream throughputs are equal.
Term
DS0 (digital signal, level 0)
Definition
The equivalent of one data or voice channel in T-carrier technology, as defined by ANSI Physical layer standards. All other signal levels are multiples of DS0.
Term
DSL (digital subscriber line)
Definition
A dedicated WAN technology that uses advanced data modulation techniques at the Physical layer to achieve extraordinary throughput over regular phone liens. DSL comes in several different varieties, the most common of which s Asymmetric DSL (ADSL).
Term
DSL modem
Definition
A device that demodulates an incoming DSL signal, extracting the information and passing it to the data equipment (such as telephones and computers) and modulates an outgoing DSL signal.
Term
DSLAM (DSL access multiplexer)
Definition
A connectivity device located at a telecommunications carrier's office that aggregates multiple DSL subscriber lines and connects them to a larger carrier or to the Internet backbone.
Term
DSU (data service unit)
Definition
A device used in T-carrier technology that converts the digital signal used by bridges, routers, and multiplexers into the digital signal used on cabling. Typically, a DSU is combined with a CSU in a single device, a CSU/DSU.
Term
E1
Definition
A digital carrier standard used in Europe that offers 30 channels and a maximum of 2.048 Mbps throughput.
Term
E3
Definition
A digital carrier standard used in Europe that offers 480 channels and a maximum of 34.368 Mbps throughput.
Term
fractional T1
Definition
An arrangement that allows a customer to lease only some of the channels on a T1 line.
Term
frame relay
Definition
A digital, packet-switched WAN technology whose protocols operate at the Data Link layer. The name is derived from the fact that data is separated into frames, which are then relayed from one node to another without any verification or processing. Frame relay offers throughputs between 64 Kbps and 45 Mbps. A frame relay customer chooses the amount of bandwidth he requires and pays for only that amount.
Term
FTTH (fiber to the home)
Definition
A service in which a residential customer is connected to his carrier's network with fiber-optic cable.
Term
FTTP (fiber to the premises)
Definition
A service in which a residential or business customer is connected to his carrier's network using fiber-optic cable.
Term
full-mesh WAN
Definition
A version of the mesh topology WAN in which every site is directly connected to every other site. Full-mesh WANs are the most fault tolerant type of WAN.
Term
head-end
Definition
A cable company's central office, which connects cable wiring to many nodes before it reaches customers' sites.
Term
HFC (hybrid fiber-coax)
Definition
A link that consists of fiber cable connecting the cable company's offices to a node location near the customer and coaxial cable connecting the node to the customer's house. HFC upgrades to existing cable wiring are required before current TV cable systems can provide Internet access.
Term
ISDN (Integrated Services Digital Network)
Definition
An international standard that uses PSTN lines to carry digital signals. It specifies protocols at the Physical, Data Link, and Transport layers of the OSI model. ISDN lines may carry voice and data signals simultaneously. Two types of ISDN connections are used in North America: BRI (Basic Rate Interface) and PRI (Primary Rate Interface). Both use a combination of bearer channels (B channels) and data channels (D channels).
Term
LANE (LAN Emulation)
Definition
A method for transporting token ring or Ethernet frames over ATM networks. LANE encapsulates incoming Ethernet or token ring frames, then converts them into ATM cells for transmission over an ATM network.
Term
local loop
Definition
The part of a phone system that connects a customer site with a telecommunications carrier's switching facility.
Term
mesh topology WAN
Definition
A type of WAN in which several sites are directly interconnected. Mesh WANs are highly fault tolerant because they provide multiple routes for data to follow between any two points.
Term
NIU (network interface unit)
Definition
The point at which PSTN-owned lines terminate at a customer's premises. The NIU is usually located at the demarc.
Term
NSP (network service provider)
Definition
A carrier that provides long-distance (and often global) connectivity between major data-switching centers across the Internet. AT&T, Verizon, and Sprint are all examples of network service providers in the United States. Customers, including ISPs, can lease dedicated private or public Internet connections from an NSP.
Term
NT1 (Network Termination 1)
Definition
A device used on ISDN networks that connects the incoming twisted pair wiring with the customer's ISDN terminal equipment.
Term
NT2 (Network Termination 2)
Definition
An additional connection device required on PRI to handle the multiple ISDN lines between the customer's network termination connection and the local phone company's wires.
Term
OC (Optical Carrier)
Definition
An internationally recognized rating that indicates throughput rates for SONET connections.
Term
OLT (optical line terminal)
Definition
A device located at the carrier's endpoint of a passive optical network. An OLT contains multiple optical ports, or PON interfaces and a splitter that subdivides the capacity of each port into up to 32 logical channels, one per subscriber.
Term
ONU (optical network unit)
Definition
In a passive optical network, the device near the customer premises that terminates a carrier's fiber-optic cable connection and distributes signals to multiple endpoints via fiber-optic cable, in the case of FTTP, or via copper or coax cable.
Term
partial-mesh WAN
Definition
A version of a mesh topology WAN in which only critical sites are directly interconnected and secondary sites are connected through star or ring topologies. Partial=mesh WANs are less expensive to implement than full-mesh WANs.
Term
PON (passive optical network)
Definition
A network in which a carrier uses fiber-optic cabling to connect with multiple endpoints - for example, many businesses on a city block. The word passive applies because in a PON, no repeaters or other connectivity devices intervene between a carrier and its customer.
Term
PRI (Primary Rate Interface)
Definition
A type of ISDN that uses 23 bearer channels and one 64-Kbps data channel, represented by the notation 23B+D. PRI is less commonly used by individual subscribers than BRI, but it may be used by businesses and other organizations needing more throughput.
Term
PSTN (Public Switched Telephone Network)
Definition
The network of lines and carrier equipment that provides telephone service to most homes and businesses. Now, except for the local loop, nearly all of the PSTN uses digital transmission. Its traffic is carried by fiber-optic or copper twisted pair cable, microwave, and satellite connections.
Term
PVC (permanent virtual circuit)
Definition
A point-to-point connection over which data may follow any number of different paths, as opposed to a dedicated line that follows a predefined path. X.25, frame relay, and some forms of ATM use PVCs.
Term
ring topology WAN
Definition
A type of WAN in which each site is connected to two other sites so that the entire WAN forms a ring pattern.
Term
RJ-48 (register jack 48)
Definition
A standard for terminating wires in an eight-pin connector. RJ-48 is the preferred connector type for T1 connections that rely on twisted pair wiring.
Term
SDH (Synchronous Digital Hierarchy)
Definition
The international equivalent of SONET.
Term
self-healing
Definition
A characteristic of dual-ring topologies that allows them to automatically reroute traffic along the backup ring if the primary ring becomes severed.
Term
signal level
Definition
An ANSI standard for T-carrier technology that refers to its Physical layer electrical signaling characteristics. DS0 is the equivalent of one data or voice channel. All other signal levels are multiples of DS0.
Term
smart jack
Definition
A termination for T-carrier wire pairs that is located at the customer demarc and which functions as a connection protection and monitoring point.
Term
SONET (Synchronous Optical Network)
Definition
A high-bandwidth WAN signaling technique that specifies framing and multiplexing techniques at the Physical layer of the OSI model. It can integrate many other WAN technologies (for example, T-carriers, ISDN, and ATM technology) and allows for simple link additions and removals. SONET's topology includes a double ring of fiber-optic cable, which results in very high fault tolerance.
Term
star topology WAN
Definition
A type of WAN in which a single site acts as the central connection point for several other points. This arrangement provides separate routes for data between any two sites; however, if the central connection point fails, the entire WAN fails.
Term
SVC (switched virtual circuit)
Definition
A logical, point-to-point connection that relies on switches to determine the optimal path between sender and receiver. ATM technology uses SVCs.
Term
symmetrical
Definition
A characteristic of transmission technology that provides equal throughput for data traveling both upstream and downstream and is suited to users who both upload and download significant amounts of data.
Term
symmetrical DSL
Definition
A variation of DSL that provides equal throughput both upstream and downstream between the customer and the carrier.
Term
synchronous
Definition
A transmission method in which data being transmitted and received by nodes must conform to a timing scheme.
Term
T1
Definition
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. T1s rely on time division multiplexing and may use shielded or unshielded twisted pair, coaxial cable, fiber optics, or microwave links.
Term
T3
Definition
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 (typically rounded up to 45 Mbps for purposes of discussion). T3s rely on time division multiplexing and require either fiber-optic or microwave transmission media.
Term
T-carrier
Definition
The term for any kind of leased line that follows the standards for T1s, fractional T1s, T1Cs, T2s, T3s, or T4s.
Term
TA (terminal adapter)
Definition
A device used to convert digital signals into analog signals for use with ISDN phones and other analog devices. TAs are sometimes called ISDN modems.
Term
TE (terminal equipment)
Definition
The end nodes (such as computers and printers) served by the same connection (such as an ISDN, DSL, or T1 link).
Term
tiered topology WAN
Definition
A type of WAN in which sites that are connected in star or ring formations are interconnected at different levels, with the interconnection points being organized into layers to form hierarchical groupings.
Term
upstream
Definition
A term used to describe data traffic that flows from a customer's site to a carrier's facility. In asymmetrical communications, upstream throughput is usually much lower than downstream throughput. In symmetrical communications, upstream and downstream throughputs are equal.
Term
virtual circuit
Definition
A connection between network nodes that, although based on potentially disparate physical links, logically appears to be a direct, dedicated link between those nodes.
Term
WAN link
Definition
A point-to-point connection between two nodes on a WAN.
Term
x.25
Definition
An analog, packet-switched WAN technology optimized for reliable, long-distance data transmission and standardized by the ITU in the mid-1970s. The X.25 standard specifies protocols at the Physical, Data Link, and Network layers of the OSI model. It provides excellent flow control and ensures data reliability over long distances by verifying the transmission at every node. X.25 can support a maximum of only 2 Mbps throughput.
Term
xDSL
Definition
The term used to refer to all varieties of DSL.