Business Data Communications Ch9

Front 1

How do the key requirements for computer room networks differ from those for personal computers?

Back 1

requirements for personal computers are more based on cheap prices; in particular the lost cost of the attachment to the network must be significantly less than the attached device. Computer room networks require High data rates, distributed access, and seen as the higher cost of the attached devices make the cost reasonable

Front 2

Other than large storage capacity, what other advantage does a SAN provide?

Back 2

The SAN creates a shared storage facility across a high speed network. The SAN also improves client-to-storage access efficiency, as well as direct storage-to-storage communications for backup and replication functions

Front 3

Differentiate between guided media and unguided media.

Back 3

Guided media is when the waves are guided along a solid medium, such as copper, twisted pair, copper coaxial cable or optical fiber. Unguided Media is when atmosphere or outerspace provide means of transmitting electronic signals but do not guide them (wireless transmission)

Front 4

Why are the wires twisted in twisted pair copper wire?

Back 4

b/c it reduces low-frequency interference, and the use of different twist lengths in adjacent pairs reduces cross talk

Front 5

What is the difference between unshielded twisted pair and shielded twisted pair?

Back 5

Unshielded twisted pair is ordinary telephone wire. These wires are unprotected and are prewired in office buildings. They are the least expensive. They are subject to external electromagnetic interference. Shielded twisted pairs have a metallic braid or sheathing that reduces interference. It provides better performance at lower data rates, but it is more expensive and more difficult to work with.

Front 6

Describe the components of optical fiber cable.

Back 6

It has greater capacity (bandwidth and data rate are much faster), smaller size and lighter weight(considerably thinner than coaxial cable or bundled twisted pair, helps for cramped conduits) , lower attenuation, and electromagnetic isolation (not affected by external electromagnetic fields, thus not susceptible to interference).

Front 7

Arrange the following in order from highest to lowest regarding bandwidth.

Back 7

Optical Fiber, Coaxial Cable, Unshielded Twisted Pair (UTP)

Front 8

What is the purpose of the IEEE 802 committee?

Back 8

They were responsible for developing the OSI architecture and relating it to LAN protocols.

Front 9

Why are there multiple LAN standards?

Back 9

?

Front 10

Explain why a data rate of 10 Mbps on all LAN segments is increasingly inadequate for many business?

Back 10

it is simply too slow for todays standards. The original commercial Ethernet and IEEE 802.3 operated at 10 Mbps, but in recent years standards have been deeveloped for 802.3 operating at 100 Mbps, 1 Gbps, and 10 Gbps. The old systems use CSMA, which do not scale well

Front 11

What is CSMA/CD?

Back 11

Carrier sense multiple access with collision detection. It is the protocol used in Ethernet networks to ensure that only one network node is transmitting on the network wire at any one time. It does not scale well or can't add computers to it easily

Front 12

What is the difference between a hub and a layer 2 switch?

Back 12

A hub receives information from any one station and then retransmits the information to all the lines that are on the hub. The layers 2 switch uses the hub and gets the information and then retransmits it to the 1 in particular line that it is supposed to go to.

Front 13

What are the differences between a bridge and a switch?

Back 13

Bridge frame handles address recognition in software, while Layer 2 switch does address recognition and frame forwarding funtions in hardware. A bridge can typically only analyze and forward 1 frame at a time, but Layer 2 switch can handle multiple frames at a time and has multiple parallel data paths. A bridge uses store-and-forward operation, but a Layer 2 switch it is possible to have cut-through instead of store-and-forward. Cut through is faster and recognizes the destination address earlier

Front 14

List the levels of Fibre Channel and the functions of each level.

Back 14

1)FC-0 physical media- includes optical fiber for long-distance, coaxial cable for high speeds over short distance, and shielded twisted pairs for lower
speeds over short distances.
2)FC-1 Transmission Protocol- Defines the signal encoding scheme
3)FC-2 Framing Protocol- Deals with defining topologies, frame format, flow and error control, and grouping of frames into logical entities called sequences and exchanges.
4)FC-3- Common Services- Includes multicasting
5)FC-4- Mapping- Defines the mapping of various channel and network protocols to Fibre Channel, including IEEE 802, ATM, IP, and the Small Computer System Interface (SCSI)

Front 15

List and briefly define four application areas for wireless LANs.

Back 15

1)LAN Extension- In most cases, an organization will have a wired LAN to support servers and some stationary workstations. When a wireless LAN is linked to a wired LANon the same premises.
2)Cross-Building Interconnect-connecting LAN's in nearby buildings together either wired or wireless LANs. They are usually connected by bridges or routers.
3)Nomadic Access- provides wireless link between a LAN hub and a mobile data terminal equipped with an antenna such as a laptop. It is where you can transfer data onto the server even if you are not close to the server
4)Ad Hoc Networking-peer to peer networking(no centralized server) set up temporarily to meet some immediate need

Front 16

List and briefly define key requirements for wireless LANs.

Back 16

1)Throughput-The medium access control protocol should make as efficient use as possible of the wireless medium to maximize capacity
2)Number of nodes-Wireless LAN's may need to support hundreds of nodes across multiple cells
3)Connection to backbone LAN- you must need interconnection with stations on a wired backbone
4)Service Area- A typical coverage area for wireless LAN has a diameter of 100 to 300 m.
5)Battery power consumption-need to have workstations that have long battery life
6)transmission robustness and security- should provide security to those accessing the LAN.
7)License Free- users would prefer to buy and operate wireless LAN products without having a secure license
8)Handoff/Roaming- The MAC protocol used in the wireless LAN should enable mobile stations to move from one cell to another

Front 17

What is the difference between a single-cell and multiple-cell wireless LAN?

Back 17

a single cell uses only one control module, which is hooked up to the wired LAN to transmit the wireless data to all the computers. A multiple cell has numerous wires connected several control modules to the wired LAN, and they transmit to the computers within each ones range

Front 18

What is the basic building block of an 802.11 WLAN?

Back 18

The basic building block for 802.11 WLAN is a basic service set (BSS), which consists of some number of stations executing the same MAC protocol and competing for access to the same shared wireless medium. A BSS may be isolated or it may connect to a backbone distributino systems

Front 19

Why is it useful to have more than one possible path through a network for each pair of stations?

Back 19

In case one of the paths fail or there is too much traffic in one of the paths the information can be re-routed to another path and get the info to its destination

Front 20

What are the four generic architectural components of a public communication network? Define each term

Back 20

Subscribers- The devices that attach to the network.
Subscriber line- The link between the subscriber and the network
Exchanges- The switching centers in the network
Trunks- the branches between exchanges

Front 21

T or F: A complete connection from end to end must be completed before data transmission can occur.

There are three basic stagesl connection setup, data transfer, and connection termination.

Circuit switching is very efficient

Back 21

T
F
F

Front 22

What is the principal application that has driven the design of circuit-switching networks?

Back 22

Public telephone network

Front 23

What is the difference between inchannel and common channel signaling?

Back 23

Inchannel- the same channel is used to carry control signals as is used to carry the call.
Common channel- control signals are carried over paths completely independent of the voice channels.

Front 24

What are some of the limitations of using a circuit-switching network for data transmission?

Back 24

?

Front 25

What is a value-added network (VAN)?

Back 25

A network provider that owns a set of packet-switching nodes and links these together with leased lines provided by a carrier

Front 26

Why is packet switching impractical for digital voice transmission?

Back 26

because it causes jitter within the conversation and makes it have pauses between words

Front 27

What are the key high-speed networking services available for wide are networking?

Back 27

T3 and Sonet/SDH, frame relay, and ATM

Front 28

How does frame relay differ from packet switching?

Back 28

Call control signaling is carried on a seperate logical connection from user data

Front 29

What are the relative advantages and disadvantages of frame relay compared to packet switching?

Back 29

Advantages-The protocol functionality required at the user-network interface is reduced, thus creating longer delays and higher throughput.
Disadvantages- the ability to do link-by-link flow and error control is lost

Front 30

How does ATM differ from frame relay?

Back 30

ATM is designed to support access speeds beyond speeds beyond 2 Mbps
- more streamlined and can support data rates several orders of magnitude greater than frame relay

Front 31

What are the relative advantages and disadvantages of ATM compared to frame relay?

Back 31

Advantages- simplified network architecture, increased network performance and reliability, reduced processing, enhanced network services

Front 32

What is the difference between a virtual channel and a virtual path?

Back 32

Virtual channel- unit of switiching, is set between two end users through the network and a variable rate.
Vartual path- a bundle of virtual channels that have the same end points and switched together.

Front 33

What geometric shape is used in cellular system design?

Back 33

Hexagon

Front 34

What is the principle of frequency reuse in the context of a cellular network?

Back 34

To determine how many cells do not intervene between two cells using the same frequency so that the two cells do not interfere with each other

Front 35

List 5 ways of increasing the capacity of a cellular system.

Back 35

1) Adding new channels
2)Cell sectoring
3)Frequency borrowing
4)Micro cells
5)Cell splitting

Front 36

Explain the paging function of a cellular system.

Back 36

The MTSO sends a paging message to BSS. Then each BS transmits the paging signal on its assigned setup channel

Front 37

What is a cellular handoff?

Back 37

When a mobile unit moves out of range of one cell and into the range of another, the traffic channel changes to the BS in the new cell without interruption

Front 38

What is the wireless application protocol (WAP)?

Back 38

An opened standard developed to provide mobile users of wireless phones and other wireless terminals access to telephony and information services.