Chapter 7 Wired and Wireless Local Area Networks

Question 1

What are the components of a Traditional LAN?

Answer 1

LANs consist of client computer, server, NIC, network circuits, hubs/switches/access points, and Network Operating System.

Question 2

What is a Network Interface Card (NIC)

Answer 2

In a wired network, the NIC connects the computer to the network cable and is one part of the physical layer connection. In a wireless network, the NIC is a radio transmitter that sends and receives messages on a specific radio frequency.

Question 3

Cable Categories and Data Rates

Answer 3

Category 1 (1 Mbps) UTP Telephone
Category 3 (10 Mbps) UTP 10Base-T
Category 5 (100 Mbps) STP 100Base-T
Category 5e (1 Gbps) UTP 1000Base-T
Category 6 (10 Gbps) UTP 10GBase-T
Category 7 (40 Gbps) STP 40GBase-T
62.5/50 (1 Gbps) Fiber 1000Base-F

Question 4

What is a Hub/Switch

Answer 4

Hubs and switches are devices that are used to connect network cables into the network through multiple ports.

Question 5

What is a Network Operating System (NOS)

Answer 5

The software that controls the network. The NOS has two sets of software one for the client and the other for the server. The server version of the NOS provides the software that performs the functions associated with the data link, network, and application layers and usually the computers own OS. The client version of the NOS provides the software that performs the functions associated with the data link and the network layers and must interact with the application software and the computes own OS.

Question 6

What is a domain?

Answer 6

Network resources are typically organized into a hierarchical tree. Each branch on the tree contains a domain, a group of related resources.

Question 7

What is a network profile?

Answer 7

A network profile specifies what resources on each server are available on the network for use by other computers and which devices or people are allowed what access to the network.

Question 8

What is Topology?

Answer 8

The basic geometric layout of the network - the way in which the computers on the network are interconnected.

Question 9

What is logical topology?

Answer 9

How the network works conceptually, much like a logical data flow diagram.

Question 10

What is physical topology?

Answer 10

How the network is physically installed, much like a physical DFD or physical ERD.

Question 11

Hub-Based Ethernet

Answer 11

Logical Topology is a bus topology. All computers are connected to one half-duplexed circuit running the length of the network. All frames from any computer flow onto the central cable (or bus) and through it to all computes on the LAN. Every computer on the bus receives all frames sent on the bus, even those intended for other computers. Before processing incoming frames, the Ethernet software on each computer checks the data link layer address and processes only those frames addressed to that computer.

Question 12

Switch-Based Ethernet

Answer 12

Ethernet topology is a logical star and a physical star. A switch is an intelligent device with a small computer built in that is designed to manage a set of separate point-to-point circuits. That means that each circuit connected to a switch is not shared with any other devices; only the switch and the attached computer use it. The switch uses a forwarding table that lists the Ethernet address of the computer connected to each port on the switch.

Question 13

Layer-2 Switch

Answer 13

A switch that communicates using Ethernet, which is a data link layer or layer-2 protocol.

Question 14

Cut-through switching

Answer 14

The switch begins to transmit the incoming packet on the proper outgoing circuit as soon as it has read the destination address in the frame. This means that the switch transmits before receiving the entire frame and without any error checking.

Question 15

Store and Forward Switching

Answer 15

The switch does not begin transmitting the outgoing frame until it has received the entire incoming frame and has checked to make sure it contains no errors.

Question 16

Fragment-free switching

Answer 16

Lies between the extremes of cut-through and store and forward switching. The first 64-bytes of the frame are read and stored. The switch examines the first 64-bytes (header information) and if all data appear to be correct, it begins to transmit the frame and assumes the remainder of the frame is error free.

Question 17

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

Answer 17

Wait until the circuit is free and then transmit. With collision detection, if the NIC detects any signal other that its own, it presumes that a collision has occurred and sends a jamming signal to resolve the collision.

Question 18

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Answer 18

Computers listen before they transmit, and I no one else is transmitting, they proceed with transmission. Wi-Fi attempts to avoid collisions. Before a computer can transmit in a WLAN, it must first establish an association with the AP.

Question 19

Associating with an AP

Answer 19

Searching for an available AP is called scanning (active or passive). During active scanning, a NIC transmits a special frame called a probe frame on all active channels on its frequency range. When the AP received the probe, it responds with a probe response that contains the association information. During passive scanning, the NIC listens on all channels for a special frame called a beacon frame that is sent out by an access point.

Question 20

Distributed Coordination Function (DCF)

Answer 20

The first media access control method is the DCF. Each frame in CSMA/CA is sent using stop-and-wait ARQ. After a frame is sent, the computer stops and waits for the ACK.

Question 21

Media Access Control

Answer 21

Collisions must be prevented, or if they do occur, there must be a way to recover from them.

Question 22

Wi-Fi Standards

Answer 22

802. 11a
803. 11b
804. 11g
805. 11n
806. 11ac
807. 11ad (WiGig)

Question 23

Redundant Array of Inexpensive Disks (RAID)

Answer 23

A special type of disk drive that builds on the concept and is typically used in applications requiring very fast processing of large volumes of data such as multimedia.

Question 24

Bottlenecks

Answer 24

1. The network server, the server lacks the capacity to process all the requests it receives.
2. The network circuit, either the access LAN, the building backbone, the campus backbone, or the circuit into the data center. The circuit lacks the capacity.

Question 25

Improve performance

Answer 25

Software: NOS is the primary approach for improving network performance. Fine tune the NOS or upgrade.
Hardware: The network server is overloaded, so may need to buy a second server to offload. If one application is causing the bottleneck, may need to upgrade server. Second, amount of memory may need to be increased. Third, number and speed of hard disks may need to be increased.
Circuit capacity: Increase the size of the circuit or segment the network (divide into several smaller circuits).