N10-007.4

Question 1

direct-sequence spread spectrum (DSSS)

Answer 1

Modulates data over an entire range of frequencies using a series of symbols called chips. A chip is shorter in duration than a bit, meaning that chips are transmitted at a higher rate than the actual data.

Question 2

carrier-sense multiple access/collision avoidance (CSMA/CA)

Answer 2

Similar to how an Ethernet device listens to an Ethernet segment to determine whether a frame exists on the segment, a WLAN device listens for a transmission on a wireless channel to determine whether it is safe to transmit. In addition, the collision-avoidance part of the CSMA/CA algorithm causes wireless devices to wait for a random back-off time before transmitting.

Question 3

Omnidirectional Antenna

Answer 3

Radiates power at relatively equal power levels in all directions (somewhat similar to the theoretical isotropic antenna). Omnidirectional antennas are popular in residential WLANs and SOHO locations.

Question 4

Personal Mode

Answer 4

In the context of wireless networking, this refers to using a preshared key (PSK) instead of a centralized server, such as RADIUS, for authentication.

Question 5

802.11ac

Answer 5

5 Ghz
Up to 1000ft range
Up to 1 Gbps Max Data Rate

Question 6

Extended Service Set (ESS)

Answer 6

WLANs containing more than one AP are called ESS WLANs. Like BSS WLANs, ESS WLANs operate in infrastructure mode.

Question 7

orthogonal frequency-division multiplexing (OFDM)

Answer 7

Whereas DSSS uses a high modulation rate for the symbols it sends, OFDM uses a relatively slow modulation rate for symbols. This slower modulation rate, combined with the simultaneous transmission of data over 52 data streams, helps OFDM support high data rates while resisting crosstalk between the various data streams.

Question 8

802.11a

Answer 8

5 GHz
54 Mbps
400 ft

Question 9

Independent Basic Service Set (IBSS)

Answer 9

A WLAN can be created without the use of an AP. Such a configuration, called an IBSS, is said to work in an ad hoc fashion.

Question 10

802.11g

Answer 10

2.4 GHz
54 Mbps
450 ft

Question 11

802.11n

Answer 11

2.4/5 Ghz
600 Mbps
825 ft

Question 12

Basic Service Set (BSS)

Answer 12

WLANs that have just one AP are called BSS WLANs.

Question 13

802.11b

Answer 13

2.4 GHz
11 Mbps
450 ft

Question 14

Channel Bonding

Answer 14

With channel bonding, two wireless bands can be logically bonded together, forming a band with twice the bandwidth of an individual band. Some literature calls channel bonding 40MHz mode, which refers to the bonding of two adjacent 20MHz bands into a 40MHz band.

Question 15

Frequency-Hopping Spread Spectrum (FHSS)

Answer 15

Allows the participants in a communication to hop between predetermined frequencies. Security is enhanced because the participants can predict the next frequency to be used but a third party cannot easily predict the next frequency. FHSS can also provision extra bandwidth by simultaneously using more than one frequency.

Question 16

Enterprise Mode

Answer 16

In the context of wireless networking, this refers to using a centralized authentication server such as RADIUS for authentication, instead of a preshared key (PSK).

Question 17

Classification

Answer 17

Classification is the process of placing traffic into different categories.

Question 18

Incremental Backup

Answer 18

A backup job that only backs up the changed data since the last incremental backup.

Question 19

Network Interface Card teaming

Answer 19

This technology permits multiple network interface cards to function as a single interface to the network. NIC teaming provides excellent redundancy.

Question 20

Mean Time To Repair (MTTR)

Answer 20

The predicted time it takes to repair a network or network object.

Question 21

Congestion Avoidance

Answer 21

If an interface’s output queue fills to capacity, newly arriving packets are discarded (or tail dropped). Congestion avoidance can prevent this behavior. RED (Random Early Detection) is an example of a congestion-avoidance mechanism.

Question 22

Load Balancing

Answer 22

Distributing client requests among different network resources that can provide the same service or data.

Question 23

Differential Backup

Answer 23

A type of partial backup of a data set. All data that has changed since the last full backup is targeted by the backup job.

Question 24

Congestion Management

Answer 24

When a device, such as a switch or a router, receives traffic faster than it can be transmitted, the device attempts to buffer (or store) the extra traffic until bandwidth becomes available. This buffering process is called queuing or congestion management.

Question 25

Latency

Answer 25

The measure of delay in a network.

Question 26

Integrated Services (IntServ) (Strict)

Answer 26

Often referred to as hard QoS because IntServ can make strict bandwidth reservations. IntServ uses signaling among network devices to provide bandwidth reservations. Resource Reservation Protocol (RSVP) is an example of an IntServ approach to QoS. Because IntServ must be configured on every router along a packet’s path, a primary drawback of IntServ is its lack of scalability.

Question 27

Policing

Answer 27

Instead of making a minimum amount of bandwidth available for specific traffic types, you might want to limit available bandwidth. Policing can drop exceeding traffic, as opposed to buffering it.

Question 28

Link Efficiency

Answer 28

To make the most of the limited bandwidth available on slower speed links, you might choose to implement compression or link fragmentation and interleaving (LFI). These QoS mechanisms are examples of link efficiency mechanisms.

Question 29

Committed Information Rate (CIR)

Answer 29

The CIR of an interface is the average traffic rate over the period of a second.

Question 30

Jitter

Answer 30

The uneven arrival of packets.

Question 31

Differentiated Services (DiffServ)

Answer 31

As its name suggests, DiffServ differentiates between multiple traffic flows. Specifically, packets are marked, and routers and switches can then make decisions (for example, dropping or forwarding decisions) based on those markings.

Question 32

Full Backup

Answer 32

A backup job that ensures all data is backed up, regardless of when this data may have been backed up previously.

Question 33

Traffic Shaping

Answer 33

Traffic shaping delays excess traffic by buffering it as opposed to dropping the excess traffic.

Question 34

Common Address Redundancy Protocol (CARP)

Answer 34

An open standard variant of HSRP (Hot Standby Router Protocol), which provides first-hop router redundancy.

Question 35

Clustering

Answer 35

Connecting systems together with the intent of delivering network services from the cluster to increase responsiveness and capacity. This solution also increases availability and redundancy.