MIDTERM REVIEW

Question 1

Identify the possible causes of LAN traffic congestion.

Answer 1

Too many hosts in a broadcast domain, broadcast storms, multicasting, and low bandwidth are all possible causes of LAN traffic congestion.

Question 2

Describe the difference between a collision domain and a broadcast domain.

Answer 2

Collision domain is an Ethernet term used to describe a network collection of devices in which on particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it. With a broadcast domain, a set of all devices on a network hears all broadcasts sent on all segments.

Question 3

Differentiate a MAC address and an IP address and describe how and when each address type is used in a network.

Answer 3

A MAC address is a hexadecimal number identifying the physical connection of a host. A MAC address is a hexadecimal number identifying the physical connection of a host. MAC addresses are said to operate on layer 2 of the OSI model. IP addresses, which can be expressed in binary or decimal format, are logical identifiers that are said to be on layer 3 of the OSI model. Hosts on the same physical segment locate one another with MAC addresses, while IP addresses are used when they reside on different LAN segments or subnets.

Question 4

Understand the difference between a hub, a bridge, a switch, and a router.

Answer 4

A hub creates on collision domain and one broadcast domain. A bridge breaks up collision domains but creates on large broadcast domain. They use hardware addresses to filter the network. Switches are really just multiple-port bridges with more intelligence; they break up collision domains but create on large broadcast domain by default. Bridges and switches use hardware addresses to filter the network. Routers break up broadcast domains ( and collision domains) and use logical addressing to filter the network.

Question 5

Identify the functions and advantages of routers.

Answer 5

Routers perform packet switching, filtering, and path selection, and they facilitate internetwork communication. One advantage of routers is that they reduce broadcast traffic.

Question 6

Differentiate connection-oriented and connectionless network services and describe how each is handled during network communications.

Answer 6

Connection-oriented services use acknowledgements and flow control to create a reliable session. More overhead is used than in a connectionless network service. Connectionless services are used to send data with no acknowledgements or flow control. This is considered unreliable.

Question 7

Define the OSI layers, understand the function of each, and describe how devices and networking protocols can be mapped to each layer.

Answer 7

You must remember the seven layers of the OSI model and what function each layer provides. The Application, Presentation, and Session layers are upper layers and are responsible for communicating from a user interface to an application. The Transport layer provides segmentation, sequencing, and virtual internetwork. The Data Link layer provides framing and placing of data on the network medium. The Physical layer is responsible for taking 1’s and 0’s and encoding them into a digital signal for transmission on the network segment.

Question 8

1. Which layer chooses and determines the availability of communicating partners along with the resources necessary to make the connection, coordinates partnering applications, and forms a consensus on procedures for controlling data integrity and error recovery?

Answer 8

The Application layer is responsible for finding the network resources broadcast from a server and adding flow control and error control (if the application developer chooses).

Question 9

2. Which layer is responsible for converting data packets from the Data Link layer into electrical signals?

Answer 9

The Physical layer takes frames from the Data Link Layer and encodes the 1’s and 0’s into a digital or analog (Ethernet or wireless) signal for transmission on the network medium.

Question 10

3. At which layer is routing implemented, enabling connections and path selection between two end systems?

Answer 10

The Network layer provides routing through an internetwork and logical addressing.

Question 11

4. Which layer defines how data is formatted, presented, encoded, and converted for use on the network.

Answer 11

The Presentation layer makes sure the data is in a readable format for the Application layer.

Question 12

5. Which layer is responsible for creating, managing, and terminating sessions between applications?

Answer 12

The Session layer sets up, maintains, and terminates sessions between applications.

Question 13

6. Which layer ensures the trustworthy transmission of data across a physical link and is primarily concerned with physical addressing, line discipline, network topology, error notification, ordered delivery of frames, and flow control?

Answer 13

PDU’s at the Data Link layer are called frames and provide physical addressing plus other options to place packets on the network medium.

Question 14

7. Which layer is used for reliable communication between end nodes over the network and provides mechanisms for establishing, maintaining, and terminating virtual circuits; transport-fault detection and recovery; and controlling the flow of information?

Answer 14

The Transport layer uses virtual circuits to create a reliable connection between two hosts.

Question 15

8. Which layer provides logical addressing that routers will use for path determination?

Answer 15

The Network layer provides logical addressing, typically IP addressing and routing.

Question 16

9. Which layer specifies voltage, wire speed, and cable pinouts and moves bits between devices?

Answer 16

The physical layer is responsible for the electrical and mechanical connections between devices.

Question 17

10. Which layer combines bits into bytes and bytes into frames, uses MAC addressing, and provides error detection?

Answer 17

The Data Link layer is responsible for the framing of data packets.

Question 18

11. Which layer is responsible for keeping the data from different applications separate on the network?

Answer 18

The Session layer creates sessions between different hosts’ applications

Question 19

12. Which layer is represented by frames?

Answer 19

The Data Link layer frames packets received from the Network layer.

Question 20

13. Which layer is represented by segments?

Answer 20

The Transport layer segments user data.

Question 21

14. Which layer is represented by packets?

Answer 21

The Network layer creates packets out of segments handed down from the Transport layer.

Question 22

15. Which layer is represented by bits?

Answer 22

The Physical layer is responsible for transporting 1s and 0s (bits) in a digital signal.

Question 23

16. Rearrange the following in order of encapsulation:
Packets
Frames
Bits
Segments

Answer 23

Segments, packets, frames, bits

Question 24

17. Which layer segments and reassembles data into a data stream?

Answer 24

Transport

Question 25

18. Which layer provides the physical transmission of the data and handles error notification, network topology and flow control?

Answer 25

Data Link

Question 26

19. Which layer manages logical device addressing, tracks the location of devices on the internetwork, and determines the best way to move data?

Answer 26

Network

Question 27

20. What is the bit length and expression form of a MAC address?

Answer 27

48 bits (6 bytes) expressed as a hexadecimal number.

Question 28

Describe the operation of Carrier Sense Multiple Access with Collision Detection (CSMA/CD).

Answer 28

CSMA/CD is a protocol that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium. Although it does not eliminate collisions, it helps to greatly reduce them, which reduces retransmissions, resulting in a more efficient transmission of data for all devices.

Question 29

Differentiate half-duplex and full-duplex communication and define the requirements to utilize each method.

Answer 29

Full-duplex Ethernet uses two pairs of wires at the same time instead of one wire pair like half-duplex.Full-duplex allows for sending and receiving at the same time, using different wires to eliminate collisions, while half-duplex can send or receive but not at the same time and still can suffer collisions. To use full-duplex, the devices at both ends of the cable must be capable of and configured to perform full-duplex.

Question 30

Describe the sections of a MAC address and the information contained in each section.

Answer 30

The MAC, or hardware, address is a 48-bit (6 byte) address written in a hexadecimal format. The first 24 bits, or 3 bytes, are called the organizationally unique identifier (OUI), which is assigned by the IEEE to the manufacturer of the NIC. the balance of the number uniquely identifies the NIC.

Question 31

Identify the binary and hexadecimal equivalent of a decimal number.

Answer 31

Any number expressed in one format can also be expressed in the other two. The ability to perform this conversion is critical to understanding IP addressing and subnetting.

Question 32

Identify the fields in the Data Link portion of an Ethernet frame.

Answer 32

The fields in the Data Link portion of a frame include the preamble, Start Frame Delimiter, destination MAC address, source MAC address, Length or Type, Data, and Frame Check Sequence.

Question 33

Identify the IEEE physical standards for Ethernet cabling.

Answer 33

These standards describe the capabilities and physical characteristics of various cable types and include but are not limited to 10Base-2, 10Base-5, and 10Base-T.

Question 34

Differentiate types of Ethernet cabling and identify their proper application.

Answer 34

The three types of cabling of cables that can be created from an Ethernet cable are straight-through ( to connect a PC’s or router’s Ethernet interface to a hub or switch), crossover (to connect hub to hub, hub to switch, switch to switch, or PC to PC), and rolled ( for a console connection from a PC to a router or switch).

Question 35

Describe the data encapsulation process and role it plays in packet creation.

Answer 35

Data encapsulation is a process whereby information is added to the frame from each layer of the OSI model. This is also called packet creation. Each layer communicates on with its peer layer on the receiving device.

Question 36

Understand how to connect a console cable from a PC to a router and switch.

Answer 36

Take a rolled cable and connect it from the COM port of the host to the console port of a router. Start your emulations program such as putty or SecureCRT and set the bits per second to 9600 and flow control to None.

Question 37

Identify the layers in the Cisco three-layer model and describe the ideal function of each layer.

Answer 37

The three layers in the Cisco hierarchical model are the core (responsible for transporting large amounts of traffic both reliably and quickly), distribution (provides routing, filtering, and WAN access), and access (workgroup connectivity into the distribution layer).