Chapter 4-7 Networking Exam
What are three ways that media access control is used in networking?
- Ethernet Utilizes CSMA/CD (for media access control) - Media Access Control Provides placement of data frames onto the media (defines the way data frames get placed on the media) - Data link layer protocols define the rules for access to different media
Which three basic parts are common to all frame types supported by the data link layer? Why?
- Header - Data - Trailer This is because these are the three basic parts that each frame type has.
What three items are contained in an Ethernet header and trailer?
- Source Mac Address - Destination MAC address - Error - Checking information
Name the seven layers of the OSI model by their layer name and layer number.
1 Physical 2 Data Link 3 Network 4 Transport 5 Session 6 Presentation 7 Application
What does the Protocol Data Unit get called in each layer of the OSI Model?
1 Physical - Bit 2 Data Link Layer - Frame 3 Network Layer - Packet 4 Transport Layer- Segment 5 Session Layer- Data 6 Presentation Layer - Data 7 Application Layer - Data
What is the Maximum length of a Segment of UTP cable? Why?
100 Meters. To avoid Data Loss.
What number layer is the datalink layer?
2
What layer of the OSI Model does the Switch operate in?
2 Data Link Layer
What layer of the OSI model does the router operate in?
3 Network Layer
in a 100 mbps transmission on UTP how many individual wires are used?
4. There are 8 wires in a twisted pair cable to be grouped into 4 pairs. Of the four pairs only pair two and pair three will be used.
Talk about the OSI Model in terms of a postal service - by layer
7 Application - A CEO wants to send a letter. The CEO tells the assistant what he wants written. 6 Presentation - The assistant puts the letter into writing 5 Session - The letter is put into an envelope and sent to the mail room. The assistant doesn't know where the letter is going but knows it's urgent and must be sent quickly. 4 Transport- The mail room must decide how to send the letter where it needs to go. Since it's a rush, they decide to use a courier. 3 Network - The courier receives the information but needs to add their own, they put the small envelope into a bigger envelope and then determines the envelope needs to get to Albany, but must travel through Chicago first. 2 Datalink - The worker takes the envelope and puts in the code for Chicago and then puts it in a box. 1 Physical - letter flies to Chicago 2 Datalink - Box is unloaded, courier envelope is removed, and put into a new box and is given to a worker to be sent to Albany 1 Physical - Plane flies to Albany 2 Datalink - Box is unloaded and the courier envelope is removed. It is then sent to the ALbany routing office 3 Network - Courier company in Albany sees that the destination is in Albany and delivers the envelope to the destination 4 Transport - The mail room removes the inner envelope from the courier envelope and delivers it to the destination's assistant 5 Session - The assistant takes the letter out of the envelope 6 Presentation - The assistant reads the letter and decides f it should be handed to the CEO, sent in an email, or call the CEO 7 Application - The assistant delivers the letter to it's destination
What is a half-duplex transmission?
A one-way street between sender and receiver
A network admin is connecting two modern switches using a straight through cable. The switches are new and have never been configured. Which three statements are correct about the final result of the connection? A.) The link between the switches will work at the fastest speed supported by both switches B.) The link between switches will work as full-duplex. C.) If both switches support different speeds, they will each work at their own fastest speed. D.) The auto-MDIX feature will configure the interfaces eliminating the need for a crossover cable. E.)The connection will not be possible unless the administrator changes the cable to a crossover cable. F.) The duplex capability has to be manually configured because it cannot be negotiated
A,B, and D
What type of communication rule would best describe CSMA/CD?
Access Method - Carrier Sense Multiple Access Collision Detection (CSMA/CD) is the access method used with Ethernet. The access method rule of communication dictates how a network device is able to place a signal on the carrier.
Which Statement is true about the CSMA/CD access methos that is used in Ethernet?
All Network devices must listen before transmitting because when one host wants to transmit a frame it listens to the medium to check is the medium is busy.
What is the function of the Data link layer?
Defines the end-to-end delivery addressing scheme and it maintains the path between the source and destination devices during the data transmission
Describe a point-to-point topology.
Each device is connected to one other device.
What is full-duplex transmission?
Enables two-way traffic at the same time. (Mobile Phones)
Describe an extended star topology.
End devices connect to a central intermediate device, which in turn connects to other central intermediate devices.
What is contained in the trailer of a data-link frame? Why?
Error Detection. The trailer within the data-link frame contains error detection information that is pertinent to the frame included in the FCS field.
What switching method has the lowest level of latency?
Fast - Forward (Fast - Forward switching begins to forward a frame after reading the destination MAC address, resulting in the lowest latency.)
What are two examples of the cut through switching method?
Fast forward switching + Fragment-Free Switching
What media type has the largest bandwidth?
Fiber Optic Cables
What are the two subcomponents of the MAC address?
First 24 Bits are the OUI next 24 bits Vendor Assigned
Name two fields or features that an Ethernet examines to determine if a received frame is passed to the data link layer or discarded by the NIC?
Frame Check Sequence + Minimum Frame Size. An ethernet frame is not processed and is discarded if it's smaller than 64 bytes or if the calculated FCS does not match the received FCS value.
Which media communication type does not require media arbitration in the data link layer? Why?
Full-Duplex because communication occurs when both devices can transmit and receive on the medium at the same time and therefore does not require media arbitration.
What is a single mode fiber optic cable?
It has a smaller core size and has a single light path but it can travel further (up to 100km)
What is a multimode fiber optic cable?
It is capable of carrying multiple light rays (modes) at the same time because it has varying optical properties at it's core
What is a characteristic of the LLC Sublayer? Why?
It puts information in the frame allowing multiple layer 3 protocols to use the same network interface and media. The LLC Defines the software processes that provide services to the network layer protocols, the information is placed by LLC in the frame and identifies which network layer protocol is being used for the frame. This info allows multiple layer 3 protocols such as IPv4 and IPv6 to use the same network interface and media.
Describe a hub and spoke topology
It uses a central device in a star topology that connects to other point-to-point devices.
What are the sublayers of the datalink layer?
Logical Link Control (LLC) and Media Access Control (MAC)
Name a few devices that commonly affect wireless networks. Why?
Microwaves, cordless phones, etc. RFI - Radio Frequency Interface - An interference that is caused by radio transmitters.
At any layer of the OSI model, the encapsulated data is known as a _______
PDU
What topology provides high availability and connects some but not all remote sites? Why?
Partial Mesh. They Provide high availability by interconnecting multiple remote sites, but do not require a connection between all remote sites.
What are two types of fiber optic cables?
Single-mode and multimode
Which fram forwarding method receives the entire frame and performs a CRC check to detect errors before forwarding the frame?
Store-and-forward switching
The Logical Address is also known as....
The IP Address
During the encapsulation process, what occurs at the data link layer for a PC connected to an Ethernet Network? Why?
The Physical Address is added. The ethernet frame includes the source and destination physical address.
What is the auto-MDIX feature on a switch?
The automatic configuration of an interface for a straight through or crossover Ethernet Cable connection. The auto MDIX enables a switch to use a crossover or straight-through Ethernet cable to connect to a device regardless of the device on the other end of the connection.
What is media arbitration?
The collection of methods used to ensure that all users can access attached resources without interference from another user.
what Statement could Describe a characteristic of the frame header fields of the data link layer? Why?
They Vary Depending on Protocols. All data link layer protocols encapsulate the layer 3 pdu within the data field of the frame. However, the structure of the frame and the fields that are contained in the header vary according to the protocol. Different data link layer protocols may use different fields.
What is the purpose of the FCS field in a frame?
To determine if errors occurred in the transmission and reception
What is the function of the CRC Value that is found in the FCS field of a frame? Why? Define "CRC" and "FCS"
To verify the integrity of the received frame. CRC - Cyclic Redundancy Check. FCS - Frame Check Sequence. The CRC value in the FCS of the received frame is compared to the computed CRC value of that frame. If the values don't match then the frame is discarded.
The MAC address is normally written in base _____.
base - 16
Describe a mesh topology
requires point-to-point links with every system being connected to every other system.
