Objective 1.2

Which of the following devices operate at the Data Link layer of the Open Systems Interconnection (OSI) model?

-Bridge -Switch (Switches and bridges function at the MAC sub-layer of the Data Link layer.)

What are two purposes for segmentation with a bridge?

-To add more bandwidth for users -To create more collision domains (Bridges and switches break up collision domains, which allows more bandwidth for users.)

TCP and UDP reside at which layer of the OSI model?

4 (TCP and UDP are Transport layer protocols. The Transport layer is Layer 4 of the OSI model.)

Simple Mail Transfer Protocol works at which layer of the OSI model?

Application (HTTP, HTTPS, SMTP, SNMP, Telnet, and FTP, among others, all work at the Application layer of the OSI model. Simple Mail Transfer Protocol (SMTP) is a common protocol for sending e-mails between servers over the Internet.)

At which layers of the OSI model do bridges, hubs, and routers primarily operate, respectively?

Data Link, Physical, Network (Bridges, like switches, are Data Link layer devices. Hubs, like repeaters, are Physical layer devices. Routers are Network layer devices.)

When data is encapsulated, which is the correct order?

Data, segment, packet, frame, bits (The encapsulation order is data, segment, packet, frame, bits.)

What layer in the IP stack is equivalent to the Transport layer of the OSI model?

Host-to-Host (The four layers of the IP stack (also called the DoD model) are Application/Process, Host-to-Host, Internet, and Network Access. The Host-to-Host layer is equivalent to the Transport layer of the OSI model.)

Which of the following is a network device that is used to connect multiple devices without segmenting a network?

Hub (A hub can be used to connect multiple devices without segmenting a network. It creates one collision domain and one broadcast domain. It is a multiple-port repeater, which receives a digital signal and reamplifies or regenerates it and then forwards it out to all active ports without looking at any data.)

Acknowledgments, sequencing, and flow control are characteristic of which OSI layer?

Layer 4 (A reliable Transport layer connection uses acknowledgments to make sure all data is received reliably. A reliable connection is defined by the use of acknowledgments, sequencing, and flow control, which is characteristic of the Transport layer (Layer 4).)

Which of the following transmission methods is used for the network using the 802.3 standard?

MAC (802.3 is the IEEE standard for Ethernet defining a mode of physical communication in LAN (local area network). The standard defines the transmission at the physical layer and MAC (media access control) sublayer of the data link layer of wired Ethernet.)

Switches/bridges use what type of addresses to segment a LAN?

MAC (Switches/bridges work at the Data Link layer and use hardware or MAC addresses to segment a network.)

Routers perform routing at which OSI layer?

Network (A router is specified at the Network layer and a router routes packets. Routers can also be called Layer 3 switches.)

At which layer of the OSI model would you find IP?

Network (IP is a Network layer protocol. TCP is an example of a Transport layer protocol, Ethernet is an example of a Data Link layer protocol, and T1 can be considered a Physical layer protocol.)

In which layer of the OSI model does IPSec operate?

Network (IPSec works at the Network layer of the OSI model (Layer 3) and secures all applications that operate above it (Layer 4 and above). Additionally, because it was designed by the IETF to work with IPv4 and IPv6, it has broad industry support and is quickly becoming the standard for VPNs on the Internet.)

Which layer of the OSI model is responsible for converting data into signals appropriate for the transmission medium?

Physical (The Physical layer's job is to convert data into impulses that are designed for the wired or wireless medium being used on the attached segment.)

At which layers of the OSI model layers do WAN protocols operate?

Physical, Data Link, Network (The WAN protocols and technologies occupy the lower three layers of the OSI model: the Physical layer, the Data Link layer, and sometimes the Network layer. Most WAN protocols work only at the Physical layer and Data Link layer.)

Which of the following mnemonic devices can you use to remember the first letter of the name of each layer of the OSI model in the proper order?

Please Do Not Throw Sausage Pizza Away. (The phrase "Please Do Not Throw Sausage Pizza Away" contains the first letters of the layers in order, from Layer 1 through Layer 7. "All People Seem To Need Data Processing" works from the top down.)

Of the following, which is the highest layer in the OSI model?

Presentation (The Presentation layer is the sixth layer of the model. Only the Application layer is higher, but it is not listed. Session is Layer 5, Transport is Layer 4, and Network is Layer 3.)

Which Layer 1 technology allows a single PRI to deliver multiple voice calls simultaneously?

TDM (A single PRI delivers multiple voice calls simultaneously using Time-division multiplexing (TDM). TDM supports different communication sessions on the same physical medium by allowing sessions to take turns. For a brief period of time, known as a time slot, data from the first session is sent, followed by data from the second session. This continues until all sessions have had a turn, and then the process repeats itself.)

What is the purpose of flow control?

To provide a means for the receiver to govern the amount of data sent by the sender (Flow control allows the receiving device to control the pace of the transmitting device so the receiving device's buffer does not overflow.)

At which layer of the OSI model does UDP operate?

Transport (Both TCP and UDP operate at the Transport layer of the OSI model. UDP is a connectionless transport protocol and offers unreliable transport such that if a segment is dropped, the sender is unaware of the drop, and no retransmission occurs. TCP is a full-duplex, connection-oriented, reliable, and accurate protocol.)

Which layer of the OSI model performs the process-to-process communication using segments?

Transport (The Transport layer performs the process-to-process communication using segments. It consists of both connection-oriented and connectionless protocols providing communications between devices on a computer network.)

You are connected to a server on the Internet and you click a link on the server and receive a time-out message. What layer could be the source of this message?

Application (If the remote server is busy or does not respond to your web browser request, this is an Application layer problem.)

Which of the following is true regarding sequencing and acknowledgments?

-Segments are sequenced back into their proper order upon arrival at their destination. -Any segments not acknowledged are retransmitted. -The segments delivered are acknowledged back to the sender upon their reception. (When sequencing and acknowledgements are used, the segments delivered are acknowledged back to the sender upon their reception. At this point, any segments not acknowledged are retransmitted, and segments are sequenced back into their proper order upon arrival at their destination.)

Which of the following are functions of the presentation layer of the OSI model?

-Data encryption -Character-code translation -Data compression (Data compression: Reduces the number of bits to be transferred. Character-code translation: Translates character code, such as ASCII to EBCDIC. Data encryption: Provides security to the data traveling across an insecure network.)

What are the advantages of using a layer 2 switch over a hub?

-Prevents broadcast storms -Has more collision domains (The advantages of using a layer 2 switch over a hub are: Prevents broadcast storms Has a single broadcast domain Has more collision domains (one per port) Intelligently transmits data to the specific ports only)

Which Layer 1 devices can be used to enlarge the area covered by a single LAN segment?

-Repeater -Hub (Not that you really want to enlarge a single collision domain, but a hub (multiport repeater) will provide this functionality for you.)

The OSI model has seven layers and the DoD has four. At which layer does SMTP works in both models?

Application (SMTP resides at the Application layer of the OSI and DoD models.)

Which layer of the OSI model provides an entry point for programs to access the network infrastructure?

Application (The top layer of the OSI model gives applications access to the services that allow network access.)

Which of the following units of data does the data-link layer send from the network layer to the physical layer of the OSI model?

Data frames (The data link layer sends data frames from the network layer to the physical layer. On the receiving end, the data link layer packs the raw bits from the physical layer into data frames.)

At which layer of OSI is the Frame Check Sequence for error detection performed?

Layer 2 (At layer 2 (data link layer), the Frame Check Sequence for error detection is performed. A frame is most commonly used to refer to Ethernet, Token Ring, or Frame Relay units of data. It is called a "frame" because it is created by taking higher-level packets or datagrams and "framing" them with additional header information needed at the lower level. It works on layer 2 (Data-link layer) of the OSI model. Note: Frame at layer 1 refers to T-Carrier Layer 1 units of data (193-bit frames).)

Which of the following OSI layers has packet as its PDU?

Layer 3 (The name given to data at different layers of the OSI model is known as Protocol Data Unit (PDU). Specifically, the PDU for Layer 1 is bit, the Layer 2 PDU is frame, the Layer 3 PDU is packet, and the Layer 4 PDU is segment.)

A user has performed multiple JSON and XML edits. This relates to an operation at which of the following OSI layers?

Presentation (The Presentation layer is the sixth layer of the OSI model. It gets its name from its purpose that it presents data to the Application layer. It is responsible for data translation and code formatting. The presentation layer performs the following functions: Data encryption/decryption Character/string conversion Data compression Graphic handling JSON and XML are the two most common formats for data interchange and therefore, the Presentation layer is responsible for how the data looks or is formatted, which is then presented to the applications working at the Application layer.)

Which layer of the OSI model is responsible for code and character-set conversion as well as recognizing data formats?

Presentation (The Presentation layer makes data "presentable" for the Application layer.)

Which of the following layers of the OSI model provides delivery and formatting of information for processing and display?

Presentation (The Presentation layer provides delivery and formatting of information for processing and display. This allows for information sent from one device on a network (the source) to be understood by another device (the destination) on the network. Encryption, compression, character sets, multimedia formats, and codecs exist at this layer.)

Which of the following devices can work at both Layer 2 and Layer 3 of the OSI model?

Switch (A switch is typically just a Layer 2 device, segmenting the network by using MAC addresses. However, some higher-end switches can provide Layer 3 services.)

Segmentation of a data stream happens at which layer of the OSI model?

Transport (The Transport layer receives large data streams from the upper layers and breaks these up into smaller pieces called segments.)