Chapter 1: Introduction to Networking

Frame

A term referring to a data link header and trailer, plus the data encapsulated between the header and trailer.

7. Which OSI encapsulation term can be used instead of the term frame? a. Layer 1 PDU b. Layer 2 PDU c. Layer 3 PDU d. Layer 5 PDU e. Layer 7 PDU

B. The term frame refers to the data-link (that is, Layer 2) data structure created by a Layer 2 protocol. As a result, the matching OSI term for protocol data units (PDUs) mentions that same layer, that is, Layer 2 PDU, or L2PDU.

TCP/IP Network layer

Logical addressing and routing. Most popular protocols are TCP & IP.

TCP/IP Application Layer

TCP/IP application layer protocols provide services to the application software running on a computer. The application layer does not define the application itself, but it defines services that applications need. For example, application protocol HTTP defines how web browsers can pull the contents of a web page from a web server. In short, the application layer provides an interface between software running on a computer and the network itself.

TCP/IP Data-Link & Physical layers

The TCP/IP model's data-link and physical layers define the protocols and hardware required to deliver data across some physical network.

Same-layer interaction

The communication between two networking devices for the purposes of the functions defined at a particular layer of a networking model, with that communication happening by using a header defined by that layer of the model. The two devices set values in the header, send the header and encapsulated data, with the receiving devices interpreting the header to decide what action to take.

Which OSI encapsulation term can be used instead of the term frame? a. Layer 1 PDU b. Layer 3 PDU c. Layer 7 PDU d. Layer 5 PDU e. Layer 2 PDU

e. The term frame refers to the data-link (that is, Layer 2) data structure created by a Layer 2 protocol. As a result, the matching OSI term for protocol data units (PDUs) mentions that same layer, that is, Layer 2 PDU, or L2PDU.

Networking model

A generic term referring to any set of protocols and standards collected into a comprehensive grouping that, when followed by the devices in a network, allows all the devices to communicate. Examples include TCP/IP and OSI.

Adjacent-layer interaction

The general topic of how on one computer, two adjacent layers in a networking architectural model work together, with the lower layer providing services to the higher layer.

IP functions at what layer of the OSI Reference Model? a. Network b. Session c. Physical d. Transport

a. The Network layer is responsible for end-to-end delivery of packets. IP running on a router examines the packet's IP destination and compares it to the IP routing table. If needed, it then fragments the packet to go out the outgoing interface.

2. Which of the following protocols are examples of TCP/IP data-link layer protocols? (Choose two answers.) a. Ethernet b. HTTP c. IP d. UDP e. SMTP f. TCP g. PPP

A and G. Of the remaining answers, IP is a network layer protocol, TCP and UDP are transport layer protocols, and SMTP and HTTP are application layer protocols.

5. The process of a web server adding a TCP header to the contents of a web page, followed by adding an IP header and then adding a data-link header and trailer, is an example of what? a. Data encapsulation b. Same-layer interaction c. OSI model d. All of these answers are correct.

A. Encapsulation is defined as the process of adding a header in front of data supplied by a higher layer (and possibly adding a trailer as well).

Which of the following protocols are examples of TCP/IP transport layer protocols? (Choose two answers.) a. Ethernet b. HTTP c. IP d. UDP e. SMTP f. TCP

D and F. Of the remaining answers, Ethernet defines both physical and data-link protocols, PPP is a data-link protocol, IP is a network layer protocol, and SMTP and HTTP are application layer protocols.

Encapsulation

The placement of data from a higher-layer protocol behind the header (and in some cases, between a header and trailer) of the next-lower-layer protocol. For example, an IP packet could be encapsulated in an Ethernet header and trailer before being sent over an Ethernet.

3. The process of HTTP asking TCP to send some data and making sure that it is received correctly is an example of what? a. Same-layer interaction b. Adjacent-layer interaction c. OSI model d. All of these answers are correct.

B. Adjacent-layer interaction occurs on one computer, with two adjacent layers in the model. The higher layer requests services from the next lower layer, and the lower layer provides the services to the next higher layer.

6. Which of the following terms is used specifically to identify the entity created when encapsulating data inside data-link layer headers and trailers? a. Data b. Chunk c. Segment d. Frame e. Packet

D. By convention, the term frame refers to the part of a network message that includes the data-link header and trailer, with encapsulated data. The term packet omits the data-link header and trailer, leaving the network layer header with its encapsulated data. The term segment omits the network layer header, leaving the transport layer header and its encapsulated data.

The process of TCP on one computer marking a TCP segment as segment 1, and the receiving computer then acknowledging the receipt of TCP segment 1 is an example of what? a. Same-layer interaction b. OSI model c. All of these answers are correct. d. Adjacent-layer interaction e. Data encapsulation

a. Same-layer interaction occurs on multiple computers. The functions defined by that layer typically need to be accomplished by multiple computers—for example, the sender setting a sequence number for a segment and the receiver acknowledging receipt of that segment. A single layer defines that process, but the implementation of that layer on multiple devices is required to accomplish the function.

Which of the following protocols are examples of TCP/IP transport layer protocols? (Choose two answers.) a. UDP b. TCP c. SMTP d. IP e. HTTP f. Ethernet

a., b.

Which of the following protocols are examples of TCP/IP transport layer protocols? (Choose two answers.) a. TCP b. IP c. SMTP d. HTTP e. Ethernet f. UDP

a., f. Of the incorrect answers, Ethernet defines both physical and data-link protocols, PPP is a data-link protocol, IP is a network layer protocol, and SMTP and HTTP are application layer protocols.

The process of a web server adding a TCP header to the contents of a web page, followed by adding an IP header and then adding a data-link header and trailer, is an example of what? a. OSI model b. Data encapsulation c. All of these answers are correct. d. Same-layer interaction

b. Encapsulation is defined as the process of adding a header in front of data supplied by a higher layer (and possibly adding a trailer as well).

IP functions at what layer of the OSI Reference Model? a. Session b. Network c. Transport d. Physical

b. The Network layer is responsible for end-to-end delivery of packets. IP running on a router examines the packet's IP destination and compares it to the IP routing table. If needed, it then fragments the packet to go out the outgoing interface.

Which of the following terms represents L3PDU in the OSI model, which includes the network layer header and its encapsulated data? a. Segment b. Packet c. Frame d. Data

b. The term L3PDU, or Layer 3 Protocol Data Unit, refers to the part of a message that includes the layer 3 header and its encapsulated data. By convention, the term packet is used as a synonym for the more formal L3PDU term.

The process of a web server adding a TCP header to the contents of a web page, followed by adding an IP header and then adding a data-link header and trailer, is an example of what? a. Same-layer interaction b. All of these answers are correct. c. OSI model d. Data encapsulation

d. Encapsulation is defined as the process of adding a header in front of data supplied by a higher layer (and possibly adding a trailer as well).

The term segment refers to which layer PDU? a. Application layer PDU b. Internetwork layer PDU c. Network Access PDU d. Transport layer PDU

d. The term segment refers to the part of a message that includes the layer 4 (Transport) header and its encapsulated data. Based on the layer, the L4PDU, or Layer 4 PDU, is used as a synonym for the less formal term segment.

Protocol Data Unit (PDU)

A generic term referring to the header defined by some layer of a networking model, and the data encapsulated by the header (and possibly trailer) of that layer, but specifically not including any lower-layer headers and trailers.

Packet

A logical grouping of bytes that includes the network layer header and encapsulated data, but specifically does not include any headers and trailers below the network layer.

OSI Model layers

Application Presentation Session Transport Network Data Link Physical

TCP/IP networking model layers

Application Transport Network Data Link Physical

4. The process of TCP on one computer marking a TCP segment as segment 1, and the receiving computer then acknowledging the receipt of TCP segment 1 is an example of what? a. Data encapsulation b. Same-layer interaction c. Adjacent-layer interaction d. OSI model e. All of these answers are correct.

B. Same-layer interaction occurs on multiple computers. The functions defined by that layer typically need to be accomplished by multiple computers—for example, the sender setting a sequence number for a segment and the receiver acknowledging receipt of that segment. A single layer defines that process, but the implementation of that layer on multiple devices is required to accomplish the function.

Segment

In TCP, a term used to describe a TCP header and its encapsulated data (also called an L4PDU). Also in TCP, the process of accepting a large chunk of data from the application layer and breaking it into smaller pieces that fit into TCP segments. In Ethernet, a segment is either a single Ethernet cable or a single collision domain (no matter how many cables are used).

De-encapsulation

On a computer that receives data over a network, the process in which the device interprets the lower-layer headers and, when finished with each header, removes the header, revealing the next-higher-layer PDU.

The process by which a TCP/IP host sends data.

Step 1. - Create and encapsulate the application data with any required application layer headers. For example, the HTTP OK message can be returned in an HTTP header, followed by part of the contents of a web page. Step 2. - Encapsulate the data supplied by the application layer inside a transport layer header. For end-user applications, a TCP or UDP header is typically used. Step 3. - Encapsulate the data supplied by the transport layer inside a network layer (IP) header. IP defines the IP addresses that uniquely identify each computer. Step 4. - Encapsulate the data supplied by the network layer inside a data-link layer header and trailer. This layer uses both a header and a trailer. Step 5. - Transmit the bits. The physical layer encodes a signal onto the medium to transmit the frame.

TCP/IP Transport layer

Transport layer protocols provide services to the application layer protocols that reside one layer higher in the TCP/IP model. The two most commonly used transport layer protocols are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

The process of HTTP asking TCP to send some data and making sure that it is received correctly is an example of what? a. Adjacent-layer interaction b. OSI model c. Same-layer interaction d. All of these answers are correct.

a. Adjacent-layer interaction occurs on one computer, with two adjacent layers in the model. The higher layer requests services from the next lower layer, and the lower layer provides the services to the next higher layer.

A user has sent a request to the server. What process does the server go through to determine what service is being requested by the user? a. Encapsulation b. De-encapsulation c. Segmentation d. Fragmentation

a. As data is sent from a sender to a receiver, the sender encapsulates the data into segments, which are encapsulated into packets, then into frames, and then sent on the wire as bits. The receiver de-encapsulates the PDUs (in the reverse order) to determine what actual data that is being transmitted. Segmentation at Layer 4 is used to chop up large data blocks into smaller parts for transmission. Fragmentation at Layer 3 is used to take a packet that may otherwise be too large to be supported on a given network and chop up the packet into smaller packets for transmission.

Which of the following protocols are examples of TCP/IP data-link layer protocols? (Choose two answers.) a. Ethernet b. IP c. HTTP d. SMTP e. UDP f. PPP g. TCP

a., f. Of the incorrect answers, IP is a network layer protocol, TCP and UDP are transport layer protocols, and SMTP and HTTP are application layer protocols.

Which OSI encapsulation term can be used instead of the term frame? a. Layer 3 PDU b. Layer 2 PDU c. Layer 1 PDU d. Layer 7 PDU e. Layer 5 PDU

b. The term frame refers to the data-link (that is, Layer 2) data structure created by a Layer 2 protocol. As a result, the matching OSI term for protocol data units (PDUs) mentions that same layer, that is, Layer 2 PDU, or L2PDU.

The process of HTTP asking TCP to send some data and making sure that it is received correctly is an example of what? a. All of these answers are correct. b. Same-layer interaction c. Adjacent-layer interaction d. OSI model

c. Adjacent-layer interaction occurs on one computer, with two adjacent layers in the model. The higher layer requests services from the next lower layer, and the lower layer provides the services to the next higher layer.

The process of TCP on one computer marking a TCP segment as segment 1, and the receiving computer then acknowledging the receipt of TCP segment 1 is an example of what? a. All of these answers are correct. b. Adjacent-layer interaction c. Same-layer interaction d. OSI model e. Data encapsulation

c. Same-layer interaction occurs on multiple computers. The functions defined by that layer typically need to be accomplished by multiple computers—for example, the sender setting a sequence number for a segment and the receiver acknowledging receipt of that segment. A single layer defines that process, but the implementation of that layer on multiple devices is required to accomplish the function.

Which layer of the TCP/IP Model defines end-to-end forwarding of packets? a. The Application layer b. The Link layer c. The Network layer d. The Transport layer

c. The TCP/IP Network layer defines the end-to-end routing of data. Also, the term packet (as mentioned in the question) defines the data that the network layer forwards from sending host to destination host.For the incorrect answers:The TCP/IP Application layer provides application software with an interface to the network in ways that simplify the interface so that the application can ask the network to deliver data to some destination address.The TCP/IP Transport layer deals with error recovery, segmentation of large application data blocks for transport, and the reassembly of segmented application data.The TCP/IP data link layer defines how to deliver data over a particular instance of a particular type of data link, for instance, over a single Ethernet LAN, serial WAN, or Ethernet WAN link. However, it does not define end-to-end routing of data.

The term segment refers to which layer PDU? a. Application layer PDU b. Network Access PDU c. Transport layer PDU d. Internetwork layer PDU

c. The term segment refers to the part of a message that includes the layer 4 (Transport) header and its encapsulated data. Based on the layer, the L4PDU, or Layer 4 PDU, is used as a synonym for the less formal term segment. For the incorrect answers: - Data refers to application data encapsulated by the segment. - Packet refers to the internework layer PDU (layer 3) - Frame refers to the data link or network access layer PDU (layer 2)

Which of the following terms is used specifically to identify the entity created when encapsulating data inside data-link layer headers and trailers? a. Packet b. Segment c. Data d. Frame e. Chunk

d. By convention, the term frame refers to the part of a network message that includes the data-link header and trailer, with encapsulated data. The term packet omits the data-link header and trailer, leaving the network layer header with its encapsulated data. The term segment omits the network layer header, leaving the transport layer header and its encapsulated data.

Which layer of the TCP/IP Model defines end-to-end forwarding of packets? a. The Application layer b. The Transport layer c. The Link layer d. The Network layer

d. The TCP/IP Network layer defines the end-to-end routing of data. Also, the term packet (as mentioned in the question) defines the data that the network layer forwards from sending host to destination host. For the incorrect answers: The TCP/IP Application layer provides application software with an interface to the network in ways that simplify the interface so that the application can ask the network to deliver data to some destination address. The TCP/IP Transport layer deals with error recovery, segmentation of large application data blocks for transport, and the reassembly of segmented application data. The TCP/IP data link layer defines how to deliver data over a particular instance of a particular type of data link, for instance, over a single Ethernet LAN, serial WAN, or Ethernet WAN link. However, it does not define end-to-end routing of data.

Which of the following terms represents L3PDU in the OSI model, which includes the network layer header and its encapsulated data? a. Data b. Segment c. Frame d. Packet

d. The term L3PDU, or Layer 3 Protocol Data Unit, refers to the part of a message that includes the layer 3 header and its encapsulated data. By convention, the term packet is used as a synonym for the more formal L3PDU term. For the incorrect answers, the term segment refers to an L4PDU while the term frame refers to an L2PDU. Data refers to the data enapsulated in any PDU.

Which of the following terms is used specifically to identify the entity created when encapsulating data inside data-link layer headers and trailers? a. Packet b. Chunk c. Segment d. Data e. Frame

e. By convention, the term frame refers to the part of a network message that includes the data-link header and trailer, with encapsulated data. The term packet omits the data-link header and trailer, leaving the network layer header with its encapsulated data. The term segment omits the network layer header, leaving the transport layer header and its encapsulated data.

Which of the following protocols are examples of TCP/IP data-link layer protocols? (Choose two answers.) a. SMTP b. UDP c. TCP d. IP e. Ethernet f. HTTP g. PPP

e., g. Of the incorrect answers, IP is a network layer protocol, TCP and UDP are transport layer protocols, and SMTP and HTTP are application layer protocols.