Chapter 1 Flashcards
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.
Adjacent-layer interaction
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 other, removes the header, revealing the next-higher layer PDU
de-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.
Encapsulation
A term referring to a data link header and trailer, plus the data encapsulated between the header and trailer.
Frame
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.
Networking model
A logical grouping of bytes that includes the network layer header and encapsulated data, but specifically does not include and headers and trailers below the network layer.
Packet
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.
Protocol data unit (PDU)
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.
Same-layer interaction
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).
Segment
What type of network is created by a corporation or enterprise?
Enterprise Network
What are small networks at home for business purposes?
Small office/home office network (SOHO)
A comprehensive set of documents that defines how a computer works.
Networking model
Logical set of rules devices must follow to communicate
Protocol
What organization in the late 1970’s created the Open Systems Interface (OSI)
International Organization for Standardization (OSI)
The OSI was developed to reduce _____ and aid _____ and to standardize data networking protocols to allow communication between all computers.
Complexity;
Competition
What networking model did the DoD create that was less-formal than OSI and is the prevailing model today?
TCP/IP (Transmission-Control Protocol/Internet Protocol
What institute defines Ethernet standards?
Institute of Electrical and Electronic Engineers (IEEE)
What are the layers of the old TCP/IP model?
Application; Transport; Internet; Link
What protocol provides services to the software running on the computer?
Application
Does the application layer define the application itself or the services the application needs?
Services the application needs
What protocol defines how web browsers can pull the contents of a web page from a web server?
Hypertext transfer protocol (HTTP)
What are the documents referred to that define protocols?
Requests for Comments (RFC)
What is the most popular TCP/IP application today?
Web Browser
What layer provides an interface between software running on a computer and the network itself?
Application layer
If Bob wants to get a web page from Larry, what does Bob need to attach with the data, which essentially are used to put information used by the protocol?
Header
In response to Bob’s webpage request, Larry would send back a return code of “200.” What defines other return codes so the server can tell the web browser if the request worked?
HTTP
Once Larry sent the first message (“200”), what would the second message include?
The first part of the requested file
HTTP transfers data by sending _____ _____.
multiple messages
To not waste space, what do additional messages omit?
header
What are the most common protocols of the transport layer?
TCP (Transmission Control Protocol)
UDP (User Datagram Protocol)
What layer does the transport layer provide a service to?
application layer
TCP provides _____ recovery to the application layer.
error
What does TCP use to notice lost data and subsequently asks the sender to try again?
Acknowledgements
Web server Larry sends a web page to web browser Bob using three separate messages, what is the term used to describe each of these separate messages?
Segments
Once Bob receives the three separate web browser messages, it then _____ the HTTP header into a segment with an added TCP header.
encapsulates
In the three messages received by Bob from Larry, the TCP header shows a sequence with each message. If Bob receives segment 1 and 3 but not 2, TCP logic causes Bob to do what?
Send TCP segment back asking for segment 2
Layers in a networking model on the same computer working together, with the layer below providing a service to the layer above.
Adjacent-layer interaction
When a particular layer on one computer communicates with the same layer on another computer. Both computers use headers to hold the information they want to communicate.
Same-layer interaction
In the TCP segments sent by the web server (Larry) to web browser (Bob), why did Larry use sequence numbers 1, 2, and 3?
So Bob would know if a segment didn’t arrive
If Larry’s (web server) TCP process creates the TCP header with the sequence number, what does Bob’s (web browser) TCP process do?
Receives and reacts to it
What is the major protocol of the Network Layer?
Internet Protocol (IP)
IP has several features but most importantly, what is IP responsible for?
addressing and routing
Do upper layers work differently when they are separated by the Internet as opposed to being on the same LAN?
No
The TCP/IP _____ and _____ layers are similar to a person sending letters through the postal service.
The (upper/lower) layers are similar to the postal service delivering the mail to the correct destination.
application; transport
Lower
The (upper/lower) layers are responsible for the physical network because they must choose how to best deliver data from one host to another.
lower
The network layer protocol defines that each host computer should have a different address, like the post office defines unique addresses for each residence.
Internet Protocol (IP)
What layer defines the details of how a network infrastructure should be created so it can deliver data to all computers in the network?
Network
In order to be defined in the network, every device that uses TCP/IP needs to have a unique _____ address so it can be defined in the network
IP
What protocol defines how to group addresses together, just like the post office does with zip codes?
Internet Protocol (IP)
_____ connect the parts of the TCP/IP network together for the purposes of forwarding IP packets to the correct destination similar to the work done by each post office site.
Routers
When routers receive packets, what do they use to make a decision on where the packet needs to be forwarded to next?
IP address
What is the term used to describe any device with an IP address that can connect to the TCP/IP network and send packets?
IP Host
What kind of header does the Network layer encapsulate the HTTP header and TCP header in?
IP
An IP header includes a _____ IP address and a _____ IP address.
source; destination
When the IP process chooses to send a packet to another router does it expect that the router will know how to forward the packet?
Yes
When the receiving router receives a packet, what address does it look at and compare to its known IP routes?
destination
The TCP/IP model’s original _____ layer defines protocols and hardware required to deliver data across some physical network.
link
What term is used to describe the physical connection between two devices and the protocols used to control those links?
Link
What layer does the Link Layer provide a service to?
Network
In the Link Layer, the IP packet is encapsulated into a/an _____ header and trailer.
Ethernet
How are the bits of an Ethernet frame physically transmitted over an Ethernet cable using _____.
electricity
Once a router receives the electrical signal over a cable, it _____ the same bits by interpreting the meaning of the signals.
re-creates
When an IP host receives and Ethernet frame, what does it remove and discard first?
Ethernet header and trailer
When Ethernet frames are sent between hosts and each link-layer processes have worked together to deliver the packet, what type of interaction is used?
same-layer
The Link Layer has a (small/large) number of protocols.
large
The _____ layer has two distinct functions; Functions related to the physical transmission of data, plus the protocols and rules that control the use of physical media.
link
How many layers does the OSI model have?
7
Layers 5-7 of the OSI model are similar to what layer/s of the TCP/IP model?
Application
In the newer TCP/IP model, what layer numbers are similar to OSI layers 1-4?
1-4
Layer 1 of the newer TCP/IP model
Physical
Layer 2 of the newer TCP/IP model
Data Link
Layer 3 of the newer TCP/IP model
Network
Layer 4 of the newer TCP/IP model
Transport
Layer 5 of the newer TCP/IP model
Application
Layer 5 of the OSI model
Sessions
Layer 6 of the OSI model
Presentation
Layer 7 of the OSI model
Application
A LAN switch is commonly referred to as a “layer _____ switch.”
2
What layer of the OSI model provides interface from application to network?
Application (7)
In the OSI model, what layer defines the characteristics of the transmission medium including connectors, pins, use of pins, electrical currents, encoding, and light modulation.
Physical (1)
What layer of the OSI model provides methods to group multiple bidirectional messages into a workflow for easier management?
Sessions (5)
What layer of the OSI model defines logical addressing, routing, and routing protocols used to learn routes?
Network (3)
What layer of the OSI model negotiates data formats such as ASCII text or images like JPEG?
Presentation (6)
What layer of the OSI model focuses on data delivery between two endpoint hosts (error recovery)?
Transport (4)
What layer or the OSI model defines protocols for delivering data over the physical network?
Data link layer (2)
Are network devices capable of understanding the protocols at multiple OSI layers?
Yes
Telnet and HTTP are protocols and specifications for what layer?
Application
SNMP, VoIP, and POP3 are protocols and specifications for what layer?
Application
FTP and SMTP are protocols and specifications for what layer?
Application
TCP and UDP fall under what TCP/IP layer?
Transport
What layer does HDLC fall under?
Data link
What layer does RJ-45 fall under?
Physical
One benefit of a layered approach that allows one vendor to write software that implements higher layers and another that can implement lower layers.
modular engineering
One benefit of a layered approach is that it utilizes same network standards to ensure that computers/network gear can work in the same network.
multi-vendor interoperability
Another benefit of a layers approach is that it is easier to _____, allowing easier program changes and faster product development.
develop
The layered approach makes it easier to _____ because it makes it easier to discuss the many details or a protocol specification.
learn
Another benefit of a layered approach are _____ _____ which allow multiple vendors to create products that fill a particular role.
standard interfaces
The layered approach makes it less _____ by breaking concepts into smaller parts.
complex
Instead of using the term frame, packet, or segment, what generic term does OSI use for messages?
Protocol Data Unit (PDU)
Which of the following protocols are examples of TCP/IP transport layer protocols (Choose 2)
a. Ethernet
b. HTTP
c. IP
d. UDP
e. SMTP
f. TCP
UDP and TCP
Which of the following protocols are examples of TCP/IP data link layer protocols (Choose 2)
a. Ethernet
b. HTTP
c. IP
d. UDP
e. SMTP
f. TCP
g. PPP
Ethernet and PPP
The process of HTTP asking TCP to send some data and making sure that it is received correctly is an example of what?
Adjacent-layer interaction
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?
Data encapsulation
Which of the following terms is used specifically to identify the entity created when encapsulating data inside data link layer headers and trailers?
Frame
Which OSI layer defines the functions of logical network-wide addressing and routing?
Layer 3
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?
Same-layer interaction
