Communicating over the network - part 2 Flashcards
What is communication governed by?
Predetermined rules called protocols
What are protocols specific to?
The characteristics of a conversation?
What is a protocol suite?
A group of inter-related protocols that are necessary to perform a communication function
What are protocols implemented in?
Software and hardware that is loaded on each host and networked device
What does a protocol stack show?
How individual protocols within the suite are implemented on a host
How are protocols viewed in the stack?
As a layered hierarchy, with protocols in the higher levels depending on some functionality defined by the lower levels
What 2 things do the lower levels in the protocol stack do?
Move data across a network and provide functionality to the higher levels of the stack
What do the upper layers of the protocol stack focus on?
The content of the message being sent and the UI
What would the physical layer represent in human communication?
The use of people using their voices
What would the rules layer represent in human communication?
How the conversation is carried out e.g.
- Common language
- Wait your turn
- Signal end of speech
What would the content layer represent in human communication?
The actual words that are spoken e.g. “Wilfried Zaha is the greatest footballer in the world”
Why are network protocols used?
To allow devices to communicate successfully
What is the 1st (4) way a network protocol suite would describe precise requirements and interactions?
The format and structure of a message
What is an example of a network protocol suite describing the format and structure of a message?
“Lets agree that each piece will be 10 letters long”
What is the 2nd (4) way a network protocol suite would describe precise requirements and interactions?
The method by which networking devices share information about pathways and other networks
What is an example of a network protocol suite describing the method by which networking devices share information about pathways and other networks?
“Let’s all agree that if one of our pathways is down, we’ll notify all connected devices”
What is the 3rd (4) way a network protocol suite would describe precise requirements and interactions?
How and when error and system messages are passed between devices
What is an example of a network protocol suite describing how and when error and system messages are passed between devices?
“Let’s all agree that error messages have a unique ID number”
What is the 4th (4) way a network protocol suite would describe precise requirements and interactions?
The setup and termination of data transfer sessions
What is an example of a network protocol suite describing the setup and termination of data transfer sessions?
“Lets all agree that sessions will end after 60s of inactivity”
What does it mean if individual protocols in a stack are proprietary or vendor specific?
One company or vendor controls how the protocol functions.
What is the 1st (2) way companies can use proprietary protocols not owned by them?
Some can be used with permission from the owner
What is the 2nd (2) way companies can use proprietary protocols not owned by them?
Some can only be implemented on equipment manufactured by the proprietary vendor
What is a standard?
A process or protocol that has been endorsed by the networking industry and ratified by a standards organisation
What is the 1st (2) network standards organisation?
Institute of Electrical and Electronics Engineers (IEEE)
What is the 2nd (2) network standards organisation?
The Internet Engineering Task Force (IETF)
How do standards help the development and implementation of protocols?
The ensure that protocols from different manufacturers can work together for efficient communication
If one end of a communication is using a protocol that governs one way communication and a protocol at the other end is assuming two way communication, what is the probably outcome?
No information will be exchanged
What is the 1st (4) protocol in a web server protocol stack?
Application protocol
What is an example of an application protocol in the web server stack
Hypertext transfer protocol HTTP
What does HTTP govern? (1st)
The way a web server and client interact
What does HTTP define (2nd)
The content and formatting of requests and responses exchanged between the client and server
What implements HTTP as part of the application (3rd)
Both the web server and client software
What does HTTP rely on other protocols for (4th)
To govern how messages are sent between client and server
What is the 2nd (4) protocol in a web server protocol stack?
Transport protocol
What is an example of a transport protocol in the web server stack?
Transfer control protocol (TCP)
What doe TCP manage (1st)
The individual conversations between web clients and web servers
What does TCP do with HTTP messages (2nd)
Divides them into smaller pieces, called segments, to be sent to the destination client
What does TCP control (3rd)
The size and rate at which messages are exchanged between the server and the client
What is the 3rd (4) protocol in a web server protocol stack?
Internetwork protocol
What is an example of an Internetwork protocol in the web server stack?
Internet protocol (IP) The most common Internetwork protocol
What are the 4 things in sequence that IP is responsible for?
- Taking the formatted segments from TCP
- Encapsulating them into packets
- Assigning the appropriate address
- Selecting the best path to destination host
What is the 4th (4) protocol in a web server protocol stack?
Network Access Protocol
What is an example of a Network access protocol in a web server stack?
Ethernet
Data link management is the 1st primary function of the network access protocol. What does it do?
Protocols take packets from IP and format them to be transmitted over media
The physical transmission of data on the media is the 2nd primary function of the network access protocol. What is the 1st (2) step of this?
Standards and protocols for physical media govern how signals wil lbe sent over media and how they will be interpreted by the receiving clients
The physical transmission of data on the media is the 2nd primary function of the network access protocol. What is the 2nd (2) step of this?
Transceivers on NICs implement the standards to be used appropriately for media that is being used
What do protocols generally not do?
Describe HOW to accomplish a particular function
Why do protocols generally not describe how to accomplish a function?
So the implementation of a protocol can be technology independent
What is the benefit of a technology independent protocol?
Any device can access a web page stored on any server, using any operating system from anywhere on the internet
How does HTTP remain technology independent?
Doesn’t specify:
What programming language is used to create a browser
Which web server software should be used to serve web pages
What OS the server runs on etc…
What is the 1st (4) benefit of using a layered model?
Assists in protocol design
How does a layered model assist with protocol design?
Protocols that act at a specific layer have defined information that they act upon and defined interfaces to the layers above
What is the 2nd (4) benefit of using a layered model?
Fosters competition because products from different vendors can work together
What is the 3rd (4) benefit of using a layered model?
Prevent technology or capability changes in one layer affecting the layers above or below
What is the 4th (4) benefit of using a layered model?
Provides a common language to describe networking functions and capabilities
What are the 2 basic types of networking model?
Protocol models
Reference models
What does a protocol model provide?
A model that closely matches the structure of a protocol suite
What is the advantage of a protocol suite?
Related protocols in a suite typically represents all functionality needed to interface the human network and the data network
What is an example of a protocol model?
TCP/IP model - describes functions that occur at each level in TCP/IP suite
What does a reference model provide?
A common reference for maintaining consistency within all types of network protocols and services
What is a reference model not intended to be?
An implementation specification or to provide detail to define precisely the services of the network architecture
What is a reference model’s primary purpose?
To aid in a clearer understanding of all the processes and functions involved
What is an example of a reference model?
Open Systems Interconnection (OSI) model
What are designers required to communicate to the industry?
Them relating their products to the TCP/IP model, OSI model or both
What is the 1st (4) layer of the TCP/IP model?
Application layer
What does the application layer represent in the TCP/IP model?
Data to the user
Encoding
Dialogue Control
What is the 2nd (4) layer of the TCP/IP model?
Transport
What does the transport layer represent in the TCP/IP model?
Supports communication between diverse devices and diverse networks
What is the 3rd (4) layer of the TCP/IP model?
Internet
What is the role of the internet layer in the TCP/IP model?
Determines the best path through the network
What is the 4th (4) layer of the TCP/IP model?
Network Access
What is the role of the network access layer in the TCP/IP model?
Controls the hardware devices and media that make up the network
How are TCP/IP protocols defined?
In a publicly available set of documents called request for comments (RFCs)
What is the 1st (3) thing that RFCs contain?
The formal specification of the data communications protocols
What is the 2nd (3) thing that RFCs contain?
Resources that describe the use of protocols
What is the 3rd (3) thing that RFCs contain?
Technical and organisational documents about the internet
What do the documents about the internet in RFCs contain?
Technical and specification documents provided by the Internet Engineering Task Force (IETF)
What is the 1st (7) step of a TCP/IP communications process?
Creation of data at the application layer of the original source end device
What is the 2nd (7) step of a TCP/IP communications process?
Segmentation and encapsulation of the data as it passes down the protocol stack of the source end device
What is the 3rd (7) step of a TCP/IP communications process?
Generation of the data onto media at the network access layer of the stack
What is the 4th (7) step of a TCP/IP communications process?
Transportation of the data across the network which includes media and intermediary devices
What is the 5th (7) step of a TCP/IP communications process?
Reception of the data at the network access layer of the destination end device
What is the 6th (7) step of a TCP/IP communications process?
Decapsulation and reassembly of data as it moves up the stack at the destination end device
What is the 7th (7) step of a TCP/IP communications process?
Passing data to destination application at the application layer of the destination end device
What is the form that data takes at any layer of the stack called?
Protocol data unit (PDU)
What is the general term for PDU at application layer?
Data
What is added to PDU at application layer?
Data
What is the general term for PDU at transport layer?
Segment
What is added to the PDU at the transport layer?
Transport header
What is the general term for PDU at Internet layer?
Packet
What is added to the PDU at the Internet layer?
Network header
What is the general term for PDU at Network Access layer?
Frame
What is added to the PDU at Network Access layer?
Frame header and Frame Trailer
What is the general term for PDU as it is transported across the medium?
Bits
What form is the PDU in as it is transported accross the medium?
1s and 0s
When sending a web page to a web client:
How does the application layer begin the process?
By delivering the HTML formatted webpage to the transport layer
When sending a web page to a web client:
What information does the application data get added to it?
Information about which process on destination computer sohuld receive the message as well as information for destination device to assemble data in correct format.
All of this comes in transport header
When sending a web page to a web client:
What does the transport layer do after adding header?
Encapsulated HTML data within segment and sends to Internet layer for IP to be implemented
When sending a web page to a web client:
What happens at the Internet layer?
The entire TCP segment is encapsulated within IP packet, with IP header attached. Then sent off to network access layer
What is the 1st (2) bit of information that the IP header contains?
Source and destination IP addresses
What is the 2nd (2) bit of information that the IP header contains?
Information necessary to deliver the packet to corresponding destination process
When sending a web page to a web client:
What happens at the network access layer ethernet protocol?
Data is encapsulated with frame header and trailer
Bits are encoded onto ethernet media by server NIC
What information is in a frame header?
Source and destination physical address
What does a physical address do?
Uniquely identifies devices on the local network
What information is in a frame trailer?
Error checking information
What is the role of the Physical layer in the OSI model?
Describes mechanical, electrical, functional and procedural means to activate, maintain and de-activate bit transmissions to and from network to device
What is the role of the data-link layer in the OSI model
Describes methods for exchanging data frames over a common media
What is the role of the network layer in the OSI model?
Provides services to exchange individual pieces of data over a network between identified common devices
What is the role of the transport layer in the OSI model?
Defines services to segment, transfer and reassemble data for individual communations between end devices
What is the role of the session layer in the OSI model?
Provides services to presentation layer to organize its dialogue and manage data exchange
What is the role of the presentation layer in the OSI model?
Provides common representation of data transferred in application layer services
What is the role of the application layer in the OSI model?
Provides means for e2e connectivity between humans over data networks
What does the network access layer of TCP/IP model do and not do?
Does : Describe hand off from internet layer to physical network protocols
Does not : Specify which protocols to use when transmitting over a physical medium
What is the 1st (2) thing that OSI layers 1 and 2 discuss?
Necessary procedures to access the media
What is the 2nd (2) thing that OSI layers 1 and 2 discuss?
Physical means to send data over a network
What is OSI layer 3, the network layer, used to document and discuss?
The range of processes that occur across all data networks to address and route message through an internetwork
What protocol used in TCP/IP stack includes functionality mentioned at layer 3 of the OSI model?
Internet Protocol (IP)
What is the 1st (3) functions performed at the transport layer?
Acknowledgement
What is the 2nd (3) functions performed at the transport layer?
Error recovery
What is the 3rd (3) functions performed at the transport layer?
Sequencing
What two protocols provide functionality in TCP/IP model for OSI layer 4?
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)
What is labelled in a PDU header for OSI layers 5, 6 and 7?
Encoded application data
What is labelled in a PDU transport header?
Destination and source ports
What is labelled in a PDU network header?
Destination and source IP addresses (logical network addresses)
What is labelled in a PDU data-link header?
Destination and source physical (MAC) addresses
What does to OSI model describe the process of?
Encoding, formatting, segmenting and encapsulating data for transmission over a network
Which addresses is layer 2 concerned with?
Addresses of end devices on a single local network
What is the layer 2 address known as when a LAN is using ethernet?
Media access control (MAC) address
What are layer 3 protocols primarily designed to do?
Move data from one local network to another local network within an internetwork
What are layer 2 addresses only used to communicate between?
Devices on a local network
What must layer 3 addresses include?
Identifiers that enable intermediary devices to locate hosts on different networks
What role does a router (or potentially another intermediary network access device) play in Layer 3 addressing?
Decapsulates frame to read destination host address in header of layer 3
What do routers do with the network identifier portion of destination host address?
Use it to determine best path to destination host
What does a router do once the best path for a frame is determined?
Encapsulates the packet in a new frame and sends towards destination end device
What does the address contained in the header at layer 4 identify?
Specific process or service at destination host that will act on data being delivered
What are source and destination port numbers used for?
To make sure only the two applications on client and server communicate about the data they need to
