3. Application Layer Flashcards
List out the upper 3 layers in OSI model
- Application
- Presentation
- Session
What does the application layer provides?
- Provides the interface between the application used to communicate, and the underlying network over which messages are transmitted
List out the application layer protocols ( 5 )
- HTTP ( Hypertext Transfer Protocol )
- FTP ( File Transfer Protocol )
- TFTP
- IMAP ( Internet Message Access Protocol )
- DNS ( Domain Name System )
What are the 3 primary function in the presentation layer?
- Formatting, or presenting, data at the source device into a compatible format for receipt by the destination device
- Compressing data in a way that can be decompressed by the destination device
- Encrypting data for transmission and decrypting data upon receipt
What are the functions in the session layer? ( 2 )
- It creates and maintains dialogs between source and destination applications
- It handles the exchange of information to initiate dialogs, keep them active, and to restart sessions that are disrupted or idle for a long period of time
What layer protocols are used by both the source and destination devices during a communication seesion?
- Application Layer Protocols
What must be done for the communication to be successful?
- The application layer protocols that are implemented on the soure and destination host must be compatible
What does TCP/IP application protocols do?
- Specify the format and control information necessary for many common internet communication functions
What does DNS ( Domain Name Search )do? Also list out the port
- Translates domain names ( youtube.com ), into IP Addresses
2.TCP, UDP client 53
*UDP 53 - Typically used for most DNS queries because it’s faster (connectionless).
*TCP 53 - Used when the response data size exceeds 512 bytes or for zone transfers between DNS servers.
What does DHCP ( Dynamic Host Configuration Protocol ) do? Also list out the port
- Dynamically assigns IP addresses to be re-used when no longger needed
- UDP client 68, UDP server 67
*Client UDP 68: When a device (like a computer or phone) joins a network, it sends a request (via UDP) to ask for an IP address on port 68.
* Server UDP 67: The DHCP server listens on port 67 to respond to those requests and assigns IP addresses.
What does HTTP do? Also list out the port
- A set of rules for exchanging text, graphic images, sound, video and other multinedia files on the World Wide Web
- TCP 80 , 8080
- Port 80: The standard port for HTTP (non-secure) communication over TCP.
- Port 8080: Sometimes used as an alternative to port 80, especially for web servers running on a machine where port 80 is already in use or for testing purposes.
What is the requesting information’s device called?
- Client
What is the responding the request’s device called?
- Server
- Application layer protocols describe the format of the requests and responses between clients and servers
What can pear-to-pear network do for 2 or more computers?
- Connected via a network and can share resources without having a dedicated server
What layer does client and server processes are considered to be in?
- Application Layer
What can an end device ( peer ) function in pear-to-pear ( 2 )
- Server
- Client
- One computer might assume the role of server for one transaction while simultaneously serving as a client for another. The roles of client and server are set on a per request basis
List out the common P2P network ( 4 )
- BitTorrent
- Direct Connect
- eDonkey
- Freenet
List out the 3 parts that the browser interprets
- HTTP / HTTPS ( Protocol / Scheme )
- www.youtube.com ( server name , URL )
- index.html ( Specific filename requested )
- HTTPS has log
List out the steps on how the web browser and web server interact
- Browser interprets 3 parts of the URL ( http , www , index.html )
- Checks the name server to convert into numeric IP address, then sending a GET request to the server and asks for the index.html file
- In response to the request, the server sends the HTML code for this web page to the browser
- The browser deciphers the HTML code and formats the page for the browser window
What is HTTP?
- Is a request / response protocol specifies the message types used for that communication
List out 3 common messages types of HTTP
- GET
- Request data
- POST
- Uploads data files ( form data )
- PUT
- Uploads resources or content to the web server ( image )
What is Email?
- Is a store-and-forward method of sending, storing, and retriving electronic message across a network
Email messages stored in where?
- In databases on main servers
List out the email protocols ( 2 )
- Send Mail
- Simple Mail Transfer Protocol ( SMTP )
- Receive Mail
- Post Office Protocol ( POP )
- IMAP