Application Layer Flashcards
Ex of application layer protocols
Http, FTP, email, smtp, pop, telnet, ssh
Main purpose
Provides network services to users applications; exchange data between source and destination hosts
Steps of application layer
- Create
- Prepare
- Convert
- Initiate transfer
- Roles of each layer
Side note:
Provides interface between apps we use to communicate and the bottom layers of osi model
Server
Runs a daemon or process in the background, not under users control; resources usually stored on server
Client
Requests something from server
Upload
Data from client to server
Download
Data from server to client
P2p network
2 more pcs via a network sharing resources without a dedicated server; central admin not required; either device can function as server or client at a time
DNS
Matches resource names with ip addresses.
Ipconfig/displaydns
Displays all cached DNS entries
DNS hierarchy
cisco.netacad.com
.com is a top level
.netacad is a second level domain
Cisco is at the lower level
HTTP, HTTPS
Control transfers of web resources from a web server to a client browser
Get message (HTTP)
Request for data
Put message (HTTP)
Uploads resources or content to the web server
Post message (HTTP)
Includes data in messages sent to server
DNS Process
- Request page
- Http server returns code
- Client web browser interprets code
MTA
Forwards email to destination
MDA
Place in appropriate mailbox; final delivery of email
FTP requires two connections:
One for commands and replies via port 21
The other for actual file transfer via port 20
Gnutella protocol
Each device on network tell the other what files are avail when queried
DHCP
Automatically configures IP address, temporarily leases subnet masks, gateway, other ip parameters
SMB
Client-server file-sharing protocol developed by Microsoft; long term connections to servers; described structure of shared network resources such as printer, directories
Telnet
Remote access to a device
