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Application Layer- Web Services
- Hyper Text Transfer Protocol
- Supports web services
- Uses port number 80
- The secure version is HTTPS
- HTTPS uses port number 443
- Transfers text, images, and hyper links
File Sharing Services/File transfer
- File Transfer Protocol
- Uses port number 21
- Built=in in MS Windows Operating Systems
- Many 3rd party programs
- Web browser works as FTP client
- Network File System
- Common language used by the majority of mail servers
- Send messages back and forth to other mail servers or email clients
POP3 "Post Office Protocol version 3"
- Collects email messages from the mail server
- Download messages on the machine
- User can work offline
- Saves quota on the server
IMAP4 "Internet Message Access Protocol version 4"
- Retrieves the message header only
- Domain Name System DNS resolves Domain Name into IP Address
Why ISO/OSI Model?
Wireless Networks Drawbacks