lec5 - Chapter 2 outline 2.1 principles of network applications 2.6 P2P applications app architectures app requirements 2.2 Web and HTTP 2.3 FTP 2.4

lec5 - Chapter 2 outline 2.1 principles of network...

This preview shows page 1 - 10 out of 51 pages.

Application Layer 2-1 Chapter 2: outline 2.1 principles of network applications app architectures app requirements 2.2 Web and HTTP 2.3 FTP 2.4 electronic mail SMTP, POP3, IMAP 2.5 DNS 2.6 P2P applications
Image of page 1
Application Layer 2-2 FTP: the file transfer protocol file transfer FTP server FTP user interface FTP client local file system remote file system user at host transfer file to/from remote host client/server model client: side that initiates transfer (either to/from remote) server: remote host ftp: RFC 959 ftp server: port 21
Image of page 2
Application Layer 2-3 FTP: separate control, data connections FTP client contacts FTP server at port 21, using TCP client authorized over control connection client browses remote directory, sends commands over control connection when server receives file transfer command, server opens 2 nd TCP data connection (for file) to client after transferring one file, server closes data connection FTP client FTP server TCP control connection, server port 21 TCP data connection, server port 20 server opens another TCP data connection to transfer another file control connection: out of band FTP server maintains state” : current directory, earlier authentication
Image of page 3
Application Layer 2-4 FTP commands, responses sample commands: sent as ASCII text over control channel USER username PASS password LIST return list of file in current directory RETR filename retrieves (gets) file STOR filename stores (puts) file onto remote host sample return codes status code and phrase (as in HTTP) 331 Username OK, password required 125 data connection already open; transfer starting 425 Can’t open data connection 452 Error writing file
Image of page 4
FileZilla https:// filezilla -project.org
Image of page 5
Application Layer 2-6 Chapter 2: outline 2.1 principles of network applications app architectures app requirements 2.2 Web and HTTP 2.3 FTP 2.4 electronic mail SMTP, POP3, IMAP 2.5 DNS 2.6 P2P applications
Image of page 6
Application Layer 2-7 Electronic mail Three major components: user agents mail servers simple mail transfer protocol: SMTP User Agent a.k.a. “mail reader” composing, editing, reading mail messages e.g., Outlook, Thunderbird, iPhone mail client outgoing, incoming messages stored on server user mailbox outgoing message queue mail server mail server mail server SMTP SMTP SMTP user agent user agent user agent user agent user agent user agent
Image of page 7
Application Layer 2-8 Electronic mail: mail servers mail servers: mailbox contains incoming messages for user message queue of outgoing (to be sent) mail messages SMTP protocol between mail servers to send email messages client: sending mail server “server”: receiving mail server mail server mail server mail server SMTP SMTP SMTP user agent user agent user agent user agent user agent user agent
Image of page 8
Electronic Mail: SMTP [RFC 2821] uses TCP to reliably transfer email message from client to server, port 25 direct transfer: sending server to receiving server
Image of page 9
Image of page 10

You've reached the end of your free preview.

Want to read all 51 pages?

  • Spring '17
  • Domain Name System, name server

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes