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Application layer

Application layer. Chapter 10 Intro to Routing & Switching. objectives. Upon completion of this chapter, you should be able to: Explain how the functions of the application layer, session layer, and presentation layer work together to provide network services to end user applications.

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Application layer

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  1. Application layer Chapter 10 Intro to Routing & Switching

  2. objectives • Upon completion of this chapter, you should be able to: • Explain how the functions of the application layer, session layer, and presentation layer work together to provide network services to end user applications. • Describe how common application layer protocols interact with end user applications. • Describe common application layer protocols that provide Internet services to end-users, including WWW services and email. • Describe application layer protocols that provide IP addressing services, including DNS and DHCP. • Describe the features and operation of well-known application layer protocols that allow for file sharing services. • Explain how data is moved across the network, from opening an application to receiving data.

  3. 10.1 Application, presentation, & session

  4. model review

  5. Application layer • Provides the interface between the applications we use to communicate & the network • Used to exchange data between source & destination • What are some of the application layer protocols?

  6. Presentation layer • Formats data so it can be read • Compress/decompress data • Encrypt/decrypt data • MPEG, JPG, GIF

  7. Application layer protocols- Part 1 • DNS • Names to IP addresses • Telnet • Remote access to servers/switches/routers/devices • DHCP • Automatically assign IP/SM/DG/DNS server addresses • BOOTP • Older version of DHCP

  8. Application layer protocols- Part 2 • HTTP • Transfers web pages • FTP • File transfer • SMTP • Transfers email • POP • Gets email from email server to client • Then deleted from server • IMAP • Gets email from email server to client • Kept on server until you delete it

  9. activity • 10.1.1.5

  10. Review- 5q • What 3 OSI layers are similar to the TCP/IP Application Layer? • Application, Presentation, Session • What are 3 functions of the Presentation Layer? • Data formatting, compression, encryption • Name some application layer protocols. • DNS, DHCP, Telnet, POP, IMAP, SMTP, FTP, HTTP, BOOTP • What protocol handles web transfer? • HTTP • What protocol handles file transfer? • FTP

  11. 10.1.1 How the protocols interact with applications

  12. Peer to peer networks • 2 or more connected computers with NO SERVER • Shares files on each other’s HD & connected printers • Every device acts as client AND server • No one device in charge • No central user accounts

  13. Peer to peer applications • P2P applications allow users to directly share specified file types across peer-to-peer or client-server networks.

  14. Common p2p applications • BitTorrent • LimeWire • No central server • Uses files found on client hard drives

  15. Client-server networks • Client requests a service from a dedicated server

  16. Review- 3Q • What type of network has centralized resources, such as central file storage? • Client-server • What type of network shares resources located on local computer hard drives? • Peer to peer • You type www.gcit.org into your web browser. A DNS request is created and then a we request is sent. What type of network is this? • Client-server

  17. 10.2.1 Common application layer protocols

  18. Common protocols • What application layer protocols would you use on a daily basis?

  19. http & html • http://www.cisco.com/index.html • HTTP is the protocol • Cisco.com is the server name • Index.html is the document you requested

  20. http & https • Layer 4 port: • HTTP: 80 • HTTPS: 443 • Browser messages • GET (requests page from web server) • POST & PUT (uploads to web server) • HTTPS • Secure • Uses SSL to encrypt

  21. SMTP, POP, IMAP • Layer 4 ports: • SMTP-25 • POP3- 110 • IMAP-143 • Send mail to server & server to server; SMTP • Get mail from email server; POP3 & IMAP • POP deletes mail from server when sent to client • IMAP sends copy of email to client and server keeps mail until deleted

  22. activity • PT Lab 10.2.1.8 Web & Email • In this activity, you will configure HTTP and email services using the simulated server in Packet Tracer. You will then configure clients to access the HTTP and email services.

  23. review • Why would you use IMAP instead of POP? • IMAP keeps the emails until manually deleted • Which protocol uses GET, PUT, and POST? • HTTP • Which email protocol send you a copy of the email and deletes it from the server? • POP • What port # is POP? • 110 • What does HTTPS use to encrypt? • SSL

  24. 10.2.2 Ip addressing services

  25. dns • Layer 4 port: 53 • Servers that translates names to IP addresses • DNS servers know some, forward rest to other DNS servers • Nslookup • Get in the mode and then enter domain • Ipconfig /displaydns • Displays cached DNS

  26. dns • DNS servers are in a hierarchy • Top-level, most trusted: • .com, .edu, .gov • Contains 2nd-level domain server records • Second-level: • Contains records for the company only • MX used for mail

  27. dhcp • Layer 4 port: 67/68 • At home, your router is a DHCP server • At work, you may have a dedicated DHCP server • Used for general purpose/PC devices • Static addressing for routers, switches, printers, Internet-accessible devices • DHCP addresses are leased

  28. dhcp

  29. activity • PT Lab 10.2.2.8 • DHCP & DNS Services • In this activity, you will configure and verify static IP addressing and DHCP addressing. You will then configure a DNS server to map IP addresses to the website names. • HW: Lab 10.2.2.9 • Observing DNS • You will observe the DNS Conversion of a URL to an IP Address, observe DNS Lookup Using thenslookupCommand on a Web Site, and observe DNS Lookup Using thenslookupCommand on Mail Servers.

  30. Review- 4Q • Which broadcast message gets sent out from a PC to a DHCP server when it turns on? • DCHPDiscover • What does the DHCP server send back to the PC? • DHCPOffer • What does the DHCP request look like? • All 255’s • Who gets & responds to that request? • Everyone in local network gets it; only DHCP server responds

  31. 10.2.3 File sharing services

  32. ftp • Layer 4 port: 20/21 • 20- data • 21- control info • Download/upload data from a server • Example: sending a designed web page to the web server

  33. ftp software

  34. smb • Server Message Block • Client-server file sharing protocol for file, printer, and directory sharing • Used for long-term connections to keep connection active • Authenticates the session • Example: • Use SMB (instead of FTP) when downloading a TON of files from a server

  35. activity • PT Lab 10.2.3.2 • In this activity, you will configure FTP services. You will then use the FTP services to transfer files between clients and the server.

  36. Review- 3q • What program runs on an FTP server that listens for requests? • FTPdaemon • What runs on a PC that will request services from an FTP server? • FTP Client software • If you need to download many files from a server, which could take hours, which protocol would you use? • SMB

  37. Review- Q • Which command did you use to manually get the name to IP information? • nslookup • What port is HTTPS? • 443 • What type of applications need a specific application interface and background service running between hosts? • P2P application, like IM

  38. summary • Applications are computer programs with which the user interacts and which initiate the data transfer process at the user’s request. • Services are background programs that provide the connection between the application layer and the lower layers of the networking model. • Protocols provide a structure of agreed-upon rules and processes that ensure services running on one particular device can send and receive data from a range of different network devices

  39. summary • HTTP supports the delivery of web pages to end devices • SMTP, POP, and IMAP support sending and receiving email • FTP enable users to share files • P2P applications make it easier for consumers to seamlessly share media • DNS resolves the human legible names used to refer to network resources into numeric addresses usable by the network • All of these elements work together, at the application layer. • The application layer enables users to work and play over the Internet.

  40. Review & study • Complete the study guide handout • Take the quiz on netacad.com • Jeopardy review

  41. Application layer Chapter 10 Intro to Routing & Switching

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