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Lecture_9_Application-Layer.pptx

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Lecture_9_Application-Layer.pptx

  1. 1. Application Layer Afsana Begum
  2. 2. Functions of this layer  The application layer is responsible for providing services to the user.  It enables the user, whether human or software, to access the network.  Services Provided are:  File transfer, access & management  Mail services  Directory services
  3. 3. Domain Name System 1/29/2023
  4. 4. IPAddress: Domain Name Space Domain Name 1/29/2023 173.194.203.106 https://www.google.com/
  5. 5. Domain name space (Hierarchical) 1st step: write www.abc.com, request will go to “resolver” 2nd step: request will go from resolver to root server (13 root server available), root server reply to resolver 3rd step: request will go from resolver to Generic server/Country server, (TLD-Top Level Domain) it will reply to resolver 4th step: request will go from resolver to Authoritative server (crickinfo), Authoritative server will reply to resolver with specific IP. 5th step: Resolver will go to the specific IP hosted server. 1/29/2023
  6. 6. February 2003 slideset 1 -6 Concept: Resolving process & Cache Resolver Question: www.ripe.net A www.ripe.net A ? Caching forwarder (recursive) root-server www.ripe.net A ? Ask net server @ X.gtld-servers.net (+ glue) gtld-server www.ripe.net A ? Ask ripe server @ ns.ripe.net (+ glue) ripe-server www.ripe.net A ? 192.168.5.10 192.168.5.10 Add to cache
  7. 7. HTTP 7 HTTP O Protocol for transfer of various data formats between server and client O Plaintext O Hypertext O Images O Video O Sound O Meta-information also transferred
  8. 8. HTTP 8 Uniform Resources O URI O Uniform Resource Identifier O Collection of URL’s and URN’s
  9. 9. HTTP Uniform Resources O URL O Uniform Resource Locator O Refers to an existing protocol O http:, wais:, ftp:, mailto:, gopher:, news: O Points to a document on a specific server O URN O Uniform Resource Name O Globally unique, persistent identifier O Independent of location (For more detail: https://en.wikipedia.org/wiki/Uniform_Resource _Name)
  10. 10. HTTP 10 URL and HTTP O All parts of URL, except parameters, used with http O Port can be omitted so long as referenced host is running on port listed in your /etc/services file O Usually port 80
  11. 11. HTTP 11 Communication O Server tells client what type of information is coming before information arrives O File extensions O .html .htm O .txt O .ps O .au O .gif .tiff .jpeg O .mpeg O .vrml .wrl O .java
  12. 12. HTTP 12 HTTP 1.0 O Defines request-response conversation O Server replies with response O http specifies syntax O Does not handle network connectivity or how information is transmitted O TCP/IP does this
  13. 13. HTTP 13 HTTP 1.0 O HTTP request O Method O URI O Protocol version O Optional other information O Method [Request URI] HTTP/1.0 <CRLF>
  14. 14. HTTP 14 HTTP 1.0 O Method O Get O Returns object O Head O Returns information about object O Post O Sends information to be stored on server or as input to script
  15. 15. HTTP 15 HTTP 1.0 O Method O Put O Sends new copy of existing object to server O Usually not allowed O Delete O Deletes object O Usually not allowed
  16. 16. HTTP 16 HTTP 1.0 O Other information O Authorization O User password GET /X/Y/Z.HTML HTTP 1.0 User Agent: Prodigy-WB/1.3e Accept: text/plain Accept: text/html Accept: application/postscript Accept: image/gif O Accept: */*
  17. 17. HTTP 17 HTTP 1.0 O HTTP response O Status line O HTTP-version Status-code Reason O Status-codes 1xx - Informational O Reserved for future use
  18. 18. HTTP 18 HTTP 1.0 O HTTP response O Status line O Status-codes 2xx - Success O The action was successfully received, understood, and accepted O 200 OK O 201 POST command successful O 202 Request accepted O 203 GET or HEAD request fulfilled O 204 No content
  19. 19. HTTP 19 HTTP 1.0 O HTTP response O Status line O Status-codes 3xx - Redirection O Further action must be taken in order to complete request O 300 Resource found at multiple locations O 301 Resource moved permanently O 302 Resource moved temporarily O 304 Resource has not modified (since date)
  20. 20. HTTP 20 HTTP 1.0 O HTTP response O Status line O Status-codes 4xx - Client error O The request contains bad syntax or cannot be fulfilled O 400 Bad request from client O 401 Unauthorized request O 402 Payment required for request O 403 Resource access forbidden O 404 Resource not found O 405 Method not allowed for resource O 406 Resource type not acceptable

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