messages in folders keeps user state across sessions names of folders and

Messages in folders keeps user state across sessions

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messages in folderskeeps user state acrosssessions:names of folders andmappings betweenmessage IDs and foldername
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IT 263 & TDC 405 ‐ Autumn 201831 Oct 2018Dr. Oteafy © 201825ASCII CodeBasic E‐mail message contents are sent usingASCII codesAmerican Standard Code for InformationInterchange – defined by AT&T in 1963.Originally 7 bits per character.Apps add ‘0’ bit as 8thbit so it uses 1 byte percharacter.To send anything outside ASCII codes requires“Transfer Encoding” method that convertsnon‐ASCII to ASCII.Printable ASCII CharactersHexCharHexCharHexCharHexCharHexCharHexChar2030040@50P60`70p21!31141A51Q61a71q22"32242B52R62b72r23#33343C53S63c73s24$34444D54T64d74t25%35545E55U65e75u26&36646F56V66f76v27'37747G57W67g77w28(38848H58X68h78x29)39949I59Y69i79y2A*3A:4AJ5AZ6Aj7Az2B+3B;4BK5B[6Bk7B{2C,3C<4CL5C\6Cl7C|2D3D=4DM5D]6Dm7D}2E.3E>4EN5E^6En7E~2F/3F?4FO5F_6Fo7F
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IT 263 & TDC 405 ‐ Autumn 201831 Oct 2018Dr. Oteafy © 201826E‐mail AddressingFormat: <local part> @ <DNS name>The <DNS name> (example: ‘gmail.com’) is looked up asan MX record on DNS server.The <local part> is passed to the SMTP server to identify aparticular mailbox on that server. This is typically a username on the e‐mail system.How does HTTP work?
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IT 263 & TDC 405 ‐ Autumn 201831 Oct 2018Dr. Oteafy © 201827Common Application Layer ProtocolsHypertext Transfer Protocol / Markup LanguageExampleURL: First, the browser interprets the three parts of the URL:1.http(the protocol or scheme)2. (the server name)3.index.html(the specific file name requested)53Hypertext Transfer Protocol / Markup LanguageURL: Browser checks with aDNS servertoconvertinto a numeric addressUsing theHTTP protocol requirements, sends aGETrequest to the server and asks for the fileindex.htmlServer sends the HTML code for this web pageBrowser deciphers the HTML code and formats the page54
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IT 263 & TDC 405 ‐ Autumn 201831 Oct 2018Dr. Oteafy © 201828HTTP and HTTPSHTTP developed topublish and retrieveHTML pagesUsed for data transferSpecifies a request/response protocolThree common message types are GET,POST, and PUT55HTTP message formatsHTTP message formats are very similar to SMTP formats:Client requests consist of 4‐letter command keyword followedby URL, options and data.Server responses consist of 3‐digit response code followed byoptions and dataMore in RFC 2616 (HTTP 1.1)56
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IT 263 & TDC 405 ‐ Autumn 201831 Oct 2018Dr. Oteafy © 201829Brief historyHTTP/1.1•RFC 2068: Jan 1997•RFC 2616: Jun3 1999SPDY•Started circa 2009•Multiple versions•Influenced HTTP/2•Deprecated 2015•Chrome no longersupports itHTTP/2•Built on SPDYframework• RFC 7540•Standardized in 2015Example: HTTP protocol58
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IT 263 & TDC 405 ‐ Autumn 201831 Oct 2018Dr. Oteafy © 201830KeywordArgument(s)ExampleGETDow nload file from server
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