Hypertext Transfer Protocol Hypertext Transfer Protocol

Protocol for transfer of various data formats between server and client
Plaintext
Hypertext
Images
Video
Sound
Meta-information also transferred
URL
Uniform Resource Locator
Refers to an existing protocol
http:, wais:, ftp:, mailto:, gopher:, news:
Points to a document on a specific server
URN
Uniform Resource Name
Globally unique, persistent identifier
Independent of location
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usually port 80
All parts of URL, except parameters, used with http
Scheme and host can be omitted when referenced object is on same machine as referring document
Port can be omitted so long as referenced host is running on port listed in your /etc/services file
Usuall

1. HTTP
Hypertext Transfer Protocol

2. HTTP 2
What It Is
Protocolfortransferofvariousdata
formatsbetweenserverandclient
–Plaintext
–Hypertext
–Images
–Video
–Sound
Meta-informationalsotransferred

3. HTTP 3
Uniform Resources
URL
–UniformResourceLocator
–Referstoanexistingprotocol
http:,wais:,ftp:,mailto:,gopher:,news:
–Pointstoadocumentonaspecificserver
URN
–UniformResourceName
–Globallyunique,persistentidentifier
Independentoflocation

4. HTTP 4
Uniform Resources
URI
–UniformResourceIdentifier
–CollectionofURL’sandURN’s

5. HTTP 5
URL
<scheme>://<host>:<port>
/<path>;<parameters>?<query>
#<fragment>
–scheme
Theprotocolyouareusing
–host
Hostnameoripnumber
–port
TCPportnumberthatprotocolserverisusing
–path
Pathandfilenamereferenceofobjectonserver

6. HTTP 6
URL
<scheme>://<host>:<port>
/<path>;<parameters>?<query>
#<fragment>
–parameters
Anyspecificparametersthatobjectneeds
–query
QuerystringforaCGIprogram
–fragment
Referencetoasubsetofanobject

7. HTTP 7
URL and HTTP
AllpartsofURL,exceptparameters,
usedwithhttp
Schemeandhostcanbeomittedwhen
referencedobjectisonsamemachine
asreferringdocument
Portcanbeomittedsolongas
referencedhostisrunningonportlisted
inyour/etc/servicesfile
–Usuallyport80

8. HTTP 8
URL and HTTP
Fullpathusedwhenreferringto
anotherserver
–Relativepathonsameserver
ReferencewithrelativepathisapartialURL
QuerypassesparameterstoCGI
Fragmentjumpstolabelswithinapage
–http://www.x.y/z#foo

9. HTTP 9
Web Documents
–html
–ASCIItext
–Preformatted
postscript
–Images
GIF
JPEG
–Video
MPEG
–VRML
–Java

10. HTTP 10
Communication
Servertellsclientwhattypeof
informationiscoming before
informationarrives
–Fileextensions
.html.htm
.txt
.ps
.au
.gif.tiff.jpeg
.mpeg
.vrml.wrl
.java

11. HTTP 11
Communication
Textandinlineimages
–Separateobjects
Clientbrowsermayoptionallysenda
listofformatsitcanaccept
Documentcanbeaprogram
–Webserverexecutesprogramandsends
resultstoclient
–Generictermforthisprogramisscript,
gateway,orgatewayscript

12. HTTP 12
Scripts
Translatesinputfromclient
Callsotherprograms
Translatesoutputfromprogramsand
returnsittoclient

13. HTTP 13
Gateways
Translatesfromoneprotocolorservice
toanother
–HTTP/databasequery
–Databasequeryresults/HTTP

14. HTTP 14
HTTP 1.0
BernersLee,Fielding,Nielsen-1995
Usedinhypermediasystemsdistributed
acrossnetworks
Definesrequest-responseconversation
–Requestingprogram(client)establishes
connectionwithreceivingprogram(server)
–Clientsendsrequesttoserver
HTTPspecifiessyntax

15. HTTP 15
HTTP 1.0
Definesrequest-responseconversation
–Serverreplieswithresponse
httpspecifiessyntax
Doesnothandlenetworkconnectivity
orhowinformationistransmitted
TCP/IPdoesthis

16. HTTP 16
HTTP 1.0
HTTPrequest
–Method
–URI
–Protocolversion
–Optionalotherinformation
–Method[RequestURI]HTTP/1.0<CRLF>

17. HTTP 17
HTTP 1.0
Method
–Get
Returnsobject
–Head
Returnsinformationaboutobject
–Post
Sendsinformationtobestoredonserveroras
inputtoscript

18. HTTP 18
HTTP 1.0
Method
–Put
Sendsnewcopyofexistingobjecttoserver
Usuallynotallowed
–Delete
Deletesobject
Usuallynotallowed

19. HTTP 19
HTTP 1.0
Otherinformation
–UserAgent
Kindofbrowser
–If-Modified-Since
Returnsobjectonlyifmorerecentthangiven
date
Otherwisereturnsstatuscode304

20. HTTP 20
HTTP 1.0
Otherinformation
–Accept
Mimetypeswhichbrowsercanaccept
–MultipurposeInternetMailExtension
text/plain
text/html
application/postscript
image/gif
image/jpeg
audio/basic
video/mpeg
x-world/x-vrml

21. HTTP 21
HTTP 1.0
Otherinformation
–Authorization
Userpassword
GET/X/Y/Z.HTML HTTP1.0
UserAgent:Prodigy-WB/1.3e
Accept:text/plain
Accept:text/html
Accept:application/postscript
Accept:image/gif
–Accept:*/*

22. HTTP 22
HTTP 1.0
HTTPresponse
–Statusline
HTTP-versionStatus-codeReason
Status-codes1xx-Informational
–Reservedforfutureuse

23. HTTP 23
HTTP 1.0
HTTPresponse
–Statusline
Status-codes2xx-Success
–Theactionwassuccessfullyreceived,understood,
andaccepted
200OK
201POSTcommandsuccessful
202Requestaccepted
203GETorHEADrequestfulfilled
204Nocontent

24. HTTP 24
HTTP 1.0
HTTPresponse
–Statusline
Status-codes3xx-Redirection
–Furtheractionmustbetakeninordertocomplete
request
300Resourcefoundatmultiplelocations
301Resourcemovedpermanently
302Resourcemovedtemporarily
304Resourcehasnotmodified(sincedate)

25. HTTP 25
HTTP 1.0
HTTPresponse
–Statusline
Status-codes4xx-Clienterror
–Therequestcontainsbadsyntaxorcannotbe
fulfilled
400Badrequestfromclient
401Unauthorizedrequest
402Paymentrequiredforrequest
403Resourceaccessforbidden
404Resourcenotfound
405Methodnotallowedforresource
406Resourcetypenotacceptable

26. HTTP 26
HTTP 1.0
HTTPresponse
–Statusline
Status-codes5xx-Servererror
–Theserverfailedtofulfillanapparentlyvalidrequest
500Internalservererror
501Methodnotimplemented
502Badgatewayorserveroverload
503Serviceunavailable/gatewaytimeout
504Secondarygateway/servertimeout

27. HTTP 27
HTTP 1.0
HTTPresponse
–Descriptionofinformation
Server Typeofserver
Date Dateandtime
Content-Length Numberofbytes
Content-Type Mimetype
Content-LanguageEnglish,forexample
Content-EncodingDatacompression
Last-Modified Datewhenlastmodified
Expires Datewhenfilebecomes
invalid

28. HTTP 28
HTTP 1.0
Problems
–HTTPisstateless
EachrequestrequiresseparateTCPconnection
Serverdoesn’trememberpreviousrequests

29. HTTP 29
Evolution of HTTP
HTTP/0.9-1990
–Requestmethod+URI+crlf
GET/pets/index.html
Justfilecontentssentback
–Noheaderinformation
Gopherinfluence
–Mediatypes
Singlecharacterindicatedoneoftentypes

30. HTTP 30
Evolution of HTTP
HTTP/1.0-1995
–Meta-informationbetweenclientand
server
Mediatypes
–MIMEtype/subtype
Statuscodes
Thisinformationinfluencedthedevelopmentof
websearchengines
–Caching
–Authorization

31. HTTP 31
Evolution of HTTP
HTTP/1.0-1995
–Problems
Scalability
–Highnumberofclientsvisitserverforshorttime
Flashcrowd
Bandwidth

32. HTTP 32
Evolution of HTTP
HTTP/1.1
–Byteranges
Requestofadocumentsubset
–Adobe'sPortableDocumentFormat
–Streamingmultimedia
Eliminates unnecessary client/server
communication
Aninterruptedtransferwhichisrestartedcan
bemoreefficient

33. HTTP 33
Evolution of HTTP
HTTP/1.1
–Contentnegotiationwithqualityfactors
Qualityfactors
–Realnumbersbetween0and1
Defaultis1
Accept-Language:fr,en-gb;q=0.8,en;q=0.7

34. HTTP 34
Evolution of HTTP
HTTP/1.1
–Chunkedencoding
Transmissionofstreamingmultimedia
–Oneframevariesinsizeandcompositionfromthe
next
Streamingvideo
–Entireimagetransmittedinfirstchunkand
differencestothepreviousimagearetransmittedin
thenextchunk

35. HTTP 35
Evolution of HTTP
HTTP/1.1
–Protocolswitching
Clientcanspecifyanotherprotocolmoresuited
todatabeingtransferred
–Messageintegritychecks
–Digestauthentication
InHTTP/1.0,usersentusernameandpassword
overthenetwork
InHTTP/1.1,theclientandtheservernever
sendtheactualusernameorpasswordoverthe
network

36. HTTP 36
Evolution of HTTP
HTTP/1.1
–Persistentconnections
InHTTP/1.0,ifasinglepageincludesinline
images,multipleframes,animation,andother
externalreferences,tobrowsethispagewould
requiremanyreconnections
In HTTP/1.1 there are multiple
request/responsetransactionsperconnection
Clientscanpipelinerequeststotheserverby
sendingmultiplerequestsatstartofsession

37. HTTP 37
Evolution of HTTP
HTTP/1.1
–Cachemanagementwithentitytags
WhenbodyofURIchanges,sodoesitsentity
tag
–Usefulformaintainingcaches,asupdatedURI
informationwouldhaveadifferententitytag
Cantellifsameresourceisbeingcachedfrom
multipleURI'sasitwouldhavesameentitytag
Strongentitytag
–Changeswhenanyportionofresourcechanges
Oneormorebyteschange
Weakentitytag
–Changesonlywhensemanticsofentity-body
changes

38. HTTP 38
Evolution of HTTP
HTTP/1.1
–Softwaremultihoming
NumberofavailableIPaddressesisaconcern
InHTTP/1.0,servercouldhavemultipleDNS
entriesandIPaddresses,eachcorresponding
todifferentdocumenttree
InHTTP/1.1,servercouldhavemultipleDNS
entriesandonlyasingleIPaddress

39. HTTP 39
The Future
HTTP-NextGeneration
–Manychannels
OneTCPconnectioncarriesmultiplechannels
forparallelcommunication
Differentprotocolsoneachchannel
–Traditionalway
MultipleTCPconnectionsbetweensameclient
andserver
Pagescontainimages,video,audio,andhtml

40. HTTP 40
The Future
Extensibility
–AddingnewMIMEheadershasbeenthe
traditionalwayofextendinghttp
–Drawbacks
Noindicationwhetherreceivingend
understandstheseextensions
Noindicationwhetherextensionisintendedfor
allpartiesalongmessagepathoronlyfor
certainintermediaries
Noindicationoforderinwhichextensions
shouldbeinterpreted

41. HTTP 41
The Future
Extensibility
–PEP
ProtocolExtensionProtocol

42. HTTP 42
The Future
Performance
–ParsingMIMEheaderswastesresources
–Stickyheaders
Persistentstatebetweenmultiplehttprequests
Notallheadershavetobeincludedinevery
httpmessage
Distributedauthoring
–Eventnotification

43. HTTP 43
The Future
Cachingandreplication
–Popularsitesarereallypopular
–Flashcrowdshappen
–Hotspotsonthenetaredynamic
–Amountofdynamicdataisincreasing

44. HTTP 44
The Future
QoS
–Qualityofservice
–Noteverythingmustbetreatedwithsame
QoS
–RequiredQoSshouldbemadeattheuser-
interface

45. HTTP 45
The Future
Real-timeprotocolsandtheweb
–Streamingprotocols
Audio/video-on-demand