note right of User: URI fragment which is already buffered
User->UserAgent: http://www.example.com/video.ogv#t=10,20
activate UserAgent
note right of UserAgent
Local copy of fragment already in buffer
But the resource could have changed on the server,
so it needs to send a conditional GET
end note
UserAgent->Proxy: GET /video.ogv HTTP/1.1 \nIf-Modified-Since: Sat, 01 Aug 2009 09:34:22 GMT \nRange: bytes=19147-22890
activate Proxy
Proxy->OriginServer: GET /video.ogv HTTP/1.1 \nIf-Modified-Since: Sat, 01 Aug 2009 09:34:22 GMT \nRange: bytes=19147-22890
activate OriginServer
note right of OriginServer: Check if the resource has changed, \nthe resource was not modified
OriginServer->Proxy: HTTP/1.1 304 Not Modified \nContent-Range: bytes 19147-22890/35614993
deactivate OriginServer
Proxy->UserAgent: HTTP/1.1 304 Not Modified \nContent-Range: bytes 19147-22890/35614993
deactivate Proxy
note right of UserAgent
Use existing buffer to serve t=10,20
which may well be slightly more (from a seekable entry point)
end note
UserAgent->UserAgent: Map byte ranges to time-offset
UserAgent->User: Serve the decoded content to the User \nfrom the appropriate time-offset