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csc flashcards chp2

topics = other half of web and http

QuestionAnswer
are notion of multi-step exchanges of HTTP messages to complete a web transaction needed no because HTTP "get" response interaction is stateless
what is not needed for a server or client to track in a multi-step exchange the state
are all HTTP requests independent or dependent on each other independent
what is not needed for client/server to do from a partially-completed-but-never-completely-completed transaction recover
what do websites and client browsers use to maintain some state between transactions cookies
what are the four main components of a cookie cookie header line of HTTP response message / cookie header line in next HTTP request message / cookie file kept on users host managed by users browser / back-end database at website
what can cookies be used for authorization / shopping carts / recommendations / user session state (web email)
how do you keep state protocol endpoints, help in maintain state at sender and receiver over multiple transactions / cookies, HTTP messages carry state
how do cookies work with privacy cookies permit sites to learn a lot about you on their site / third party persistent cookies allow common identity to be tracked across multiple websites
what is a web caches goals satisfy client request without involving origin server
how does web caches work user configures browser to point to a web cache / browser sends all HTTP requests to cache
what happens when an object is in cache it returns object to the client
if object in cache isn't returned. what happens cache requests the object from origin server, caches receive object then returns object to client
does web cache act as a client or a server both
how does a web cache act as both client and server server for original requesting client / client to origin server
how is web cache installed by an ISP (uni, company, res ISP)
why is web cache an advantage to websites reduced response time for client request (because cache is closer to client) / reduced traffic on an institutions access link / internet is dense with caches (enables poor content providers to more effectively deliver content)
examples on slides 38>41 on how to calc. access link utilization practice it eventually
what is the main goal of a conditional "get" method don't send object if cache has up to date cached version (no object transmission delay / lower link utilization)
what formula is used to specify date of cached copy in HTTP request if-modified-since:<date>
what does a server do if cached copy is up to date response contains no object
what is the main goal of HTTP/2 decreased delay in multi-object HTTP requests
what did HTTP1.1 introduce multiple, pipelined "gets" over a single TCP connection
how does the HTTP1.1 server work works on a first come first served scheduling (FCFS) to "get" requests, small object may have to wait for transmission behind larger objects (head-of-line blocking)
what does HOL stand for regarding transmission head-of-line
how does loss recovery work it retransmits lost TCP which in turn stalls other object transmission
how does HTTP decrease delay in multi-object HTTP requests increased flexibility at server in sending objects to client
are methods, status codes and header fields different from HTTP/2 and HTTP1.1 no
what method is used to transmit requests in HTTP/2 requested objects based on client-specified object priority, doesn't use FCFS
are unrequested objects pushed to clients in HTTP/2 yes
how are objects mitigated in HTTP/2 for HOL blocking divide objects into frames and schedule the frames into mitigate
what does HTTP/2 over single TCP connection mean recovery from packet loss still stalls all object transmissions / opposite to HTTP1.1 browsers open multiple parallel TCP connections to reduce stalling and increase overall throughput
what type of security does HTTP/2 to HTTP/3 have no security over vanilla TCP connection
what does HTTP/3 add to HTTP/2 adds security, per object error and congestion control which means more pipelining over UDP
next section = email / SMTP / IMAP slide 48
Created by: NtokozoN
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