$2\mathrm{.}2-4$ HTTP $1\mathrm{.}1$ GET $($re$-$request$)$ with an embedded object. Suppose an HTTP client makes a $$rst GET request to the gaia.cs$.$umass.edu web server for a base page that it has never before requested, which contains an embedded object, which causes the client to make a second GET request. A very short time later, the client then make a third GET request $-$ for the same base page, with that third GET request having an

If$-$Modi$$ed$-$Since $$eld $($as does the $4$th GET request that the client makes for the embedded object$).$ Neither the base object nor the jpeg object have changed.

How many round trip times $($RTTs$)$ are needed from when the client $$rst makes the third GET request $($i$.$e$.,$ when it requests the base object for the second time$)$ to when the base page and the jpeg $$le are displayed a second time, assuming that:

$$ any time needed by the server to transmit the base $$le$,$ or the jpeg $$le into the server's link is $($each$)$ equal to $1/2$ RTT

$$ the time needed to transmit an HTTP GET into the client's link is zero?

$$ the time needed by the server to transmit a reply that does not contain the base page or an embedded jpeg object is zero

You should assume that persistent HTTP $1\mathrm{.}1$ is being used and should think about the consequences of the If$-$Modi$$ed$-$Since $$eld being used in the third and fourth GET requests$).$ You should take into account any TCP setup time required before an HTTP GET is actually sent by the client, the time needed for the server to transmit a requested object $($see assumptions above$),$ and any propagation delays not accounted for in these amounts of time.

$5$ RTT

$4$ RTT

$2\mathrm{.}5$ RTT

$1$ RTT

$2$ RTT