Suppose within your browser you click on a link to obtain a webpage (whose URL i
ID: 3590046 • Letter: S
Question
Suppose within your browser you click on a link to obtain a webpage (whose URL is already cached in the local host). This webpage contains a very small amount of HTML text, and references 6 objects (located on the same server), each about 1500 bytes in size.Suppose that the average transmission rate from the given HTTP server to this client is 1.5 Mbps, and the average RTT time is 2 seconds. For each of the three scenarios below, calculate the amount of time that elapses from when the client clicks on the link until the requested page is fully loaded. Show calculations! (HINT: the requested page consists of 7 objects total) a) Persistent HTTP without parallel TCP connections b) Non-persistent HTTP with no parallel TCP connections c) Non-persistent HTTP with the browser configured for 4 parallel connections
Explanation / Answer
a) Time to send message from sourc
e host to first packet switch =
7.5 × 10
6
/
1.5 × 10
6
sec
= 5
sec . With store
-
and
-
forward switching
, the total time to move
7
.5 × 10
6
message from source host
to destination host = 5 sec× 3 hops = 15 sec
.
b) Time to send 1st packet from source host to first packet switch = 1.5 × 10
3
/
1.5 × 10
6
sec = 1
m
sec. Time at
which 2nd packet is received at the
first switch =
2*
(
1.5 × 10
3
/
1.5 × 10
6
)
=
2 m
sec
.
T
ime at which 1st packet is received at the
second switch = 2 × 1 m sec = 2 m sec
.