Some of these factors have more of an impact on the download time than others. F

Question

Some of these factors have more of an impact on the download time than others. For example, the transfer time from the server hard disk is not really an issue, because data is read from hard disks very fast, tens or hundreds of megabytes per second. Unless the server is very busy sending out files to hundreds of users the disk transfer time is not an issue.

The size and number of packets are determined by two things: the protocol used to transfer the file and the size of the file. A reliable transport protocol must be used. This is handled by TCP (Transmission Control Protocol). TCP will encapsulate a higher level protocol (FTP or HTTP) to carry the file data and requires acknowledgement packets from the receiving device that indicate the transmitted packets were received properly. The following figure shows this sequence.

The figure shows an image file being transferred using HTTP on top of TCP. Even though the packet length is 1434 bytes, only 1380 bytes are available for file data due to the TCP and HTTP packet headers and other fields within the packet. Notice that two file packets are sent before a 54-byte ACK packet is returned. We will utilize this format in our calculations.

The number of packets that must be transmitted from the server depends on the size of the image file being downloaded. For example, a 250 KB image file will require 186 packets of data, as shown in this calculation. Note that 1KB is 210 bytes which is 1024 bytes

Knowing how many packets must be transmitted we now turn our attention to how long it takes a packet to be transmitted from the server and received at the user device. The packet transmission time depends on the data rate of the network card in the server as well as the data rate across the Internet as the packets move between routers and is received and retransmitted by each router. Not knowing how many routers there might be we just use an estimate. So, let

Explanation / Answer

1 no of packets =1024*1024/1380=759.8=760 packets

so tranfer time for 760 packets=tranfer time for 380 exchanges (other time are same as question data)

so T=380*23.5=8.930 seconds

2 changing the distance will only effect the tiem taken to travel physically Tx

so for d=20 mile Tx=20/(0.7*186000)=0.153 millisec

so tranfer time for 186 packets=tranfer time for 93 exchanges (other time are same as question data)

so T=93*(2*(11.47+0.153)+0.432)=93*23.678=2.202 seconds

so for d=50 mile Tx=50/(0.7*186000)=0.384 millisec

so tranfer time for 186 packets=tranfer time for 93 exchanges (other time are same as question data)

so T=93*(2*(11.47+0.384)+0.432)=93*24.14=2.245 seconds

so for d=100 mile Tx=100/(0.7*186000)=0.768 millisec

so tranfer time for 186 packets=tranfer time for 93 exchanges (other time are same as question data)

so T=93*(2*(11.47+0.768)+0.432)=93*24.908=2.316 seconds

so for d=1000 mile Tx=1000/(0.7*186000)=7.68 millisec

so tranfer time for 186 packets=tranfer time for 93 exchanges (other time are same as question data)

so T=93*(2*(11.47+7.68)+0.432)=93*38.732=3.602 seconds

3 by changing the data rate we change the value of Ta time taken by the packet to be transmitted through the channnel so when data rate is 500kbps we have Ta=1434*8/500*1000=22.94 millisec

so tranfer time for 186 packets=tranfer time for 93 exchanges (other time are same as question data)

so T=93*(2*(22.94+0.076)+0.432)=93*46.464=4.321 seconds

4 from the above calculation we get that transfer time is not effec ted by physical distance much but the data rate greately effects the transfer rate of oackets through a network

5 downloading 100 photos editing them and again uploading them has a somewhat different sceanrio

if the photos are same then there is no need to download 100 same image sas copies can be made in uch less time. but if the images are different then time taken to download 100 images wiil be much larger and agialn uploading the will take even more time as file read from machine side is much slowr as compared to speed of server file read.if the same images are downloaded many times then also speed will be reduced due to tha caching ability of the routers.

also the bandwidth anvialable for uploading will not be used upto that extent as we see uploading speed is slow than downloading speed so it will have a completely different scanrio.

6 smartphones use wireless 3g network which have a significant hifh speed of data rate that is dheir downloading speed is much faster howwver the size of packets aslo conteributes to transfer time

so if the smaert phone usue the same packet size aas the size given in question then definately the transfer time will be reduced considerably

as far as lab portion are considered then the photo shows the packet cpature of wireshark tool this file can be used to analyse the network tarffic up to graet extent.

the file provides infop about source ,destination type of pritocol used at different layer and also in some case the content of packet header .so alllthis info are very useful and can be usd to preduct any kind of threat possible.

WELL I HAVE TRIED MY BEST TO ANSWER THIS IF U WANT SOME MORE PLZ LET ME KNOW

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