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Posted on 2011-05-08
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An HTTP request is 205 bytes in length. The request is encapsulated in a TCP packet. The TCP
packet is encapsulated in an IPv4 packet. The IPv4 packet is then sent via ATM.

(Ignore retries, options and session establishment.)

A. What is the total number of bytes required to send the HTTP request?
B. What is the overhead, as a percentage of total bytes sent?

I think the percentage of total bytes sent is 22.34%
I'm not sure

could i get any suggestion !!
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Question by:Alarjwan

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Expert Comment

Here's a page on the TCP part http://en.wikipedia.org/wiki/Transmission_Control_Protocol and it looks like the minimum overhead is 128 bytes which is over 30% already.  And here's a page on the IPV4 packet http://en.wikipedia.org/wiki/IPv4#Packet_structure which looks like another 128 bytes minimum.  And here's an ATM page http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode but I don't understand it.
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Accepted Solution

The minimum IPv4 datagram size is 20 bytes. The same applies for TCP/IP.

ATM transmits in packets of 5 byte header and 48 byte body - originally designed to bust small packets over a network so as to avoid "hogging the line". These days the networks are fast enough so one uses ethernet packets rather than ATM.

So assuming that the IP packet is 205+20+20 = 245 bytes, this will be transmitted in 6 packets each needing an additional 5 byte header = 6*5 + 245 = 275. The overhead is then around 25%.
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Author Closing Comment

it was evry clear and helpfull
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