School Network Question! PLEASE HELP

[twEEkerAreUs]

Hey guys, I have a question for the Network masters in here.

What is the transmission efficiency of a 1,000-byte file sent in a response to a Web request HTTP, TCP/IP, and Ethernet? Assume the HTTP packet has 100 bytes in addition to the 1,000-byte file. Hint: Remember that efficiency = (user data/total transmission size).

I know the answer because I looked in the teacher's book, but I have no idea how you get the "Total Transmission Size". Please don't reply if you have no idea or just want to post for the sake of posting. Really stumped on this even though it seems so simple.

The answer is:


1000/1171=.82

1000 = User Data & 1171 = Total Transmission Size

How the hell do you get 1171? Do you have to look at the TCP/IP & Ethernet Package to determine to add it on or what?

[su root]

100bytes + 1000 bytes = 1100 bytes to transmit. Packets must be under 1500bytes, so it'll fit in one packet.

Ethernet Frame:
http://www.inetdaemon.com/tutorials/lan/ethernet/frame_format.html
Start Frame Delimiter = 1 byte
Destination MAC = 6 bytes
Source MAC = 6 bytes
Length = 2 bytes
FCS (trailer) = 4 bytes

TCP header:
http://www.freesoft.org/CIE/Course/Section4/8.htm
Source Port = 2 Bytes
Destination Port = 2 Bytes
Sequence Number = 4 Bytes
ACK Number = 4 Bytes
Data Offset = 4 BITS
Reserved = 6 BITS
Control Bits = 6 BITS (2 bytes total for this, and the two above)
Window = 2 Bytes
Checksum = 2 Bytes
Urgent = 2 Bytes
Option = Varies, for this, 1 byte
Padding = varies, to make sure the packet header is exactly 32 bytes

IP Header = 20 Bytes
http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/ip-packet.html


19 + 32 + 20 = 71 bytes transmission overhead + 1100 data = 1171 bytes transmitted.

[twEEkerAreUs]

Thanks su root! :clap: