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I am slightly confused in 40 Gbps.

When to use 2^30 and when to use 10^3 in conversion.

When, we are dealing with number of bits in sequence number data, then we can take 2^30. This makes calculations damn easy.

You can even follow my answer to GATE 2022 q. I implemented this method in this year’s GATE exam too https://gateoverflow.in/371886/gate-cse-2022-question-50?show=381401#a381401

@Abhrajyoti00

Can you please explain a bit more.

I cann’t open 2022 link because I have to solve it as mock test.

See, it’s true that we take B/W as $10^x$ and Data as $2^x$ while calculation. But its mainly used in Sliding Window Protocol qs, Ethernet qs. But in most of the Qs of TCP, where Sequence number has to found out based on Maximum Segment Life (MSL) , Wrap Around time (WAT), etc. we use Bandwidth as $2^x$ because we know that the sequence number field is $32$bits. Thus the powers of two can be canceled easily.

In COA, however in all of the PYQs, you can take GB as $2^{30}$ or $10^9$ (specially in I/O qs where Disk speed needs to be found out) and all your answers will be correct. Tried and tested by me :P

I think 10^3 is used for KB but it is for bandwidth & 2^30 is used for GB it is for data.

see data is always in binary form so we have only two no. that is 0,1 that’s why we have used 2^n for data bits & for bandwidth it can’t be in discrete form it can be any no. that’s why we have used to 10^n for bandwidth.

that is decimal system is used in bandwidth & binary system used in for data.

simply  in Decimal SI (base 10), 1 Kilobyte is equivalent to 1000 bytes. On the other hand in Binary (base 2) system, 1 Kilobyte is equal to 1024 bytes.

@ankitgupta.1729 Sir, that sounds interesting!

@ankitgupta.1729 Sir, if IIT’s professor will set the question according to this concept then cutoff will be only 10 marks.

@Nisha Bharti Someone who knows all these things probably would always mention all these things while asking questions if he/she doesn’t want to confuse people like just have seen mentioning $1$ Kbps = $10^3$ bps here

in case of bandwidth we use 10^x

in case of data we use 2^x

here we should use 10^9 thus more appropriate answer is 0.8589934592