263 views

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.

@Nisha Bharti

For Data     2^x is used e.g. K = 2 ^10

For Bandwidth 10^x is used eg. 10^3 for Kbps.

But confusion here is 40 Gbps is Bandwidth. Then why  2^30 is used.

@GateOverflow04 As TCP is the transport layer protocol & till now i haven’t studied transport layer that’s why i am also confused as i have answered FLOW CONTROL based @Abhrajyoti00 can u please explain what’s the reason as i have also not studied COA.

@Nisha Bharti Basically all the values are nearby. Eg. $2^{30}$ is $1.073742e+9$ and $10^9$ = $1.000000e+9$. Now depending on qs, we need to use appropriate values so that calculation becomes easy. If there are powers of $2$, try to take in powers of $2$ (Eg in qs like these  https://gateoverflow.in/371886/gate-cse-2022-question-50?show=381401#a381401Again if there are powers of $10$, (eg. link speed is given as $2*10^8 m/s$) use powers of $10$.

Now depending on qs, we need to use appropriate values

Suppose, we don’t need to solve questions and someone asks, whether $1$ Gbps is equal to $10^9$ bps or $2^{30}$ bps, what would you say ?

@ankitgupta.1729 I would say $10^9$ bps.

why would you say $10^9$ bps ?

@Abhrajyoti00 You want to say that 2^7 & 10^2 approximately both are same but 2^8 it will be 256 then how can we compare this no. to 10^x? can we compare it with 10^2 ?

edited

Speaking of $K$ as $10^3$ or $2^{10}$, $M$ as $10^6$ or $2^{20}$, $G$ as $10^9$ or $2^{30}$ are what becomes approximately closer as and when we grow in value. I didn’t say $2^7$ as approximately equal to $10^2$.

@ankitgupta.1729 Sir, as $M$ is $10^3$ times of $K$ so on and so forth. Ok Now, I got to know there's a difference between $Gbps$ and $Gibps$ .

NameSymbolbit per secondbyte per secondbit per second (formula)byte per second (formula)
 gigabyte per second GB/s 8,000,000,000 1,000,000,000 8 × 109 109 gibibyte per second GiB/s 8,589,934,592 1,073,741,824 233 230

Source : Data-rate units

@Abhrajyoti00 Similarly, when you go in more depth, you will know that $1$ Byte is not always equal to $8$ bits and $1$ GB is not always equal to $2^{30}$ Bytes though some authors like Tanenbaum, Peterson follow that but this is not the absolute truth.

@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