46 votes
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What happens when an internet connection is faster than the storage write speed?

Many protocols, including TCP which is most widely used protocol on the Internet, use something called flow control. Flow control simply means that TCP will ensure that a sender is not overwhelming a ...
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  • 675
45 votes
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Why are so many internet protocols text-based?

When the world was younger, and computers weren't all glorified PCs, word sizes varied (a DEC 2020 we had around here had 36 bit words), format of binary data was a contentious issue (big endian vs ...
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  • 13.6k
32 votes

If the two generals problem is unsolvable how can we human beings agree on things?

I disagree with other answers that the communication channel needs to be modelled differently. Malice is irrelevant, simple lost messages with any non-zero probability are sufficient to create the two ...
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24 votes

Why are so many internet protocols text-based?

One advantage that might be overlooked is the ability to experiment. If you're shoving bits down the tube, you're going to need to write some utility that translates ...
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18 votes

If the two generals problem is unsolvable how can we human beings agree on things?

Central (pun intended) to the Two Generals problem is a malicious enemy in between. Although this models an unreliable channel, it models it in a way that we normally don't encounter. In the problem, ...
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16 votes

If the two generals problem is unsolvable how can we human beings agree on things?

The "unsolvability" of the "Two Generals" problem (or called "Coordinated Attack" problem) is restricted to its context, i.e., in a totally asynchronous distributed system with unreliable, untrusted ...
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  • 9,179
14 votes
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Measuring one way network latency

The following diagram, from a blog post I wrote, is a visual proof that it's impossible: Notice how the packet arrival times on each side stay the same, even as the one-way latencies change (and even ...
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  • 5,712
12 votes
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TCP Connection Termination - FIN, FIN ACK, ACK

A TCP implementation might send a standalone FIN in the first closing segment. However, it can also send a FIN ACK, instead. The latter is strictly better: the implementation can bundle a "free" ACK ...
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  • 14.1k
12 votes

What happens when an internet connection is faster than the storage write speed?

what would happen? The bytes that cannot be written to the HDD in time would be buffered temporarily somewhere; very likely some of them would be buffered in the application that "converts" the ...
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  • 1,145
9 votes

Why are so many internet protocols text-based?

It's not that many internet protocols are text based. In fact, if I were to guess I'd say that text based protocols are in the minority. For almost every text based protocol you see on the internet ...
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  • 589
7 votes
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How internet speed is manipulated at the physical level

This is a very wide topic indeed. Basically, there are two ways to measure and control the speed of a connection: physical speed and logical speed. Physical speed is determined by the technology, ...
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  • 186
6 votes
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What are the underlying mechanisms allowing us to unsend an email?

The e-mail system has no way of manipulating already sent e-mails, no. The only services I've seen which allow you to "unsend" an e-mail simply delay the e-mail being sent for a user-determined ...
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  • 76
5 votes

Why is CAN protocol preferred to be used in automotive application?

A few reasons : CAN was developed by BOSCH, which have a lot of influence in automotive equipment (engine control, braking, body, gearbox control...). BOSCH ensured that CAN killed competitors like ...
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  • 1,756
5 votes

Why is the throughput (performance) of the Aloha protocol ≈ 0.18?

This number is reached first by assuming that messages will be produced and sent according to a Poisson process. $$P[(N(t + \tau) - N(t)) = x] = \frac{{e^{ - \lambda\tau } (\lambda\tau) ^x }}{{x!}}$$...
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  • 2,785
5 votes

What's the point of Subnet Masks?

The main benefit is in the size of routing tables. Instead of having to store an entry for every machine on the network, you only need to store an entry for the particular subnet. For example ISP ...
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5 votes
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Why arrival process of packets at a switch is not a Poisson Process?

"new flow arrivals" means "arrivals of new flows". A flow is a TCP connection (roughly); each individual TCP connection is a separate "flow". So, this is talking about new TCP connections, and the ...
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  • 140k
5 votes

How would I add 0.0.15.255. to 172.1.6.255.?

You don't. Adding IP addresses makes no sense. It's like asking "How would I add an apple to a kiwi?" (Sounds like a setup for some bad joke, I know.) Not all things can be added. There's no ...
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  • 140k
5 votes
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Go Back N ARQ Question

1-2-3 is correctly sent and acknowledged so the sender's window is now over 4-5-6. 4 is ...
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  • 1,304
5 votes

How does Server know window size for TCP Header?

The Window Size field in the TCP packet header is the number of bytes the sender will buffer for the response. Basically, during the handshake each side will say how large its receive window is. That ...
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5 votes
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How to distinguish between bits?

If the computer starts in the middle of the stream, it has no way to know—it will be completely confused. Fortunately, that's not how the protocol works. The computer and terminal have to sync up ...
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  • 6,920
5 votes

How do web browsers find out the MAC address?

So, how does the computer find out the MAC address of the server? It doesn't. The MAC address only has validity inside a local area network (LAN), which, as the name says, is local. Unless the ...
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  • 4,889
5 votes
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ip/tcp packet decoding without wireshark

My guess is that what you are seeing is a Level 2 Ethernet frame and therefore the preamble is missing. Also the Ethernet checksum seems to be missing. In this case everything seems to line up (the ...
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  • 22.7k
5 votes

Why is TCP known as reliable protocol?

TCP is said to be reliable because when an application receives data, it knows that this is exactly the data that the sender sent. No part of the data was lost, reordered, etc. Error control is the ...
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4 votes
Accepted

Why is the throughput (performance) of the Slotted Aloha protocol ≈ 0.36

Unlike in the regular ALOHA protocol, where other nodes can send messages that interfere with ours at any time, in the Slotted ALOHA protocol, the only other time a message can be sent to interfere ...
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  • 2,785
4 votes
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Why is CAN protocol preferred to be used in automotive application?

Historical reasons, for the most part. Automotive systems started using CAN because nothing else was good, and now they've all standardised on it. Having said that, CAN has one particular feature ...
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  • 18.7k
4 votes

Algorithm for Dynamic Client Side Throttling

this is a fairly basic problem in control theory and there are "design patterns" in this area to handle this type of system, and think there is probably an example right out of a control theory book ...
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  • 10.8k
4 votes

Till which layer does the loopback packet goes?

When you say "layer", you are probably thinking of the OSI model, also known as the seven-layer model. However, real TCP/IP implementations don't actually fit the OSI model very well. The OSI model ...
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  • 140k
4 votes

Why not use the channel capacity as the sliding window size?

Sliding windows are used to: Keep track which packets were sent and received, hence the data transmission is reliable Keep track of the memory available to the receiver. The receiver may fill its ...
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  • 797
4 votes
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Difference between 2f+1, 2f and 3f+1

$2f$ and $2f + 1$ are just numbers. A set of $2f + 1$ nodes has a majority of non-faulty nodes, as you say; a set of $2f$ nodes can be deadlocked between the non-faulty and faulty nodes. A total of $...
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  • 875
4 votes
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Why is the vulnerable time in pure aloha twice the frame time?

This is because in pure ALOHA, even if a bit of a frame collides with a bit of another frame, both the frames get discarded. Also, in pure ALOHA, a station doesn't listen to the medium before ...
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