Questions tagged [computer-networks]

Questions about problems that arise when you connect multiple computers to form a network.

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Which overhead is smaller - function call or passing variables between processes?

the question is related to networking frameworks; callback-based approach requires you to call a callback function every time you receive a new data packet; this is not a good approach for high-load ...
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How does AH header in IPSec prevents replay attacks?

According to Tanenbaum's Modern operating systems, The purpose of this field is to detect replay attacks. These sequence numbers may not wrap around. If all $2^{32}$ are exhausted, a new security ...
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What happens at the receiver side in Pretty Good Privacy [closed]

Say Alice and Bob want to communicate. Alice-: PGP hashes the message using MD5. Encrypts hash using private RSA key of Alice(D_A) Encrypted hash and original message are concatenated. Compressed ...
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How to solve modulo math equation in RSA algorithm?

$(3 \cdot d) \mod 8=1$. I know the answer is $d=3$ by common sense. But what is the mathematical approach to solve this problem? How do I solve this mathematically? How do we get this value of 125^107 ...
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4answers
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Why is TCP known as reliable process?

Is it because it uses 3 way handshaking, it is reliable? Or is it due to other reasons? Like due to congestion control, flow control and error control in TCP? Why do we call TCP as reliable?
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Need a token bucket algorithm

What is actually token bucket algorithm in algorithmic form? I couldn't find any algorithms anywhere. I have seen 1 example of token bucket but unable to comprehend it. Can anyone explain this?
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How are these two leaky bucket algorithms related?

I am studying about leaky bucket algorithm but I am unable to relate these 2 algorithms
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1answer
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How many /20-subnets are in the network 130.149.0.0/16?

I'm new to networking so please bear with me. My textbook gives 4 as an answer, but I'm not sure I understand the question: What's a "/20-subnet"? My understanding is that a network mask (/...
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3answers
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Mutual Friends in a Network?

I always seem to have trouble finding a formal way to analyze this (be through proofs or whatever). The problem statement is as such: If A and B are friends, and B and C are friends, then A and C are ...
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Reference request on computer networks

I read about correctness of iterative and recursive algorithms.I need a sequence of book recommendations for learning mathematical aspects of computer networks and data communtions such as ...
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What are Cloud Infrastructure & Sevices, Distributed Computer Systems, and Internet-of-Things (IOT) Concepts and Applications?

I'm looking for experts to explain these Computer Science subjects that I have to choose in my university. Currently, it seems that IOT and Cloud Infrastructure are quite popular. What are their ...
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Can you ELI5 what makes it that people retain control over their data stored in SOLID servers?

Please, note that I'm not a dev and I'm not sure this is the right stackexchange, but really would like to understand this one. So, I've recently discovered the SOLID project: https://solidproject.org/...
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Encoding with Differential Manchester

I am trying to understand how encoding is done with differential Manchester, if you have a binary string, for example 10000000011010100010, how would we encode it? or would I need more information to ...
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1answer
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How does asynchronous operations save time in I/O

I'm reading a book CLR via C# which says how Windows does asynchronous I/O: To read data from the file, ReadAsync internally allocates a Task object to represent the pending completion of the read ...
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While considering the wrap around time, why are the headers not considered?

In many texts and places as in here the wrap around time is found as : $$\text{Wrap-Around Time = $\frac{2^{32} \text{ bytes}}{\text{Bandwidth in Bytes/sec}}$} $$ The wrap-around time is defined as ...
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1answer
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What is the actual formula for the efficiency in CSMA/CD?

Let there are $n$ devices in the setup. Let each device sends data with a probability $p$. Successful transmission for a slot (hence of the setup in general) occurs when only one device communicates. ...
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Confusion about the definition of “Exponential Average”

I was having doubt regarding the concept of "exponential averaging". Till now I have come across the concept twice and they seem to be quite similar (except that they have minor but sharp ...
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1answer
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What is the difference between broadcast and gossip/epidemics?

Everything is in the title. What is the difference between broadcast and gossip in the context of message-passing distributed systems? According to Wikipedia, gossip and epidemic protocols/epidemics ...
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Can synchronous data transfer be used for transferring large data in case of computer architecture and organization?

I am learning computer architecture and organization. I have this confusion, can synchronous data transfer be used for transferring large data in case of computer architecture and organization? I ...
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Why does the author say that the sender in GBN protocol resends packet n to N(window size) when ack for packet n gets lost?

I was reading about the comparison of TCP with GBN protocol and I came across this text in the book Computer Networks: A Top Down Approach, 6th Edition by Jim Kurose on page 249; Consider also what ...
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Is e-mail communication peer-to-peer?

In his networking textbook, the world-renowned computer science expert Tanenbaum says that e-mail communication is inherently peer-to-peer. Here is the paragraph from the book: Peer-to-peer ...
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Tearing down the FSM description of congestion control

I was going through the text Computer Networking- A Top-Down Approach by Kurose and Ross, there I found subtleties with the TCP congestion control FSM which is shown below: Mainly I am having ...
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Is peer to peer and client-server a type of network or protocol?

Is peer to peer and client-server a type of network or protocol? Because my book mentions this under types of network heading under the subsection of "Types of network on the basis of component ...
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How to use butterfly network for data copy?

I know butterfly networks (and benes as well) allow routing a packet from any input to any output node. Congestion is $\sqrt{n}$ but with bene it can be $1$. Now assume that in a butterfly network, ...
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About the paper Privacy-preserving in association rule mining using an improved discrete binary artificial bee colony

I don't understand two parts in this paper: The min notion on page 4 line 357 (equation 10d): I understand this as to find all the $M_{10}$, $M_{11}$, $M_{01}$ first and then try to minimize the ...
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Problem on probability given frame sizes and their error correction probabilities in a wireless system

I am stuck trying to solve the following question for a while Bit error rate after demodulation in an wireless system = 1.0e-03. The system has 4 possible frame sizes – 48 bytes, 96 bytes, 72 bytes ...
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1answer
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How to reconcile the different definitions of asynchrony?

There are 3 definitions of asynchrony that I know of: In event-based programming, asynchrony refers to the execution of tasks in a non-sequential way, which may involve creating another thread. For ...
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1answer
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multicasting in ethernet

I am learning this topic and there is a concept that LSB ( bit ) of MSB ( byte ) should be set to 1 for multicasting . But why we need to do so as multicast address is unique so why can't we assign ...
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What are overlay & underlaying topologies in DHT?

We are covering Distributed Hash Tables in my "Networks" class and one of the subsections is about the improvements that can be made to increase the performance of the chord. Here, the ...
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Storing Network Packets in Tabular Form

For network packets coming over TCP/IP protocol, have you ever confronted a situation where you need to store those network packets in tabular form similar to how tabular tables in databases? For ...
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2answers
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How a 10GB network can copy 1TB data in 2 hours?

In the slides of a university lecture, the following phrase got my attention. Assuming 10GB network, it takes 2 hours to copy 1TB. My calculation was as follows. 10GB network = 10 gigabits per ...
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Does the host operating system know the content of your messages in a messaging applications?

Let's say you are using a messaging application (Microsoft Team, Skype, Telegram,..) on an operating system (Windows, MacOS, Linux). Does the OS know what you are sending or receiving? If yes, how? ...
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modelling communication costs on a network

Consider a set of $N$ computers. Each computer needs to send some data to $K$ other computers, and each computer is receiving data from $K$ other computers (ie. the communication pattern can be ...
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Can someone explain how to calculate what time each host started and finished?

The diagram at right shows a WIFI network with an access point, X and three hosts, A, B and C. The large circles indicate the coverage areas of the three hosts. The coverage area for X is not shown, ...
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Two Generals' Problem Definition

I've read various descriptions of the TGP, most of which seem vague or conflicting on the precise constraints of the problem. Specifically: is it always or sometimes impossible to reach consensus ...
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Computer Networks Link layer error detection

I am aware that Link-Link error detection and correction takes place as an optimization to the error detection taking place at the Transport Layer at the destination host's end. I was wondering if ...
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Throughput of slotted ALOHA when one node goes out of sync

What would be the throughput of slotted ALOHA when one node goes out of sync? Closer to ALOHA or slotted ALOHA? According to my calculations: For ALOHA we have probability of success = $N \cdot p \...
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Automated API negotiation

Is there a way for two programs or computer nodes to communicate with each other without knowing each others APIs? Or is there a least a reasonable approach to make them talk in some settings? Let a ...
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1answer
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Is there any guarantee in asynchronous systems?

We know that in an asynchronous system, no assumptions about process execution speeds or message delivery times are made. My question is: can we present any guarantee in asynchronous systems? Some ...
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How do I compress data vectors in broadcast messages?

Let us model a wireless broadcast network as an undirected graph $G(V,E)$ where there is an edge between every pair of nodes ${i,j}\in V$ if they are in transmission range of each other. $w_{i\to j}$ ...
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Calculating minimum frame size

I'm actually quite stuck on a question I have for an assignment...I'd appreciate any help with this: Consider a CSMA/CD network with maximum cable length of 8km and where the ratio of > ...
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265 views

Decode TCP Payload data

I'm trying to find out what the data of a packet means. I'm a newbie to networking, and I try to find what's sent in this packet: https://pastebin.com/hZEqjmBx How can I do that? What does that data ...
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Application for large graphs compression

I am looking for an application in which it is desired to perform an efficient lossy compression of very large graphs, that preserve the general structure of the graph but may delete some edges. Can ...
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Finding the approximate weight of intra graph paths

Say that you have access to a source $a$ and destination $b$ in a weighted graph $G$ with $n$ vertices. There exists a path $p$ from $a$ to $b$ with 2 or more vertices in it. We know the total cost of ...
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Is it possible to transmit bits digitally?

I have learnt that all data transmission is analog. Is there any mediums that could transmit bits digitally?
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Andrew Tannenbaum exercise

A bit string, 0111101111101111110, needs to be transmitted at the data link layer. What is the string actually transmitted after bit stuffing? There isn't any END DELIMETER given here, Answer given ...
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SSID evaluation within the 802.11 protocol

Inspired by a question on superuser, I was reading up on the 802.11 protocol. This made me wonder if the SSID is actively used outside the authentication and association process. I know that it can be ...
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network question on Go back n

A Go-back-N sender just receives an ACK packet with sequence number 𝑡. Before this ACK is received, sender’s window is [𝑘, 𝑘 + 𝑁 − 1] where 𝑁 is the window size. Suppose 𝑘 > 𝑁, packets may ...
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Socket API in TCP

According to me Statement S1 and S2 is True while S3 is False. The Solution says 'S3' is correct ? Am I Wrong ? Kindly help with explanation . I know Connect() in TCP is used by the client side for ...
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Mainstream publication venues for Internet of Things (IoT)

I am interested in reading the research literature on Internet of Things (IoT). I am especially interested in theoretical research (eg. papers where techniques from graphs or algorithms are utilized)....

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