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# Questions tagged [computer-networks]

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

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### Go back n on server side

I am implementing a UDP based go back n example and I am a bit stuck on how the server should respond to packets. If my client has a sliding window of say 5, it can send 5 packets to the server ...
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2 votes
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### questions about queuing delay

I am learning computer network, and confused by the queuing delay. In my textbook, it says that when La/R approaches 1, and with random inter-arrival times, then the average queuing delay is closer to ...
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1 vote
1 answer
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### Trying to understand a Router's Forwarding Table

I am trying to understand how a router's forward table works. As such, I am working on the following problem. Problem: A router’s forwarding table has the following entries. \begin{array} {|r|r|}\...
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1 answer
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### If the probability of frame being lost is $P.$ Then, calculate the mean no. of transmission for the frame to make it success$.$ [closed]

Here the probability of frame being lost is $P.$ So the probability of frame reaching safely would be $(1-P).$ Now lets consider that the frame will reach safely in $k$-th transmission. That means ...
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1 vote
1 answer
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### How does concept of "redirection" works in ICMP?

I am trying to understand this figure, what it is trying to say? What I already know? Routing table is updated dynamically. However, for efficiency, hosts do not take part in the routing update ...
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### Why does diskless system doesn't contain IP address?

I am studying about RARP. What is the IP address of a given hardware address? Used by diskless systems to find their own IP address. https://www.cse.wustl.edu/~jain/bnr/ftp/f15_arp.pdf So, why do ...
2 votes
1 answer
61 views

### Name for scheme and host of URL

Is there a specific name when we refer to just the scheme and host of URL, for example http://localhost of the URL ...
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2 votes
2 answers
2k views

### How is this example sequentially consistent but not linearizable?

Background information that I know(But not understand with examples, I will be glad if you could explain it to me with examples) A replicated service is said to be linearizable if for any executin ...
1 vote
0 answers
13 views

### Distributed Graph Consensus to fit a distribution?

$G$ is a strongly connected graph with nodes $V$ and edges $E$. Each node $v_i$ receives a sample $x_i$ from a Gaussian $\mathcal{N}(\mu,\sigma^2)$ with unknown mean and variance. The objective is for ...
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1 vote
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### How is this example related to Lamport clock theory? I can't relate algorithm example with the algorithm theory. Share some insights please [closed]

I have asked 1 type of question but I have asked that in many questions. So bear with me. My question is about 1 topic, I just didn't find it right to create separate questions for each of these ...
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-1 votes
1 answer
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### If primary server's UTC source fails, how will synchronization be possible in NTP(network time protocol)?

If a primary server's UTC source fails, then it can become a stratum 2 secondary server. If a secondary server's normal source of synchronization fails or becomes unreachable, then it may synchronize ...
• 263
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1 answer
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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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1 vote
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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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-2 votes
2 answers
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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 ...
• 263
7 votes
5 answers
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### Why is TCP known as reliable protocol?

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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1 answer
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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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3 answers
153 views

### 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 ...
2 votes
0 answers
40 views

### 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 ...
1 vote
1 answer
156 views

### 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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1 vote
1 answer
1k views

### 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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1 vote
2 answers
375 views

### 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 ...
1 vote
1 answer
54 views

### 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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2 votes
0 answers
553 views

### 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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1 vote
1 answer
454 views

### 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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2 votes
0 answers
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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, ...
1 vote
0 answers
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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 ...
0 votes
1 answer
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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 ...
0 votes
1 answer
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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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### 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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2 answers
2k views

### 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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2 answers
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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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238 views

### 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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1 answer
55 views

### 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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1 vote
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55 views

### 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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### 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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3 answers
175 views

### 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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### 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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### 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 ...
0 votes
1 answer
194 views

### Probability of loss using a binary symmetric channel

Today we talked about Information Theory and the binary symetric channel. For newbies here is a little explanation : For instance if I want to send a binary to someone : The bit will be "flipped&...
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2 answers
67 views

### Can we improve internet speed by serializing timestamps?

If we (scientists) came up with a way of representing numerical timestamps as letters hence reducing the number of bytes needed to represent timestamps, would that mean an improvement in internet ...
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1 answer
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### Does an insecure router bypass the privacy guarantee of a VPN connection?

If I have a router that has a vulnerability that allows an attacker to gain full control it, does using a VPN on the network with the said router prevent an attacker from being able to snoop on the ...
1 vote
1 answer
269 views

### Is this applet implementation for the Go-Back-N ARQ protocol correct?

I was reading a textbook describing the Go-Back-N (GBN) protocol with Finite State Machines as pictured below: $\Lambda$ just means "initial state" or "no action", depending on ...
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1 answer
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### Go-Back-N Protocol not efficient?

Let's say we have five packets p1 p2 p3 p4 p5 to be sent sequentially: and for some reasons, p3 got delayed so it the the last packet to arrive recevier. so below is the receiving order on the ...
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3 answers
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### Computer networks - Can there be an out of order frames in a noiseless channel?

In a noiseless channel can frames in the 2 layer of OSI model(Data link layer) reach to the destination out of order? *I am studying from Computer networks 5 Edition of Andrew S. Tanenbaum
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1 answer
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### Can application DNS requests bypass a firewall on Windows and Linux

Assuming I have firewall set to block an application from accessing the Internet, would I DNS request go through? I tried using C (gethostbyname) on Windows and the answer is no. It seems that the ...
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-1 votes
1 answer
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### What is the meaning of this error message I get when downloading documents?

Every so often I'll hop on my laptop, open google, and eventually try to download and open some document, only for the document to wind up looking like this: What on earth does all this mean? What ...
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3 votes
1 answer
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### How private IP address is determined?

Today I presented about IP address during my online class based on Computer Networks by Andrew S. Tanenbaum and during QnA session, I was asked about private IP Address range. ...
2 votes
0 answers
23 views

### Does RLNC (Random Linear Network Coding) still need interaction from the other side to overcome packet loss reliably?

I'm looking into implementing RLNC as a project, and while I understand the concept of encoding the original data with random linear coefficients, resulting in a number of packets, sending those ...
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1 vote
1 answer
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### Is IP masquerade and Network Address Port Translation(NAPT) the same?

Is IP masquerade and Network Address Port Translation(NAPT) the same? I'm not sure whether it is the same thing or not but I realized the mechanism is almost the same where both IP masquerade and NAPT ...
0 votes
1 answer
54 views

### What does route aggregation is an automatic process means?

Here is an excerpt from Andrew S. Tanenbaum, Computer Networks, 5th edition, Chapter 5 (The Network layer), page 448: When aggregation is turned on, it is an automatic process. It depends on which ...