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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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9 views

The size of a router's forwarding table

Consider a home network. Say three computers, a network printer and an internet connection. The three computers and the network printer will use the router to communicate with each other. I am ...
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18 views

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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32 views

RPI cluster performance related to network performance

I'm writing my thesis and i have built a RPI cluster, containing 10 nodes which consists of RPI model 3b. I've them connected to two gigabit switches. I don't know the CAT of the cables. They are not ...
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Does what I need exist? I want a switch ethernet but I can't find one that fits my needs [closed]

I want a switch ethernet where I can connect an ethernet that's connected to my router and then have all ethernets ports for my TV, PC... But all I find are ethernet switches that have to be connected ...
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1answer
173 views

If the probability of frame being lost is $P.$ Then, calculate the mean no. of transmission for the frame to make it success$.$

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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1answer
183 views

Finding maximal and average number of time slots in an Adaptive tree walk protocol

Tried to research here and on other sites with no luck regarding finding the maximal and average number of time slots in an Adaptive tree walk protocol. i'll explain what i mean here: In a simple(...
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1answer
64 views

S/Kademlia dynamic crypto puzzle

In S/Kademlia two crypto puzzles is used, one static and dynamic. The static is used to generate a key pair that makes an eclipse attack difficult to achieve, the dynamic to make Sybil attacks harder. ...
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31 views

How probability P is chosen in P-persistent CSMA?

I am struggling to understand how the probability value P is chosen for P-persistent CSMA for any particular station, what's the logic behind this.I have read from Wikipedia . P-persistent This ...
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1answer
303 views

Wifi throughput calculation

I have a problem which i don't know how to calculate or more specifically what am I missing. The subject is about 802.11 (wifi) The selected PHY rate is 54Mbit/s, that is whenever DATA is being sent ...
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1answer
37 views

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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1answer
22 views

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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18 views

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 ...
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35 views

How much byte do we need to record the route taken by a packet?

I am studying about IPV4 header. For some options, such as one that records route a packet has taken, 40 bytes is far too small, making that option useless. What does this mean? What I know? IHL ...
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1answer
7k views

Calculating the end-to-end delay of a message sent over a network

This is a problem from a MOOC on computer networking: We wish to send a message of size $150,000$ bytes over the network. There are four hops, each of length $20$ km and running at $100$ Mb/s. ...
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1answer
833 views

Bit times and propagation delay

Nodes A and B are accessing a shared medium using CSMA/CD, with a propagation delay of 245-bit times between them (i.e., propagation delay equals the amount of time to transmit 245 bits). The minimum ...
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2answers
85 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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1answer
34 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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265 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 ...
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3answers
40 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 ...
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2answers
113 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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15 views

Is ordering achieved by central server algorithm?

ME3 specifies that the first process be granted access before the second Ordering-: Requests are granted in the order they were requested. Colouris Distributed Systems book-: The reader should ...
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0answers
14 views

Clock synchronization in distributed system-What is this slide trying to say?

For over an hour I am trying to decode this slide. When each machine has its own clock, an event that occurred after another event may nevertheless be assigned an earlier time. Here event output.o ...
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11 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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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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1answer
36 views

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 ...
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4answers
376 views

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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1answer
52 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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2answers
487 views

Difference between DNS Spoofing and DNS Hijacking?

DNS Spoofing and DNS Hijacking, both of them basically are type of attacks where the request is redirected to some other malicious website or some other web page. But I did not find some concrete ...
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1answer
3k views

Go-Back-N ARQ Protocol Throughput Question

I am an undergraduate studying Data Coms and Networking and this question about go-back-N ARQ popped up that I am struggling to get my head around and cant find anything similar online. Any help at ...
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29 views

What is the difference between content type and content description in MIME header?

I am following article which says-: Content type-: defines the data present in body of message. eg-: text,image,video,application etc. Content description-: It is used when body of message can't be ...
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1answer
38 views

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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0answers
22 views

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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2answers
52 views

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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1answer
31 views

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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33 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 ...
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11 views

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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2answers
39 views

What is the the relation between the amount of data transmitted and line distance?

I am wondering what is the relation between line distance and the amount of data transmitted on that line. I know only the basic of computer science. Let's say I want to calculate the time it takes ...
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6answers
9k views

Why are so many internet protocols text-based?

From what I have found, a very large amount of protocols that travel over the internet are "text-based" rather than binary. The protocols in question include, but are not limited to HTTP, ...
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1answer
849 views

Exercise: Sliding window protocol: Bits for sequence number

This is a task in a lecture on computer networks: "Suppose you are designing a sliding window protocol for a 1-Mbps point-to-point link to the moon, which has a one-way latency of 1.25 seconds. ...
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11 views

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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2answers
61 views

Why does Slotted Aloha work?

So the way I understand it, if station A and station B, for example, try to transmit a frame at the same slot, a collision occurs, leading to an attempt at the next slot. But wouldn't the algorithm ...
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5answers
10k views

Why is the vulnerable time in pure aloha twice the frame time?

The time required to send a frame is called frame time. Vulnerable time is the time during which no transmission should be done to avoid any collision. My question is what kind of problem will be ...
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1answer
129 views

'Half-Close' figure of Data Communications and Networking, 5/e

In the Figure 24.13 of Data Communications and Networking, 5/e the first ACK message from the server holds y-1 in it's Sequence no. field. Note that the first FIN ...
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1answer
24 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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1answer
45 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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10 views

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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26 views

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
34 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 ...
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16 views

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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