Questions tagged [computer-networks]
Questions about problems that arise when you connect multiple computers to form a network.
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How does non-DMA transfers really work?
I recently discussed DMA and non-DMA with my OS professor. Here is my current understanding:
disk controller has its own CPU, maybe own ISA, tiny program that simply handles reading from the disk (...
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Write-Ordering Problem, Idempotency in Distributed File Systems
I have recently finished reading the section on Distributed Systems in OSTEP. For NFS, they briefly mention the cache consistency problem and say how it is solved for reads by maintaining an attribute ...
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Small doubt in vulnerable time of CSMA/CD and pure aloha
I understand that vulnerable time is the time when collision is possible.
In CSMA/CD, the vulnerable time is Tp because it takes Tp time for bit to travel from source to destination and collision ...
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Why is vulnerable time equal to 2*Tp where Tp is Transmision time? (pure-ALOHA)
In pure aloha the if one frame is been transmitted and another is send during the transmission then the whole frames get destroyed.
Vulnerable time is the time period where there is the chance for ...
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'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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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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Finding the optimal packet size
I have recently started reading the book Computer Networking: A Top-down Approach in hopes to get introduced to computer networks. When attempting one of the questions
from the book for practice, I ...
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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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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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Minimum spanning tree with dynamic edge cost based on degrees
I have a problem that I'm struggling to solve or even name, I'd really appreciate any help or pointer to potential existing solutions.
Suppose there is a connected graph $G$ and we are trying to find ...
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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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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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Window slider difference between GoBackN vs Selective Repeat
I am trying to learn about GoBackN and Selective Repeat ARQ. And I have the following practice question:
Consider sender A and receiver B which communicate using an ARQ
protocol. The current window ...
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Introductory books on Computer Networks
While I have come to learn some computer science, I find that I have next to no knowledge on computer networks.
Are there any good books at a basic level that cover some of the fundamental topics? ...
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which devices use parity checking?
I've just started learning computer architectures and I'm having trouble understanding where these are used.
I know that parity checking is testing for accurate data transmission between nodes in a ...
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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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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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distribution choice for network latency
Consider this situation. A few clients are connected to a server over the internet.
I define network latency as the time between request leaving the client and reaching the server.
What distributions (...
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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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k-compact vectored I/O
I have a practical programming problem that I am struggling to find an optimal algorithm for, in part because I don't know what to call it. The problem concerns vectored I/O (scatter/gather).
Consider ...
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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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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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How to understand CSMA/CD algorithm from this graph?
I am currently studying Computer Network, and I have some problems when encountered CSMA/CD, I can understand how it works, but I am struggling in understanding this graph, anyone can give me some ...
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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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Find connected components in a graph of computer network with parallel pairwise tests
I have N nodes, a node might have an undirected edge to other nodes, resulting in K connected components (K<=N, K unknown).
I can test if a given pair is connected. In each step in time, I can run ...
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What happens when an internet connection is faster than the storage write speed?
If one attempted to download a file at a speed of 800 Mb/s (100 MB/s) onto a hard drive with a write speed of 500 Mb/s (62.5 MB/s), what would happen? Would the system cap the download speed?
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How to resolv this NAT problem?
I am taking my first network class and I came across a question I just cant wrap my head around.
We have an external machine that has a public IP address from using NAT, the external machine want to ...
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Manchester encoding [closed]
How clock rate is doubled in the Manchester encoding? clock cycle depends on bit interval time . In NRZ , Manchester encoding and every other Encoding the clock cycle time is same as bit interval is ...
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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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Can the traffic relation between two nodes of a communications network be governed by an exponential law?
Disclaimer: This question was initially asked in Network Engineering SE, yet got closed due to its research nature.
Assume a (hypothetical) communications network constituted by many nodes including ...
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If the two generals problem is unsolvable how can we human beings agree on things?
If the two generals problem is unsolvable how can we human beings agree on things?
I mean, we communicate everyday and have the same limitations as any communication problem handled by computer ...
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Two Generals Problems - What's wrong with my approach?
Some time ago, I've come across the Two Generals Problem and that it cannot be resolved. Now, recently, I've had an idea how to approach it. IMHO, it is a very obvious way to handle it but I haven't ...
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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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Diffie-Hellman with offline attack
There is a protocol that aims to transfer a password securely between the user and the server. The protocol is based on the Diffie-Hellman method.
In the protocol, p is a prime number, g is a ...
D.W.♦
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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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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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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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TCP Warp Around time - Sequence number Problem
Consider a long-lived TCP session with an end-to-end bandwidth of 1Gbps. The session starts with a sequence number of 1234. The minimum time (in seconds, rounded to the closet integer) before this ...
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How does caching increases scalability in distributed file system?
There are clusters of LAN connected computer systems. California cluster has cached "viral video" at first stage, when client near California requested the file firstly.
Now, another client ...
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What is 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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In IPv4, why is the number of host addresses available per network given by $2^\textrm{host bits} - 2$? This is in the context of classes
For some reason—at least when classes are involved (which I don't know the reason for yet)—in IPv4 the number of host addresses available per network is given by $2^\textrm{host bits} - 2$. Why don't ...
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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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Dynamic routing algorithm
In static routing where the network parameters dont change, we can use Djikstra's or Bellman-Ford's algorithm to find the shortest path to send data from source to destination.However in dynamic ...
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Count-to-infinity avoidance techniques and hold-down timeout based question
I am trying to understand count-to-infinity avoidance techniques, and came across this topology. Now, suppose the interface eth1 on R1 has gone bad, and assuming that split horizon, triggered updates ...
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why use log operation in shannon capacity?
In shannon capacity, it uses log operation.
bandwidth * log2(1 + SNR)
Why they use log operation instead of just using SNR?
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why use bellman-ford instead of Dijstra in RIP routing?
The RIP routing protocol was published in 1988 and uses Bellman-Ford algorithm to calculate shortest path. Also more recent version of RIP (RIPv2 and RIPng) use the same algorithm. The Djikstra ...
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Efficiency of UDP protocol
When 54 bytes of data is transferred using the UDP protocol, the efficiency is? (In per cent)
IN UDP, the maximum datagram size can be $2^{16}-1 \, bytes$
Now to this, 8 Bytes of UDP header is ...
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why vulnerable time in pure aloha is not tp
I understand that vulnerable time in CSMA cd is Tp (Propagation time). This is because collision can occur in Tp duration since one bit has to travel to the end.
My question is- Why that is not true ...
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Construction of Omega Network
I understand that we could draw N * N Omega Network,
But can we draw an Omega Network to connect 6 CPUs to 4 memories? (The number of CPUs does not equal the number of memories)
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What's wrong in this network topology?
What are the six mistakes that were made in the configuration of the following network?
I could only find 3. Since the subnet on the left has 192.168.10.33 as ...
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