Questions tagged [computer-networks]

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

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How does waiting 7ms and atomic clock help GCP spanner create external consistency?

My understanding why distributed transaction need synchronized clock is the following Assume NTP max drift is 250ms ...
olaf's user avatar
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How do you tell whether a binary number is positive or negative?

Consider the figure in Exercise 2. If the current machine code that executes is 0x214bfffd and the values of the registers in the processor are as shown below, what is then the value of the input WD3 ?...
First_1st's user avatar
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Do I need to consider the header size to calculate the original datagram?

The following question is related to finding the size of the original datagram. The formula for original datagram size is: Data length of first packet + (Total length of subsequent packets * no. of ...
Anonymous Stranger's user avatar
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Would the computers be able to communicate if all of them had same name hardcoded in their OS? Why not?

The name of a computer should never be bound into an operating system at compile time. Explain why. I don't see a reason why this should not be allowed? Say we have couple of computers all with the ...
barnyard9's user avatar
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A mathematical question on error detection

For a bit of context, I was going through the previous year questions of my college computer networks course and found this in one of the papers. I don't even know how to go about solving this problem,...
FullMetalChains's user avatar
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What is practical implication of Bandwidth delay product?

It's given that the bandwidth-delay product defines the number of bits that can fill the link; while the sender can send (1+(2 * Bandwidth * Delay)) units before getting acknowledged for the first ...
SUNITA GUPTA's user avatar
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Question on vulnerable time of pure aloha, and why it does include propagation time

I have read that pure Aloha's vulnerable time is 2*transmission time. But shouldn't it also include propagation time? What if a frame is propagating in media and gets collided with another frame (...
Rani's user avatar
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Throughput and response time

I have read that a decrease in response time does not necessarily entail an increase in throughput, but I'm struggling to understand the exact way that this can happen. What I'm imagining is a server ...
Addem's user avatar
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Current research in TCP congestion control?

Question: What are the current main challenges in TCP congestion control algorithms? Are there any foundational trade offs that algorithms need to make? E.g. minimizing router buffer sizes while ...
Edvard Fagerholm's user avatar
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1 answer
90 views

How does OSI model and TCP/IP work?

If I go into google browser and type in the name of a website, this is the application layer of the OSI. HTTP protocol is being used and is a request-response, so when exactly does my computer send ...
ED2468's user avatar
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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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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 ...
idontknow's user avatar
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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 ...
quanecon's user avatar
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167 views

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 (...
user129393192's user avatar
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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 (...
whoisit's user avatar
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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 ...
George Hodgkins's user avatar
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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 ...
Gili Nachum's user avatar
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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 ...
Eric's user avatar
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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 ...
feter's user avatar
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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 ...
Rama Siva Subrahmanyam's user avatar
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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 ...
Aamod Thakur's user avatar
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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 ...
altoid's user avatar
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1 vote
2 answers
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Do all computers use parity checking? When does it happen?

I know that parity checking is testing for accurate data transmission between nodes in a communication network. When does this parity checking happen on a computer? Does it happen every time data is ...
gurung's user avatar
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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 ...
Jun Seo-He's user avatar
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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 ...
Ramon Zarate's user avatar
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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?
new_be's user avatar
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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 ...
Giovanni's user avatar
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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 ...
Karla's user avatar
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Can anyone please help me understand the definition of Store-and-Forward delay from the Kurose and Ross Networking Book?

I have gone through the questions related to store-and-forward and transmission delays but they didn't answer my question. My question is directly related to one of the excerpts in the book (Computer ...
shiva's user avatar
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Would 256.256.256.256 be considered a valid hostname?

We know an valid IPv4 address is each part not greater than 255, so, will 256.256.256.256 be considered a valid hostname rather an IP address? I'm just curious how ...
huang's user avatar
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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 ...
user3699192's user avatar
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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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2 votes
1 answer
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How do distributed joins work in a distributed relational database system?

I have been looking around for a few days trying to find a clear and concise description of how, at a technical/implementation level, how distributed joins work, but haven't found much. The best so ...
Lance's user avatar
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1 vote
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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 ...
Packeto's user avatar
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3 votes
1 answer
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How does a single-node system get Availability in CAP theorem?

I have a question. I read many blogs, websites about CAP theorem. They say that single-node systems are CA, but how can it be "A" if that single node goes down ? Because if it does, the ...
Sake's user avatar
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Finding efficiency in Stop and Wait protocol

Suppose that the stop-and-wait protocol is used on a link with a bit rate of 64 kilobits per second and 20 milliseconds propagation delay. Assume that the transmission time for the acknowledgment and ...
Sameer Raj's user avatar
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Can this algorithm achieve eventual consistency?

There are $M$ interconnected nodes in a peer-to-peer network. Initially, each node numbers itself with any integer from $1$ to $N$, $N \leq M$. Each node counts the most occurrences of neighboring ...
leslie-wung's user avatar
-1 votes
2 answers
79 views

How does ssl handshake secures TCP connection?

I will explain whatever I understand about SSL handshake or simply SSL. First client sends hello to server Server sends signed certificate with its public key. Client checks if certificate is valid, ...
jacnab's user avatar
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1 answer
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Queuing delay in packet switched network

So I was going through the exercises in the 'Kurose and Ross' book. Suppose users share a 2 Mbps link. Also, suppose each user transmits continuously at 1 Mbps when transmitting, but each user ...
Gopalakrishnan Ganesan's user avatar
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the store and forward mechanism transmission delay

In a computer network, the store and forward mechanism is used. In this mechanism, the packet is sent from one system to the next along the network path, and in the second system, the complete packet ...
Solo Developer's user avatar
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1 answer
131 views

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 ...
7p4's user avatar
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2 votes
1 answer
580 views

What is difference between fetching, accessing and downloading in web?

I need more clarity about what is the main difference between fetching, accessing and downloading in web? which is differentiating these three words in web?
kaviyarasu's user avatar
1 vote
2 answers
201 views

How do websites verify that an email exists during the registration process?

Everybody knows that if you try to register to a website with an email that does not exist, the website labels the email as "invalid". How do they know that?
user144536's user avatar
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1 answer
1k views

Which one of the following is NOT a function of transport layer?

A. routing B. flow-control C. congestion control D. All of the above My guess is flow-control only because routing and congestion is part of the network layer. The network layer is the third later and ...
Manoj Selvakumar's user avatar
1 vote
2 answers
407 views

Why timeout in TCP is not a predefined fixed value?

Why timeout in TCP is not a predefined fixed value? I know there is a set value of 15 for a timeout value but I was asked why timeout in TCP is not a predefined fixed value which I couldn't find an ...
Manoj Selvakumar's user avatar
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1 answer
551 views

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? ...
Flumpo's user avatar
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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 ...
berimbolo's user avatar
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2 votes
0 answers
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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 ...
shino's user avatar
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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|}\...
Bob's user avatar
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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 ...
S. M.'s user avatar
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