Questions tagged [computer-networks]

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

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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 ...
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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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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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why during low load the channel efficiency is d/(d+N) whereas during high load the channel efficiency is d/(d+1) in bitmap protocol?

This excerpt is from Computer Networks by A Tanenbaum page 271. It's about channel efficiency in bitmap protocol which is one of Collision free protocols. My question is why during low load the ...
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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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Headers in data link layer protocols and network layer protocol

Despite being adjacent in a protocol stack, Data Link Layer protocols and Network Layer protocols each employ a number of similar fields in their headers (i.e. a field named 'X' appears in the headers ...
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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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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 ...
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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 ...
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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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If I open & connect with 1 protocol to every port (all 65535) can we still open another protocol socket?

I understand and have googled how TCP & UDP can work simultaneously BUT does this assume there are unused ports to dynamically allocate? So if all ports are used by TCP can UDP still connect & ...
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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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Vulnerable Time in ALOHA

Why do we not consider the Propagation Delay (Tp) and only the transmission delay(Tt) while calculating the Vulnerable Time is ALOHA? A collision may occur even after the frame has been put on the ...
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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 ...
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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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With suitable example briefly explain the function of service primitives for execution of protocols in a protocol suite

I am searching about the function of service primitives for execution of protocol in protocol suite got this Service Primitives were formalised for each protocol in OSI reference model. Each protocol ...
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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 ...
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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 ...
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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 ...
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Calculate the probability that a second packet is received before the first packet leaves the router in M/M/2/2 model

$\textbf{Question:}$ Given an M/M/2/2 model with an arrival rate $\lambda$ and a service rate $\mu$, I need to calculate the probability that a second packet is received before the first packet leaves ...
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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, ...
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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 ...
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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 ...
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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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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?
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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?
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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 ...
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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 ...
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Method for minimizing relays in a switching/steering network - combinatorics/CSP algorithm exists?

This question is borne from the electrical engineering world, so I first asked it there, but it's really more of an algorithm optimization problem that everyone here might be better suited to help ...
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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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What are the chances of fusing a quantum computer and a parallel computer and what potential dangers/ benefits does it bring?

From my EPQ research I came to know that quantum computers require certain conditions to function optimally such as: low temperature so that electrons do not get disturbed etc. I've also read a book ...
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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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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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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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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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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 ...
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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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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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1 vote
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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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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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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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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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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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