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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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Could Web 3.0 exist without cloud and vice-versa? [on hold]

I would want to know if could web 3.0 exist without cloud and vice-versa? Would I want to know also why? and some examples. Thank you.
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Calculating p-persistent CSMA Network probability

Let's say that, in a p-persistant CSMA network one station, X, is ready to transmit data. All other stations are idle for 5 time slots after X has become ready. What is the probability that X ...
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Finding current levels when encoding information in a channel

I am stuck with the following question: In a noised channel with a bandwidth of 4 kHz that has the signal-noise ratio of 30 decibels, if it is known that the maximal broadcasting speed is 16000 bps,...
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Maximal number of parallel cellular calls with no adjacent cells in a hexagonal setting

Is it possible to find an optimization to the following theoretical case? Given is a cellular (phone) system with hexagonal cells, where the volume of transmission and the size of the cells are ...
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A file is sent from host A to client B, the packet passes through router R on its way to B. Calculate the total delay for the file to reach B

This is a question from an old exam that ive been trying to work out: The 40000 bit file is split into 10 packets with a 400 bit header added to each packet The link from A to R is 500 km long and ...
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1answer
52 views

Network throughput with random delay selected from uniform distribution

Background: I am working with IoT devices which broadcast status messages over a wireless channel periodically and at a rather high rate (500-5000 Hz). Receiving every message is not crucial but the ...
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Networks-on-Chip : separable allocator VS wavefront allocator

How is separable allocator different from wavefront allocator ? See page 86 and 87 of On-Chip Networks, Second Edition Synthesis Lectures on Computer Architecture
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Application deployement and network models [closed]

I am a self-taught in computer science. I am interested on have a robust test book on which study the nut and bolt of application deployment. I mean all the processes involved in getting new software ...
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1answer
11 views

Maximum number of nodes connected when the link has a large buffer

A link of capacity 100 Mbps is carrying traffic from a number of sources. Each source generates an on-off traffic stream;when the source is on, the rate of traffic is 10 Mbps, and when the source is ...
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1answer
23 views

What is the name of the domain or theoretical problem of transmitting game states in an online game

For example, in chess (or any online game), you broadcast the game state to other players at certain times (every n-milliseconds or after a move is made). Thereupon, a player's game client renders the ...
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a key step in speech processing is to extract the “words” appeared in the conversation?

You overheard a computer engineering student saying that a key step in speech processing is to extract (or “tokenize”) the “words” appeared in the conversation, pretty much like what a compiler needs ...
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transmit delay end to end

If PC1 divided the original packet (1.5 MB) to three equal packets (each packet is the length of 512 KB), then how much time is needed to transmit the 3 packets back-to-back. how can i solve this ...
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44 views

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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1answer
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Why does packet delivery time only count transmission time once?

Why is packet delivery time equal to transmission time + propagation delay, and not equal to 2*(transmission time) + propagation delay? At the end of packet delivery time, doesn't that mean that ...
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2answers
52 views

How to decide which bytes will form a packet ?(computer networks)

In wireless communication , I understand what it means to transmit a "bit" but I wanted to understand what exactly does it mean by a packet . *******POST EDIT/RECEIVING INITIAL ANSWERS******* I got ...
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Stop and Wait Efficiency

A sender uses Stop and Wait protocol for transmission of 8000K bits size frames on a 1Gbps satellite channel with a propagation delay of $400ms$.What will be the link utilization(in percent),if ...
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28 views

Computer Networks, bandwidth calculation

I don't know if this is the right place to ask this kind of questions, but I'm a little desperate and I can't find the answer to this Computer Networks exam question. "A point to point 1000 km ...
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Understanding acknowledgement mechanism in sliding window protocol

I came across following problem: Node A sends packets to B through router R. The link A-R is instantaneous , but the R->B link transmits only 1 packet each second , one at a time . Assume A sends ...
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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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1answer
78 views

Private IP and public IP

What we see on our devices is essentially the private IP given to us by the ISP; thereby, whenever we access the internet, this private IP is first converted to public IP (by ISP through NAT), ...
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1answer
32 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
30 views

The role of the root switch after Spanning Tree Protocol has established a tree network in a LAN?

In Spanning Tree Protocol, a root switch is selected at first, and then somehow, the shortest path from each other switch to the root is obtained. Thus we established a tree network. My questions ...
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1answer
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What exactly is transmission time?

Seems very trivial but I'm confused which one of these correctly define transmission time. Time taken by a message to reach receiver. Time taken to push message on the link by the sender. Which ...
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Stop and Wait retransmission of packets?

In a communication link out of p packets one packet will be lost. If stop and wait protocol is used then expected number of retransmissions for a packet? (A) P/(1-P) (B) P (C) 1/(1-P) (D) 1/P I ...
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1answer
160 views

The min number of distinct sequence numbers required to ensure correct operation of the ARQ scheme is

In a sliding window ARQ scheme, the transmitter's window size is N and the receiver's window size is M. The minimum number of distinct sequence numbers required to ensure correct operation of the ARQ ...
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Anonymous Visibility Check in P2P networks

I'm working on a problem for a P2P network for games. The problem is the following: Consider two opponents on a grid, each stores it's own position. Player 1 wants to know if it sees player 2. In ...
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1answer
39 views

why not just one header in TCP/IP?

I was reading through the computer network fundamentals. I noticed that there are headers added at each layer in the OSI model. However, can we not have just one header above the App layer that ...
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2answers
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When packets are not full?

When in computer networks it happens that the packets are not full? I have heard that sometimes in UDP that happens, if that’s the case, why not all the space is not used?
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1answer
53 views

Paxos Consensus

how does Paxos Consensus algorithm behave in an asynchronous environment? Because as far as I know Paxos only work in synchronous environment. Correct me if I am wrong :) Sorry for the noob question,...
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1answer
43 views

How can average queuing delay exceed 1 if the $La/R \leq 1$?

Consider a router with a packet arrival rate of $a$ where each packet has $L$ bits, and a transmission rate (in bits/s) of $R$. My textbook describes the traffic intensity as $\frac{La}{R}$ and states ...
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73 views

What will happen if congestion window size touches to zero in congestion control mechanisms in TCP?

Folowing is the Congestion Control Window graph of TCP. What will happen if Congestion Window reaches to zero when timeout occurs ?
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1answer
17 views

Is it possible to give a guarantee about the accuracy of the local time?

Assuming there is no attack/bug and I use NTP: Are there any formal guarantees about the accuracy of the local time? Can there be any over the network? Even if the communication is going directly ...
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Local to global algorithms in gossip based P2P networks

Suppose we have a peer to peer network of, say, $n$ peers. Peers communicate by an asynchronous randomized gossip protocol (Push, Pull, Push/Pull doesn't really matter here). The task is for any local ...
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Does UDP always deliver packets inorder to the application layer

I was reading about UDP and TCP. TCP is a stream-oriented, connection-oriented protocol and always delivers the segments in order to the application layer. But UDP being connectionless, does it also ...
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1answer
56 views

IP Address CIDR Bitmask Conversion

In looking for a programming function to validate an IP address within a subnet, I had to calculate the subnet mask from a given CIDR bitmask value ie. 192.168.0.0/24, the value 24 in this example. ...
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1answer
57 views

How to distinguish between bits?

I read a post about differences between synchronous and asynchronous transmission modes. That post has a picture about how bits flows from terminal to computer in async mode. But how computer can ...
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2answers
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What is the difference between “backhaul” and “core” network in cellular networks?

I was reading some publications on cellular networks. They constantly mention two similar concepts — backhaul network and core network. I am not sure if these two are the same stuff, or in any way ...
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2answers
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Password authentication over an insecure connection

I was thinking a way to send password to server secure way without using secure connection,I found one solution.I want to find flaw in this.(Note: I am begginer,dont judge me, I know little about ...
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CDMA vs FDMA vs TDMA efficiency

I am taking a course in Computer Networking and got the following question. Defining efficiency in terms of resource utilisation, CDMA (Code Division Multiple Access) with a chipping sequence ...
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1answer
136 views

CSMA/CD with binary exponential backoff: Do both back off or just the loser?

I've been given two PC's that are connected via Ethernet, and as such are using CSMA-CD with binary exponential backoff. Now, both PC's, let's call them $A$ and $B$, are trying to send data ...
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42 views

Agreeing on a Time in a Trustless Network

Imagine a chord-like network $N$. each machine $m \in N$ is directly connected to $N_m \subset N$. Without relying on official timeservers, I want all machines to synchronize to some time with ...
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1answer
63 views

Two dimensional 3 bit parity check

Can someone explain how do we find these parity bit errors?
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1answer
40 views

How to make smart contracts work in a small network?

Suppose we have a small computer network, there are 30 random people who have provided their computers to perform any computational tasks on them. Let's call these 30 computers nodes. We can access ...
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Relevance of Pure ALOHA for small network load G?

The theoretic performance of Pure ALOHA networks is a vastly studied topic and references can easily be found , e.g. on https://en.wikipedia.org/wiki/ALOHAnet#cite_note-tann-14 Using a Poisson ...
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1answer
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how to defend against DOS caused by SYN cookies? [closed]

i have read about SYN cookies and i understood that they help to avoid DOS .. BUt my prof wants an answer as how SYN cookies can be used to cause DOS and how can it be avoided ? any help woul dbe ...
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Binary Exponential Backoff

I have a frame X, where it says K = 512 bit transmission times. And for the first collision I have to wait either 0 or 1 slot times. For the second I have to wait {0,1,2,3}*K time units, 3rd collision ...
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1answer
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How come Datagram Packets between same source-destination pair may take different routes?

This might be a rookie question, but I wanted to understand, the following line. My book says, each time a host wants to send a packet, it places the address of the destination host in the packet's ...
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290 views

Go-back-N ARQ Question

I am trying to solve the following problem but i do not have the final answer A system uses the Go-back-N ARQ Protocol with a window size of 7. If each packet carries 1000 bits of data, how long does ...
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Concurrent server with preallocated Threads

Can we implement a mechanism described below with mutex and a condition variable? If yes, then what r the structures, code of the master and slave threads used in it? Mechanism -" Consider a ...