Questions tagged [computer-networks]
Questions about problems that arise when you connect multiple computers to form a network.
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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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22 views
The technical definition of a packet in computer network theory
In wireless communication , I understand what it means to transmit a "bit" .
There will be a signal of certain frequency, $ \omega $ which is transmitted .If the amplitude crosses a threshold then ...
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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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21 views
What are resources in computer networks? [on hold]
Examples of resources in computer networking are printers,file servers,internet and others. What is the definition of resources?
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18 views
What are resources in computer networking? [on hold]
What is the definition of resource in computer networking?
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19 views
How can I calculate attenuation from signal strength values? [on hold]
I want to measure attenuation caused by a material. In order to do this, I first measured the signal strength of the access point which is my mobile phone (hotspot). Then, I wrapped my phone with the ...
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24 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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16 views
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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1answer
37 views
What are the things one can do with the internet without the World Wide Web? [on hold]
If the question above makes any sense!
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30 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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1answer
77 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
22 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
27 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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Does the secrecy rate decrease as the number of users increases when the number of transmitter antennas is fixed?
I am a student who started studying network communication.
I want to find secrecy rate. e.g. I have 3 transmitter antennas and 2 receivers where eavesdropper wants to eavesdrop the communication.
Tx....
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1answer
19 views
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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0answers
43 views
CISCO Packet Tracer Subnetting
I am learning subnetting, and I am using Packet Tracer to design a network for a building with five storeys. I have used subnetting, with each floor having its own subnet. As a result, it is not ...
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1answer
41 views
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
44 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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0answers
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If the generator has more than one term and the coefficient of $x_0$ is $1$, all single errors can be caught
I am trying to understand criteria in designing generator for different types of errors. I do not understand why the term $X_0$ should be $1$ ? If the term $X_0$ is $1$, it means our $g(X)$ is an odd ...
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2answers
27 views
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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What is the arrival data distribution for a base station with respect to integrated QoS classes?
If I classify all data as interactive voice, interactive video, streaming video, bulk data, best effort....
Then what is the percentage of these data for a general base station?
You can consider the ...
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1answer
49 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
40 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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51 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
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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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2answers
295 views
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
36 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.
...
3
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1answer
53 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
89 views
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
51 views
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
118 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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0answers
40 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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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
25 views
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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217 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 ...
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Designing and implementation a publish subscriber system [closed]
I have to build a simple publish-subscribe system in say C++ for example that can handle multiple subscriber. I have never done anything like that although I have made HTTP server and client, but not ...
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19 views
A network that can not be completely blocked
There is the idea of implementing a network (in the sense of a group of servers on the internet), access to which could not be limited in practice.
For convenience's sake, let's call this network a ...
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Train Communication (networking)
I have an essay question and I just want to make sure I have things right.
2 trains need to be able to communicate with eachother at any time.
Based on research i've settles on a wired network ...
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Slowstart, fast transmit and fast recovery
I have some questions for tcp slowstart that i can't seem to find an answers for.
When a packet is lost, when do i start the timer for a timeout?
On a packet loss do you continue sending packets ...
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How to calculate a required channel capacity for server?
We have a server that can accept and send files to clients. How can I calculate a required channel capacity (How much does my program load the network) to know what network channel should I provide ...
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1answer
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how applications send tcp data to internet?
What i know is that applications create "socket"(visualized concept for high level programmers),the socket will address the ip addresses and send to internet and forward the feedback data.What i ...
