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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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3
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2answers
2k 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
381 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
84 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 ...
2
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2answers
1k 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
109 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 ...
3
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1answer
281 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
45 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
1k views

Two dimensional 3 bit parity check

Can someone explain how do we find these parity bit errors?
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1answer
43 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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1answer
34 views

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 ...
4
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1answer
85 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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0answers
17 views

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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0answers
56 views

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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1answer
38 views

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 ...
3
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0answers
113 views

How does a vpn connection work?

I have been looking into vpn (virtual private network). And I wanted to know more about the theory, how does it work really: what does it do with the packages? why is it secure? (or why can it be ...
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0answers
146 views

CRC: false positive under some circumstances

Consider two computers $A$ and $B$. $A$ uses $G$ and $B$ uses $G'$ for the CRC computation. It is given that $\deg G \ne \deg G'$. Computer $A$ wants to send a data $D$. The claim says that: There ...
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1answer
109 views

Counting to infintiy problem

I came across this explanation for count to infinity problem However, i don't understand that after the BC link broke, followed by which B erroneously updated the path to C at a cost of 3; Now why ...
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2answers
763 views

Why is RTS/CTS optional?

I was reading in Wikipedia about it and one of the main things that were pointed out was that it is only an optional mechanism. This bugs me more than it should as I cannot find any information that I ...
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1answer
2k views

How does Server know window size for TCP Header?

I'm trying to understand TCP right now. In the header there is "Window Size" which to my understand is the maximum amount of data that can be sent at once. My question: How does the server know how ...
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1answer
284 views

Subnets in computer network

Question: Given: Class B IP address 169.202.0.0. Network when divided into 4 sub networks, each one requires 16,000 IP addresses. They need to be assigned sequentially without gaps. Find the sub ...
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0answers
872 views

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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3answers
8k views

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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0answers
40 views

How many times does a pair of numbers co-occur in a list?

Imagine you have N distinct people and that you have a record of where these people are, exactly M of these records to be exact. For example ...
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0answers
77 views

Broadcasting in Cable Internet: How does it work? [closed]

Sorry for the long post. I tried to make it small but couldn't make it any smaller. Any help would be really appreciated. It would be great if you can explain from the basics. In the book "Computer ...
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1answer
833 views

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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2answers
3k views

What is bit time in Ethernet CSMA/CD

"Propogation delay betwween two links is 200 bit times" I am little confused here, Propogation delay should be in seconds, milliseconds etc but here it is in bit times. I also want to know what is bit ...
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1answer
269 views

Difference between bit times and milli seconds

The propagation delay between two links is 200 bit time .....i want to know what is the difference between 200 bit time and 200 mill seconds
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1answer
33 views

Does two system's clock synchronises to communicate with each other?

If two computer system's has to do some kind communication like data transfer or receiving should its clock sync to do that?If not then how they transfer bytes without having syced clocks?
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5answers
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Why is the vulnerable time in pure aloha twice the frame time?

The time required to send a frame is called frame time. Vulnerable time is the time during which no transmission should be done to avoid any collision. My question is what kind of problem will be ...
1
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1answer
468 views

When you do a remote desktop connect to another pc which pc's processing power do you have? [closed]

Are you just accessing the data and things on the PC you are connecting to or, if it had a better processor/ram/etc, are you able to take advantage of that?
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1answer
515 views

Computer Networks: Does integrity depend on confidentiality?

I'm taking the course computer networks and we currently had our second lecture. We got the following question: What are the differences between integrity and confidentiality of a message? Is ...
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0answers
20 views

Degrees of Separation Minimization & Pathfinding Elimination Strategy for Large Networks

Assume you have a graph/network N; Boundary Conditions: each vertex/node $n \in N$ can support a maximum number of $e_{max}$ connections Nodes can join and leave the graph. Each node $n$ has an ...
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0answers
136 views

calculate signal to noise ratio

I am trying to calculate a signal to noise ratio to achieve a rate of 300Mbps on a bandwidth of 3Mhz. The shannon capacity formula C = B*Log(x,(1+SNR)) should be ...
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2answers
58 views

How does a computer distinguish two separate transmissions on a wire

My basic idea of networking at the lowest layer is that one computer will send a bunch of parallel bits at a time down a cable and another computer will read these bits. For example, computer #1 ...
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0answers
137 views

Probability in Dynamic frame aloha

If I've RFID Collision Arbitration System that is based on multi-frame dynamic frame ALOHA. How can compute the probability of the average tag resolution $L_n$? ,$P_s$ is probability for packet ...
3
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3answers
2k views

Minimum frame size in ethernet

Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48-bit jamming signal is 46.4 μs. The minimum frame size is: a) 94 b) 416 c) 464 d) 512 My approach:- I have read in the ...
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1answer
7k views

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. ...
1
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1answer
1k views

Number of Retransmission in case of Go Back N

While Going through Exercise problem of " Computer Networking A Top-Down Approach" by Kurose and Ross, i encountered this problem.I am giving my approach and the point where i am stuck at. ...
2
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1answer
86 views

IP Fragmentation

I have an IPv4 packet, 3523 byte of information Data a MTU (maximum transmission unit) of 516 (496 byte + 20 byte IP header), also an TCP header with 20 byte. How does this result is created from the ...
10
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1answer
31k views

TCP Connection Termination - FIN, FIN ACK, ACK

I've been reading that to terminate a TCP connection 3 handshakes are required: FIN, FIN ACK, and ACK. However, when closing a connection, Wireshark displays FIN ACK, FIN ACK, ACK; it never displays ...
3
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2answers
72 views

Hashing methods for validating dowloaded files

The standard algorithm to generate hashes of files which are downloaded is MD5. For example, when ISO files of Linux distributions are offered most of the time they also give the MD5 sum so that you ...
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2answers
789 views

Difference between Bandwidth and Propagation Speed in computer networks?

I want to know the difference between Bandwidth and propagation speed. How are they associated with each other i.e. the impact on bandwidth if propagation speed varies or the impact on speed if ...
3
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1answer
2k views

Combine the following IP Addresses into a single block

I was asked to combine the ip addresses into a single block: 16.27.24.0/26, 16.27.24.64/26, 16.27.24.128/25 I managed to convert the given ip addresses into binary: 00010000.00011011.00011000....
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1answer
3k views

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 ...
1
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1answer
128 views

Lower limit on the number of check bits needed to correct single errors

I was going through Andrew S. Tannenbaum's computer networks book, and on page 206 of it, he has derived the number of check bits needed to correct single bit errors. The derivation goes as follows: ...
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0answers
40 views

What are networking technologies to distribute the file faster with storing on more replicas?

Question: Suppose you launch a job on 10,000 machines in your own data centre. The job is slow to start because all the machines are trying to load the same large executable file. Name two networking ...
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1answer
202 views

Do networking ports come from "port-mapped I/O"?

Do networking ports come from "port-mapped I/O"? I was watching a hardware basic video by Brian Will: https://www.youtube.com/watch?v=9-KUm9YpPm0 And they brought up this concept at 18:15 ...
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0answers
96 views

Paris-Traceroute and Traceroute Difference

I am trying to understand the difference between Paris-traceroute and normal traceroute. I am using this website ( https://paris-traceroute.net/about) and trying to get the idea, what is Paris-...
1
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1answer
43 views

New Idea for accessing memory across an inter-network connected system

I have the following idea for a network-based operating system. Suppose we have two computers A and B in a network. If computer B wants to access the memory of computer A, it can access by using the ...
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2answers
156 views

If all frames are naturally broadcast in a LAN, what is the need for a broadcast address?

The Ethernet MAC address FF:FF:FF:FF:FF:FF is reserved for broadcasts. If all frames are naturally broadcast in a LAN, what is the need for a broadcast address?

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