Questions tagged [computer-networks]

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

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Problem on probability given frame sizes and their error correction probabilities in a wireless system

I am stuck trying to solve the following question for a while Bit error rate after demodulation in an wireless system = 1.0e-03. The system has 4 possible frame sizes – 48 bytes, 96 bytes, 72 bytes ...
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Why should you use IP addresses instead of hostnames when using Sockets?

I am currently trying to send Get requests to a website, and it takes longer to find the IP address than to just use the hostname. I've been told this is better but why?
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How to reconcile the different definitions of asynchrony?

There are 3 definitions of asynchrony that I know of: In event-based programming, asynchrony refers to the execution of tasks in a non-sequential way, which may involve creating another thread. For ...
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multicasting in ethernet

I am learning this topic and there is a concept that LSB ( bit ) of MSB ( byte ) should be set to 1 for multicasting . But why we need to do so as multicast address is unique so why can't we assign ...
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What are overlay & underlaying topologies in DHT?

We are covering Distributed Hash Tables in my "Networks" class and one of the subsections is about the improvements that can be made to increase the performance of the chord. Here, the ...
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The size of frames generated in transferring files

An application sends a $5*10^{10}$ bytes file. The next layer breaks the file into a number of segments. Each segment carries 1400 bytes of file data and 24 bytes of headers. Then, a segment is ...
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Cache structure in a particular case

A memory unit consists of 64KB of main memory, 1 KB of cache memory organized in direct mapped cache the cache line consists of 16 bytes. What is the size of address bus? How many bits are required ...
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Storing Network Packets in Tabular Form

For network packets coming over TCP/IP protocol, have you ever confronted a situation where you need to store those network packets in tabular form similar to how tabular tables in databases? For ...
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55 views

How a 10GB network can copy 1TB data in 2 hours?

In the slides of a university lecture, the following phrase got my attention. Assuming 10GB network, it takes 2 hours to copy 1TB. My calculation was as follows. 10GB network = 10 gigabits per ...
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Calculate effective throughput for file transfer

Consider a file of 3MB that needs to be transmitted over a 1Gbps link with RTT of 80ms, What is the effective throughput? A) 36.2  Mbps B)  9.26 Mbps C)  9.9  Mbps D) 28.85 Mbps Here is what I did - ...
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Does the host operating system know the content of your messages in a messaging applications?

Let's say you are using a messaging application (Microsoft Team, Skype, Telegram,..) on an operating system (Windows, MacOS, Linux). Does the OS know what you are sending or receiving? If yes, how? ...
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modelling communication costs on a network

Consider a set of $N$ computers. Each computer needs to send some data to $K$ other computers, and each computer is receiving data from $K$ other computers (ie. the communication pattern can be ...
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Can someone explain how to calculate what time each host started and finished?

The diagram at right shows a WIFI network with an access point, X and three hosts, A, B and C. The large circles indicate the coverage areas of the three hosts. The coverage area for X is not shown, ...
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Two Generals' Problem Definition

I've read various descriptions of the TGP, most of which seem vague or conflicting on the precise constraints of the problem. Specifically: is it always or sometimes impossible to reach consensus ...
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Computer Networks Link layer error detection

I am aware that Link-Link error detection and correction takes place as an optimization to the error detection taking place at the Transport Layer at the destination host's end. I was wondering if ...
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Throughput of slotted ALOHA when one node goes out of sync

What would be the throughput of slotted ALOHA when one node goes out of sync? Closer to ALOHA or slotted ALOHA? According to my calculations: For ALOHA we have probability of success = $N \cdot p \...
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Automated API negotiation

Is there a way for two programs or computer nodes to communicate with each other without knowing each others APIs? Or is there a least a reasonable approach to make them talk in some settings? Let a ...
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Is there any guarantee in asynchronous systems?

We know that in an asynchronous system, no assumptions about process execution speeds or message delivery times are made. My question is: can we present any guarantee in asynchronous systems? Some ...
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How do I compress data vectors in broadcast messages?

Let us model a wireless broadcast network as an undirected graph $G(V,E)$ where there is an edge between every pair of nodes ${i,j}\in V$ if they are in transmission range of each other. $w_{i\to j}$ ...
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Calculating minimum frame size

I'm actually quite stuck on a question I have for an assignment...I'd appreciate any help with this: Consider a CSMA/CD network with maximum cable length of 8km and where the ratio of > ...
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Decode TCP Payload data

I'm trying to find out what the data of a packet means. I'm a newbie to networking, and I try to find what's sent in this packet: https://pastebin.com/hZEqjmBx How can I do that? What does that data ...
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Application for large graphs compression

I am looking for an application in which it is desired to perform an efficient lossy compression of very large graphs, that preserve the general structure of the graph but may delete some edges. Can ...
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Finding the approximate weight of intra graph paths

Say that you have access to a source $a$ and destination $b$ in a weighted graph $G$ with $n$ vertices. There exists a path $p$ from $a$ to $b$ with 2 or more vertices in it. We know the total cost of ...
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Is it possible to transmit bits digitally?

I have learnt that all data transmission is analog. Is there any mediums that could transmit bits digitally?
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Andrew Tannenbaum exercise

A bit string, 0111101111101111110, needs to be transmitted at the data link layer. What is the string actually transmitted after bit stuffing? There isn't any END DELIMETER given here, Answer given ...
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SSID evaluation within the 802.11 protocol

Inspired by a question on superuser, I was reading up on the 802.11 protocol. This made me wonder if the SSID is actively used outside the authentication and association process. I know that it can be ...
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network question on Go back n

A Go-back-N sender just receives an ACK packet with sequence number 𝑡. Before this ACK is received, sender’s window is [𝑘, 𝑘 + 𝑁 − 1] where 𝑁 is the window size. Suppose 𝑘 > 𝑁, packets may ...
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Socket API in TCP

According to me Statement S1 and S2 is True while S3 is False. The Solution says 'S3' is correct ? Am I Wrong ? Kindly help with explanation . I know Connect() in TCP is used by the client side for ...
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Mainstream publication venues for Internet of Things (IoT)

I am interested in reading the research literature on Internet of Things (IoT). I am especially interested in theoretical research (eg. papers where techniques from graphs or algorithms are utilized)....
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Probability of loss using a binary symmetric channel

Today we talked about Information Theory and the binary symetric channel. For newbies here is a little explanation : For instance if I want to send a binary to someone : The bit will be "flipped&...
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Can we improve internet speed by serializing timestamps?

If we (scientists) came up with a way of representing numerical timestamps as letters hence reducing the number of bytes needed to represent timestamps, would that mean an improvement in internet ...
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Does an insecure router bypass the privacy guarantee of a VPN connection?

If I have a router that has a vulnerability that allows an attacker to gain full control it, does using a VPN on the network with the said router prevent an attacker from being able to snoop on the ...
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Is this applet implementation for the Go-Back-N ARQ protocol correct?

I was reading a textbook describing the Go-Back-N (GBN) protocol with Finite State Machines as pictured below: $\Lambda$ just means "initial state" or "no action", depending on ...
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Go-Back-N Protocol not efficient?

Let's say we have five packets p1 p2 p3 p4 p5 to be sent sequentially: and for some reasons, p3 got delayed so it the the last packet to arrive recevier. so below is the receiving order on the ...
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Computer networks - Can there be an out of order frames in a noiseless channel?

In a noiseless channel can frames in the 2 layer of OSI model(Data link layer) reach to the destination out of order? *I am studying from Computer networks 5 Edition of Andrew S. Tanenbaum
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Can application DNS requests bypass a firewall on Windows and Linux

Assuming I have firewall set to block an application from accessing the Internet, would I DNS request go through? I tried using C (gethostbyname) on Windows and the answer is no. It seems that the ...
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What is the meaning of this error message I get when downloading documents?

Every so often I'll hop on my laptop, open google, and eventually try to download and open some document, only for the document to wind up looking like this: What on earth does all this mean? What ...
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How to solve Bluetooth intermittent connectivity in multi hop communication?

In a specific area mobile devices are connected with Bluetooth multi-hop connectivity with intermediate mobiles for data communication purpose as per in below figure. Now in scene 1 from source (MD1) ...
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How private IP address is determined?

Today I presented about IP address during my online class based on Computer Networks by Andrew S. Tanenbaum and during QnA session, I was asked about private IP Address range. ...
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Does RLNC (Random Linear Network Coding) still need interaction from the other side to overcome packet loss reliably?

I'm looking into implementing RLNC as a project, and while I understand the concept of encoding the original data with random linear coefficients, resulting in a number of packets, sending those ...
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Is IP masquerade and Network Address Port Translation(NAPT) the same?

Is IP masquerade and Network Address Port Translation(NAPT) the same? I'm not sure whether it is the same thing or not but I realized the mechanism is almost the same where both IP masquerade and NAPT ...
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What does route aggregation is an automatic process means?

Here is an excerpt from Andrew S. Tanenbaum, Computer Networks, 5th edition, Chapter 5 (The Network layer), page 448: When aggregation is turned on, it is an automatic process. It depends on which ...
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Difference between DNS Spoofing and DNS Hijacking?

DNS Spoofing and DNS Hijacking, both of them basically are type of attacks where the request is redirected to some other malicious website or some other web page. But I did not find some concrete ...
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Why are processes on the internet not required to use TCP or UDP?

Here is an excerpt from Andrew S. Tanenbaum, Computer Networks, 5th edition, Chapter 5 (The Network layer), Page 455: [Fifth, processes on the Internet are not required to use TCP or UDP. If a user on ...
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Why NAT is a disadvantage when TCP source port field is 16 bits?

Here is an excerpt from Andrew S. Tanenbaum, Computer Networks, 5th edition, Chapter 5 (The Network layer), Page 455: My question is on the second paragraph. From what I understand, basically this ...
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Possible error in Computer Networks, V Edition by Tanenbaum & Wetherall

Under section 5.4 Quality of Service on page 404: Multimedia applications in particular, often need a minimum throughput and maximum latency to work. Isn't this statement incorrect? Shouldn't it be :...
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MAC protocol with throughput of 1

Consider a MAC protocol (ALOHA, CSMA, TDMA, etc.) that, even for very high loads, always results in a throughput of 1 (normalized with respect to the channel speed). Why is that not good if the ...
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Why does Slotted Aloha work?

So the way I understand it, if station A and station B, for example, try to transmit a frame at the same slot, a collision occurs, leading to an attempt at the next slot. But wouldn't the algorithm ...
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118 views

'Half-Close' figure of Data Communications and Networking, 5/e

In the Figure 24.13 of Data Communications and Networking, 5/e the first ACK message from the server holds y-1 in it's Sequence no. field. Note that the first FIN ...
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What are some advanced background topics I'll need for distributed systems and networks research?

I am a new graduate student in Computer Science who would like to be able to read and understand modern and new distributed systems research papers. My current background / courses and understanding ...

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