Questions tagged [computer-networks]

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

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What are possible formats of URL? [closed]

I know that you can access a website via a web browser using the following address formats: https://google.com 216.58.208.174 However, I have been told that you could use hexa and other formats. Can ...
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20 views

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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31 views

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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Calculate the probability of undetected errors for the whole file (not packets) in the CRCs

If we have a large file, I want to know how this will affect the probability of undetected errors, especially in CRCs. I know that undetected error rate (packet or chunk) is BitR * BER * 0.5k where k ...
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1answer
19 views

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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1answer
36 views

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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1answer
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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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1answer
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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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1answer
98 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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Finding the timestamps of processes implementing Lamport's clocks

I have been asked this question, but don't know how to go about answering it. Three process, which are implementing Lamport's clocks, are running and a lot of events are taking, place including some ...
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1answer
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Manually Performing ECB & CBC

I am learning about block ciphers and while I understand the concept of Electronic Codeblock mode and cipher block chaining, I could not find any relevant practical examples online. Can someone ...
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Proper network address

Which of the following are proper network (not host) addresses? 192.168.23.0/24 193.205.16.132/26 172.16.4.0/20 10.57.13.64/28 How can I tell? What is a proper network address? Is a proper network ...
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1answer
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binary representation of ip prefixes

How does an ip prefix 90.0.0.0/4 translate to 0101∗ in binary and 10.0.0.0/2 to ...
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2answers
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What is the the relation between the amount of data transmitted and line distance?

I am wondering what is the relation between line distance and the amount of data transmitted on that line. I know only the basic of computer science. Let's say I want to calculate the time it takes ...
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1answer
21 views

RPI cluster performance related to network performance

I'm writing my thesis and i have built a RPI cluster, containing 10 nodes which consists of RPI model 3b. I've them connected to two gigabit switches. I don't know the CAT of the cables. They are not ...
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encrypt with permutation ciphers

I came across this question: You are given a permutation cipher defined by the bijection t: N -> N where, ...
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1answer
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tcp congestion avoidance

I came across this question: ...
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network address translation

I'm having some difficulty understanding ip addresses. Let's say: Question Info: private subnet 192.168.0.0/24 IP addresses 212.201.49.1-5 Now, a host 192.168.0.2:1234 retrieves a web page from ...
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231 views

ip/tcp packet decoding without wireshark

How can we manually read and interpret packets properly without using wireshark? Now from the Ethernet header I know that the Destination MAC Address should be at the 5th byte (after converting bits/...
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Why do we need to connect the computers to a LAN cable when we can use the internet [closed]

why don't we put a network card or usb adapter to connect to wifi and connect all the computer to the internet without LAN and WAN cables i may act stupid so please explain it to me my friend
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Decryption of RSA

How can we decrypt an RSA message if we only have the public key? For example, Message: 21556870,12228498 Public Key: ...
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Duplicating ACKs and Window Sizes

After reading an answer at this link: https://serverfault.com/questions/503345/three-duplicate-acknowledgementss I am confused. Do ACK values repeat when a packet is lost or when an out of sequence ...
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data carried during TCP control flow

I am learning about TCP control flow and came across a question about how much data is carried by the 4th segment. The answer is supposed to be 1200 (2230 - 1030) but I don't quite understand why. ...
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Urgent Flag of TCP, Computer Networks

The Urgent Flag(URG) is set whenever the sender's Application Layer wants to send some urgent data to the receiver. In this case, the Transport Layer does not wait for enough data to achieve maximum ...
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1answer
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About P2P networking

In P2P(peer-to-peer) networking, it is possible for the server program(software) and the client program(software) to be running on the same computer. So the two must have the same IP address. I am ...
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What happens when there are two same IP addresses?

IPv4 addresses run out few years ago. But everywhere I can see mine or someone elses IP address it's in IPv4, not IPv6. I understand that world switched to IPv6? So why we can see address in older ...
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Understanding connection between length of codeword and hamming distance in Hamming code

I came across following in Huffman coding: Minimum Hamming distance to correct up to s errors is $2s + 1$ because that way the legal codewords are so far apart that even with $s$ changes the ...
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1answer
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Why does $x^{15}+x^{14}+1$ detect all errors at most 32768 bits apart?

Reference Question from Forouzon Book Computer Network. Find the status of the following generator related to two isolated, single-bit errors. $$x^{15} + x^{14} + 1$$ Answer given : This polynomial ...
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Sending infinite frames in One-Bit Sliding WIndow Protocol?

I am reading Computer Networks by Andrew S. Tanenbaum and I wonder if there is a mistake in the protocol as I can't find any solution for the following scenario. Suppose the transmitter (A) has only ...
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What are the underlying mechanisms allowing us to unsend an email?

I am currently studying Computer Networking, and I was reading about the different types of Application Layer Protocols. In the book I am reading (Computer Networking: A Top-down Approach) it is ...
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Good citation/source for size of the internet

I am writing an introduction for a paper and want to cite something for a sentence such as "over the past thirty years, the internet has grown from hundreds of nodes to blah blah blah" (basically ...
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Count to infinity problem (routing) between unsynchronized stations(tricky)

i was wondering, will count to infinity can occur in the following cases? if so, will it necessarily occur or can the routing tables stabilize themselves? Distances: From A to B - 3 from B to C - 4 ...
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1answer
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S/Kademlia dynamic crypto puzzle

In S/Kademlia two crypto puzzles is used, one static and dynamic. The static is used to generate a key pair that makes an eclipse attack difficult to achieve, the dynamic to make Sybil attacks harder. ...
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IGMP Multicasting

The definition about IGMP on the internet goes like this--> The Internet Group Management Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IPv4 networks to ...
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distance of a code name in scheme

i wonder: is it true that if we take a information word, call it M(with m bits) for example, and code it by first coding M using a code, that we don't know anything about, except of it a length of k, ...
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Expected number of retransmissions for a packet

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 ...

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