Questions tagged [communication-protocols]

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51
votes
5answers
8k views

Why are so many internet protocols text-based?

From what I have found, a very large amount of protocols that travel over the internet are "text-based" rather than binary. The protocols in question include, but are not limited to HTTP, SMTP, FTP (I ...
26
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6answers
8k views

If the two generals problem is unsolvable how can we human beings agree on things?

If the two generals problem is unsolvable how can we human beings agree on things? I mean, we communicate everyday and have the same limitations as any communication problem handled by computer ...
8
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1answer
25k 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 ...
6
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2answers
9k views

Difference between CRC and Hamming Code

I am a bit confused on the difference between Cyclic Redundancy Check and Hamming Code. Both add a check value attached based on the some arithmetic operation of the bits in the message being ...
5
votes
3answers
430 views

Why is it seemingly easier to resume torrent downloads than browser downloads?

I really wonder how torrent downloads can be resumed at later point of time. If such a technology exists, then why is it not possible in browsers? It is often not possible to pause a browser download ...
5
votes
1answer
199 views

Could a standardized ternary system be more efficient than the binary system? [duplicate]

Could a standardized ternary (base-3) system be more efficient than the binary (base-2) system? Binary is efficient for processing using logic gates, but can be bulky when using for file storage or ...
5
votes
3answers
9k views

Link utilization of sliding window protocol

Before I ask my doubt I would like to state that problem which led me to my doubt. It can also serve as a good example scenario. A $20\ Kbps$ satellite link has a propagation delay of $400\ ms$. ...
5
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2answers
2k views

Algorithm for Dynamic Client Side Throttling

Problem I am trying to come up with an algorithm that will dynamically throttle a client's number of outstanding requests based on the response times of completed requests. Response times are ...
5
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2answers
15k views

Why is the throughput (performance) of the Slotted Aloha protocol ≈ 0.36

I've read that the throughput - that is, the amount of good useful messages relative to capacity - of the Slotted ALOHA protocol for communication networks is roughly 0.36%. But its not clear how we ...
5
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0answers
84 views

How to ensure connectedness in a masterless gossip protocol?

This is a theoretical question about how gossip protocols work; I am not asking about any specific implementation or piece of software. I've read the wikipedia page https://en.wikipedia.org/wiki/...
4
votes
1answer
48 views

Compute the union of two sets between two endpoints minimizing communication complexity

I have two endpoints, $a$ and $b$, that can communicate through a channel. $a$ is storing a set of fixed-length strings $A = \{a_1, \ldots, a_{N_A}\}$, and $b$ is storing another set of fixed-length ...
4
votes
1answer
40 views

What is a “name/variable of base type” in applied $\pi$-calculus?

I'm studying the articleVerifying privacy-type properties of electronic voting protocols which uses Applied $\pi$-calculus to formalize voting protocols and verifies some privacy-related properties. ...
4
votes
2answers
397 views

Does a collision occur if two packets are sent at the same time in Slotted AHOLA?

There's something I don't really understand about the Slotted AHOLA protocol, and I hope you can help me: what happens if a station wants to send two packets at the same time? Will it be considered as ...
4
votes
2answers
975 views

Byzantine generals problem with signed messages (Lamport)

I have some trouble understanding Lamport's paper about the Byzantine generals problem when it comes to signed messages. He showed that, with signed messages, the number of generals must be at least $...
3
votes
3answers
4k views

Why is CAN protocol preferred to be used in automotive application?

Is it only because of the fact that it is asynchronous and can be used for long distance message transfer. An example of where other protocols will fail would help. Thanks.
3
votes
1answer
658 views

What is the best you can do with a noisy message?

You play a TV game in which you have to open one door out of $n$. Behind each door, there is a treasure with probability 1/2, independent of the other doors, so your apriori chance of winning is 1/2. ...
3
votes
1answer
61 views

Block detection in repeated stream

I need to recover a data block from a repeated stream of data. I'm looking to see what algorithms may already exist for this as it does not feel like a novel situation. Here are the specifics: There ...
3
votes
1answer
88 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), ...
3
votes
1answer
504 views

The throughput of the ALOHA protocol if the Binomial distribution was used

In all the examples of ALOHA I've seen, the Poisson distribution is used. Theoretically, how could the throughput be calculated if a Binomial distribution was used instead? For example, in the case ...
3
votes
2answers
243 views

How does TCP manage to discard segment received from a source other than the one with which the connection has been established?

It is known that TCP is a connection oriented transport layer protocol of the TCP/IP suite. But TCP (and UDP) operate over a connection less network layer protocol, the IP (internet protocol). What ...
3
votes
2answers
133 views

Finding the total capacity of two communication channels

I have the transition matrices of two communication channels. I am able to find the capacity of each by performing an optimization calculation, however I need the total capacity of the two channels. ...
3
votes
0answers
4k views

Merits and demerits of convolutional and linear block codes

Continuing on from my previous post... Both convolution and linear block codes can be used for error correction. The main benefits I gathered from using convolutional codes is that, it's easy to ...
3
votes
0answers
5k views

totally ordered multicast with Lamport timestamp

I'm studying Distributed Systems and synchronization and I didn't catch this solution of totally ordered multicast with Lamport timestamps. I read that it doesn't need ack to deliver a message to the ...
2
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1answer
779 views

Why is the throughput (performance) of the Aloha protocol ≈ 0.18?

I've read in a few places (like here that the throughput - that is, the amount of good useful messages relative to capacity - of the ALOHA protocol for networks is roughly 0.18%. But its not clear ...
2
votes
1answer
437 views

What's the point of Subnet Masks?

I'm having trouble understanding the point of Subnet Masks. I was reading a nice article on Tech-FAQ on the topic, but it has left me a bit confused. When I first heard about Subnets, it was ...
2
votes
1answer
49 views

Looking for two-way communication/consensus/contract algorithm for use in marriage proposal

I am looking for some sort of communication or consensus algorithm with the following properties: Can be used with just two parties (and ideally doesn't collapse to a trivial case with two parties) ...
2
votes
1answer
84 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 ...
2
votes
1answer
158 views

Example of reduction in communication complexity

Let us assume the standard situation in communication complexity with two players $P_1,P_2.$ We have a function $f:[n] \times [n] \mapsto \{0,1\}$ that both players known in advance. They wish to ...
2
votes
1answer
102 views

Is the capacity achieving input of a discrete memoryless channel unique?

Consider a classical discrete memoryless channel (DMC). Let $p$ be an input probability distribution and $Q$ be the channel's transition matrix. $q = Qp$ is a valid output probability distribution. ...
2
votes
1answer
85 views

Temporal compression protocol

Recently it occurred to me that one could potentially design an interactive "compression" scheme which seems to allow for arbitrarily high compression ratios, at the sole expense of time. ...
2
votes
2answers
3k views

Why does packet data don't need trailer/footer while frame needs it?

Why does packet don't need trailer/footer while frame needs it? I am trying to understand networking concept regarding OSI & TCP/IP layering. I have googled a bit and it says that the footer in ...
2
votes
1answer
136 views

Classification of technologies used for communication in distributed systems

I am currently writing a State of Art about technologies used for distributed communication (like CORBA for example). I want to structure the document in way that I don't leave any subset of this ...
2
votes
1answer
100 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 ...
2
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0answers
31 views

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 ...
2
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0answers
55 views

Authority section in DNS packet always contains NS records?

I'm new to DNS and I'm trying to understand the DNS packet format. From what I understand, the authority section of a DNS packet gives information about servers that are authoritative for the domain ...
1
vote
2answers
84 views

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 ...
1
vote
1answer
344 views

Convolutional and Linear block codes

Both convolution and linear block codes can be used for error correction. The main benefits I gathered from using convolutional codes is that, it's easy to implement and does better (than linear codes)...
1
vote
1answer
116 views

Is a “protocol” a set of algorithms and data structures?

I'm not major in science at all and would like to verify whether my understanding is correct or not. I just did some googling about the definition of protocol, such as in this, this one, this one and ...
1
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1answer
138 views

Basic Question in networking - why max data size of ip datagram 65535 BYTES and not 65535 bits?

I recently started computer networks with some understanding of algorithms and discrete mathematics. I am completely new. Kindly elaborate following - data size of ip datagram = 16bits. So with this $...
1
vote
1answer
74 views

Is data received after transmission immediately stored and can that be recovered?

When I send a message from one device to another, during the process during which the other device is receiving the data, is that data stored temporarily on some place on the device or is it ...
1
vote
1answer
434 views

Serial communication and parity bit

I was revising Computer Science and I got these two doubts to which I've found contradictory answers on Google: In a serial communication which bit is sent first? When using a parity bit with ASCII ...
1
vote
1answer
5k views

Probability of Success in Slotted Medium Access

Suppose you have a network which uses time division multiplexing (i.e. Slotted Aloha). There are $N$ nodes each transmitting in a given slot with probability $p$. I understand that the probability a ...
1
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2answers
2k views

How does DNS work if there is no recursive querying?

Suppose I type in the website www.youtube.com. The computer first asks a local domain name server (DNS) what the IP address of this website is. If it can't find it,...
1
vote
1answer
21 views

Communication Complexity for Product Distributions

In general for the (two-party) set disjointness problem for inputs of length n, we know that the parties need to communicate $\Omega(n)$. Surprisingly, today I discovered (if I understood correctly) ...
1
vote
1answer
38 views

Reaching Shannon capacity of a channel

Suppose I have the following from alphabet $\mathcal{X} = \{0 ,1\}$ to $\mathcal{Y} = \{0 ,1\}$. The channel simply does \begin{align} 0 \rightarrow 0&\quad \text{with probability 1} \\ 1 \...
1
vote
1answer
137 views

How is the literal meaning of “rendezvous” related to its usage in distributed computing?

I am trying to figure out the difference between RPC and Rendezvous. Is it correct that they differ only on their implementation on server side: RPC will involve creating a new process/thread to ...
1
vote
1answer
63 views

Resending old frame when a damaged frame has been received in one bit sliding window protocol

I'm reading Tanenbaum's and Wheterall's book on Computer Networks. I'm trying out some examples of situations that can occur in the one bit sliding window protocol for a datalink layer. The code for ...
1
vote
1answer
69 views

How is a communication protocol a mechanism?

Given a finite set $\Sigma$ and a positive integer $n$, a mechanism is a set $\{ \mu_x \vert x \in \Sigma^n \}$ such that $\mu_x$ is a probability measure on some $\sigma-$algebra for each $x$. Now ...
1
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1answer
26 views

Guaranteed existence of a blocking set in the accept definition of Stellar

In the SCP, condition 2 of the accept definition allows a node to vote for one statement and later accept a contradictory one. Condition 2 assumes the existence of a v-blocking set which has not only ...
1
vote
1answer
110 views

Complexity of sending an $n$-bit string

Consider a $2$-party communication model in which $A$ wish to send to $B$ an $n$-bit string. It is very easy to prove that any deterministic protocol for this problem requires $\Omega(n)$ bits to be ...