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Questions tagged [protocols]

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47
votes
5answers
6k 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 ...
20
votes
4answers
6k views

Measuring one way network latency

This is a puzzle about measuring network latency that I created. I believe the solution is that it's impossible, but friends disagree. I'm looking for convincing explanations either way. (Though it is ...
13
votes
1answer
334 views

Break an authentication protocol based on a pre-shared symmetric key

Consider the following protocol, meant to authenticate $A$ (Alice) to $B$ (Bob) and vice versa. $$ \begin{align*} A \to B: &\quad \text{“I'm Alice”}, R_A \\ B \to A: &\quad E(R_A, K) \...
8
votes
2answers
87 views

Running an algorithm on data remotely and ensuring answer has not been tampered with

I´ve been thinking about this particular computing/crypto/database problem for years and I just want to know if there are already solutions to it. To be honest I don´t even know what field this ...
4
votes
1answer
115 views

Break an authentication protocol based on a pre-shared symmetric key, with message numbers

Consider the following protocol, meant to authenticate $A$ (Alice) to $B$ (Bob) and vice versa. $$ \begin{align*} A \to B: &\quad \text{“I'm Alice”}, R_A \\ B \to A: &\quad E(\langle 1, R_A\...
3
votes
2answers
1k views

Till which layer does the loopback packet goes?

I want to know exactly till which layer in the OSI model the 127.0.0.1 (loopback) packet goes till it is returned to the upper layer. I read some where it goes till data link layer. but as i was told ...
3
votes
1answer
427 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
1answer
81 views

Randomized and Deterministic Communication Complexity of a function

I have a problem I'm trying to answer for my homework. The question is: Let $p$ be a prime number and let $GF(p)$ denote the finite field of size $p$. Suppose that A has input $x∈GF(p)$ encoded with $...
3
votes
1answer
64 views

Explanation for the proof “Every 2-thread consensus protocol has a bivalent initial state”

From the book 'the art of multiprocessor programming': A protocol state is bivalent if the decision value is not yet fixed: there is some execution starting from that state in which the threads ...
3
votes
0answers
238 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. ...
2
votes
1answer
226 views

Can Eve impersonate Alice or Bob by using a replay attack?

For my computer science study, I have to design a replay attack (if possible) for the following authentication protocols. I use the standard security protocol notation. In these protocols, $A$ is ...
2
votes
2answers
520 views

MESI Protocol Invalid cache line is attempted to be stored?

I am implementing a sample MESI simulator having two levels of cache (write back). I have added MESI status bits to both levels of cache. As it is a write back cache, the cache line is updated to L2 ...
1
vote
1answer
38 views

Solving/mitigating the free rider problem without requiring identification?

Is there any algorithm/protocol out there to solve/mitigate the free rider problem without requiring identification? In a web system, I want to distribute exactly one virtual dollar per day to each ...
1
vote
1answer
42 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
vote
1answer
73 views

Is there a zero-knowledge protocol for bit vector agreement?

Suppose Alice knows a secret vector of $N$ bits, say $A=\langle a_1, a_2, \ldots, a_N\rangle$ and Bob similarly knows $B=\langle b_1, b_2, \ldots, b_N\rangle$. Is there a protocol that allows them to ...
1
vote
1answer
231 views

Sliding window protocol when number of packets is equivalent to the window size

I am currently taking a course in computer networking and I am curious about the following situation: Given $n$ packets and a window size of $n$ (i.e., the number of packets is equivalent to the ...
1
vote
1answer
30 views

Is there an existing protocol where a sender does not know who he is sending data to?

I was thinking about how the BitTorrent protocol automatically gives every peer a list of IPs of every other user who is currently seeding / leeching off the torrent in question. Is there an existing ...
1
vote
1answer
42 views

Finding maximal and average number of time slots in an Adaptive tree walk protocol

Tried to research here and on other sites with no luck regarding finding the maximal and average number of time slots in an Adaptive tree walk protocol. i'll explain what i mean here: In a simple(...
1
vote
0answers
76 views

Importance of Needham–Schroeder Protocol

I'm working on a paper about model checking on cryptographic protocols and many of the papers I have read, base their approaches in the Needham-Schroeder protocol. I undestand this was one of the ...
1
vote
0answers
371 views

How Can a Network Server Identify a Specific Computer, Is There a Computer Fingerprint?

Most of websites put some restrictions on how to use their services; the following paragraphs are taken from “Terms of Service” of such website: Only one account per computer is allowed to view ads. ...
1
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0answers
100 views

computational and messages complexity equivalence between STP and Leader election

I'm doing a presentation for a distributed systems and networks course. I'm using the book "Design and Analysis of Distributed Algorithms", written by Nicola Santoro. This book contains the proof of ...
1
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0answers
44 views

Is this protocol suitable for transaction services?

The paper Eventually-Serializable Data Services (PODC'96) presented an eventually-serializable data service. In the abstract, it says: … and generalizes their algorithm (in the related work Lazy ...
0
votes
2answers
531 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 ...
0
votes
2answers
57 views

How to decide which bytes will form a packet ?(computer networks)

In wireless communication , I understand what it means to transmit a "bit" but I wanted to understand what exactly does it mean by a packet . *******POST EDIT/RECEIVING INITIAL ANSWERS******* I got ...
0
votes
1answer
77 views

Chord protocol - How should I go about mapping nodes to placeholders on the ring?

In the real world, how is a node mapped to the position on the ring, Each nodes's IP address is hashed using SHA-1 hashing algorithm which will produce this hash - 73.128.154.69 hashed into ...
0
votes
1answer
114 views

Can parallel downloading with many ip's possible?

I am not too intelligent,but i got this in my mind.Lets say i download a file from abc.com and the speed is limited for an IP(say 60kbps).Can i initiate parallel downloads from multiple ip addresses ...
0
votes
1answer
117 views

How can one come up with reasonable IP subnet allocations?

An ISP has following chunk of CIDR-based IP addresses available with it: 245.248.128.0/20 The ISP wants to give half of this chunk addresses to Organization A, and ...
0
votes
1answer
696 views

Owned state in MOESI protocol-transitions?

I understand that MESI is a subset of the MOESI cache coherency protocol. But what does the Owned state in the MOESI protocol represent? What are the differences in state transition due to the extra ...
0
votes
0answers
10 views

Given two or more nodes in a network, is it possible to determine the one-way link latencies between two nodes that share a bi-directional connection?

We already know that detecting the one-way latency between only two nodes is impossible. However, if I have a number of nodes in the same subnet that all know about each other, can measure round-trip ...
0
votes
0answers
15 views

Go Back N question(netwrok)

Hello I am trying to understand the GBN protocol and I encountered the following question during my homework. Assume that we have GBN protocol with a window size of 20. The sender sends 15 packets ...
0
votes
0answers
53 views

Intuition for the convergence of the distance vector routing protocols

What is an intuitive way to think about the convergence of the distance vector routing algorithm? According to Wikipedia: Distance-vector routing protocols use the Bellman–Ford algorithm and Ford–...
0
votes
0answers
42 views

utilization of bitmap protocol

I am curious about utilization calculation in the bitmap protocol. especially if there's a difference between if only station 0 wants to broadcast(and the others doesn't) or only some other station ...
0
votes
0answers
9 views

theoretical question about difference between transmitting stations in Bit-Map Protocol

i am wondering about the difference between the transmitting station in a bit map protocol. for instance, if we have 8 broadcasting stations numbered 0-7, and the racing (contenting) time is $t_0$ ...
0
votes
0answers
24 views

Affects of altering a line in “stop and wait” protocol(no noises)

what will happen if we change "to_physical_layer(&s)" to "to_physical_layer(&r)" in the following code(marked in the code where)? does it make the protocol fail? if so, show a scenario it ...
0
votes
0answers
159 views

How is there a CPU read misses on exclusive caches?

If the lower level cache contains blocks that are not present in the higher level cache or other caches then it is said to be exclusive. It is exclusive because it is only there. How can there be ...
-1
votes
2answers
29 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?