EvilZone

first am sorry to re-post on this thread but while studying for my exam i found some thing weird .

In a network HDLCILAPB two machines "A" and "B" wish to exchange information .

"A" owns 9 frames to send , it is assumed that the window size is 2 , and that possessing frames as N ( s) = 2 and N ( s) = 5

arrive with error for the first time sent out, and then after a retransmission had come without error.

build the diagram of exchange of information between  "A" and "B" indicating for each case the value of N (R ) and N ( S).




this diagram isnt full i just showed the part where the weird thing was.
well the window size is 2 from the start they been sending 2 information frames at the same time but suddenly n(s)=7 and n(s)=0 are sent 1 by one can any1 explain this ? is it an error in the solution,or for some reason it should be sent one by one

Calculate the  transmission time of a 2,000 byte file size sent over a network possessing the following characteristics:
bandwidth = 5000 HZ
report signal / noise =1000
We assume that  the network uses 50 % of its Max capacity .

Ok i'll start by talking what is clear to me .
transmission time=file size/Debit
file size is equal 2000*8=16000 bits
because file size is calculated in bits and a byte has 8 bits.
Debit is the capacity used by the network ? (am not sure about this that's where i need help)
because in my solution Debit is equal to 50% max capacity=max capacity /2.
max capacity =badnwidth*log2(1+S/N)   S/N is the signal / noise report
                         =5000 log2 1001
                          =49836 bit/s
debit =49836/2=24918 bit/s
transmission time= file size/Debit
                                =16000/24918
                                =0.642s

so as you've noticed the only thing i want to know is if it's true that debit is equal to the capacity used by the network

yep me again need help understanding CRC correction now

calculate the CRC of the binary sequence : 11101111100010111 having as polynomial generator X6 + X4 + 1 .
what i know is that you need to transform the polynomial generator to binary and that's easy x6+x4+1 is 1010001 in binary
second you need to add six zeros to the binary sequence because 6 is the degree of the polynomial generator
then you divide the binary sequence number by the binary polynomial generator

11101111100010111000000|1010001
1010001                                      |1
-------------                                     |
                                                      |


as first qustion i need help to know how 1110111is calculated ?
                                                                        1010001

do i add those 2 binary numbers ?how this whole binary division is made ?
or i just need to substract them just like a normal division
in my opinion its a substraction but some1 told me i need to add them so i was confused

anw if it's a substraction i know that in substraction
0-0=0
1-0=1
1-1=0
10-1=1

  1001101
 -
  1010001
         1100

so far thats gd but now 100-101 is left and im confused how to continue here

i did try to start with a subnet for 17000 machines and now i could understand everything just to make sure this i'll show you my result

17000 machines
ip 123.64.0.0
netmask 255.255.128.0
brodcast 123.64.127.255

15000 machines
now the starting ip would be 123.64.128.0
the subnetmask is 255.255.192.0
broadcast is 123.64.255.255

i did find this before posting here but couldn't understand it so if some1 could explain that exercise step-by-step that would be great

@Deque that wasn't my problem anw i managed to make it work
import java.util.Scanner;
import java.sql.*;
public class testDatabase{

 
public static void main (String args[]) {
           Scanner in=new Scanner(System.in);
     
      try {
  String a=in.next();
      Connection c= null;
      Class.forName("org.sqlite.JDBC");
      c = DriverManager.getConnection("jdbc:sqlite:numbers.db");
         System.out.println("connected");
Statement myStmt =c.createStatement();
ResultSet myRs =myStmt.executeQuery("SELECT * FROM numbers WHERE NAME='"+a+"'");
while(myRs.next()){
System.out.println(myRs.getString("name")+"\t\t\t"+myRs.getInt("number"));
}
}

  catch (Exception e)
     { 
         e.printStackTrace(); 
     }

    }
 }
   

SELECT number FROM numbers WHERE id=userinput

well thats what i need to do to a database using java

You did a really good job for a beginner. Here's my feedback (not hating):

1. I crashed your code by entering ^. The problem was, scanner was looking for an integer not a character. When I entered a character it didn't have anything to catch the exception. You can fix this by adding a try and catch statement to your code.

try {

//your code
} catch (exception e) {

System.out.println("caught");
}

2. Just comment a little better

Overall incredible job.

yep i already know