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If an attacker discovers the presence of the Juniper Networks security device, the
attacker might launch a denial of service (DoS) attack against the security device
instead of the network behind it. A successful DoS attack against a firewall amounts
to a successful DoS attack against the protected network in that it thwarts attempts
of legitimate traffic to traverse the firewall. This section explains the two methods
an attacker might use to fill up the session table of a Juniper Networks security
device and thereby produce a DoS: session table flood and SYN-ACK-ACK proxy
flood.

Session Table Flood

A successful DoS attack overwhelms its victim with such a massive barrage of false
traffic that the victim becomes unable to process legitimate connection requests.
DoS attacks can take many forms—SYN flood, SYN-ACK-ACK flood, UDP flood,
ICMP flood, and so on—but they all have the same objective: to fill up their victim’s
session table. When the session table is full, that host cannot create any new
sessions and begins rejecting new connection requests.

One method of attempting to gain access to a resticted area of the network is to insert a bogus source address in the packet header to make the packet appear to come from a trusted source. This technique is called IP spoofing.

ScreenOS has two IP spoofing detection methods, both of which accomplish the same task:
determining that the packet came from a location other than that indicated in its header. The method that a Juniper Networks secrutiy device uses depends on whetehr it is operating at Layer 3 or Layer 2 in the OSI Model.

import java.util.Random;
class quick2
{
    static int a[];
    public static void main (String args[])
    {
        int i;
        a=new int[10];

        Random random = new Random ();
        for (i=0;i<10;i++)
        {
            a[i]=random.nextInt(100);
            System.out.print(a[i]+"  ");
           
        }
        System.out.println ("");
        System.out.println ("----------------------------------------");
       
       
        quick_sort(0,9);
       

    }

    static void quick_sort (int l, int r)
    {
        int i,j,k,x,w;
        i=l; j=r;
        k=(i+j)/2;
       
        x=a[k];
        do
        {   while (a[i]<x) i++;
            while (x<a[j]) j--;
            if (i<=j)
            {
            w=a[i];
            a[i]=a[j];
            a[j]=w;
            i++;
            j--;
            print_line();
            }
        }while (i<=j);
        if (l<j) quick_sort(l,j);
        if (i<r) quick_sort(i,r);
    }
   
    static void print_line()
    {
        int i;
        for (i=0; i<10;i++)

            System.out.print (a[i] + "  ");
            System.out.println();
           
   
    }

}