Notification based replication will result in immediate replication between sites… remember that this will increase your replication traffic with 20-30%.

1. Start  ADSIedit.msc and connect to the configuration container.
2. Go to Inter-Site Transports – CN=IP.
3. Right-click the site link object, and then click Properties.
4. Select options.
5. If the Value box shows <not set>, type 1. If the Value(s) box contains a value, you must 
   derive the new value by using a Boolean BITWISE-OR calculation on the old 
   value, as follows: old_value BITWISE-OR 1. For example, if the value in the 
   Value(s) box is 2, calculate 0010 OR 0001 to equal 0011. Type the integer 
   value of the result in the Edit Attribute box; for this example, the value 
   is 3.
6. Click OK.

Links

http://blogs.technet.com/tmintner/archive/2006/04/12/425111.aspx