Douskalis, Bill. <br/><br/>
Putting VoIP to work :  softswitch network design and testing / 
​ Bill Douskalis. 
 - Upper Saddle River, N.J. :  Prentice Hall,  2001. 
 - 400 p. ;  23 cm. 
<br/><br/><label>ISBN: </label>0130409596