From: grahn+nntp@snipabacken.se   
      
   On Wed, 2013-06-12, rahul.dev.agg@gmail.com wrote:   
   ...   
   >> Are you doing this out of curiosity, or are you trying to solve a   
   >> problem?   
   >>   
   > Thanks for your reply. I am just doing it out of curiosity. I am   
   > trying to understand how path mtu discovery works.   
      
   Ah, but that is more than curiosity!  Learning about PMTU discovery is   
   a good thing.   
      
   I wish I could suggest a better way to do this ...   
   (Perhaps the others who responded did; I haven't read those responses   
   carefully.)   
      
   When Stevens wrote his famous "TCP/IP Illustrated" books he had access   
   to several networks and a SLIP link, and he used this in his examples   
   (SLIP has a much smaller MTU than Ethernet).   
      
   Maybe some kind of tunneling protocol could help you.  Tunneling   
   usually (always?) creates a new link with a lower MTU.   
      
   Or maybe you can use iptables to drop packets larger than size N and   
   generate an ICMP "too big" response?  If you can get that to work, you   
   can also change N over time, and see if PMTU discovery discovers the   
   change.   
      
   But I think you need more than one Ethernet to do this well.  PMTU   
   discovery is about detecting things which happen more than one hop   
   away from the source. Maybe you can use virtual machines and simulated   
   networks.   
      
   /Jorgen   
      
   --   
     // Jorgen Grahn    O  o   .   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)