From: barmar@alum.mit.edu   
      
   In article ,   
    Jorgen Grahn  wrote:   
      
   > On Wed, 2011-09-14, Alfred Nagl wrote:   
   > > martinfnp@yahoo.com wrote:   
   > >   
   > >> Can somebody help? How is TCP/IP stack designed in OSes if different   
   > >> physical   
   > >> drivers with different physical maximal size of frames need to be   
   > >> transferred? Does IP stack do any interrogation during startup   
   > >> procedure to investigate how much is maximal length of the frame of   
   > >> particular device - e.g. Ethernet, FDDI, WiFi? Thanks.   
   > >   
   > > You may want to read about PMTU:   
   > > and MSS:   
   >   
   > Seems to me he's not talking about the path, but about the link --   
   > "particular device" etc.   
   >   
   > To answer the original question: of course IP must know about the   
   > capabilities of the various link layers on the local host. And of   
   > course it can find out.  It can't be done during "startup" though on   
   > any OS I know of, since network devices may come and go.   
      
   Right.  It's generally done at the time that a socket is being   
   initialized.  When the socket is told to connect to a destination, the   
   stack interrogates the routing table to determine which interface will   
   be used.  Then it finds out the MTU of this interface, and uses this to   
   specify the MSS of the connection.   
      
   --   
   Barry Margolin   
   Arlington, MA   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)