XPost: comp.os.linux.networking   
   From: spam@andyfurniss.entadsl.com   
      
   Resent - forgot to re-add comp.os.linux.networking   
   Jorgen Grahn wrote:   
      
    > I can add that there's most likely at least one bottleneck: at one   
    > point your packets go over GTP over UDP over IP, on Ethernet.   
    > *Someone* will get hurt if you use 1500-octet packets -- possibly the   
    > operator.   
      
   They shouldn't get hurt if they know what they are doing - most recent   
   ISP type kit should be able to run MTU > 1500 to handle this.   
      
   In the UK alot of ISPs use the dominant teleco for transport and they   
   use L2TP - and explicitly state in the specs that the ISP must run a   
   higher MTU to allow for this.   
      
    > You've mentioned this several times recently.  What about PMTU   
    > discovery -- doesn't that work for you?  It seems to work well enough   
    > (or never kick in) for me.   
      
   Does your ISP restrict your inbound to < 1500, though. If it doesn't you   
   are not likely to have problems.   
      
   In the case of pppoe type ISPs the 1492 they (may) run is overcome by   
   the fact that consumer dsl modem/routers mss clamp TCP avoids PMTUD   
   black hole faliures.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)