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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: PMTU-D: remember, your load balancer is broken
In message <[email protected]>, [email protected] .edu writes: > >b) If you're a webserver or something else providing service Out >There to random users, just nail the MTU at 1500, which will >work for any Ethernet/PPP/SLIP out there. And if you're load >balancing to geographically disparate servers, then your users >are probably Out There, with an MTU almost guaranteed to be 1500. > >I assert that the chances of PMTU-D helping are in direct ratio to the >number of end users who have connections with MTU>1500 - it's almost >a sure thing that you probably won't have users with an MTU on their >last-hop that's bigger than their campus backbone and/or Internet >connection's MTU. > >Is anybody seeing any documentable wins by using PMTU-D? There are two places where it's very important. First, some server farms are on FDDI rings, so they have a higher MTU. Second -- and this one is growing in importance -- tunnels, for IPsec, PPTP, etc. -- generally have smaller MTUs. This very reply will travel over a tunnel with an MTU of, I believe, 1480. --Steve Bellovin
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