Re: MTU and Postfix
On 9/4/2011 5:40 AM, Camaleón wrote:
On Wed, 31 Aug 2011 16:09:23 +0000, Camaleón wrote:
I'm still monitoring this but if this is the "cure" to prevent such
errors, are there any expected drawbacks for lowering MTU "system-wide"?
Slightly lower overall performance when communicating with remote hosts.
Almost zero difference on the LAN.
If you want optimal performance, you should enable jumbo frames on all
LAN hosts (9000 bytes) since you're using GbE, and install an edge
router that handles jumbo frames. Then you need not worry about any of
this. Just make sure you find out from your service provider what size
frames they use. Then program the WAN interface on the router with that
frame size (MTU).
Problems such as yours are always caused by MTU mismatches. In most
cases the mismatch is between the customer's edge device and the service
provider equipment. Good routers will handle this just fine as long as
the WAN port MTU is programmed to match the service provider equipment.
Worth noting is that different network technologies use different frame
sizes. For instance, ethernet uses a 1514 octet frame. Fiber channel
uses 2112. FDDI uses 4500. SONET is 2430.
You mentioned a "FTTH gigabit router" previously. Is this SP equipment
or your independent equipment? The MTU mismatch most likely exists
inside that box. If it was provided to you, then someone probably
didn't program it correctly. It should have worked fine with different
MTUs on both sides.