[afnog] MTU Size for transit links for ISPs

[Mark Tinka]

On Monday, September 23, 2013 02:42:54 PM Perreau, Luc 
wrote:

> After intense troubleshooting over a few long days, we
> have found that our MUX though having 4 Ethernet ports,
> two of them have larger buffer sizes than the other two.
> 
> We connected one link on a large buffer size port, and
> the other on a smaller buffer size link. Using EIGRP
> with a variance of 2, we got very unstable performance.
> 
> The minute we corrected that, the links started
> performing as expected!

Glad it all got sorted.

Buffer issues can be exacerbated if the upstream interface 
or bandwidth is larger than what you get at the choke point, 
e.g., a 10Gbps port handling traffic toward a 1Gbps port on 
a device with tiny buffers.

I'm not saying having large buffers is good (Google buffer 
bloat), but at least you've identified ports on your mux 
which have insufficient buffers for your traffic flow rates.

Mark.
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