[afnog] MTU Size for transit links for ISPs

[Perreau, Luc]

Cheers Mark :)

Luc Perreau
I.P. Specialist
Cable & Wireless (Seychelles) Ltd
 
Office:  +248 428 4256
Mobile: +248 251 3505
Fax:     +248 432 4019
www.cwseychelles.com



-----Original Message-----
From: Mark Tinka [mailto:mark.tinka at seacom.mu] 
Sent: Monday, September 23, 2013 11:08 PM
To: Perreau, Luc
Cc: Randy Bush; Nishal Goburdhan; afnog at afnog.org
Subject: Re: [afnog] MTU Size for transit links for ISPs

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.