The biggest thing I have run across is on an IX where everyone may be running a different MTU if you just set yours to 9K then your router will utilize all of it in it’s BGP messaging.  If the peer is not also set to 9K then things will get unstable once your router generates a BGP message that is larger than your peer’s MTU.  You would want to think about using something like “ip tcp adjust-mss 1460” to keep the BGP messaging smaller. Than 1500 while still supporting packets up to 9000

Hi all,

We are migrating our connections to 10G, and I’m wondering if I should request jumbo frames. 

I’m trying for due diligence, and apologize if this is a rudimentary question.  Nanog searches do not have clear recommendations, or maybe I did not search enough.

My experience with jumbo frames indicates to me that I should be safe with 9000 byte frames, but there could be PMTU discovery and fragmentation issues during transit or on the receiving side. 

Would you or would you not enable 9K frames with IXP and ISP connections?  I just do not have enough experience in this regard, so I am thankful for any thoughts here.

My inclination is to go with 9K frames, yet I do not want to deal with ancillary issues that I cannot anticipate, discern, or troubleshoot – especially during a cut.

Any experience from the group is appreciated.

Thank you,

Jamison Masters

Verus Corporation

jamison@veruscorp.com

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