Are Jumbo Frames (MTU up to 9k) realistic/common over the open Internet?

I've got an application that would benefit from larger Ethernet frames. (In theory, we could reduce the number of outbound packets by > 50%, maybe even 66%.)

I'm also in the process of specifying networking requirements with candidate hosting companies for a new installation of my application servers. It would be nice to, at a minimum, not restrict client connections from benefiting from Jumbo Frames.

But how realistic is this? Some general questions, assuming the segment of the network we can control is Jumbo Frame-friendly (switches are large MTUs capable, ICMP MTU path discovery allowed, etc.):

• Is it realistic to send Jumbo Frames over the public Internet?
• Is it inviting endless networking problems trying to support Jumbo Frames over the public Internet?
• Are there any other concerns that I've not considered?

The key here is that you can control your little segment of the network and enable large MTUs but you can't control the path your packets take over the internet and certainly can't control the configuration of the routers your packets will pass through. Most internet routers aren't configured above 1500 so you aren't going to have much luck with this solution. Worse, sometimes larger packets will actually get dropped by routers that don't support jumbo frames so I think you'd actually find things are worse if you try sending jumbo frames to the internet.

Jumbo frames are great on your internal network - especially for networks doing streaming or iSCSI.

1. Unless your view of the internet is from you via a single entity who will allow you to be extremely specific about this issue with and then on to some equally controllable end point then there's a >99.9% chance you traffic will not be transited 'intact' and maintain it's JF's. The reason is that JF's are an ethernet specification and not all of the internet is ethernet so they get disassembled, reassembled, transited then re-packetised.
2. Problems - probably not, maybe on day one you may run into a problem or two but once it's up and working it should be fine.
3. I would say that unless you have complete control of every part of the chain from server to client I'd be tempted to engineer my system considering the lowest, not highest, common denominators, i.e. get it working then tune, not the other way around.

A lot of the tertiary education networks (AARNET, JANET, Internet2) have end to end enabled jumbo frames on their networks. If you are serving people on those networks I would suggest it is worthwhile.