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I am often told by Sales Engineers and Product managers that a Layer 2 Ethernet service is not fit for purpose if the maximum supported frame size is in the 1518-1522 range (enough to support standard Ethernet frames or VLAN tagged frames).

Or in other words: an MTU of 1500 is not enough (see this blog post for my definition of MTU and a short rant on how the term is often misused)

I am never able to get any details from them on:

a) What proportion of customers (Enterprise / SMB) require Jumbo frames

b) What are typical expectations on frame size for Jumbos on WAN links? 1600, 2000, 9k, etc...

I know that in Telco and Data Centre environments Jumbos are pretty common, but I am after some insight as to how common this is within Enterprise and SMB networks.

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Have you found anything out so far elsewhere? I'm in search of similar information. –  Stu Thompson Mar 2 '10 at 8:21
    
I know Aruba APs will send a jumbo frame back to their controller every 120 seconds. I havn't been able to switch it back to the controller(due to old hardware). Other than that I still wonder when/if it's being used. Possibly ISP grade problems? –  Robert Mar 12 '10 at 19:31
    
A lot of people have posted comments on situation where they use Jumbos locally but not on the WAN. Can anyone comment on this: Would you consider a WAN ethernet link to be broken if it only allowed for a 1500 byte MTU? It seems the consensus so far is no. –  Russell Heilling Apr 1 '10 at 10:53

4 Answers 4

As for small business, from my own experience, there is little or no need to implement Jumboframes. In other words: there is only a need to implement Jumbo frames if you need to move huge amounts of data.

If I calculated correctly you only need about a quarter of the frames you'd normally need, so your overhead due to using the IP protocol will drop by three quarters.

I cannot imagine, however, there will be much ISPs offering Jumbo frame support. Not to mention the number of hosts offering Jumbo frame support (namely not a lot).

So there seems no need to implement them, other then on the local network if and only if one would have to move large quantities of data.

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We use jumbo frames on our iSCSI infrastructure, nowhere else. I doubt you'll find Jumbo Frames on a WAN anywhere,

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nanog.org/meetings/nanog42/presentations/scholl.pdf seems to confirm your WAN comment (for the public Internet, at least). –  Gerald Combs Mar 22 '10 at 21:34

EqualLogic suggests 9K frames on their SANs, and this suggestion tends to be widely adopted for storage-area networks on sites using EqualLogic hardware.

That said -- even though we're following that suggestion for our storage network, my employer still uses default 1500 byte frames on the primary (non-storage) network.

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We have employed jumbo framing specifications on enclosed networks - networks that are configured for internal usage and do not have any WAN connectivity other than the nodes that are connected to it.

Jumbo frame support is only as good as it is when all participants within the network are utilizing it. There is no need to implement jumbo framing unless you see a need to do so.

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