On 26 May 2014 19:24, James Harper <james@ejbdigital.com.au> wrote:
On 26 May 2014 18:07, Russell Coker <russell@coker.com.au> wrote:
On Mon, 26 May 2014 17:47:06 Toby Corkindale wrote:
I don't understand why you're worried about enabling the jumbo frames though. It doesn't break backwards compatibility. Your 100baseT stuff will continue to function fine.
Except that a switch will drop a jumbo packet destined for a non-jumbo port. So you can have situations where things work at low speed but break as soon as you send lots of data and get a larger TCP segment size.
I've never seen that in practice, and I've been running gigabit networks for a while. Rather than totally dropping the packet if the destination port doesn't support it, the switch should alert the sender that they must fragment their packets. Path MTU discovery. Although actually I think some (most?) switches instead just do the fragmentation themselves.
This almost certainly isn't possible unless it's an L3 managed switch, and even then I've never heard of such a thing. IP is Layer 3 while Ethernet is Layer 2, which is all most switches do.
Ah OK. I stand corrected. There's definitely some mechanism that lets a jumbo-frame client talk to a non-jumbo-frame client via a switch though. I swear I do this and it Just Works(tm). Perhaps MSS at the IP layer then?