Quoted: So what are jumbo frames? I thought ethernet was based on a 1500byte packet.... |
Ethernet was, but some of the new, nicer gigabit equipment supports larger packets.
With large files and older computers, the jumbo packets can really make a huge difference. For us, it decreased the time our backups took by almost 25% on a set of four backup systems because their seven year-old CPU's were already being used 100% for compression and Reed-Solomon parity calculations.
Do gig nics send in larger frames by default, and some switches dont handle that? |
As far as I know, the switches always support them by default. I haven't seen one where you had to do something to enable jumbo packet support.
The cards don't do it by default. With Linux it is easy to set the MTU. You simply type "ifconfig eth0 mtu 9000". With Windows it is much harder. You usually have to enable jumbo frames with the driver under Device Mangler. Then you have to change the MTU in a separate place. Windows gets the math wrong so while you setup good systems to 9000 byte MTU, you have to use 9014 bytes with Windows because Microsoft includes the size of the IP headers in addition to the data when they shouldn't. I've done it with three different gigabit cards, and the procedure was different for each one. As usual, Windows is very inconsistent.z