Jumbo Frames - worth using now?

[jrichrds]

Years ago, I read up on Jumbo Frames and it seemed the consensus was it wasn't worth enabling and would cause more issues than its benefits.

How about now? I'm all gigabit now except for a couple networked printers. Is it something I can just enable and set to 9K on computers connected to my jumbo frame-capable gigabit switch (Zyxel), and not worry about compatibility issues?

And if I have a couple computers left over with Realtek 8169 PCI gigabit cards that only support up to 7K jumbo frames, can I still enable jumbo frames and the 9K computers will auto-negotiate down to 7K for them? Or do I need to leave it disabled?

They're all Win7 SP1 machines except for the networked printers. Internet connectivity is thru a gigabit router that's not jumbo frames capable (Belkin F7D7301 with TomatoUSB firmware)

 

[VirtualLarry]

All computers on an L2 domain need to be set to the same size jumbo frames. They don't auto-configure.

Most routers these days don't do jumbo, that I am aware of. Some gigabit-enabled routers may, I would be curious to hear more about this if someone knows any specifics.

 

[imagoon]

Except in storage (IE iSCSI not a "home NAS") no. There is no need.

 

[JackMDS]

If all LAN's Devices are set to Jumbo Frames (9600) local LAN transfer is usually more Robust.

However, it should be checked with pre and after Internet Download. In many cases when using Entry Level Devices' with Jumbo frames (as oppose to typical 1500/1492 setting) Internet "Speed" might be attenuated.

 

[imagoon]

9012, 9018, 9216. 9600 doesn't exist. It also offers nothing. I think it is a very long stretch to call it "Robust."

 

[JackMDS]

9012, 9018, 9216. 9600 doesn't exist. It also offers nothing. I think it is a very long stretch to call it "Robust."

"Jumbo Frames in Cisco 2960.

Select the "Bits per second" drop-down menu in the "Port Settings" window and click "9600." Select "None" in the "Flow control:" drop-down menu and press the "Enter" key. Press "Enter" repeatedly until the Cisco command line prompt appears".

​

 

[jrichrds]

All computers on an L2 domain need to be set to the same size jumbo frames. They don't auto-configure.

Haven't done any speed tesitng yet, but I enabled 9K jumbo frames on some but not all computers and could still transfer fine between the 9K jumbo and regular computers. So I assume there's some sort of "lowest common denominator" going on to be able to communicate.

 

[jrichrds]

So the consensus is still nobody bothers using it?

 

[imagoon]

Haven't done any speed tesitng yet, but I enabled 9K jumbo frames on some but not all computers and could still transfer fine between the 9K jumbo and regular computers. So I assume there's some sort of "lowest common denominator" going on to be able to communicate.

Frame error and retransmit until it makes it. Not very efficient since you need to fail to get a retry.

 

[VirtualLarry]

"Jumbo Frames in Cisco 2960.

Select the "Bits per second" drop-down menu in the "Port Settings" window and click "9600." Select "None" in the "Flow control:" drop-down menu and press the "Enter" key. Press "Enter" repeatedly until the Cisco command line prompt appears".

​

No offense Jack, but the paragraph you quoted, looks like instructions for setting up a serial console program, to connect to the Cisco command line, not a setting for jumbo frames.

 

[imagoon]

"Jumbo Frames in Cisco 2960.

Select the "Bits per second" drop-down menu in the "Port Settings" window and click "9600." Select "None" in the "Flow control:" drop-down menu and press the "Enter" key. Press "Enter" repeatedly until the Cisco command line prompt appears".

​

That is the serial port console config. Not Ethernet jumbo frames.

 

[JackMDS]

Sorry about this mistake. Looking for short precise links to demonstrate an issue has it short-comes (like Jack Not paying enough attention to the read :$).

Never the less, 9600 is the upper limit of Jumbo frames setting and it is useful in many situations.

 

[imagoon]

Sorry about this mistake. Looking for short precise links to demonstrate an issue has it short-comes (like Jack Not paying enough attention to the read :$).

Never the less, 9600 is the upper limit of Jumbo frames setting and it is useful in many situations.

Sorry, I really am not trying to be a jerk... Right now 16110 is the max frame size supported by any equipment (that I know of.) The issue is that beyond 9000 bytes of payload FCS starts to break down because single bit errors have a chance to be undetected. The Jumbo frame spec there for has a max limit of 9000 bytes. 9012 9016 and 9216 are common values supported by switching equipment to make sure that the 9000 byte payload makes it around the network. Things like the preamble, ethertype and interframe gap are included in those sizes (sometimes, this is why jumbo frames are a pain, as some devices consider 9000, 9012 and 9016 as "the same setting." 9216 at the switch layer allows for things like QinQ where the Jumbo frame has extra headers attached to support these techs.

So in short, a 9600 byte frame might make it through the network, it is larger than what the "big guys" like Cisco, Juniper, and etc generally support so it will likely be silently dumped. There is also Super Jumbo frames but I haven't seen those really used anywhere yet.

The reason why Jumbo frames went away is because they existed to solve a specific problem, CPU / Processing overhead. Since even a many cell phones now have enough CPU to handle Ethernet even at gigabit speeds, the usage has generally fallen. Storage being common because it lets the 4kb storage frame sits nicely inside one packet.