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[Cliff]

Can anyone tell me how jumbo frames work? I have JF set to 9000, but I can still access the nas with my wireless laptop, which obviously isn't using JF. So does the 323 negotiate JF's with each connection and turn it on and off as needed? Or are JF's turned off if one device connects without using JF's?

What happens if one of the nics doesn't support 9000 frames, but is set to 6000? Will the 323 use a frame size of 6K with that device only? Turn off JF for that device?

Sorry for all the questions, but I can't seem to find any good info on this.

[csewrx]

I'm a noob on here but this is straight from the Dlink web help in the DNS-323

JUMBO FRAME SETTINGS
Standard Ethernet Frames are 1,500 bytes in size. Enabling Jumbo frames allows you to increase the Frame size from 3,000 to 9,000 bytes which increases network throughput and performance.

In order to use Jumbo frames your network must support Jumbo frame packets. In the event that you enable jumbo frames and can no longer access your unit you will need to reset your unit to defaults to disable the Jumbo Frame packet support.

My knowledge of jumbo frames is limited but here's my thoughts. 

Your router must be a GB router and must support GB to GB connections in order for jumbo frames to work.  Now while there are some GB routers out there, ones for home use in most cases do not do a good enough job at GB throughput (compared to a switch) to support it. And since no wireless connection support GB throughput yet My guess is that's your problem. 

It also explains why the thing stops responding from your other post.  Per this web help, reset it back to factory defaults (stinks I know) and reset it up.  You shouldn't lose any data (shouldn't but I make no guarantees) and that should fix both your problems. 

I have a GB router at the house and tested that jumbo frame packets and actually saw no difference in throughput from the home PC (hard-wired, GB NIC, GB router) compared to simply leaving it alone.  In addition packet loss went through the roof which in turn my throughput actually dropped. 

Try resetting it and see what happens.  Good luck

[hilaireg]

Agreed,

Disable all 'Jumbo Framing' options in your devices and stick with standard TCP framing.  As 'csewrx' has noted, 'Jumbo Framing' requires many pre-requisites (hardware & software) to function correctly.

Unless your budget allows, I wouldn't spend the extra dollars on CAT6 at this point in time - CAT5e should be sufficient for your requirements.

Cheers,

[fordem]

You can - if you so choose - run jumbo frame on part of your network - what is required is that the devices you wish to link using jumbo frame and the network in between those devices must support the frame size you wish to use.

As an example, you can have your DNS-323 with jumbo frame enabled, connected to a network switch (or router) that supports jumbo frame, and one more computer that supports jumbo frame, and every thing else on the network supporting standard frame sizes only - it will negotiate the frame size using something known as MSS - maximum segment size.

Please note - the switch is not a part of this negotiation, it takes place between the 'end-point' devices, and if you have two end points configured for a 9000 byte frame size and a switch that does not support jumbo frame, or does not support a 9000 byte frame size, you will see lost packets and reduced throughput.

In personal tests, using 9000 byte frames, the DNS-323 can deliver as much as an additional 50% throughput over standard frame sizes (over 30MBytes/sec).

Here's something to think about - let's assume that jumbo frame does not automatically negotiate the frame size - how would you enable jumbo frame on the DNS-323?

Could you enable jumbo frame on your PC and then enable it on the DNS-323 - no, the connection would fail.
Could you enable jumbo frame on your DNS-323 and then enable it on the PC - possibly - because the failed connection would not present a problem for the PC.

In reality you can configure either end first - it doesn't matter - and you can run a mix of jumbo frame and non-jumbo frame devices in the same network, provided the network path between the jumbo frame devices supports jumbo frame

[hilaireg]

Interesting 'fordem' ...

... my understanding was that *all* devices on the network *must* support 'Jumbo Frames' and that one should not mix-n-match between standard & jumbo. 

Otherwise, the switch would determine that the 'big frames' are oversized and discard them.  My interpretation of the documentation I've read to date indicates that a Gigabit Ethernet interface that is configured to accept frames greater than a 10/100 interface would be dropped - in other words, jumbo frames that ingress on a Gigabit Ethernet interface and egress on a 10/100 interface are dropped.

Additionally, because the 'Jumbo Frame' implementation was still very much 'vendor-specific', compatibility between devices was difficult to achieve.

Your insights on this topic are welcomed.

Cheers,

[fordem]

hilaireg

If you search the internet you will find many documents that insist that for jumbo frame to work the entire network must support it - I believe this to be a misunderstanding of a much simpler statement - for jumbo frame to work, the entire network path linking the two devices must support it.

Ascii graphics time the (j) indicates that jumbo frame is supported, a doubled line represents gigabit (with or without jumbo frame and a single line represents 100 mbps

host1(j)<====>switch1(j)<====>host2(j)
                        ||
host3<-------->switch2<------->host4

You can use jumbo frame between host1 and host 2 provided switch1 supports jumbo frame - host3, host4 & switch2 do not need to support jumbo frame, and you can communicate just fine between host1 and host3, despite the fact that one is gigabit with jumbo frame and the other one is 100 mbps.

router<------>switch1(j)<======>host1(j)
                       ||
                    switch2(j)<======>host2(j)
                       ||
host3<------>switch3<========>host4(j)

I've added a router and another switch here - now let's assume switch 3 does not support jumbo frame but host4 does and you configure it for jumbo frame - you will find that you can communicate between host 3 (which is 100 mbps) and any of the other hosts, you can communicate between host 1 & host 2, but not between host1 & host4 or host2 & host4.

What will happen here is that the hosts negotiate the MSS between them (the switch does not participate in the negotiaition) and agree to a jumbo frame of a particular size which they both support, but, if the network path linking the two cannot accomodate the frame size, the packets will be dropped.

My network actually looks like this

DNS-323<=========>Netgear GS108T<===========>IBM xSeries 206
                                  ||         ||
Netgear FVS124G<==> Netgear FS728TS<------------->Linksys WAP54GP
                               ||    |    |    |    |
Dell Optiplex and other client systems mixed gigabit and 100 mbps

The pairs of doubled lines linking the switches are a LAG (just for the heck of it), and jumbo frame is enabled only on the top row (the DNS-323, the GS108T and the IBM server) and everything works great.

It should be noted that some of what I have here is, strictly speaking, not required for what I need to do, but was installed to allow me to do some "lab practicals" - spanning tree, VLANs, LAGs, adapter teaming (the IBM has dual Intel gigabit cards)

[hilaireg]

Very interesting 'fordem' ...

I avoided 'Jumbo Framing' as most information at the time I looked into to it was sparse or implied that all devices needed to support the feature.

As like you, I use my network for lab practicals ... I'm going to make some time after my current project to enable 'Jumbo Framing' and see what results I yield.

Appreciate the time ... and ASCII graphics 

Cheers,

[fordem]

I'm not certain if you're aware of the "parallel DNS-323" forums at http://forum.dsmg600.info/f3-DNS323-General-Discussion.html, but if you're not, come on over - you'll meet a much more dynamic (and in some cases arguementative) group of individuals, some of whom really push the envelope on the DNS-323.

There's also a handy dandy little throughput tester called NASTester that can be used to make "meaningful" measurements - in that the other folk are also using it, so you can compare your numbers directly to theirs.

Jumbo frame was available through telnet before D-Link put it in the 1.05 firmware and although I don't see much of a "real world" improvement, it's fun to play with it.

[hilaireg]

Awesome ... thanks. 

I'd come across that site before but usually looking to solve a problem ... never stopped long enough to have a read.

Cheers,

PS: My DELL PowerConnect switches have a few handy diagnostics features ... be interesting to compare the results with the utilities.

[fordem]

I'm not certain how that post got there - it was supposed to be in a PM - I guess I must've slipped up.

So far - I have found that the NASTester utility's figures seem to correlate nicely with the SNMP results I get from my switches.

[Cliff]

Thanks for a great reply Fordem. So in your opinion, JF's do improve performance.

I currently have my main pc running an onboard gigabyte gb card. The configuration settings don't have a JF option, so I will assume it doesn't support it. The DNS-323 and the GigaPC are both connected to a DLink 1008D switch. Two other PC's are connected to a 1005D switch which is in turn connected to the 1008d. One of those has a linksys 1032 GB and a Dlink 530T adapter.

So, if I want to see a performance improvement, should I replace the onboard and linksys cards with cards that do support JF's, like the 530T ?

[fordem]

Cliff

Since you have switches and at least one adapter that support jumbo frame, I would suggest you enable jumbo frame and do your own testing - you don't have to rely on my opinion - all you need is an hour or two of your time, and if you get stuck just holler.

Go to the other forum that I mentioned and search for NASTester - it's a little utility that runs on a Windows PC and measures the time it takes to transfer files, both to & from the NAS - or any other storage device.

Test with jumbo frame disabled, and then enable one end and then the other and last the switch(es) in between (I'm not certain if those switches let you disable jumbo frame) - try it with different frame sizes - the tests only take a few minutes (with 200MB file sizes).  You should find that throughput increases when both ends have been enabled and that with one end enabled there should be no significant degradation (as compared to no jumbo frame).

After you've satisfied yourself that jumbo frame does enhance throughput - in my tests I saw as much as 50% over standard frame sizes) use it with jumbo frame for awhile and see if you can detect the improvement in your real world environment, and if you feel it's worth the while to spend the money for new NICs.

It's been my experience that unless you are frequently moving large files, jumbo frame, at least, on a DNS-323 is neither here nor there - with smaller files, which is what I'm typically transferring - the overhead stacks up and the throughput drops off - for me it's not worth the trouble, but, that's my environment, yours might be different.

Note - the DNS-323's processor limits throughput to somewhere around 270~290 mbps (30~35 MBytes/sec) when writing to the disks, running network throughput tests that run purely out of memory, I think you can push close to 400 mbps through the network interface, as compared to in excess of 800 mbps in an Intel PC environment.

I'm not saying that jumbo frame does not have it's advantages, but that jumbo frame on the DNS-323 will not boost throughput to the point where I think it's worth the while to run out and spend money to get it, if you're going to spend the money anyway, by all means get it.

[Cliff]

Another thoughtful reply. Thanks fordem.

I don't mind doing my own testing, but if I may push your good nature for a second.

Will the DNS-323 benefit with jumbo frame enabled devices if some devices are not using it. Right now I have jumbo frames enabled, but not all of the devices are JF capable. If this is true, and a mixed environment is possible, I would definitely enable my main PC with JF and forget about the onboard ethernet.

[fordem]

In my experience a mixed environment is possible - I'm running one

[Cliff]

Thanks fordem.
What kind of GB cards are you using, or are there any you have had good experience with?

Intel Pro 1000T
DLink DGE-530T