Maximum PC

Ok. I recently bought a SMC 5 port Gigabit switch and am getting piss poor performance. I'm not sure if it's the switch or... whatever.

Info:
Main Rig:
Intel P4 2.4C @ 3.0Ghz
Abit IS7-G
1GB OCZ PC3700EL Gold Rev.3
ATi AIW 9700 Pro W/ Zalman Heatpipe Cooler
2x 80GB Seagate 7200.7 RAID-0 on ICH-5R
Pioneer DVR-108 DVD Burner
Soundblaster Audigy 2
Zalman ZM-MFC1 Fan Controller
Antec True Power 480Watt PSU
Lian-Li PC62
Windows 2000 Pro

Domain Controller/File Server:
2x Xeon 3.06Ghz
2GB PC2100 ECC Reg. Kingston Value RAM
Supermicro X5DAE
Matrox G400 (Hey, it's a server)
2x 160GB Seagate 7200.7's in RAID-1 on an Intel SRCS14L RAID Controller
3x Lian-Li RH-600 Removable bays. (Currently not in use)
Onboard Audio
Sony DRU-510A
Lite-On 16x DVD-ROM ('cause the Sony SUCKS for ripping DVD's)
Antec True Power 550 EPS12V
Lian Li PC70
Windows 2000 Server
(C&P'd from my Commport profile.. Yeah, I'm lazy. )

I have those 2 PC's connected directly to the SMC switch Via CAT6. The SMC is then connected (using CAT5e) to my Netgear Router for Internet access/DHCP. Network is using TCP/IP.
The Server has an Intel Pro/1000 MT NIC onboard and the MainPC has a 3Com 3C940 Gigabit NIC onboard. Both are set to Autosense, I've also tried hardcoding it to 1000mb. Either way gets the same results.

According to Sygate (My firewall) I average about 18MB/s transfer rate (Transferring a 4GB file). C'mon, I know damn well my HDD's can sustain a hell of a lot more than that reading or writing.

I've tried disabling my firewall and A/V and FAH temporarily.

Only things I can think of are:
1.) Having that 100mb connection between switches is hindering speed
2.) I get what I pay for (cheap switch)
3.) 3Com NIC in Main PC (I don't care for 3Com and I'm looking for a scapegoat. )

I'll be assigning temporary static IP's to these 2 PC's to test, so I'll be (possibly) ruling out #1 soon.

Any other Ideas?


MB/s = MegaBytes Per Second
mb/s = MegaBits Per Second

i have a few old 3Com POS's around, they're not great, but also not the worst. i'd blame the switch. a cheap litttle 4 port linksys switch wont run you too much and that will easily eliminate that variable. i'd also make sure of your cabling, are they homemade cables you put together in 2 seconds or bought cables?

How cheap is this 'cheap linksys'? Remember, it's gotta be Gigabit. Most people I talk to (That know Networking, like Logik)seem to hold SMC with higher reguard than Linksys.

The cables are Premolded. I forget the MFG.

I make CAT5 Cables all the time. I take my time with them 'cause I want 'em right. I wish I could get my co-workers to do the same.

Actually

Its the Router...

You have a Gigabit Switch - that you are sending to the router for DHCP requests..

Its killing your speed - I had the SAME problem - now mind you - I agree that you should consider (at some point) upgrading your switch to netgear or linksys or something - but I wouldn't call it a switch problem until I tested the router issue.

If you can (if only for a test) put DHCP and DNS on the Dual-Proc Domain Server and see what happens..

That has fixed it for at least 4 clients....

Tuathal

Cool, thanks. I'll try that.

No offense, but you gotta explain that one to me. As long as the router, via DHCP, is placing both PCs on the same IP network then packets that go between the PCs never hit the router! Here's how it works:

PC1 wants to establish a TCP/IP connection with PC2, and since they are both on the same IP network PC1 sends out a broadcast Address Resolution Packet (ARP) to request the Media Access Control (MAC) address of PC2. MAC addresses are sometimes called "hardware addresses" and are hard coded into network interfaces by the companies that make them. PC2 "hears" the broadcast ARP and responds with its MAC address. PC1 then uses that MAC address (along with the IP address of PC2) to establish the TCP/IP connection -no router involved.

As an experiment I just looked at the ARP table on a RedHat machine that's on the same IP network as my laptop. The only MAC address that it had was the MAC address of the default gateway (normally that would be the only MAC address that it would ever need since there are no servers running on the local LAN). I "pinged" my laptop from the RedHat box and then took another look at the ARP table -sure enough my laptop's MAC address is in the RedHat PC's ARP table.

I then went to my laptop, which is running XP, brought up a "DOS" window, and typed arp -a and pressed return. The RedHat PC's MAC address is now in my ARP table as well. So the RedHat box pinged my laptop without going through the default gateway (a router) -if the packets had gone through the default gateway then the ARP table on both machines would only contain the MAC address of the router...

Now for my .02 on why the transfer speeds are so slow:

1) Your running Windows -I'm not a Microsoft basher. It's just that OS's like Unix are much faster at handling Input / Output requests and Windows OSs have a difficult time "feeding" GigE NICs...

2) The transfer speed on your network depends a lot more on just the speed of your hard drives; everything factors in. If the NICs cost less that $50 then most, if not all, of the TCP/IP stack is being processed by your CPU and OS (the NIC isn't much more than a digital to analog converter). How quickly can the data be read off of your hard drive, packaged in a TCP/IP packet by the CPU, and then transferred to the NIC?...

3) How much buffer space is in that switch? Is the switch sending out ICMP source quench messages to force your transfer rate down so that it doesn't get over run and drop packets? Or is the switch getting over run and dropping packets because either it doesn't have ICMP source quench functionality or the sending PC is ignoring ICMP source quench messages?

18MB per second may be the top end for your network without spending more $ on a better switch, NICs, and or changing the OSs, etc...

ICMP

DHCP

TCP/IP

Getting Connected -an explanation of how data is transferred over a network.

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Network News and Reviews

Absolutely a valid and impressive explanation...

I haven't ever seen the problem when running linux machines so I cannot discuss how your test would couple itself with my experiences in the past...

But - If the machines (for whatever reason) choose to ping the router for DNS information (instead of using their own hosts files) then its going to go through the router to report that information.

Will the data transfer through the router? nope - and therefore you'd think that the bottleneck would not be a problem - afterall how big of a pack do i need to send just to get an IP resolution (even if I go through the router for that info)....

I've seen your site - you are certainly well versed in Networking information - and I applaud your content.

I was stating what my thought was - based on past experience.

It was not my attention to discount your initial information (nor is it my intention to discount this information)...

I, again, was merely stating what I have seen fix the problem in the past... Was it due to poor quality switches.. or router?
Sure could be - is it a problem through the specifications of TCP/IP or packet routing? No I agree with you on that one and do not think it is.

But - when we are seeing behavior that is different than whats expected - its time to try out various troubleshooting methods...

When moving DHCP/DNS off the router and completely inside the network fixed the speed problems that the customer was having - saving them from spending more money on hardware as well - I have to say that irregardless of the information regarding TCP/IP and how it doesn't work that way.... It did in this case...

Cheers,
Tuathal

PS: Dalen is probably right, in that, the true culprit lies in the NIC or switch area (I've personally had no problems getting Windows to go Giga... so I can't speak as to his experience there).

The possiblility definitely exists that there is a driver concern on one of the machines - or there could be a problem with switch... Cisco had some gigabit capable switches that we had to RMA about a year ago - their firmware had a glitch in it so that if the switch ended up talking to a 100MB connection - it would drop connection intermittently or reset itself at 10MB... Cisco kindly (and promptly) replaced the switches for us to resolve the issue... Could be that you are having a similarly odd problem with your switch...

Just food for thought - based solely on past experience - not technical specs hehe
Tuathal

I was in no way, shape, or form trying to put you down -I have seen some odd network problems and nothing surprises me anymore, so what you've seen may in fact be valid for the network you were trouble shooting. It's just that two machines on the same IP network will "talk" directly to each other irregardless of how they get DNS or DHCP. As soon as the sending machine "detects" that it is trying to establish a connection to another node on the same IP network a broadcast ARP goes out from the sender to resolve the IP address of the receiver to a MAC address. If two machines are on the same physical network but different IP networks then any traffic going between nodes has to pass through a "router" (router, bridge, layer 3 switch, etc.) -and that may be what you've run into in the past.

NT can't feed GigE -not efficient enough no matter what hardware you run it on. Windows 2K can, but you have to throw top of the line hardware in the box -and from re-reading the original post the OS may not be an issue. Odds are it's the switch...

Aye
I agree with your assessment of the situation as well - me thinks the problem probably is in the switch :0

PS: I love your site and use it on a regular basis instead of having to remember all of that stuff <grin>

Kudos to your repertoire of Network info hehe

(and no worries - I don't offend easily so...)
I was never bothered by the thread I just like to give out as much info as possible for the next guy who has some sort of similar issue

Tuathal

Well... That sucks. I don't have identical hardware running linux so I can' t really test that.


Well, both of my NIC's support some sort of hardware assistance. The Intel seems to support more. It lists:
Offload IP checksum recieve
Offload TCP Checksum recieve
Offload IP checksum send
Offload TCP checksum send
The 3Com merely has a 'hardware checksumming' option.


Here's the page for that switch:
SMC8505T Page
SMC8505 Spec Sheet - PDF Format


Ok, it looks to me like it's probably the switch. So, what do you recommend that's not going to break the bank? I'll just throw this up on the appraisal table later on.

I must say, I'm dissapointed. If something is advertised as Gigabit, it damn well ought to be able to perform that. Hell, even if it was performing at half it's rated speed I would have been happy. I figure 1gb = 128MB/s
factoring in overhead, it's probably more like 90-100MB/s. So, If I would have been able to get 45MB or so, I wouldn't be complaining but this is unacceptable, IMO.

BTW, great site. It's people such as you and Logik that make me glad I decided to visit the Commport some years ago.

Thanks for the help/suggestions.

Thanks for the props! I put it together so I would't have to type answers to questions all the time

I need to borrow some time so I can write some new articles -so much to do, so little...

Logik is a tough act to follow...

What about a Cisco 2948G? I don't know if a grand would break the bank for you though...

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Network News and Reviews

yup yup - Dalan's switch suggestion would be what I'd try to go with if at all possible...
Tu

Yeah, that's a bit of overkill. This is for home, so I don't need 48 Gbe ports.

I wish my boss would hurry up and take these HP Procurve switches out of the books and give them to us. They're just sitting here wasting away.

Procurve 4000M

Nice.
I've not used them - but I've heard others who liked em

hey - Netgear makes a (imho) decent / good line of business products

what about this one: Netgear GS108

Excellent suggestion!

I take it both of you agree this is a good switch? If so, I'll go ahead and get that. I'll just throw this SMC on the appraisal table.

hehe looks like it -
hmmm
kk - lock this thread and make it sticky - I have dalentech support for Netgear W()()H()()

(lol I'm seriously stoked by that)

Holy shit Tuathal...Where'd you learn all this?



You're hardcore into this, huh?

lol that was Dalantech

I luckily don't have to get that indepth (at least not often enough to be able to give that kind of explanation) hehe

Damn impressive ain't it?
Tuathal