Strange Mac Network Speed Problem
 

I had high speed cable installed 2 weaks ago and have been fighting with them over slow speeds since. I signed up for the 4.0Mbps service and the fastest I have got is about 2.5 They have sent line techs out several times and everytime they tell me there is nothing wrong and they are getting 5.0+ speeds at the pole.

I have been waiting for Apple to come out with the new PowerBooks but so far they haven't so I bought a nice but inexpensive HP laptop running XP Home for now untll Apple gets off their butts.

I plugged the cable modem line into the HP laptop and was totally shocked at what I saw. Almost every speed test page gave me 3.5+Mbps every time. I unplugged the network cable and put it back into the iMac and ran several tests getting the same 1.5-2.5 speeds, switched back to the HP and 3.5+

dslreports is the main test site i have used to test speed.

I checked all the settings on my iMac, energy settings off and CPU set at highest speed. Networking is networking either on Macs or PC's so does anyone have any ideas ? I am totally lost on this one.



P....

Try the diagnostic tool here:
http://jlab4.jlab.org:7123/

Which iMac do you have? What version of OS X?

Could be the ethernet port on the iMac is bad. Since you've already got two computers and probably will have a third when the new Powerbooks come out, I suggest getting a router. Then you can connect both (all three?) to the web at the same time, and network them together as well. Then, if the iMac still has speed problems, you probably should call Apple.

i'm using a new 20" iMac with 1gig ram running OSX 10.3.7

i just ran the test page you posted and i got the following

laptop pc 3.76Mbps 1st try
laptop pc 6.38Mbps 2nd try

iMac 1.20Mbps 1st try
iMac 2.60Mbps 2nd try

using the same motorola cable modem and network cable

something is wrong !



P....

But you didn't show us the most important info that that diagnostic tool gives you - it tells you why your speed might be lower. Didn't it mention any possible problems?

And, just to be sure, does your cable-modem hook up to your Mac via an Ethernet cable? (Or is it possibly hooked up via USB?)

First of all, DSLReports' little speed tester thing should NOT be considered accurate at all. Try a different browser on your iMac with that DSLReports thing and I bet you'll see different results.

Second, just because you have a 4Mbps connection does not mean that it is 4Mbps just for you. In most cases the cable company shares that 4Mbps with a decent-sized neighborhood, so your speed will vary depending upon other's usage.

Third, there's no way to know what equipment/lines are between you and DSLReports or any other site for that matter. If for some weird reason, you get routed through an overloaded router somewhere, you may see slower than 4Mbps throughput. This is not the cable company's fault. This is not Apple's fault. Welcome to the internet.

What I would suggest before calling Apple to complain is that you transfer some big files between your iMac and your new laptop. Keep in mind that the 100Mbps that your network adaptor refers to is the theoretical best....never happens, so don't get mad at HP or Apple when you don't see that.

The one part of this that isn't clear is why your new HP laptop would appear faster when accessing DSLReports. My guess is they probably created/tested their speed tester with a PC in mind and it works differently when accessed from a Mac.

Well, I think I've got the answer now.

I went to DSL reports and checked out the Speed Test thing. It's Java-based. Java under Mac OS X is HORRIBLY slow. That's the issue.

I tried here at work as I have a PC and a Mac side by side on two separate ports, and I know that our LAN is not slowing things down for either machine (tested those speeds tooo and both mac and PC get the sam results in downlaod speeds) but once I got to DSL reports, the Mac was at half the speed of the PC... So... most probably a java issue as was said in the previous post...

Raven - Congrats on your 1,024th post! Your megapost.

why should java on the mac run slower, that kinda bums me out.

i thought my Mac would at least be as fast as a windoze machine.


does this mean the Mac is slower at everything on the internet
or only java related apps ?



P....

Actually, that would be Kilopost…

1) I don't think it is true that Java is generally slower on OS X than on other platforms. Some things will be slower (per GHz) on the Mac compared to Windows, some things will be faster. Most people see a 1 GHz Mac G5 as equivalent to something like a 1.3 to 1.5 GHz Pentium4.

2) I think the difference in your DSL reports results may reflect a difference in what is being measured. I.e. I think it is likely that the tests are not correctly measuring the bandwidth when run on the Mac.
I don't know why this would be.

3) As others have said, the best test of bandwidth is to do a download of a big file and see how long it takes on your 2 machines.

4) You still haven't shown us the interesting part of the results from the diagnostic tool I pointed you to - their summary of what is wrong with your connection. Press the "Statistics" button on their web page to get the detailed report from your test.

5) You didn't answer my question as to whether your modem hooks up to your Mac with Ethernet or with USB.

Try this site:

http://www.bandwidthplace.com/speedtest/

or this one:

http://www.pcpitstop.com/internet/Bandwidth.asp

My results varied as expected, but they weren't half of the 3mbps my cable company provides. :D

By the way, I tried the test that Hayne recomended and got these results:
/Web100 Network Diagnostic Tool v5.2.0f
click START to begin
Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done
running 10s outbound test (client to server) . . . . . 239.63Kb/s
running 10s inbound test (server to client) . . . . . . 3.04Mb/s
Your Workstation is connected to a Cable/DSL modem

If your new iMac (G5?) is consistantly getting half the speed of the PC on this test, I think you've got a hardware problem.

heres the statistics

WEB100 Enabled Statistics:
Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done
running 10s outbound test (client to server) . . . . . 181.64Kb/s
running 10s inbound test (server to client) . . . . . . 531.22kb/s

------ Client System Details ------
OS data: Name = Mac OS X, Architecture = ppc, Version = 10.3.7
Java data: Vendor = Apple Computer, Inc., Version = 1.4.2_05

------ Web100 Detailed Analysis ------
Cable modem/DSL/T1 link found.
Link set to Full Duplex mode
Information: throughput is limited by other network traffic.
Good network cable(s) found
Normal duplex operation found.

Web100 reports the Round trip time = 97.63 msec; the Packet size = 1368 Bytes; and
No packet loss - but packets arrived out-of-order 44.97% of the time
This connection is network limited 99.85% of the time.
Contact your local network administrator to report a network problem
Contact your local network admin and report excessive packet reordering

Web100 reports TCP negotiated the optional Performance Settings to:
RFC 2018 Selective Acknowledgment: OFF
RFC 896 Nagle Algorithm: ON
RFC 3168 Explicit Congestion Notification: OFF
RFC 1323 Time Stamping: ON
RFC 1323 Window Scaling: OFF
Information: Network Middlebox is modifying MSS variable
Server IP addresses are preserved End-to-End



heres the More Details


WEB100 Kernel Variables:
Client: localhost/127.0.0.1
AckPktsIn: 229
AckPktsOut: 0
BytesRetrans: 0
CongestionSignals: 0
CountRTT: 127
CurrentCwnd: 8208
CurrentMSS: 1368
CurrentRTO: 330
CurrentRwinRcvd: 65535
CurrentRwinSent: 5792
CurrentSsthresh: 2147483647
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 673056
DataPktsIn: 0
DataPktsOut: 492
DupAcksIn: 103
ECNEnabled: 0
FastRetran: 0
MaxCwnd: 10944
MaxMSS: 1368
MaxRTO: 540
MaxRTT: 200
MaxRwinRcvd: 65535
MaxRwinSent: 5792
MaxSsthresh: 0
MinMSS: 1368
MinRTO: 280
MinRTT: 80
MinRwinRcvd: 65535
MinRwinSent: 5792
NagleEnabled: 1
PktsIn: 229
PktsOut: 492
PktsRetrans: 0
Rcvbuf: 128000
SACKEnabled: 0
SACKsRcvd: 0
SmoothedRTT: 100
Sndbuf: 128000
SndLimTimeRwin: 0
SndLimTimeCwnd: 10317669
SndLimTimeSender: 14914
SndLimTransRwin: 0
SndLimTransCwnd: 1
SndLimTransSender: 1
SndLimBytesRwin: 0
SndLimBytesCwnd: 673056
SndLimBytesSender: 0
SumRTT: 12400
Timeouts: 0
TimestampsEnabled: 1
WinScaleRcvd: 0
WinScaleSent: 7
DupAcksOut: 0
StartTime: 2147483647
CurrTime: 10337910
c2sData: 2
c2sAck: 2
s2cData: 8
s2cAck: 2

Checking for mismatch condition
(cwndtime > .3) [0.99>.3], (MaxSsthresh > 0) [0>0],
(PktsRetrans/sec > 2) [0>2], (estimate > 2) [106.89>2]
Checking for mismatch on uplink
(speed > 50 [0.52>50], (xmitspeed < 5) [0.18<5]
(rwintime > .9) [0>.9], (loss < .01) [1.0E<.01]
Checking for excessive errors condition
(loss/sec > .15) [1.0E>.15], (cwndtime > .6) [0.99>.6],
(loss < .01) [1.0E<.01], (MaxSsthresh > 0) [0>0]
Checking for 10 Mbps link
(speed < 9.5) [0.52<9.5], (speed > 3.0) [0.52>3.0]
(xmitspeed < 9.5) [0.18<9.5] (loss < .01) [1.0E<.01], (link > 0) [100>0]
Checking for Wireless link
(sendtime = 0) [0.00=0], (speed < 5) [0.52<5]
(Estimate > 50 [106.89>50], (Rwintime > 90) [0>.90]
(RwinTrans/CwndTrans = 1) [0/1=1], (link > 0) [100>0]
Checking for DSL/Cable Modem link
(speed < 2) [0.52<2], (SndLimTransSender = 0) [1=0]
(SendTime = 0) [0.0014433951316916592=0], (link > 0) [100>0]
Checking for half-duplex condition
(rwintime > .95) [0>.95], (RwinTrans/sec > 30) [0>30],
(SenderTrans/sec > 30) [0.10>30], OR (link <= 10) [100<=10]
Checking for congestion
(cwndtime > .02) [0.99>.02], (mismatch = 0) [0=0]
(MaxSsthresh > 0) [0>0]

bw = 106.89 based on packet size = 10Kbits, RTT = 97.63msec, and loss = 1.0E-6
The theoretical network limit is 106.89 Mbps
The transmit buffer (125.0 KByte) limits the application to 10.00 Mbps
Your receive buffer (63.0 KByte) limits the application to 5.12 Mbps
The network based flow control limits the application to 0.85 Mbps

Client Data reports link is 'T1', Client Acks report link is 'T1'
Server Data reports link is 'OC-48', Server Acks report link is 'T1'




not sure what it all means ?




P....

i also tried downloading a 200MB file from microsoft.
the pc averages 3.7-4.1 Mbps the whole time and the
mac averages 1.5-2.2 Mbps

i tried this several times and the speeds were pretty
consistant.

i need to take the iMac into the local Mac store and let
them look at it.


P....

It seems to be reporting a problem with your network, but that might be anything between you and your ISP.
You should repeat the test, getting the details with your HP laptop, and then compare what it says. Of course you need to run the two tests (Mac & HP) as close together in time as possible since otherwise changes in the condition of the Internet will muddy the issue.

And you still haven't answered my question (#5) about how your modem is connected to your Mac or HP !

You may find that they find nothing wrong with it since the problem might be due to the particular network setup that you have at home.

i'm using the same modem (Motorola SB5100) and network cable
for both machines. i unplug the cable (at computer end) and switch
to other machine.




P....

here is statistics from laptop pc


WEB100 Enabled Statistics:
Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done
running 10s outbound test (client to server) . . . . . 363.58Kb/s
running 10s inbound test (server to client) . . . . . . 3.78Mb/s

------ Client System Details ------
OS data: Name = Windows XP, Architecture = x86, Version = 5.1
Java data: Vendor = Sun Microsystems Inc., Version = 1.4.2_05

------ Web100 Detailed Analysis ------
Cable modem/DSL/T1 link found.
Link set to Full Duplex mode
No network congestion discovered.
Good network cable(s) found
Normal duplex operation found.

Web100 reports the Round trip time = 123.74 msec; the Packet size = 1380 Bytes; and
No packet loss - but packets arrived out-of-order 34.47% of the time
This connection is receiver limited 79.43% of the time.
Increasing the current receive buffer (63.0 KB) will improve performance
This connection is network limited 20.41% of the time.
Contact your local network administrator to report a network problem
Contact your local network admin and report excessive packet reordering

Web100 reports TCP negotiated the optional Performance Settings to:
RFC 2018 Selective Acknowledgment: ON
RFC 896 Nagle Algorithm: ON
RFC 3168 Explicit Congestion Notification: OFF
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: OFF
Information: Network Middlebox is modifying MSS variable
Server IP addresses are preserved End-to-End


MORE.....

WEB100 Kernel Variables:
Client: localhost/127.0.0.1
AckPktsIn: 670
AckPktsOut: 0
BytesRetrans: 0
CongestionSignals: 0
CountRTT: 438
CurrentCwnd: 66240
CurrentMSS: 1380
CurrentRTO: 340
CurrentRwinRcvd: 65535
CurrentRwinSent: 5840
CurrentSsthresh: 2147483647
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 4738920
DataPktsIn: 0
DataPktsOut: 3434
DupAcksIn: 231
ECNEnabled: 0
FastRetran: 0
MaxCwnd: 66240
MaxMSS: 1380
MaxRTO: 340
MaxRTT: 180
MaxRwinRcvd: 65535
MaxRwinSent: 5840
MaxSsthresh: 0
MinMSS: 1380
MinRTO: 280
MinRTT: 80
MinRwinRcvd: 65535
MinRwinSent: 5840
NagleEnabled: 1
PktsIn: 671
PktsOut: 3434
PktsRetrans: 0
Rcvbuf: 128000
SACKEnabled: 3
SACKsRcvd: 0
SmoothedRTT: 130
Sndbuf: 128000
SndLimTimeRwin: 7958955
SndLimTimeCwnd: 2045855
SndLimTimeSender: 14725
SndLimTransRwin: 1
SndLimTransCwnd: 1
SndLimTransSender: 1
SndLimBytesRwin: 4200720
SndLimBytesCwnd: 538200
SndLimBytesSender: 0
SumRTT: 54200
Timeouts: 0
TimestampsEnabled: 0
WinScaleRcvd: 2147483647
WinScaleSent: 2147483647
DupAcksOut: 0
StartTime: 2147483647
CurrTime: 10025710
c2sData: 2
c2sAck: 2
s2cData: 8
s2cAck: 3

Checking for mismatch condition
(cwndtime > .3) [0.20>.3], (MaxSsthresh > 0) [0>0],
(PktsRetrans/sec > 2) [0>2], (estimate > 2) [85.08>2]
Checking for mismatch on uplink
(speed > 50 [3.78>50], (xmitspeed < 5) [0.36<5]
(rwintime > .9) [0.79>.9], (loss < .01) [1.0E<.01]
Checking for excessive errors condition
(loss/sec > .15) [1.0E>.15], (cwndtime > .6) [0.20>.6],
(loss < .01) [1.0E<.01], (MaxSsthresh > 0) [0>0]
Checking for 10 Mbps link
(speed < 9.5) [3.78<9.5], (speed > 3.0) [3.78>3.0]
(xmitspeed < 9.5) [0.36<9.5] (loss < .01) [1.0E<.01], (link > 0) [100>0]
Checking for Wireless link
(sendtime = 0) [0.00=0], (speed < 5) [3.78<5]
(Estimate > 50 [85.08>50], (Rwintime > 90) [0.79>.90]
(RwinTrans/CwndTrans = 1) [1/1=1], (link > 0) [100>0]
Checking for DSL/Cable Modem link
(speed < 2) [3.78<2], (SndLimTransSender = 0) [1=0]
(SendTime = 0) [0.001469629079593015=0], (link > 0) [100>0]
Checking for half-duplex condition
(rwintime > .95) [0.79>.95], (RwinTrans/sec > 30) [0.10>30],
(SenderTrans/sec > 30) [0.10>30], OR (link <= 10) [100<=10]
Checking for congestion
(cwndtime > .02) [0.20>.02], (mismatch = 0) [0=0]
(MaxSsthresh > 0) [0>0]

bw = 85.08 based on packet size = 10Kbits, RTT = 123.74msec, and loss = 1.0E-6
The theoretical network limit is 85.08 Mbps
The transmit buffer (125.0 KByte) limits the application to 7.89 Mbps
Your receive buffer (63.0 KByte) limits the application to 4.04 Mbps
The network based flow control limits the application to 4.08 Mbps

Client Data reports link is 'T1', Client Acks report link is 'T1'
Server Data reports link is 'OC-48', Server Acks report link is 'Ethernet'

Weird that there are indications about there being network congestion with the Mac but not the PC... Did you run both tests one after the other or at realy different time ?

I found the manufacturer's web page for that modem:
http://broadband.motorola.com/noflash/sb5100.html

But I ask again - are you using an Ethernet cable or a USB cable to hook the modem up to the Mac ? If you need help in understanding the question or in telling the difference between these two different types of cables, let us know.

(Here's an image that shows what the USB symbol looks like:
http://www.iomega.com/support/manual...ct_usb_com.gif )

Actually, he seems to have problems with both. I suspect the cable modem.

His PC:

Web100 reports the Round trip time = 123.74 msec; the Packet size = 1380 Bytes; and
No packet loss - but packets arrived out-of-order 34.47% of the time
This connection is receiver limited 79.43% of the time.
Increasing the current receive buffer (63.0 KB) will improve performance
This connection is network limited 20.41% of the time.
Contact your local network administrator to report a network problem
Contact your local network admin and report excessive packet reordering

His Mac:

No packet loss - but packets arrived out-of-order 44.97% of the time
This connection is network limited 99.85% of the time.
Contact your local network administrator to report a network problem
Contact your local network admin and report excessive packet reordering




My Mac:

Web100 reports the Round trip time = 163.30 msec; the Packet size = 1368 Bytes; and
No packet loss was observed.
This connection is receiver limited 92.79% of the time.
Increasing the current receive buffer (63.0 KB) will improve performance
This connection is network limited 7.05% of the time.

Did tests too, and both mac and PC come up with something around .2% being out of order, wish is ok... but the numbers coming out for this cable modem are incredibly high... Probably the source of the issue indeed... Maybe its in need of firmware updates ?

i am using ethernet cable to connect the modem between the two
computers. the modem is new and the cable is new plus i have
tried using other cables with the same results.



P....

This is all quite strange, but I would suggest you do as cwtnospam has suggested above - buy a router (which, as he has said, you will be needing anyway in order too be able to connect more than one computer to Internet) and plug the router into the modem and then plug your Mac into the router and redo the bandwidth tests.

Yes, a router may help. Remember, however, that you are having some problems, although not as severe, with the PC's connection, too. That's why I suspect the cable modem. It could also be the drop from the street to your home, or signal leak(s) in the house. If it's any of these, the company to call is your cable provider.

the cable drop from the pole to the house and then to the modem is
all 2 weaks old. the modem is 2 weaks old.

i bought a Linksys router this morning and hard wired both machines
into it.

on the laptop pc i get 3.5-4.0 Mbps
on the mac i get 1.5 - 2.5 Mbps

the packets-out-of-order is about the same on both machines.

i called motorola and they had me bring up a diag page showing the
download "SNR" being 35db and the download power lever at 7db
the upload power lever is 39 dBmV and told me there is nothing
wrong with the modem and that i should call the cable provider.



P....

Do you have any cables coming out of the wall, but not plugged into anything like a tv or cable modem? Have you spliced any of the coaxial cable yourself?
I'm thinking signal leak is affecting the Mac more than it is the PC for some reason.

Edit:
When you call the cable company, be sure to show them that BOTH computers are affected. The PC is merely less affected. This is critical because it demonstrates that the problem is somewhere from the cable modem to their office.

This seems pretty definitive in indicating a problem on the Mac.
But just to be sure, did you unplug the PC when doing the test on the Mac (and vice versa) so that you are sure that the other machine is not using any network bandwidth?
And you swapped the cables and ports you are using between the PC and Mac as well - to eliminate all possible variables?

I disagree. Both systems report packets arrived out of order. Something external is causing that.

I'm wondering if the packets that the Mac is sending are larger than the PCs. If they are, they would be more susceptible to interference and that would explain the slower speed and packets arriving out of order. Anyone know the answer or how to find it?
I know this still leaves the underlying problem, but it may help us understand what's going on. :rolleyes:

Please check your MTU and Firewall settings... :)

A similar disparity between bandwidth as measured on a PC and Mac was reported in this other thread:
http://forums.macosxhints.com/showthread.php?p=178976
There it was found that the problem was due to network settings that had been changed by Broadband Optimizer. Putting the settings back to the system defaults solved the problem.

Make sure your Mac isn't doing anything else on the network - one other throttled IP task can cut your bandwidth in half. Any P2P programs running (eDonkey/Acquisition)? If you're not sure, show us the results of:

sudo netstat -na | grep ESTABLISHED

Also, if you have the Mac OS X firewall on, turn it off.