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Gigabit Conundrum

anguskype (apparently) - 07:06am Jan 3, 2007 PST
via email

Happy New Year everyone.

I greet the new year with networking problems.

Kindly see here, exhibit A, a brand new 17" Core 2 Duo MacBook Pro.

Everything seems to work fine with it except I am not getting Gigabit
Ethernet speeds on it.

See Exhibit B here, a Linksys SD2005 Gigabit Switch. It connects my
Linksys broadband router, my MacBook Pro, an iBook G4 and my RAID
appliance (an Infrant ReadyNAS NV).

I had switched (no pun intended) out an older switch (10/100) for the
new switch to get Gigabit speeds. The RAID has a 1 Gigabit-capable
Ethernet adaptor, and I figured I can get Gigabit speeds with my MacBook
Pro once the new switch was in. But no! I am still just getting Fast
Ethernet throughout.

I checked my cabling. It is all Cat 5e, so things should be good in
that, ah, category.

I tried manually setting my Mac's Network prefs to only use Gigabit, and
it connects to the RAID but I am not getting Gigabit speeds. I can copy
large files at Fast Ethernet speeds only.

A friend came over with his 15" PowerBook G4 (1.5 GHz) and it looked to
have Gigabit speeds. I plugged that into my switch and also manually
forced it to use Gigabit only. It connected fine but also could transfer
only Fast-E speeds to both the RAID and the 17" MBP.

Trying to narrow down the culprits, I then shared the Internet
connection on my 17" (from the Airport Express connection, to the
Ethernet port) and connected the 15" PB directly to the 17" MBP. I still
only got FE speeds, so it's probably not the switch or the RAID (but
then, why couldn't I get the 15" to transfer at Gigabit to the RAID?)

I have now reasonably eliminated most of the components of this topology
and can only conclude that either more than one of these devices is
malfunctioning (which seems rather unlikely) or there is some kind of
tweak that I need to do to *truly* enable Gigabit performance on my Mac
(or any Mac, since even the 15" did not achieve Gigabit speeds).

I am thus quite stumped and hope someone here can help.

Thanks,
Angus

Mark as Read

chuck goolsbee (apparently) - Jan 4, 2007 6:36 am (#1 Total: 9)

via email - chuck goolsbee

Posts: 433

Re: Gigabit Conundrum

>Everything seems to work fine with it except I am not getting Gigabit
>Ethernet speeds on it.

First off 'speed' is a measure of time & distance, 'gigabit' is a
measure of data capacity. The only time a network would be measured
in 'speed" is if it were dropped from a great height. If speed were a
factor in networking, we'd all strive to have REALLY short cables. ;)

So, in your description of troubleshooting steps, I never saw you
eliminate the most likely cause, in this case, the Linksys switch.
Have you connected two components directly and checked throughput
over a single cable? Is the switch "manageable"... meaning can you
connect to it via telnet/ssh/http and configure it? If so, what
feedback does it provide?

BTW: Autonegotiation and sensing of port bandwidth is something that
has never been implemented very well, or even consistently among
switch vendors.

_________________________________________
chuck goolsbee - fully RFC 1925 compliant

jeffreym205 (apparently) - Jan 4, 2007 6:36 am (#2 Total: 9)

via email

Posts: 29

Re: Gigabit Conundrum

On Jan 3, 2007, at 8:06 AM, Angus Wong wrote:

> I had switched (no pun intended) out an older switch (10/100) for the
> new switch to get Gigabit speeds. The RAID has a 1 Gigabit-capable
> Ethernet adaptor, and I figured I can get Gigabit speeds with my
> MacBook Pro once the new switch was in. But no! I am still just getting Fast
> Ethernet throughout.

http://www.macosxhints.com/article.php?story=20060616112919669

That might help you get started in the right direction. File Sharing
benefits from faster networks, however, file sharing, is a science
all to itself. I'm not sure what you meant by 'fast ethernet
throughput', unless you actually measured similar systems using only
FastE on a FastE switch. For example, in real world situations,
moving data on a 100B/T switched network, depending on types of files
and tranfer protocols, might be moving along at 5-8MB/s (megabytes/
second), but often it is actually slower, in the 2-4MB/s range. And
so, on a Gigabit switched network, achieving 10-15MB/s throughput is
noticeably faster. However, with some fine tuning and knowledge of
the kinds of files being transferred, it is possible to get closer to
30-40MB/s in the real world over a switched gigabit network.

Jeffrey

Todd Ruston (apparently) - Jan 4, 2007 6:36 am (#3 Total: 9)

via email

Posts: 41

Re: Gigabit Conundrum

On 1/3/07 at 6:06 AM, Angus Wong <anguskype

gmail.com> wrote:

> I have now reasonably eliminated most of the components of this
> topology

In all these tests how, exactly, are you measuring your transfer rates?
What protocol(s) are you using to connect and transfer data between
machines?

Have you searched Infrant's support site? Have you tried this
suggestion:

<http://www.infrant.com/wiki/index.php/FAQ#I.
27m_getting_poor_performance_with_my_Mac.__Is_there_anything_I_can_do.3>

I have no clue whether that's relevant to your issue, but I'm curious to
know what you find out.

- Todd

Chris Pepper (apparently) - Jan 8, 2007 12:05 pm (#4 Total: 9)

via email

Posts: 844

Re: Gigabit Conundrum

Angus,

        First, try the cross-over cable as Chuck suggested and see if
the two laptops run any faster. If not, you at least know the switch
isn't the problem.

        Using auto-sensing and when connected through thte switch,
type "ifconfig" and check the "media" line under en0 -- does it say
100 or 1000?

        Check /var/log/system.log -- I think it tells you how you're
connected whenever you connect an Ethernet cable.

        You're not getting confused by bits vs. bytes, are you?
Maximum speed over a gigabit connection is about 100mbytes/sec, as
someone alluded previously. It's unlikely you'd see that, but if
you're able to transfer at 13+ mbytes/sec, you're definitely
connected at gigabit.

        FWIW, I had trouble with an Asante GE switch some time ago,
and was told it didn't autonegotiate properly with cables under 7'
long. Your cables are probably fine, but perhaps one is bad...

                                                Chris
--
Chris Pepper: <http://www.reppep.com/~pepper/>
                             <http://www.extrapepperoni.com/>
Rockefeller University: <http://www.rockefeller.edu/>

jwblist (apparently) - Jan 9, 2007 6:40 pm (#5 Total: 9)

via email

Posts: 768

Re: Gigabit Conundrum

On Jan 8, 2007, at 11:05 AM, Chris Pepper wrote:

> FWIW, I had trouble with an Asante GE switch some time ago,
> and was told it didn't autonegotiate properly with cables under 7'
> long. Your cables are probably fine, but perhaps one is bad...

Ethernet (thankfully) isn't like SCSI, but nonetheless there are
oddities with cables.

At our office, I plugged my old IBM laptop into the proper hub some
years ago ("hub" ===> years ago ;-) ) and had no connection. Removed
and reinserted each end a couple of times...no connection after each
insertion. I switched the cable end-for-end (I have lots of miles
under me sailing), and it worked fine.

Why the end-for-end switch? It was easier than going down to the
basement to get another cable.

(We are presently having a hard time convincing some servers that
they should talk at 1G speeds; I feel the original poster's pain.)

--John

butchfag (apparently) - Jan 9, 2007 7:02 pm (#6 Total: 9)

via email

Posts: 67

Re: Gigabit Conundrum

On 1/8/07, Chris Pepper <pepper

reppep.com> wrote:
> First, try the cross-over cable as Chuck suggested and see if
> the two laptops run any faster. If not, you at least know the switch
> isn't the problem.

Hang on, Gigabit Ethernet uses a different spec for crossover cables
than 100TX...

http://logout.sh/computers/net/gigabit/

So you have to be sure you have a _Gigabit Crossover Cable_. But it's
my understanding that you can connect two Macs with a straightthrough
cable. Have you given that a go ? (This probably won't work to connec
to your RAID device, however).

Cordially,

Christopher Appell
European Market
SpecialtyJobMarkets.com
FreeRecruiting.com
JobMart.com

Chris Pepper (apparently) - Jan 10, 2007 11:49 am (#7 Total: 9)

via email

Posts: 844

Re: Gigabit Conundrum

At 6:02 PM -0800 2007/01/09, Christophe Appell wrote:
>On 1/8/07, Chris Pepper <pepper

reppep.com> wrote:
>>First, try the cross-over cable as Chuck suggested and see if
>>the two laptops run any faster. If not, you at least know the switch
>>isn't the problem.
>
>Hang on, Gigabit Ethernet uses a different spec for crossover cables
>than 100TX...
>
>http://logout.sh/computers/net/gigabit/
>
>So you have to be sure you have a _Gigabit Crossover Cable_. But it's
>my understanding that you can connect two Macs with a straightthrough
>cable. Have you given that a go ? (This probably won't work to connec
>to your RAID device, however).

        Why not? I'd expect the "Auto-MDI/MDI-X" detection on the Mac
to reverse its polarity, so it matched what the other end was
expecting, but I'm not an expert...

                                                Chris
--
Chris Pepper: <http://www.reppep.com/~pepper/>
                             <http://www.extrapepperoni.com/>
Rockefeller University: <http://www.rockefeller.edu/>

Lewis Butler (apparently) - Jan 11, 2007 11:58 am (#8 Total: 9)

via email

Posts: 1080

Re: Gigabit Conundrum

On 9-Jan-2007, at 19:02, Christophe Appell wrote:
> On 1/8/07, Chris Pepper <pepper

anguskype (apparently) - Jan 11, 2007 5:19 pm (#9 Total: 9)

via email

Posts: 11

Re: Gigabit Conundrum

Guys,

Thanks for all your input. I am going through all your recommendations,
but slowly, since the crazy work routine has resumed now that we're out
of the holiday period and it's harder now to debug the topology AND also
suffer downtime when I am unplugging networking gear and fooling around
with my computers.

Just two points to bring up in the interim: first is I had eliminated
the switch already as I did try connecting both Macs directly (I had
written that I tried sharing the connection via my Ethernet port from my
17" MBP to the 15" PB) but I will try again using the parameter tweaking
(once I get another Gigabit-equipped Mac to be at my place).

The other is a curious point and which was alluded to by some folks here
already: A co-worker advised me that he had discovered through much
painful trial and error that the PHYSICAL cabling is crucial in this
area. His words were "Cat 5e is a myth!" He had been debugging pretty
much the same set-up as me (I had recommended the Infrant ReadyNAS to
him) and he ended up splicing his own Cat 6 cabling to make it work. So
this is what I might have to go try. He had said that it's funny that
after all the attempts to debug Layers 2 and up, it was Layer 1
engineering that was overlooked.

Anyway, I'll let you guys know what I end up finding out about my
particular setup.

Thanks again for the inputs.

Angus

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