Solved

What is the max Full duplex throughput of Gigabit Ethernet ?

Posted on 2011-09-15
11
1,718 Views
Last Modified: 2012-06-27
Hi!

This question comes from a friendly argument.

Theoritically, Gigabit Ethernet can Transmit/Receive about 100 MB/Sec.
Now most people understand that Full-Duplex means that you can Transmit/Receive at the same time (in otherwords transmitting and receiving data are independable).


Now this friend says that : "this is very resonable.  BUT in reality Gigabit Ethernet boards do not Transmit/Receive simultanouosly".

So, Who is right ?
Is the theoretical throughput of Transmit + Receive at the same time 100 MB or 200 MB ?
Is it true that in practice "Gigabit Ethernet boards do not Transmit/Receive simultanouosly" ?
I had spent yesterday a lot of time searching for the answer, but did not find :-(


Now here are 2 practical questions :
1) If I connect 2 Windows PCs directly, and try to transmit "tons of data in both directions", what is maximal expected throuput (Using Fullduplex gigabit Ethernet) ?
2) If I connect 2 Windows PCs through a "good gigabit Ethernet switch", and try to transmit "tons of data in both directions", what is maximal expected throuput (Using Fullduplex gigabit Ethernet) ?

Is there some where a C/C++ code which gives the answer for the two above questions ?


zmau
0
Comment
Question by:zmau
  • 4
  • 4
  • 2
  • +1
11 Comments
 
LVL 6

Accepted Solution

by:
netjgrnaut earned 500 total points
ID: 36542281
Gigabit Ethernet provides a 1000Mbps (mega bits, not bytes) channel.  This equates to 125MBps (1000 bits / 8 = 125 bytes).

Full duplex is as you describe it (simultaneous transmission).  Here's a reference from Wikipedia:  

1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of adaptive equalization and a 5-level pulse amplitude modulation (PAM-5) technique.
(link to full article)

Your practical questions are a bit too vague to answer, as effective throughput will depend on what "tons of data" means, as well as what network protocol you're using for the transfer - not to mention all the OS-level variables.  

For detailed answers and methods for testing your effective throughput (aka "goodput"), spend some time with this Wikipedia article.

I hope that answers your basic question, and provides a good jumping off point to better understand network throughput.

If you have questions about developing network test applications in C/C++, I suggest you post that as a separate question in a more programming-oriented zone.

Good luck!
0
 
LVL 6

Assisted Solution

by:netjgrnaut
netjgrnaut earned 500 total points
ID: 36542313
Sorry - I left out some math...

As you've probably figured out from the original post, full duplex gigabit Ethernet would have a theoretical throughput of 250 mega bytes per second.  That's for the channel - not any given computer on the link.

Such "double the speed for full duplex" numbers are often misleading marketing speak.  The link is still 125MBps in one direction, so a given host can only SEND 125MBps max.  The fact that it can simultaneously RECEIVE 125MBps means the channel size (bandwidth) is 250MBps.

This means that "tons of data in both directions" can theoretically move at 125MBps in *each* direction *at the same time*.  So (very simply) if you had 250MB of data to send in *each* direction, it works out like this...

half-duplex link:
(computer 1 x 250MB = 2 seconds) + (computer 2 x 250MB = 2 seconds) = 4 seconds

full-duplex link:
(computer 1 x 250MB = 2 seconds) & (computer 2 x 250MB = 2 seconds) = 2 seconds

Hope that helps!
0
 
LVL 35

Expert Comment

by:Ernie Beek
ID: 36542315
By default Gigabit Ethernet is full-duplex but it supports half-duplex for hubs (repeaters).

In a departure from both 10BASE-T and 100BASE-TX, 1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of adaptive equalization and a 5-level pulse amplitude modulation (PAM-5) technique.

Source: http://en.wikipedia.org/wiki/Gigabit_Ethernet

The theoretical speed would be 125MB/s, though normally the speed depends on a lot of factors, not only the line speed. Bearing that in mind the maximal throughput in Q1 and Q2 would be: 125MB/s in either direction (theoretically speaking of course ;)
0
 
LVL 35

Expert Comment

by:Ernie Beek
ID: 36542321
Ok, didn't realize I was typing that slow :-~
0
 
LVL 6

Expert Comment

by:netjgrnaut
ID: 36542333
It must be my full duplex fingers. ;-)
0
Control application downtime with dependency maps

Visualize the interdependencies between application components better with Applications Manager's automated application discovery and dependency mapping feature. Resolve performance issues faster by quickly isolating problematic components.

 
LVL 35

Expert Comment

by:Ernie Beek
ID: 36542339
Ah now I see, I had autonegotiation turned off :)
0
 
LVL 1

Author Comment

by:zmau
ID: 36542351
You are greate guys.
0
 
LVL 35

Expert Comment

by:Ernie Beek
ID: 36542356
Just trying to do the best we can (be it full or half duplex ;).
0
 
LVL 7

Expert Comment

by:susguperf
ID: 36542420
That's why we guys have always are link up ;) Loved to read it...

~SG~
0
 
LVL 6

Expert Comment

by:netjgrnaut
ID: 36542432
You can show some love by awarding points and marking this question as answered.  :-D
0
 
LVL 1

Author Closing Comment

by:zmau
ID: 36544577
I am sorry it took me so long to mark this question as answered.
I am not always near my computer...
0

Featured Post

Save on storage to protect fatherhood memories

You're the dad who has everything. This Father's Day, make sure your family memories are protected. My Passport Ultra has automatic backup and password protection to keep your cherished photos and videos safe. With up to 3TB, you have plenty of room to hold the adventures ahead.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Super Scope, DHCP 5 52
nipper studio 2 34
Etherchannel trunking 10 41
Looking for a network enabled locker remotely controlled like Amazon locker 2 27
If your business is like most, chances are you still need to maintain a fax infrastructure for your staff. It’s hard to believe that a communication technology that was thriving in the mid-80s could still be an essential part of your team’s modern I…
ADCs have gained traction within the last decade, largely due to increased demand for legacy load balancing appliances to handle more advanced application delivery requirements and improve application performance.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

920 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

13 Experts available now in Live!

Get 1:1 Help Now