Solved

What is the max Full duplex throughput of Gigabit Ethernet ?

Posted on 2011-09-15
11
1,816 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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 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
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 
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
 
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 8

Expert Comment

by:Sushant Gulati
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

What, When and Where - Security Threats from Q1

Join Corey Nachreiner, CTO, and Marc Laliberte, Information Security Threat Analyst, on July 26th as they explore their key findings from the first quarter of 2017.

Question has a verified solution.

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

For many of us, the  holiday season kindles the natural urge to give back to our friends, family members and communities. While it's easy for friends to notice the impact of such deeds, understanding the contributions of businesses and enterprises i…
This article explains the fundamentals of industrial networking which ultimately is the backbone network which is providing communications for process devices like robots and other not so interesting stuff.
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
NetCrunch network monitor is a highly extensive platform for network monitoring and alert generation. In this video you'll see a live demo of NetCrunch with most notable features explained in a walk-through manner. You'll also get to know the philos…
Suggested Courses

626 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