How many concurrent connections can a standard NIC handle?

Posted on 2004-11-10
Last Modified: 2012-05-05
This question stems from running network applications that run many threads and thus have many concurrent connections.
When buying firewalls and routers they advertise the number of concurrent connections  that the device can handle. SOHO routers/firewalls can gennerally handle 6000, with small business equipment handling 35,000 and above. I beleive this number is advertised because the equipment has to smartly handle each connection, thus it becomes a limiting factor. But what I am hunting for is if I hook a Standard network card up to a network, how many raw concurrent connections  can it handle before dropping connections?  I dont need a definite number from you guru's, but a general idea would help me greatly.

Thank you so much in advance I know I am asking the question in the right forum.


Sarasota, FL

I am assigning this question a level of difficult because the only way you know the answer is to of run into a similiar problem in the real world.
Question by:merchantsportal
    LVL 79

    Expert Comment

    Generally speaking, assuming TCP/IP only, the limit is around 65,000 because that is all the ports that are available in IP. Each simultaneous connection requires a unique destination port.
    Just as in the products that actually state claims of concurrent connections, it is based on available bandwidth, CPU, memory and other internal limitations of the product, the same would apply to any "standard" NIC. There really is no "standard" performance-wise. It is all relative to the NIC manufacturer, and the system that it is installed in.
    LVL 5

    Accepted Solution

    There is no such thing as "concurrent connections" for NIC - its not relevant. For the NIC its all bits and bytes...:)
    It doesn't know whether there is a connection or not. NICs performance is measured in bandwidth its able to pass through it and this parameter depends on the drivers and operating system they are running on.

    Regarding the "connections" - the connections can be opened but idle (no traffic is passed on the connection itself) or it can be really loaded. Another parameter that is important "ability to open amount of connection per period of time - like 1000 connections opened per second") - all these measurements and benchmarks are coming from the higher level than NICs physical layer (ethernet).

    Your question probably is addressed to "how many frames per second can the NIC's driver pass?" or  "what is the max bandwidth utilisation?".
    For these questions the asnwer "depends on driver" is the best fit, because every driver for the NIC differs in performance, e.g. we are developing a hardware appliance and our best throughput was something like 100mbps of short packets (64bytes) on a gigabyte ports of the NIC, so we rewrote those drivers and optimised their performance and today it goes around 700mbps. This example is coming to emphasize the idea of NICs performance parameters and to explain once more that "amount of connections" per NIC is not a valid parameter in general.


    Author Comment

    After some research ont he pointed answers above, muhalok's answer is very on track.

    Thank You

    Featured Post

    6 Surprising Benefits of Threat Intelligence

    All sorts of threat intelligence is available on the web. Intelligence you can learn from, and use to anticipate and prepare for future attacks.

    Join & Write a Comment

    Suggested Solutions

    This solves the problem of diagnosing why an internet connection is no longer working. It also helps identify the likely cause of the lost connection if the procedure fails to re-establish your internet connection. It helps to pinpoint the likely co…
    Cable Modem Provisioning from DPoE compliant server  This Article is to support CMTS administrators to provide an overview of DOCSIS compliance configuration file, and to provision a cable modem located at customer place from a Back office serve…
    It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. It works on many operating systems, in many languages.
    Internet Business Fax to Email Made Easy - With eFax Corporate (, you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, fr…

    746 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

    15 Experts available now in Live!

    Get 1:1 Help Now