How many concurrent connections can a standard NIC handle?

Posted on 2004-11-10
Medium Priority
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

ID: 12554578
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.

Accepted Solution

muhalok earned 1000 total points
ID: 12612855
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

ID: 12614449
After some research ont he pointed answers above, muhalok's answer is very on track.

Thank You

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