How can Fedora determine the maximum speed of network computer cards?

[Paul Smith]

On Fri, Nov 13, 2015 at 6:06 PM, Rick Stevens <ricks at alldigital.com> wrote:
>>>
>>> Is there something in Fedora that I might use to determine the
>>> maximum
>>> speed the network card of my computer can attain on Internet? I am
>>> thinking about wired Internet and not about wireless Internet.
>>>
>>> Thanks in advance,
>>
>>
>> You might need to explain the reason for your request since, it may
>> change the answer.
>>
>> As an example, my computer has a GigE port that runs to a 100Mbit
>> simple switch before getting to anything else.  So I would be limited
>> to a theoretical maximum of 100Mbit but I might want to know how fast I
>> can transfer files to/from another computer in my LAN.  The bottleneck
>> here could be the switch, my NIC, the other computers NIC, OS limits,
>> firewall slowdowns etc.
>>
>> So, for me I would really want to test an actual file transfer using a
>> number of setups.  Depending on each computer I could try Samba, FTP,
>> SCP.  I might run a wire to bypass the switch.  I might try with
>> firewalls and antivirus disabled.
>>
>> All this will also give me some clue on how fast I could run if I was
>> able to get a fiber connection, to let me know if my system would be a
>> serious limit to getting the full 1G of true fiber.  Obviously the
>> switch would have to be upgraded in my case.
>
>
> Generally speaking, any given NIC that has proper firmware and is in
> a relatively modern computer will run very close to the rated wire
> speed--provided the other end of the cable can handle it as well. Note
> that the effective transfer rate will usually be about 80-95% of that
> (for a 1Gbps NIC, 800-950Mbps).
>
> This does not include any overhead involved in the protocol used. You
> will find that things like FTP, rsync and the like will show lower
> data transmission rates (e.g. multiplying the number of bytes
> transferred by 8 to get number of bits transferred) due to their
> overhead and that they're dealing with TCP's inherent nagle algorithm
> and handshaking. TCP is designed to make sure things get to where
> they're supposed to go, and with that comes a lot of overhead. Things
> like UDR (rsync-over-UDP) will show much closer to the theoretical data
> transmission rate due to its use of UDP.
>
> The most common bottleneck to raw speed is the wire, switch, router,
> gateway or ISP that the NIC is connected to. You'll rarely find the NIC
> itself the limiting factor.

Thanks to all respondents! I could now determine that my network card
is a 100Mbps Fast Ethernet, and now it is clear why the speed test
(http://www.speedtest.net/) shows a download speed of just 85 Mbps
when my contracted speed is 120 Mbps.

Paul