Network performance...

This is probably a frequently asked question but I have not found any discussion on the subject, so help me out people as I am far from a networking guru and even further from a Linux guru - I am a programmer… LOL.

Either way, I have a local server that is running Centos that is basically a test bed and file server. My router practices load balancing, which is a real pain when transferring more than large files.

The question: Would there be any benefit for me to run two NIC's in the machine, for instance one NIC for incoming data and one NIC for outgoing data?

7 Replies

Mostly, these discussions concern themselves with Linux running on a Linode, but I guess we can always try to help a fellow Linux user, regardless of platform.

However, I don't understand the question. You have a local server - so what load balancing is your router performing and why is this a pain during large file transfers? Load balancing normally implies distributing inbound network traffic across two or more servers.

In all but the most exceptional circumstances, having multiple NICs in one machine connected to the same network segment is a waste of hardware.

Thanks for your reply.

My network is setup as follows, I have a cable modem connected to a 4 port router/switch. Connected to the switch I have 3 boxes, 2 of which are just normal computers that I work on everyday. The third is my testbed/samba file server. The load balancing that my router performs as I understand it is dividing all traffic by 4, uploads included. So if my way of thinking is right it's limited by a quarter before I even start transfering files backwards and forwards over the cable. There go, I figure if I have one nic for incoming data and one for outgoing data it'll be faster.

What's the manufacturer / model number of the router/switch?

its a netgear fr114p w/ latest firmwear

Its not load balacnig, its standard routing.

You can get routers that do QoS (quality of service)/shaping, but that only affects outoging packets which you have control over. You may want to give VOIP packets the highest priority or ftp the lowest priority.

You dont have fine-grained control over what packets are coming in. You may have n inward TCP connections open but you are not guaranteed of 1/n bandwidth for each.

You cant try

  • limiting inward bandwidth at the application level eg the –limit-rate= option of wget

  • build your own router with shaping eg http://www.opalsoft.net/qos/DS.htm or better still www.openbsd.org and http://www.openbsd.org/faq/pf/index.html

  • increasing tcp buffers to reduce latency; heres what I do

echo 262144 > /proc/sys/net/core/wmem_max

echo 262144 > /proc/sys/net/core/rmem_max

echo 1 > /proc/sys/net/ipv4/tcp_timestamps

echo 1 > /proc/sys/net/ipv4/tcpwindowscaling

echo 1 > /proc/sys/net/ipv4/tcp_sack

echo 8388608 > /proc/sys/net/core/wmem_max

echo 8388608 > /proc/sys/net/core/rmem_max

echo "4096 87380 4194304" > /proc/sys/net/ipv4/tcp_rmem

echo "4096 65536 4194304" > /proc/sys/net/ipv4/tcp_wmem

echo 65536 > /proc/sys/net/core/rmem_default

echo 65536 > /proc/sys/net/core/wmem_default

ifconfig eth0 txqueuelen 1000

I'm not sure what exactly you are asking, but it sounds like what you're looking ofr is traffic shaping. It's been awhile since I've messed around, but if you check out the "tc" linux program and google "linux traffic shaping" you should be headed the right direction.

Thanks for all your input guys, my conclusion, drawn from your input and some reading I've done since is that what pclissold said holds a lot of water. That is to say, in this case having more than one NIC in this machine is a waste of hardware.

Since now I have a grasp on the whole Unix thing, to an extent, I've decided to implement it on a wider basis. See, I am what you'd call a Windows junky, it's quick and easy. Until recently I've held nothing but contempt for Unix (pure ignorance based on no expirience with it).

I also plan to upgrade my current box and make it my router as one of you suggested. I've had so much trouble with my Netgear router, the firewall setup is pathetic. I also intend to upgrade my VoIP system here soon and my router refuses to play nicely with my phone system so Asterisk here I come.

Once again, thanks for all your input and you're all much more helpful than Windows people…LOL

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