Linux network bonding... use case?

eccerr0r

I wonder if this works:

I have an old laptop PC with built-in 10/100 Ethernet, no USB3, no PCMCIA, and 802.11n that seems to top out at 7MB/sec on a good day.
I have a USB2 10/100 Ethernet dongle.

Can I bond the two Ethernet devices together and plug both network connectors into two ports of a Gbit switch, and have them communicate to a machine with a native single Gbit Ethernet at 20MB/sec with no software hacks on that machine? I suspect a 10/100 switch with a GbitEthernet uplink to a Gbit machine should work similarly instead of wasting two Gbit ports?

If that works, what happens if the USB disconnects? One of the Ethernets disconnects?

Could I also bond the 802.11n and get all three to speed data along?

Other than a USB2 HDD, I wonder if this is a legit way to get data faster in/out of this machine... Anyone tried this and if it works, had good scalable results?
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bbgermany · Posted: Thu Sep 29, 2022 9:01 am Post subject:

Hi,

in theory, yes, you can bond them, but...

1. if you want a bit more "bandwdith" you need a managed switch, where you can config either lacp (802.3ad) or something similiar
2. if you use something like round robin, there is a chance, that you can use it without a managed switch, but it will not really improve throughput.

mostly you wont get more then the typical 10-12mb/s throughput, even with lacp, because "one bit" cannot be devided at last ;-)

if the usb disconnects and you have something like active-standby config, it will continue to run your network after maybe 2-5 loss packets. but this shouldn't be a problem at all.

greeting, Stefan
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eccerr0r · Posted: Thu Sep 29, 2022 3:04 pm Post subject:

At the physical layer, how does the "other" computer connected to the switch chose which bonded interface to send to...this seems very messed up IMHO, seems to require the other machine to know the topology of the machine with the bonded interface.

I think I have two manageable switches that I'm either using or in storage, but running them unmanaged at the moment. I'm not even sure they can do link aggregation (one is a Dell PC2708), that would make more sense than the so-called bonding.

I was hoping for much higher than 10-12MB/sec throughput, I already get 10-11MB/sec through the 10/100Mb onboard Ethernet by itself. Would be nice to get higher speeds through USB2 (480Mb/sec theoretical, have seen 30MB/sec to USB HDDs) and if I could aggregate 150Mb 802.11n too (seen 7MB/sec), that would be great.

My "pie in the sky" would be near 50MB/sec, hopefully using commodity hardware.
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szatox · Advocate Joined: 27 Aug 2013 Posts: 3131

eccerr0r · Posted: Fri Sep 30, 2022 12:23 am Post subject:

So what I'm hearing is that there's nothing really special about bonding and it only helps availability and sharing of the resource to multiple clients versus to one specific client. Sort of what I thought initially, but got a little giddy when I thought I read that it could share to one target...which would be what I need.

I don't think my switches support link aggregation so that's probably out of the question.

I may still have to implement this on my server to squeeze a bit more out of the network interfaces to multiple clients...
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Princess Nell · l33t Joined: 15 Apr 2005 Posts: 916

Recommended reading: /usr/src/linux/Documentation/networking/bonding.rst.

A very neat use case along those lines is the lagg device on FreeBSD, e.g https://docs.freebsd.org/en/books/handbook/advanced-networking/#network-aggregation, example 3. It shows a config for failover between a laptop's wired and wireless interface for seamless networking and retaining the same IP, no matter how you're connected. It's very simple and IMHO much easier than https://matoski.com/article/wifi-ethernet-autoswitch/.

Spanik · l33t Joined: 12 Dec 2003 Posts: 942 Location: Belgium

I have bonded the 2 ethernet interfaces in the desktop and set them to LACP. Likewise the NAS has 2 interfaces bonded and set to LACP. The switch in between has for the desktop and NAS a couple of bonded ports with LACP. Each time this are "identical" ports, same type and brand of chips. The idea was to have good bandwidth between NAS and desktop.

What I see is that one port is almost exclusively used for transmitting, the other for receiving and I get about 300Mbps continuously when transfering files. Files are about 30-100MB each, 300 to 1000 files at a time with rsync.

I do have a second switch that I planned to install downstairs and link both switches in the same way. But when I see the disappointing result (not even half of what a single interface can do in theory) I'm having second thoughts about that. Now I don't know where the bottleneck is. Could be that I cannot get the data fast enough from the HD in the desktop (doubt that with 6Gb sata), that the switch cannot do better (there isn't much connected to it that really moves much data) or is it the NAS that cannot accept data faster (QNAP running TrueNAS).
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Princess Nell · l33t Joined: 15 Apr 2005 Posts: 916

Look at xmit_hash_policy.