B3 as gateway, throughput issues ...

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Joined: 02 Nov 2014, 02:26

B3 as gateway, throughput issues ...

Post by kennywest » 29 Jun 2020, 10:17


I have a B3 running Debian buster that serves as a gateway. The B3 is running a list of iptables rules to accomplish this.
The B3 is right behind my ISPs modem.
When connecting a regular laptop directly to the modem, I'm getting download speeds up to 280Mbps, which is expected (I am using https://www.speedtest.net/).
When connecting the same laptop directly to the LAN port of the B3, and connecting the B3's WAN port to the modem, the download speeds drop to 140/160Mbps. Even the simplest list of rules yield the same results:

iptables -t nat -A POSTROUTING -s -j SNAT --to-source
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -p icmp -o eth0 -j ACCEPT
iptables -A FORWARD -p tcp -m multiport --dports 80,443,110,53 -j ACCEPT
iptables -A FORWARD -p udp --dport 53 -j ACCEPT

I have another B3 running squeeze (IIRC) yielding the same results.
Are there any known issues regarding throughput or speed of network interface? Any idea how to speed things up?

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Re: B3 as gateway, throughput issues ...

Post by MouettE » 30 Jun 2020, 14:55

I'd say that it's expected. Remember that the B3 hardware is over 10 years old, even if the network interfaces are gigabit, routing in done by the OS. I don't know however if others have done detailed benchmark on the network speeds but I never had tremendous performance.

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Joined: 27 Jul 2011, 12:31

Re: B3 as gateway, throughput issues ...

Post by fredrikj » 01 Jul 2020, 03:11

I seem to recall that someone posted the results of network throughput tests here on the forum before. Probably many years ago. If you search the forums you might get lucky.

N.B: It might be that I confuse it with disk performance tests though, because I'm certain there are several theads about that topic.

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Re: B3 as gateway, throughput issues ...

Post by Gordon » 01 Jul 2020, 06:14

To think that twenty years ago people were happy with 56k (kggggg - kadoing - kadoing - priiiii) :shock:

I don't really think it is the age of the B3, more the choices that were made during its design. Considering that the B3 came with Debian Squeeze and this OS was released in 2011, the B3 can't be more that 10 years old BTW. What this does prove however is that the designers could have also chosen an ARMv7 main CPU (released in 2007), but they selected the "older" single core ARMv5te (released in 2006). From this there are multiple reasons why you are unlikely to reach maximum throughput. First of all being that firewalling requires packets to be rewritten and thus requires several CPU cycles to be involved between receive and send. Second that because the CPU is single core it can only the traffic from one network interface at the same time.

For me that does not pose any issue, because I only have a 50Mbit link, but I do notice increased sluggishness on Tor if at the same time a large download is running.

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Joined: 02 Nov 2014, 02:26

Re: B3 as gateway, throughput issues ...

Post by kennywest » 09 Jul 2020, 03:39

Thank you all for your replies.
I gave up on using the B3 as gateway for my Internet and decided to use an edgerouter from ubiquity instead. I also moved my DNS sinkhole to a dedicated pi-hole raspberry pi (to remove even more load from the B3). So for the moment, the B3's sole purpose is now being a file server (nfs + samba), authentication server and Active Directory.

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Re: B3 as gateway, throughput issues ...

Post by stasheck » 17 Jul 2020, 14:12

That's expected, and the reason I went from B3 as router (was fine enough for 150 Mbps link) to running OPNSense on Proxmox on Celeron J1900 (along with some other VMs) to reasonably work with 350 Mbps link.

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