Sorry, I have to correct myself, as I spread some misinformation in my previous 
email.

The hard limit of 2 relays per IPv4 was bumped up to 8.

There were also several typos, as I was at work when writing that e-mail, i.e. 
under time pressure.

I hope I could help you anyway.

Best Regards,
-GH
On Friday, February 7th, 2025 at 12:22 PM, George Hartley via tor-relays 
<[email protected]> wrote:

> Hi there "usetor",
> 

> I am going to answer a few of your questions:
> 

> 

> 1. "If a full IPv4 /24 Class C was available to host Tor relays, what are 
> some optimal ways to allocate bandwidth, CPU cores and RAM to maximize 
> utilization of the IPv4 /24 for Tor?"
> 

> With 2 IPv4 addreses per relay as a hard limit, the biggest bottleneck you 
> will encounter is that most of Tor's code-base is singe-threaded, except for 
> maybe onionskin decryption and compression of files.
> 

> I used to host a Tor exit node on a single IPv4 address, which was running 
> inside an encrypted ArchLinux VM through QEMU/KVM on our colocated dedicated 
> server.
> 

> Here is the config I used for libvirtd: https://pastebin.com/cxSicEnN
> 

> I had the relay bandwidth limit using the following config:
> 

> > BandwidthRate 75 MBits
> > BandwidthBurst 100 MBits
> 

> 

> 

> After starting up the relay for the first second, and waiting 2 weeks for the 
> relay to get some traffic, it was using up 75-90 MBit/s constantly, or around 
> 30TB per month.
> 

> To get the maximum out of my machine, I used the following config options:
> 

> > NumCPUs 4
> > HardwareAccel 1
> 

> 

> 

> The second option made use of my CPU's AES instruction, which should be 
> available in all Intel and AMD server CPU's made since the year 2011.
> 

> Even when doing 100MBit/s, the use of hardware accelerated AES only made the 
> Tor process use ~30%, on an Intel Xeon E5-2620 running at only 2 GHz.. 
> without the bandwidth restrictions, I imagine it could have done 350MBit/s 
> easily.
> 

> 

> 2)  If a full 10 Gbps connection was available for Tor relays, how many CPU 
> cores, RAM and IPv4 addresses would be required to saturate the 10 Gbps 
> connection?"
> 

> Another user already calculated how much it would take to saturate 2GBit/s, 
> so you can take it from there.
> 

> However I disagree with the memory limit of 512MB, is okay in my opinion but 
> not less.. you can achieve that by using the following config option:
> 

> > MaxMemInQueues 1024MB
> 

> 3) Same for a 20 Gbps connection, how many CPU cores, RAM and IPv4 addresses 
> are required to saturate?
> 

> Look at my answer for question 2.
> 

> I also suggest you to use the seccomp syscall sandboxing options built into 
> Tor:
> 

> > Sandbox 1
> 

> 

> Also, remember one very important thing: Make sure that your relays are 
> located in a host, datacenter and country that is not already saturated with 
> Tor nodes.
> 

> 

> At last, thank you for running Tor nodes!
> 

> All the best,
> -GH
> 

> On Monday, February 3rd, 2025 at 5:00 PM, usetor.wtf via tor-relays 
> [email protected] wrote:
> 

> > Hi All,
> > 

> > Looking for guidance around running high performance Tor relays on Ubuntu.
> > 

> > Few questions:
> > 1) If a full IPv4 /24 Class C was available to host Tor relays, what are 
> > some optimal ways to allocate bandwidth, CPU cores and RAM to maximize 
> > utilization of the IPv4 /24 for Tor?
> > 

> > 2) If a full 10 Gbps connection was available for Tor relays, how many CPU 
> > cores, RAM and IPv4 addresses would be required to saturate the 10 Gbps 
> > connection?
> > 

> > 3) Same for a 20 Gbps connection, how many CPU cores, RAM and IPv4 
> > addresses are required to saturate?
> > 

> > Thanks!
> > 

> > Sent with Proton Mail secure email.

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