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by anonymous

After a number of modem connection issues, resolved by updating to the latest RUTOS firmware, I'm still plagued by the following performance issue: The RUT955 I use has ~210 devices connected, almost all are statically assigned, connected by ethernet via a bunch a switches.

What I am seeing in about 10-20 of the devices is a necessary persistent TCP connection failing ("timeout" according to the devices) where I'd previously never had a problem, and a basic ping to those URLs seem to have no problem.

When I restart a handful of devices that have lost connection, they usually establish successful connections. But what I see at the destination server end is that this causes a handful of other devices to lose connection, so that there is always ~15 devices with timed out connections. It is like Whack-a-mole- restore some bad connections, and others get kicked off instead.

 Looking at Live Data>Connections, there are about 600 connections at one time, with ~700 reported peak. What is the maximum connections that the 955 can handle?

I'm wondering if by incrementally adding devices, I have now reached a limit of the RUT955?

As an additional data point, I have an RUT240 with its own subnet and mobile connection as a failover, but connected to the RUT955 via Wifi for its primary WAN.

The ~30 devices on the RUT240 subnet do not have this TCP connection timeout issue. Only devices on the RUT955 subnet are showing this problem.

1 Answer

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by anonymous

Thank you for the detailed report on the issue.

The maximum number of records of connections that the RUT955 can handle in its connection tracking table is 16384.

However, that does not necessarily translate to actual operable connections capable of handling sufficient data streams.

The thing to keep in mind is that RUT955 uses 10/100Mbps speed ethernet ports, including WAN port. The LTE module is also Cat4, which theoretically tops at 150Mbps downstream.

I will enquire testing, if anything similar has been tested before, but it is likely, that you are hitting the limits of the router.

Best regards,
by anonymous

Thank you for the reply - some comments on your answer:

  • The connections are very low bandwidth - realtime data page for WAN,WAN6 says 1Mbit/s peak, average in and out is ~150Kbit/s, for 200 devices (this included my own connection while monitoring that webui).
  • The primary WAN is via Ethernet (Starlink). LTE is supposed to be only failover (so should not be a limit)
These make me think it is not a limit of the RUT955, but perhaps your suspicion is still correct?
If this is a limit of the 955, can you help me find the information to select a model that supports further increase to 600 devices?
I was considering RUTXR1 - does this have a specification that supports more devices and more connections?
Thank you!
by anonymous

Tests with tcpgoon and curl-loader were performed and reached connection numbers close to the previously mentioned limit value, however, in terms of real life applications, such a case has not been performed. It would be interesting, if you could provide a troubleshoot file from RUT955 by going to System -> Administration > Troubleshoot section to check the device. 

In regards to a more capable device, 16384 is a limit on all of the routers, but RUTX series is definitely a place to look. These have more throughput, RAM and processing power, thus, should outperform RUT955.

by anonymous
Thank you, I have attached the troubleshoot file to the original post.