After struggling for over 20 hours, I wanted to share the results of my investigation regarding very poor Internet upload erformance.
Setup
- Proxmox Server with a Single 10GbE NIC
- OPNsense VM on Proxmox
- OPNsense uses VirtIO NICs tied to the 10GbE Linux Bridge
- upstream Gateway is a OpenWRT router with 1GbE uplink
- Zyxel XS1930 Switch connecting Proxmox Host and Gateway
Problem
Internet download speeds are fine (900Mbit/s) but upload speeds are not (5-15MBit/s instead of 50MBit/s)
Solution
Various OPNsense tunables (configured for 8 CPU cores)
hw.ibrs_disable = 1net.isr.maxthreads = -1net.isr.bindthreads = 1net.isr.dispatch = deferrednet.inet.rss.enabled = 1net.inet.rss.bits = 6kern.ipc.maxsockbuf = 16777216net.inet.tcp.recvbuf_max = 4194304net.inet.tcp.recvspace = 262144net.inet.tcp.sendbuf_inc = 16384net.inet.tcp.sendbuf_max = 4194304net.inet.tcp.sendspace = 262144net.inet.tcp.soreceive_stream = 1net.pf.source_nodes_hashsize = 1048576net.inet.tcp.mssdflt = 1240net.inet.tcp.abc_l_var = 52net.inet.tcp.minmss = 536kern.random.fortuna.minpoolsize = 128net.isr.defaultqlimit = 2048
Enabling Multiqueue in Proxmox for the VirtIO NICs
(binary stepping, 1 Queue for 2 cores, 2 Queues for 4 cores, 3 Queue for 8 cores ect, total amount of all Queues mustn’t be greater then the VMs CPU cores)
Enabling Flow Control on all involved Network devices
- Proxmox hardware NIC:
ethtool -K nic0 rx on tx on - OpenWRT lan interfnace:
uci set network.lan.txpause='1'
uci set network.lan.rxpause='1'
uci commit
reload_config
- Zyxel Switch:
Port -> Port Setup - Checked all Ports
Enabling Port Buffering
Zyxel Switch:
Port -> Port Buffer - Checked the Port with the Gateway
Reason
The Main reason for this problem seems to be the down-stepping of 10Gbit traffic to 1Gbit devices. Without Flow control enabled on all involved devices, the sending rate can't be adjusted. But without enabling Port Buffering, the Switch won't allocate resources for adjusting the traffic flow rate for slower devices.
This Problem should only affect people who use devices with different link speeds on the same switch.
Given that your original problem was related to WAN upload performance, why did your investigation lead you to Ethernet flow-control? An ISP connection generally deals in packets at Layer 3 ("network", eg IP) of the OSI model, whereas Ethernet is a Layer 2 ("data-link") layer technology.
If there is a bottleneck at your WAN modem, then that will cause congestion at layer 3, but Ethernet flow-control can only deal with congestion that exists at layer 2. What has likely happened is that you have configured your gateway so that congestion at layer 3 is mirrored onto your layer 2 LAN. And if flow-control is enabled, then that would result in back-pressure propagating back to your VMs. Your VMs will then slow down their layer 2 rate, which conveniently forces the layer 3 traffic to also slow down.
This is an incredibly round-about and inefficient way to do traffic shaping. You should not configure a network so that L3 and L2 issues bleed into each other. A major consequence of using flow-control in this way is that it reduces the capacity of your LAN, even for traffic that isn't going out to the WAN.
The customary approach for keeping L2 and L3 separate is to perform traffic shaping solely at the threshold where your LAN meets the bottleneck. This would be OpenWRT, since after OpenWRT would be the WAN (50 Mbps upload). OpenWRT would be configured with some sort of QoS feature so that certain L3 packets are selectively dropped.
You cannot do effective L3 traffic shaping without dropping packets. In fact, all competent L3 protocols expect dropped packets in order to slow down their data rate: SCTP and TCP have their own exponential congestion control mechanism, UDP simply accepts that some packets won't make it through, and QUIC has its own mechanism as well. Simply put, all L3 protocols only understand one signal that tells them to slow down, and it is to drop a few packets. They will adjust accordingly, finding the stable equilibrium where traffic flows at the very cusp of congestion.
This is a red-herring, for the reasons I've outlined above. With 1+ Gbps connections on your LAN, your L2 network is an order of magnitude faster than your WAN upload. It cannot be the case that a fast LAN makes a slow WAN slower. This is not RF impedance where step-transitions cause reflections; we are dealing in packet-switched networks, where queuing theory controls.
TL;DR: please try OpenWRT QoS instead
This is mostly going over my head, but I read all of it and it is very well written. Objective and factual (it seems to me). No belittling, just genuinely trying to deliver helpful criticism and explanation.
🤝🙇♂️
Good on you for being a good fellow human.