BrandMeisterUDPTX is BrandMeister-own UDP communication library, used to transmit and receive UDP traffic fast. It is very important for BrandMeister to spend less time to send and receive packets, it makes transmission (and finally sound) more smooth.
UDP Transmitter
At this moment BrandMeister provides several backends (options) to send outgoing UDP:
- socket
- raw
- AF_XDP
- DPDK
socket
This is standard default backend that uses Berkley sockets for sending a traffic. It tries to send the data in non-blocking mode and has special transmission thread to re-send failed packets.
You have to use it if you have
- non-ethernet interfaces
- more than one interface for outgoing traffic (such as public + AMPR, or one for IPv4 and another one for IPv6)
- huge routing tables
Performance
Passed performance tests to transmit to 5K connections
Configuration
transmitter = "socket";
raw
This is fast forwarding backend that uses RAW (PACKET_MMAP) socket of Ethernet interface for sending a traffic. It allows to save up to 50% CPU time and has great compatibility.
Limitations
- Requires to use a single ethernet interface for BrandMeister's traffic (IPv4 and IPv6, local site connectivity will not work)
- All traffic will be routed via default gateway (except loopback, see next bullet)
- Loopback addresses (127.0.0.1 and ::1) are handled by using Berkley sockets
Performance
Passed performance tests to transmit to 20K connections
Configuration
transmitter = "raw:<interface name>";
transmitter = "raw:eth0";
AF_XDP
This is faster forwarding backend that uses AF_XDP socket of Ethernet interface for sending a traffic and in most cases communicates directly with Linux network interface driver.
Limitations
- The same set of limitations as raw
- Requires Linux kernel >= 4.18
- Interface have to be configured to use the same count of TX and RX queues (please read man ethtool)
Performance
Passed performance tests to transmit to 30K connections
Configuration
transmitter = "xdp:<interface name>";
transmitter = "xdp:eth0";
DPDK
This is fastest forwarding backend that uses kernel-bypass NIC driver for sending a traffic. It allows to save much more CPU time due to direct poll communications to the NIC and CRC offload features of some NIC models. In some tests we got up to 75% acceleration. List of supported NIC models can be found here.
Limitations
- The same set of limitations as raw
- You have to have separate NIC or virtual detachable NIC port allowed to use for the DPDK transmission
- Only DPDK port #0 will be used
- We added support of dpdk-proc-info and dpdk-pdump
Performance
Passed performance tests to transmit to 40K connections
Configuration
transmitter = "Modules/DPDK-edge.so:<reference interface> <EAL parameters> [--] <module parameters>";
transmitter = "Modules/DPDK-edge.so:eth0 -w 0000:af:00.0 --file-prefix bm --lcores '(0-3)@0'";
- Reference interface is a kernel attached interface used for normal communications (please read about raw mode). DPDK will reuse its IPs and default gateway
- For EAL parameters please read this documentation
- It will use so many NIC queues as defined amount of slave logical cores minus one in startup parameters.
- The best performance on NUMA machines could be reached by using the same CPU as NIC connected by pinning logical cores via EAL's parameter lcores and BrandMeister's parameter affinity
- Also in most cases it requires to run BrandMeister with root privileges, you can do this by overriding systemd configuration (beandmeister@.service.d):
# /etc/systemd/system/brandmeister@.service.d/override.conf [Service] User=root
Module parameters
All these parameters are optional and override default settings of PMD or DPDK module
--queue-size <n> - set queue size to <n> slots (instead of automatically generated)
--batch-size <b> - set maximum batch size to <n> slots (instead of automatically generated)
--pthresh <n> |
--hthresh <n> |
--wthresh <n> | See https://doc.dpdk.org/guides/prog_guide/poll_mode_drv.html#configuration-of-transmit-queues
--rs-thresh <n> |
--free-thresh <n> |
UDP Receiver
In reception part UDPTX's driver works in parallel with socket receiver. All it does, is accelerate reception of UDP packets on particular interface.
eBPF + AF_XDP
This is modern method to accelerate UDP reception in BrandMeister Core. It allows to save up to 30% CPU time.
Limitations
- Requires Linux kernel >= 4.18
- Interface have to be configured to use the same count of TX and RX queues (please read man ethtool)
- eBPF handles traffic before iptables
- Works with only a single instance of BrandMeister Core on the single machine
Configuration
receiver = "Modules/ExpressFilter.o:<interface name>";
receiver = "Modules/ExpressFilter.o:eth0";
eBPF + AF_XDP + XDPHelper
This is method is fully the same as eBPF + AF_XDP but uses small additional daemon XDPHelper to load and share eBPF program between several BrandMeister Core instances. XDPHelper is supplied with BrandMeister Core and starts automatically only when required (thanks to systemd and D-BUS activation). By default XDPHelper uses eBPF program ExpressFilter.o (see xdphelper.service).
Limitations
- The same list of limitations as in case of eBPF + AF_XDP except support of multiple instances
- All instances of BrandMeister Core should use the same network interface
Configuration
receiver = "xdp:<interface name>";
receiver = "xdp:eth0";