Requirement
- Basic Linux/Unix knowledge
- Basic networking knowledge
In article #005 you learned how RARE/freeRouter is controlling a P4Emu/pcap dataplane. We also demonstrated that this setup could be integrated into real networks.
Requirement
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Though P4Emu/pcap can be used for SOHO and can handle nx1GE of traffic, this comes at a high CPU load cost and thus a higher power consumption.
"Why write yet another software dataplane as freeRouter has already a working native software dataplane ?" The partial answer to the question raised in the previous article was: "decoupling control plane from the dataplane" We learned that P4Emu:
However, even though libpcap is a performant packet processing library, the kernel is still heavily sollicited and the higher the traffic rate is, the higher CPU workload becomes. |
In this article we'll using freeRouter setup deployed in #005 and replace P4Emu/pcap's dataplane by P4Emu/dpdk dataplane.
The Data Plane Development Kit (DPDK) is an Open source software project managed by the Linux Foundation. It provides a set of data plane libraries and network interface controller polling-mode drivers for offloading TCP packet processing from the operating system kernel to processes running in user space. This offloading achieves higher computing efficiency and higher packet throughput than is possible using the interrupt-driven processing provided in the kernel. |
It is important to note that though its name implies, P4Emu/dpdk is not emulating V1Model. P4Emu is emulating router.p4 packet processing logic and uses a packet forwarding library to effectively transmit packets at specific ingress port to the right egress port defined by freeRouter control plane message. However, in this precise case, packet processing is offloaded from the kernel to user space. The consequence is the ability with dpdk compatible NIC and driver, to reach tremendous traffic rate. DPDK is not available on all hardware, please refer to DPDK HCL. |
In our example we will use the ubuntu focal as we need dpdk 19.11.1 (latest current version is 20.05.0)
and we add a bridge network interface to or laptop RJ45 connection.
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FreeRouter uses 2 configuration files in order to run, let's write these configuration files for R1 in ~/freeRouter/etc
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In this article you:
This essential paradigm is used to ensure communication between freeRouter and P4Emu/dpdk dataplane. It is ensured by pcapInt binary from freeRouter net-tools that will bind freeRouter socket (veth0a@locathost:22001) to a virtual network interface (veth0b@localhost:22002) connected to CPU_PORT 1.
freeRouter is doing all the control plane route computation and write/modify/remove message entry P4 entries are created/modified/removed accordingly from P4Emu/dpdk tables. Although the name is P4Emu, it does not emulate BMv2 V1Model.p4, but rather router.p4
dpkg port_id allocation follow pci_id port naming convention starting from id 0. p4dpdk.bin is invoked with the parameter: (number_of_dpdk_port - 1) + 1 <--- CPU_PORT
dpkg removed the kernel intervention calls for each packet processed. In that configuration packet processing is now off loaded to user space. Reducing kernel intervention to ~ 0%. Congratulation you have a hardware NIC assisted forwarding is system !
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