General architecture
NetScaler BLX is a software form factor of NetScaler and provides the same functionality as other form factors. It runs as a user space application on a Linux host.
BLX uses the Linux drivers for Rx/Tx of packets and for managing the NIC ports. Virtual Ethernet (veths) interfaces blx0 and blx1, created during the boot-up phase, are used for communication between the Linux host and BLX. For example, BLX uses veths to send log information to the syslog daemon on a Linux Host.
In BLX, the NIC ports of the Linux host specified in the /etc/blx/blx.conf (boot-up config file of BLX) file are dedicated to BLX. These NIC ports are not shared with other applications running on the host. Only BLX can see the dedicated NIC ports.
The IP addressing scheme is similar to a traditional NetScaler. BLX can have different IP addresses for NetScaler IP (NSIP), Virtual server IP (VIP), and Subnet IP (SNIP).
BLX receives the packets from the external network, processes the received packets, and responds directly through the configured dedicated Linux NIC ports. It has a full-fledged TCP/IP stack to process the packets, bypassing the TCP/IP stack of the Linux kernel. BLX interacts directly with the Linux kernel driver to pick the raw packets from the NIC ports.
Although BLX bypasses the network stack of the Linux kernel, there is still an overhead in transferring packets between Linux kernel memory and user space memory. This overhead affects the overall performance of packet processing. We recommend using the Data Plane Development Kit (DPDK) compatible NICs for high packet processing performance. For the list of DPDK-compatible NICs supported by BLX, see Hardware requirements of Linux host.
DPDK is a set of open-source Linux libraries and network interface controllers used for better network performance. For more information on DPDK, see the official DPDK website at https://www.dpdk.org/.
DPDK helps to bypass the kernel memory and delivers the packets directly to the user space memory for processing. DPDK combined with the Linux UIO module, allows BLX to receive and transmit packets without involving the Linux kernel overhead of copying packets from the kernel memory to the user space memory. Once memory is allocated, DPDK manages its buffer to achieve better performance.
Note:
BLX might start without DPDK support if one of the following conditions is met.
- BLX does not support the dedicated DPDK-compatible NIC ports.
- DPDK does not support the dedicated NIC ports.
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