XDSR is the upcoming ultra-fast DSR (Direct Server Return) load balancer from Inlab Networks for contemporary Linux operating systems. The name XDSR is an acronym for “eXpress Direct Server Return”.

XDSR utilizes AF_XDP in zero-copy mode and runs “busy polling” for minimum latency.

What is AF_XDP? #

AF_XDP is a raw socket optimized for high performance packet processing and allows zero-copy between kernel and applications. As the socket can be used for both receiving and transmitting, it supports high performance network applications purely in user space.

References #

• https://www.kernel.org/doc/html/latest/networking/af_xdp.html
• https://en.wikipedia.org/wiki/Express_Data_Path
• https://ebpf-docs.dylanreimerink.nl/linux/concepts/af_xdp/

What is Consistent Hashing? #

For load balancing Consistent Hashing effectively allows to agree on how packets are distributed to real servers algorithmically instead of maintaining and synchronizing a session table.

The typical destination ring of XDSR Consistent Hashing is represented by a skiplist data structure (see the Inlab Scheme reference below).

References #

• https://en.wikipedia.org/wiki/Consistent_hashing
• https://www.the-paper-trail.org/post/2020-06-23-maglev/
• https://scheme.inlab.net/reference-manual/data-types/skiplist/

Recommended / tested Intel drivers #

During development we focus somewhat on Intel drivers and their corresponding NICs:

• e1000e
• igb
• ixgbe
• i40e
• ice

Planned Linux distribution packages #

• RHEL 9
• Alma 9
• Rocky 9
• CentOS Stream 9
• Debian 12
• Ubuntu 24 LTS

XDSR Release Date #

A release date is not yet available.