Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Direct Server Return load balancing across Layer 3 boundaries
C Perl Shell
tree: 4096f81700

Fetching latest commit…

Cannot retrieve the latest commit at this time

Failed to load latest commit information.
docs
freebsd
linux
yvipagent
README

README

Direct Server Return (DSR) load balancing is a common way to distribute
network traffic using an approach that currently requires the load
balancer and all hosts behind the Virtual IP (VIP) to be within the same
Layer 2 network.  This is a severe limitation that hinders scaling VIPs
beyond a single contiguous subnet.  To overcome this limitation, we
present a method to perform DSR load balancing across Layer 3 boundaries
(``L3DSR''), a solution that allows Yahoo! to serve up to ten times as
many VIPs on a single hardware Load Balancer compared to other Layer 3
load balancing methods.

In order to overcome Layer 2 limitations, we use the 6-bit bit
Differentiated Services Code Point (DSCP) field of the IPv4 header used
for packet classification to relay information to the server.  The server
inspects the header and rewrites the destination address based on the
value of the DSCP field and according to its own mapping of DSCP values to
destination addresses.

L3DSR is currently supported by:
 - A10 AX3200 >= 2.2.5
 - Brocade ADX Series >= 12.1d
 - Brocade/Foundry ServerIron 450
   - M7 and JetCore blades
   - >= 12.2.01p
 - Citrix Netscaler running 8.x, 9.x

On the server, L3DSR is currently supported by:
 - FreeBSD >= 6.x
 - RHEL >= 5.x

L3DSR was developed at Yahoo! Inc.  If you have questions or comments,
please contact Jan Schaumann <jschauma@yahoo-inc.com> or Carl Stanley
<cstan@yahoo-inc.com>.
Something went wrong with that request. Please try again.