Summary

From PicOS2.9.1, OVS support Symmetric Hashing in LAG interface and ECMP interface.

Traffic from the production network is transferred to DPIs by session based load balancing.

Session based load balancing means same session uplink and downlink packets are transferred to same DPI.
In current image, the packets that are transferred to same DPI have same IP addresses and L4 port numbers symmetrically with each other.

1, Symmetric hashing is supported on Helix4 , Trident2, Trident2+, Trident3 and Tomahawk platform switches.

2, Symmetric hash key only include: ip address, ip address+l4 port number.

3, If the hash fields include other keys: mac address, vlan, etc. Symmetric hash will be influenced.

Command

Enable/Disable symmetric hash in lag interface

ovs-vsctl set-symmetric-hash lag true
ovs-vsctl set-symmetric-hash lag false

Except enable lag symmetric hash in glocal, user also need configure advance field in lag interface.

ovs-vsctl -- set Interface ae1 options:hash-mapping=advance

Configure IP addresses symmetrically in lag advance hash mapping fields.

ovs-vsctl set-lag-advance-hash-mapping-fields nw_dst nw_src

Configure IP addresses and L4 port numbers symmetrically in lag advance hash mapping fields.

ovs-vsctl set-lag-advance-hash-mapping-fields nw_dst nw_src port_src port_dst

Enable/Disable symmetric has in ecmp interface

ovs-vsctl set-symmetric-hash ecmp true
ovs-vsctl set-symmetric-hash ecmp false

Configure IP addresses symmetrically in l3 ecmp hash fields.

ovs-vsctl set-l3-ecmp-hash-fields nw_src nw_dst

Configure IP addresses and L4 port numbers symmetrically in l3 ecmp hash fields.

ovs-vsctl set-l3-ecmp-hash-fields nw_src nw_dst port_src port_dst

Example

1. Configure symmetic in lag interface.

1, Add bridge and ports.
ovs-vsctl add-br br0
ovs-vsctl add-port br0 te-1/1/1 vlan_mode=trunk tag=1
ovs-vsctl add-port br0 te-1/1/2 vlan_mode=trunk tag=1
ovs-vsctl add-port br0 te-1/1/3 vlan_mode=trunk tag=1
ovs-vsctl add-port br0 ae1 vlan_mode=trunk tag=1 -- set interface ae1 type=pica8_lag options:members=te-1/1/2,te-1/1/3
 
2, Configure advance hash mapping field and apply to ae1.
ovs-vsctl -- set Interface ae1 options:hash-mapping=advance
ovs-vsctl set-lag-advance-hash-mapping-fields nw_dst nw_src port_src port_dst


3, Enable lag symmetric.
ovs-vsctl set-symmetric-hash lag true
 
4, Add flow entry.
ovs-ofctl add-flow br0 in_port=1,actions=output:1025

2. Configure symmetic in ecmp interface.

1, Add bridge and ports.
ovs-vsctl add-br br0
ovs-vsctl add-port br0 te-1/1/1 vlan_mode=trunk tag=1
ovs-vsctl add-port br0 te-1/1/2 vlan_mode=trunk tag=1
ovs-vsctl add-port br0 te-1/1/3 vlan_mode=trunk tag=1
 
2, Configure ecmp group.
ovs-vsctl set-group-ranges ecmp-select-groups=1-10000
 
3, Configure l3 ecmp hash field.
ovs-vsctl set-l3-ecmp-hash-fields nw_src nw_dst port_src port_dst
 
4, Enable ecmp symmetric.
ovs-vsctl set-symmetric-hash ecmp true
 
5, add group and flow.
ovs-ofctl add-group br0 group_id=1,type=select,bucket=set_field:00:00:00:11:11:11-\>eth_src,set_field:00:00:00:22:22:22-\>eth_dst,output:2,bucket=set_field:00:00:00:33:33:33-\>eth_src,set_field:00:00:00:44:44:44-\>eth_dst,output:3
ovs-ofctl add-flow br0 in_port=1,actions=group:1

PICOS-4.3.3_Configuration_Guide

Symmetric Hashing in lag and ecmp