From 363b34f0a3e91143da2ca664fdf32a572ac6ad89 Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Mon, 25 Jan 2016 08:40:39 -0800 Subject: [PATCH] FAQ: Explain hash function for select groups. Signed-off-by: Ben Pfaff Acked-by: Jarno Rajahalme --- FAQ.md | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/FAQ.md b/FAQ.md index 29b2e19f9..15056b0cb 100644 --- a/FAQ.md +++ b/FAQ.md @@ -1979,6 +1979,25 @@ A: When a switch sends a packet to an OpenFlow controller using a buffering that the OpenFlow specification requires implementations to document. +### Q: How does OVS divide flows among buckets in an OpenFlow "select" group? + +A: In Open vSwitch 2.3 and earlier, Open vSwitch used the destination + Ethernet address to choose a bucket in a select group. + + Open vSwitch 2.4 and later by default hashes the source and + destination Ethernet address, VLAN ID, Ethernet type, IPv4/v6 + source and destination address and protocol, and for TCP and SCTP + only, the source and destination ports. The hash is "symmetric", + meaning that exchanging source and destination addresses does not + change the bucket selection. + + Select groups in Open vSwitch 2.4 and later can be configured to + use a different hash function, using a Netronome extension to the + OpenFlow 1.5+ group_mod message. For more information, see + Documentation/group-selection-method-property.txt in the Open + vSwitch source tree. (OpenFlow 1.5 support in Open vSwitch is still + experimental.) + Development ----------- -- 2.20.1