The Open vSwitch remains fully supported and developed with the earlier deprecation notice issued with XenServer 6.2 now rescinded within XenServer 6.5

Background: Open vSwitch is the default networking stack in XenServer 6.x.

An Open vSwitch (OVS) network flow is a match between a network packet header and an action
such as forward or drop. A typical server VM could have hundreds or more connections to clients,
and OVS needs to have a flow for each of these connections. As the number of VMs on the host
builds up, the OVS flow table in the Dom0 kernel fills and induces round-trips to the OVS userspace
process, which can degrade the network throughput to and from guests. In OVS v1.4, present in
XenServer 6.2, the flow had to have an exact match for the header. XenServer 6.5 includes the latest
version, OVS 2.1.3, which supports megaflows.
Megaflow support reduces the number of required entries in the flow table for most common
situations and improves the ability of Dom0 to handle many server VMs connected to a large
number of clients.

Details in the XenServer 6.5 vSwitch Controller Users Guide: http://bit.ly/1zLZ8NI