In networks, the connection between a server port and its first hop switch port is called a server-network edge. At this connection point, network configurations such as VLANs and link aggregations must be the same on the server port and the switch port. For these types of configuration, the Data Center Bridging Capability Exchange (DCBX) can automate the configuration on both sides of the edge. See Chapter 8, Managing Converged Networks by Using Data Center Bridging in Managing Network Datalinks in Oracle Solaris 11.4.
However, with network virtualization, multiple virtual ports for virtual machines (VMs) lie behind the server port. Consequently, for network virtualization, the following requirements are added for the server-network edge, which the EVB feature addresses.
Support for switching between the virtual machines through the external switch so that inter-VM traffic is subjected to policies configured on the switch
Extension of virtual port properties into the network
In a virtualized server, packets between its VMs are looped back by the virtual switch within the host itself. Therefore, any policies that are configured on the external switch are not applied to inter-VM packets. With EVB, these inter-VM packets can be serviced by the external switch, which means that the switch can enforce policies on the inter-VM packets.
Additionally, EVB enables information exchange between VNICs and the switch. The switch can then automatically configure VNIC properties such as bandwidth limits, bandwidth shares, and MTU on the network. Without this feature, the server administrator and the network administrator must manually coordinate with each other to reconfigure the switch every time a VNIC is created, modified, or deleted on the server.
Overall, EVB helps increases efficiency in the use of networking resources. For example, the switch can enforce bandwidth limit on packets before they arrive at the host.
Reflective relay is the mechanism that enables VMs to communicate through the external switch. The switch itself must support the use of LLDP and its EVB type-length value (TLV) unit, which enables automatic configurations. Otherwise, you would have to manually configure reflective relay on the switch.
For information about how to manually configure reflective relay, refer to the switch manufacturer's documentation. See also Controlling Switching Between VMs Over the Same Physical Port. For more information about the LLDP TLV units, see Information the LLDP Agent Advertises in Managing Network Datalinks in Oracle Solaris 11.4.
Oracle Solaris uses the Virtual Station Interface Discovery and Configuration Protocol (VDP) defined in IEEE 802.1Qbg to exchange VNIC information with the switch. If the switch supports VDP, then VNIC properties are automatically configured on the switch. The switch can then apply VNIC settings to packets destined for that VNIC. The mechanism parallels DCBX which enables information exchange between host and switch about physical link properties.