Application Priority Configuration

Application Priority advertises to the peer a preferred priority for frames carrying application-specific traffic. Applications are defined by protocol (Ethertype, TCP, UDP, or Layer 4 port) and protocol ID. Priority tagging is performed by the peer, not by the device advertising the Application Priority. The peer receiving the Application Priority TLV tags its traffic to the advertised priority. Application Priority works with Enhanced Transmission Selection and priority-based flow control in that tagged protocol-specific traffic for the specified priority enforces Enhanced Transmission Selection and priority-based flow control behaviors on the traffic.

For example, Application Priority could advertise to its peer that all iSCSI traffic be tagged with priority 5. In this case, the TCP protocol on well known port 3260, as assigned to iSCSI by IANA, is specified. The peer receiving the Application Priority TLV will tag iSCSI traffic for priority 5 in the Priority Code Point (PCP) tag of its 802.1Q header. Both Enhanced Transmission Selection and priority-based flow control will use this priority 5 setting if each functionality is configured to do so.

Note

The Application Priority feature requires that the peer supports the LLDP willing bit and the willing bit is enabled for priority tagging to occur on the peer. Extreme Networks switches do not currently support the LLDP willing bit. Extreme Networks switches can advertise to the peer a preferred priority for frames carrying application-specific traffic, but an Extreme Networks switch peer will not perform Application Priority tagging.

Use the set lldp port tx-tlv application-pri command to enable the advertising of the Application Priority configuration to the link peer using the LLDP-DCB Application Priority TLV.

This example shows how to advertise to the peer priority 4, for the UDP service type dpkeyserv with well known port 1780, for port ge.1.2 and to enable the sending of LLDP-DCB Application Priority TLVs from that port:

System(rw)->set dcb appPri ge.1.2 protocol udp protocol-id 1780 priority 4
System(rw)->set lldp port tx-tlv application-pri ge.1.2