QoS for VxLAN Layer 2 gateways

SLX-OS VxLAN Layer 2 gateways can support QoS.

A VxLAN L2 gateway can interconnect tenants in the same subnet through the VxLAN configuration. The VxLAN L2 gateway interconnection of tenants in the same subnet figure as shown below illustrates a simple use case where a packet is sent from VM1. If it is a BUM packets, Leaf-A floods through the packets to all the VTEPs in the same VxLAN segment, until the MAC table at Leaf-A is populated with corresponding entries through mechanisms such as EVPN. Meanwhile, the known unicast packets is forwarded in unicast mode to the corresponding VTEP only.

At Ingress-VTEP, incoming packet's VLAN PCP derives the Traffic-Class (TC). Derived TC is then used to derive the outer DSCP value for VxLAN Encapsulated packet which is sent out via the Tunnel Interface.

At the Egress-VTEP, incoming VxLAN encapsulated packet‘s outer DSCP value is used to derive the Traffic-Class(TC). Post decapsulation the packets VLAN PCP is derived from the TC derived above and the packets DSCP value is derived based on the qos-dscp-mode configuration.

For information on how to use the qos-dscp-mode command, refer the Extreme SLX-OS Command Reference for this release.

For VxLAN tunnel, the qos-dscp-mode configuration has no effect at ingress-VTEP.

MCT ICL tunnels are Internal VxLAN tunnels. The behaviour explained about TC selection, DSCP and VLAN-PCP calculation for overlay-gateway is applicable to MCT Internal Tunnel as well. MCT ICL Tunnel QoS model is Pipe mode always. As these are Internal VxLAN Tunnels, Uniform Mode is not applicable.

VxLAN L2 gateway interconnection of tenants in the same subnet

VxLAN QoS TTL:

• VxLAN being virtualization Tunnel, VxLAN TTL model is “Pipe Mode” always. “Pipe mode” function is set both at Ingress-VTEP and Egress -VTEP.
• AT Ingress-VTEP, VxLAN Header Outer TTL is a constant value (255). Inside the encapsulated packet, the incoming packet TTL (Payload TTL) is retained same.
• Egress -VTEP validates VxLAN Header Outer TTL for non-Zero value, then discards it. Post decapsulation, the Payload TTL value is retained same without any changes.
• The MCT ICL Tunnels are Internal VxLAN Tunnel. VxLAN TTL behavior explained for Overlay-GW is applicable to MCT ICL internal Tunnel. MCT ICL internal Tunnel TTL model is “Pipe Mode” always.

Configuring QoS for VxLAN Layer 2 gateways

Enter the qos-dscp-mode pipe command to set the QoS type mode to pipe, which is the default, when configuring the VxLAN L2 gateway. For example, enter the following commands when configuring the gateway for the ingress (tunneling) side of packet forwarding:

SLX# conf t
Entering configuration mode terminal
SLX(config)# overlay-gateway  1
SLX(config-overlay-gw-1)# qos-dscp-mode ?
Possible completions:
  pipe      Pipe
  uniform   Uniform
SLX(config-overlay-gw-1)# qos-dscp-mode pipe ?
Possible completions:
  <cr>
SLX(config-overlay-gw-1)# qos-dscp-mode pipe

Note

For information about QoS configuration on VxLAN L3 gateways and on VLAN L2 and L3 gateway interconnections, refer to "QoS for VxLAN Layer 3 gateways" and "QoS for VxLAN Layer 2 and Layer 3 gateway interconnections".