User manual

11-8
Cisco ONS 15310-CL and Cisco ONS 15310-MA Ethernet Card Software Feature and Configuration Guide R8.5
78-18133-01
Chapter 11 Configuring Quality of Service on the ML-Series Card
ML-Series QoS
Egress Priority Marking
Egress priority marking allows the operator to assign the IEEE 802.1p CoS bits of packets that exit the
card. This marking allows the operator to use the CoS bits as a mechanism for signaling to downstream
nodes the QoS treatment that the packet should be given. This feature operates on the outer-most
IEEE 802.1p CoS field. When used with the QinQ feature, priority marking allows the user traffic (inner
Q-tag) to traverse the network transparently, while providing a means for the network to internally signal
QoS treatment at Layer 2.
Priority marking follows the classification process, and therefore any of the classification criteria
identified earlier can be used as the basis to set the outgoing IEEE 802.1p CoS field. For example, a
specific CoS value can be mapped to a specific bridge group.
Priority marking is configured using the MQC set-cos command. If packets would otherwise leave the
card without an IEEE 802.1Q tag, then the set-cos command has no effect on that packet. If an
IEEE 802.1Q tag is inserted in the packet (either a normal tag or a QinQ tag), the inserted tag has the
set-cos priority. If an IEEE 802.1Q tag is present on packet ingress and retained on packet egress, the
priority of that tag is modified. If the ingress interface is an QinQ access port and the set-cos policy-map
classifies based on ingress tag priority, this classifies based on the user priority. This is a way to allow
the user-tag priority to determine the SP tag priority. When a packet does not match any set-cos
policy-map, the priority of any preserved tag is unchanged and the priority of any inserted IEEE 802.1Q
tag is set to 0.
The set-cos command on the output service policy is only applied to unicast traffic. Priority marking for
multicast/broadcast traffic can only be achieved by the set-cos action of the policing process on the input
service policy.
Ingress Priority Marking
Ingress priority marking can be done for all input packets of a port, for all input packets matching a
classification, or based on a measured rate. Marking of all packets of an input class can also be done with
a policing command of the form police 96000 conform-action set-cos-transmit exceed-action
set-cos-transmit. Using this command with a policy map that contains only the “class-default” will
mark all ingress packets to the value. Rate based priority marking is discussed in the “Marking and
Discarding with a Policer” section on page 11-5.
QinQ Implementation
The hierarchical VLAN or IEEE 802.1Q tunneling feature enables the service provider to transparently
carry the customer VLANs coming from any specific port (UNI) and transport them over the service
provider network. This feature is also known as QinQ, which is performed by adding an additional
IEEE 802.1Q tag on every customer frame.
Using the QinQ feature, service providers can use a single VLAN to support customers with multiple
VLANs. QinQ preserves customer VLAN IDs and segregates traffic from different customers within the
service-provider infrastructure, even when traffic from different customers originally shared the same
VLAN ID. The QinQ also expands VLAN space by using a VLAN-in-VLAN hierarchy and tagging the
tagged packets. When the service provider (SP) tag is added, the QinQ network typically loses any
visibility to the IP header or the customer Ethernet IEEE 802.1Q tag on the QinQ encapsulated frames.
On the ML-Series cards, the QinQ access ports (IEEE 802.1Q tunnel ports or QinQ UNI ports) have
visibility to the customer CoS and the IP precedence or IP DSCP values; therefore, the SP tag can be
assigned with proper CoS bit, which would reflect the customer IP precedence, IP DSCP, or CoS bits. In