Flow Control Pause And Qos; Figure 14-6 Qinq - Cisco ONS 15454 SDH Configuration Manual

Chapter 14 Configuring Quality of Service
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 the proper CoS bit, which would reflect the customer IP precedence, IP DSCP, or CoS bits.
In the QinQ network, the QoS is then implemented based on the IEEE 802.1p bit of the SP tag. The
ML-Series cards do not have visibility into the customer CoS, IP precedence, or DSCP values after the
packet is double-tagged (because it is beyond the entry point of the QinQ service).
Figure 14-6
Figure 14-6
CoS
Customer VLAN Tag
IEEE 802.1Q Tag
The ML-Series cards can be used as the IEEE 802.1Q tunneling device for the QinQ network and also
provide the option to copy the customer frame's CoS bit into the CoS bit of the added QinQ tag. This
way, the service provider QinQ network can be fully aware of the necessary QoS treatment for each
individual customer frame.

Flow Control Pause and QoS

When flow control and policy-map are enabled for an interface and the policy-map is configured only
with 'class-default' having policer action, flow control handles the bandwidth. For all the packets, which
match policers drop criteria, PAUSE frames are sent upstream so that far end device can reduce it's
transmit rate accordingly. If the far end device honours the received PAUSE frames, there will not be any
drops on ML card due to policer configuration. However, if the policer gets noncompliant flow, the
packets are dropped or demarked using the policer definition of the interface.
Note The above statement is valid for an interface, which has a policer with not only a class-default ( i.e with
non-default class) configured. When the policy-map is configured only with class-default, the policer
acts instead of allowing the flow control to drop or demark the frames.
illustrates the QinQ implementation on the ML-Series card.
QinQ
6
6
2
IEEE 802.1p 2
(3 bits)
2
2
CFI
2
VLAN ID
4
Cisco ONS 15454 and Cisco ONS 15454 SDH Ethernet Card Software Feature and Configuration Guide, R8.0
Destination Address
Source Address
Type=8100
Tag Control Information
Type=8100
Tag Control Information
Type/Length
MAC DATA
PAD
FCS
Ingress Priority Marking
SP CoS bit
(3 bits)
CoS CFI
VLAN ID
Service Provider Tag
QinQ Tag
14-9