Juniper QFX3000-G QFabric, Руководство по развертыванию, Страница: 89 / 652

Fabric forwarding class sets (fabric fc-sets) are similar to the fc-sets (priority groups)
you configure on Node devices. The major differences are:
1.
Fabric fc-sets group traffic for transport across the QFX3008-I or QFX3600-I
Interconnect device (the fabric). Node device fc-sets group traffic on a Node device
for transport across that Node device.
2.
Fabric fc-sets are global. They apply to the entire fabric. Node device fc-sets apply
only to the Node device on which they are configured.
3.
You can configure class of service (CoS) scheduling for Node device fc-sets, but you
cannot configure CoS for fabric fc-sets.
4.
Fabric fc-sets map to Interconnect device fabric output queues statically—you cannot
configure the mapping of fabric fc-sets to fabric output queues. All traffic in a fabric
fc-set maps to the same output queue.
Node device fc-sets include forwarding classes that map to Node device output
queues, and you can configure the mapping of forwarding classes to output queues
(or you can use the default mapping). Because output queues are mapped to
forwarding classes, different classes of traffic in a Node device fc-set can be mapped
to different output queues.
Node device fc-sets consist of forwarding classes containing traffic that requires similar
CoS treatment. (Forwarding classes are default forwarding classes or user-defined
forwarding classes.) You can configure CoS for each fc-set to determine how the traffic
of its forwarding classes is scheduled on a Node device.
When traffic exits a Node device interface and enters an Interconnect device fabric
interface, the Interconnect device uses the same forwarding classes to group traffic. The
forwarding classes are mapped to global fabric fc-sets for transport across the fabric.
Like fc-sets on a Node device, fabric fc-sets also contain traffic that requires similar CoS
treatment. Unlike fc-sets on a Node device, you cannot configure CoS on fabric fc-sets.
Fabric fc-sets reside on the Interconnect device and are global to the QFabric system.
Fabric fc-sets apply to all traffic that traverses the fabric. The mapping of forwarding
classes to fabric fc-sets is global and applies to all forwarding classes with traffic that
traverses the fabric from all connected Node devices. You can change the mapping of
forwarding classes to fabric fc-sets. All mapping changes you make are global. For
example, if you change the fabric fc-set to forwarding class mapping of the default
best-effort forwarding class, then every Node device’s best-effort forwarding class traffic
that traverses the fabric is mapped to that fabric fc-set.
This topic describes:
• Default Fabric Forwarding Class Sets on page 64
• Fabric Forwarding Class Set Configuration and Implementation on page 67
•
Fabric Forwarding Class Set Scheduling (CoS) on page 69
•
Support for Flow Control and Lossless Transport Across the Fabric on page 71
63 Copyright © 2015, Juniper Networks, Inc.
Chapter 4: Software Features