Juniper QFX3000-G QFabric, Deployment Manual, Page: 99 / 652

The QFabric system supports six lossless priorities (forwarding classes) under most
conditions. The priority group headroom that remains after allocating headroom to
lossless flows is sufficient to support best-effort and multidestination traffic.
Table 11 on page 73 shows how many lossless priorities the QFabric system supports
under different conditions (fiber cable lengths and MTUs) in cases when the QFabric
system supports fewer than six lossless priorities. The number of lossless priorities is the
same regardless of how many Node device FTE ports are connected to the Interconnect
device. However, the higher the number of FTE ports connected to the Interconnect
device, the lower the number of total lossless flows supported. In all cases that are not
shown in
Table 11 on page 73 , the QFabric system supports six lossless priorities.
NOTE: The system does not perform a configuration commit check that
compares available system resources with the number of lossless forwarding
classes configured. If you commit a configuration with more lossless
forwarding classes than the system resources can support, frames in lossless
forwarding classes might be dropped.
Table 11: Lossless Priority (Forwarding Class) Support for QFX3500 and
QFX3600 Node Devices When Fewer than Six Lossless Priorities Are
Supported
Maximum Number of Lossless
Priorities (Forwarding Classes) on
the Node Device
Fiber Cable Length in
Meters (Approximate)
MTU in Bytes
5 100 9216 (9K)
5 150 9216 (9K)
NOTE: The total number of lossless flows decreases as resource consumption
increases. For a Node device, the higher the number of FTE ports connected
to the Interconnect device, the larger the MTU, and the longer the fiber cable
length, the fewer total lossless flows the QFabric system can support.
Viewing Fabric Forwarding Class Set Information
You can display information about fabric fc-sets using the same CLI command you use
to display information about Node device fc-sets:
user@switch> show class-of-service forwarding-class-set
Forwarding class set: fabric_fcset_be, Type: fabric-type, Forwarding class set
index: 1
Forwarding class Index
best-effort 0
Forwarding class set: fabric_fcset_mcast1, Type: fabric-type, Forwarding class
set index: 5
Forwarding class Index
73 Copyright © 2015, Juniper Networks, Inc.
Chapter 4: Software Features