Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
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Tip
All of Extreme Networks VSP series of Core and Distribution platforms are pre-configured
for eight QoS classes.
Extreme Networks ERS series access platforms can be configured to use QoS queue-sets
with one to eight QoS classes (the default queue-set uses two queues)
ExtremeXOS platforms can support up to eight Egress QoS Profiles (QP1-8) of which only
QP1 & QP8 are configured by default.
QoS Implementation Over SPB
In an SPB backbone, all packet forwarding is performed at Layer 2 using the BMAC outer Ethernet header
of the Mac-in-Mac encapsulation. The Mac-in-Mac header always carries in the B-TAG a Backbone Priority
Code Point (PCP; i.e., p-bits in the Backbone VLAN Q-tag) and a Drop Eligible Indicator (DEI) bit. These are
the QoS markings that will be used to derive the PHB by every transport (BCB) node encountered along
the SPB shortest path as well as the terminating egress BEB node.
The 802.1ah Mac-in-Mac encapsulation Service instance I-TAG can also carry a Priority Code Point (I-PCP)
3-bit field and Drop Eligible Indicator (I-DEI) 1-bit (the I-TAG field also carries the I-SID information), which
can provide an extra mechanism to tunnel QoS marking across the SPB fabric, when those markings have
been removed or are missing in the encapsulated payload.
Figure 76 QoS Fields in an SPBM Mac-in-Mac Frame
Note
The use of I-PCP and I-DEI bits is defined in IEEE802.1ah (section 25.4)
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and is needed
when interconnecting Q-in-Q networks over an SPBM backbone where the S-TAG may be
stripped before applying the Mac-in-Mac encapsulation and thus the I-PCP bits are needed
to relay the S-TAG PCP and DEI bits.
Tip
An MPLS label carries the QoS marking in the Experimental bits field, which is also a 3-bit
field like the Ethernet PCP fields. There is no equivalent of the DEI bit in MPLS.
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See Reference Documentation [4].