Lenovo ThinkSystem NE2552E, Application Manual

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© Copyright Lenovo 2018 Chapter 15: Fibre Channel over Ethernet
261
In the assignment model shown in Figure 26 on page 260 , priority values 0 through
2 are assigned for regular Ethernet traffic, which has “best effort” transport
characteristics.
Priority 3 is typically used to identify FCoE (SAN) traffic.
Priorities 4 ‐ 7 are typically used for latency sensitive traffic and other important
business applications. For example, priority 4 and 5 are often used for video and
voice applications such as IPTV, Video on Demand (VoD), and Voice over IP
(VoIP). Priority 6 and 7 are often used for traffic characterized with a “must get
there” requirement, with priority 7 used for network control which is requires
guaranteed delivery to support configuration and maintenance of the network
infrastructure.
Note:
The default assignment of 802.1p priority values on the NE2552E changes
depending on whether CEE is on or off. See “Turning CEE On or Off” on page 246
for details.
Priority Groups
For ETS use, each 801.2p priority value is assigned to a priority group which can
then be allocated a specific portion of available link bandwidth. To configure a
priority group, the following is required:
 CEE must be turned on ( “Turning CEE On or Off” on page 246 ) for the ETS
feature to function.
 A priority group must be assigned a priority group ID (PGID), one or more
802.1p priority values, and allocated link bandwidth greater than 0%.
PGID
Each priority group is identified with number (0 through 7, and 15) known as the
PGID.
PGID 0 through 7 may each be assigned a portion of the switch’s available
bandwidth.
PGID 8 through 14 are reserved as per the 802.1Qaz ETS standard.
PGID 15 is a strict priority group. It is generally used for critical traffic, such as
network management. Any traffic with priority values assigned to PGID 15 is
permitted as much bandwidth as required, up to the maximum available on the
switch. After serving PGID 15, any remaining link bandwidth is shared among the
other groups, divided according to the configured bandwidth allocation settings.
All 802.1p priority values assigned to a particular PGID should have similar traffic
handling requirements. For example, PFC ‐ enabled traffic should not be grouped
with non ‐ PFC traffic. Also, traffic of the same general type should be assigned to
the same PGID. Splitting one type of traffic into multiple 802.1p priorities, and then
assigning those priorities to different PGIDs may result in unexpected network
behavior.
Each 802.1p priority value may be assigned to only one PGID. However, each
PGID may include multiple priority values. Up to eight PGIDs may be configured
at any given time.