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5.15.1.10 Mapping to IETF Diffserv Classes
The mapping between priority classes discussed in this chapter and elsewhere is shown below.
T
ABLE
5-6
M
APPING
B
ETWEEN THE
S
WITCH AND
IETF D
IFFSERV
C
LASSES
Gigabit Port P7 P6 P5 P4 P3 P2 P1 P0
Megabit Port P3 P2 P1 P0
IETF NM EF AF0 AF1 AF2 AF3 BE0 BE1
As the table illustrates, P7 is used solely for network management (NM) frames. P6 is used for
expedited forwarding service (EF). Classes P2 through P5 correspond to an assured forwarding (AF)
group of size 4.
Finally, P0 and P1 are two best effort (BE) classes.
For 10/100 Mbps ports, the classes are merged in pairs—one class corresponding to NM+EF, two AF
classes, and a single BE class.
Features of the Switch that correspond to the requirements of their associated IETF classes are
summarized as the following.
Network management (NM)
and Expedited forwarding
(EF)
Global buffer reservation for NM and EF
Shaper for EF traffic on 1 Gbps ports
Option of strict priority scheduling
No dropping if admission controlled
Assured forwarding (AF) Four AF classes for 1 Gbps ports
Configurable bandwidth partition, with option of WFQ
service.
Option of delay-bounded service keeps delay under
fixed levels even if not admission-controlled.
Random early discard, with configurable levels
Global buffer reservation for each AF class
Best effort (BE)
Two BE classes for 1 Gbps ports
Service only when other queues are idle means that
QoS not adversely affected
Random early discard, with programmable levels
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