User manual

C HAPTER 12 | Quality of Service
Creating QoS Policies
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ES-2000 Series
respectively. The maximum size of the token bucket P is BP and the
maximum size of the token bucket C is BC.
The token buckets P and C are initially (at time 0) full, that is, the token
count Tp(0) = BP and the token count Tc(0) = BC. Thereafter, the token
count Tp is incremented by one PIR times per second up to BP and the
token count Tc is incremented by one CIR times per second up to BC.
When a packet of size B bytes arrives at time t, the following happens if
trTCM is configured to operate in Color-Blind mode:
■
If Tp(t)-B < 0, the packet is red, else
■
if Tc(t)-B < 0, the packet is yellow and Tp is decremented by B, else
■
the packet is green and both Tp and Tc are decremented by B.
When a packet of size B bytes arrives at time t, the following happens if
trTCM is configured to operate in Color-Aware mode:
■
If the packet has been precolored as red or if Tp(t)-B < 0, the
packet is red, else
■
if the packet has been precolored as yellow or if Tc(t)-B < 0, the
packet is yellow and Tp is decremented by B, else
■
the packet is green and both Tp and Tc are decremented by B.
◆ The trTCM can be used to mark a IP packet stream in a service, where
different, decreasing levels of assurances (either absolute or relative)
are given to packets which are green, yellow, or red. Refer to RFC 2698
for more information on other aspects of trTCM.
Random Early Detection – RED starts dropping yellow and red packets
when the buffer fills up to 0x60 packets, and then starts dropping any
packets regardless of color when the buffer fills up to 0x80 packets.
COMMAND USAGE
◆ A policy map can contain 128 class statements that can be applied to
the same interface (page 153). Up to 32 policy maps can be configured
for ingress ports.
◆ After using the policy map to define packet classification, service
tagging, and bandwidth policing, it must be assigned to a specific
interface by a service policy (page 153) to take effect.