Cisco Catalyst 4500 Series, Руководство по настройке программного обеспечения

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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 44 Configuring Quality of Service
Overview of QoS
•
Classification is the selection of traffic to be marked.
•
Marking , according to RFC 2475, is the process of setting a Layer 3 DSCP value in a packet; in this
publication, the definition of marking is extended to include setting Layer 2 CoS values.
•
Policing is limiting bandwidth used by a flow of traffic. Policing can mark or drop traffic.
Basic QoS Model
Figure 44-2 illustrates a high-level flow of QoS function.
Figure 44-2 QoS Packet Processing
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1. MSb = most significant bit
Table 44-1 IP Precedence and DSCP Values (continued)
3-bit IP
Precedence 6 MSb
1
of ToS 6-bit
DSCP 3-bit IP
Precedence 6 MSb
1
of ToS 6-bit
DSCP
8 7 6 5 4 3 8 7 6 5 4 3
P a cket
Reception
Inp u t
O u tp u t
Inp u t Qo S
Cl ass ific a tion
Inp u t
Policing
a nd M a rking
Forw a rding
Look u p
O u tp u t Qo S
Cl ass ific a tion
O u tp u t
Policing
a nd M a rking
Active Q u e u e
M a n a gement
Port/Q u e u e
S ched u ling
( S h a ring/
S h a ping)
P a cket
Tr a n s mi ss ion
20
3
97
3