Cisco Catalyst 4500 Series Administration Guide

42-5
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
OL_28731-01
Chapter 42 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 42-2 illustrates a high-level flow of QoS function.
Figure 42-2 QoS Packet Processing
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1. MSb = most significant bit
Table 42-1 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
876 543 876 543
Packet
Reception
Input
Output
Input QoS
Classification
Input
Policing
and Marking
Forwarding
Lookup
Output QoS
Classification
Output
Policing
and Marking
Active Queue
Management
Port/Queue
Scheduling
(Sharing/
Shaping)
Packet
Transmission
203973

Cisco Catalyst 4500 Series Specifications

General

Series	Catalyst 4500 Series
Category	Switch
Layer Support	Layer 2, Layer 3
Form Factor	Modular chassis
Stackable	No
Chassis Slots	3, 6, 7, 10
Power Supply Options	AC, DC
Redundancy	Power supply, Supervisor engine
Network Management	Cisco IOS Software CLI, SNMP, Cisco Prime Infrastructure
Features	Security, QoS
Port Density	Up to 384 ports per chassis
Security Features	802.1X, ACLs, DHCP Snooping, Dynamic ARP Inspection, IP Source Guard
Supervisor Engine	8-E