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ES-2724 User’s Guide
Chapter 27 Differentiated Services
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H A P T E R
27
Differentiated Services
This chapter shows you how to configure Differentiated Services (DiffServ) on the switch.
27.1 DiffServ Overview
Quality of Service (QoS) is used to prioritize source-to-destination traffic flows. All packets in
the flow are given the same priority. You can use CoS (class of service) to give different
priorities to different packet types.
DiffServ is a class of service (CoS) model that marks packets so that they receive specific per-
hop treatment at DiffServ-compliant network devices along the route based on the application
types and traffic flow. Packets are marked with DiffServ Code Points (DSCPs) indicating the
level of service desired. This allows the intermediary DiffServ-compliant network devices to
handle the packets differently depending on the code points without the need to negotiate
paths or remember state information for every flow. In addition, applications do not have to
request a particular service or give advanced notice of where the traffic is going.
27.1.1 DSCP and Per-Hop Behavior
DiffServ defines a new DS (Differentiated Services) field to replace the Type of Service (ToS)
field in the IP header. The DS field contains a 2-bit unused field and a 6-bit DSCP field which
can define up to 64 service levels. The following figure illustrates the DS field.
DSCP is backward compatible with the three precedence bits in the ToS octet so that non-
DiffServ compliant, ToS-enabled network device will not conflict with the DSCP mapping.
Figure 83
DiffServ: Differentiated Service Field
The DSCP value determines the forwarding behavior, the PHB (Per-Hop Behavior), that each
packet gets across the DiffServ network. Based on the marking rule different kinds of traffic
can be marked for different priorities of forwarding. Resources can then be allocated
according to the DSCP values and the configured policies.
27.1.2 DiffServ Network Example
The following figure depicts a simple DiffServ network consisting of a group of contiguous
DiffServ-compliant network devices.
DSCP (6 bits)
DS (2 bits)
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Страница 7: ...ES 2724 User s Guide Safety Warnings 5 This product is recyclable Dispose of it properly...
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Страница 48: ...ES 2724 User s Guide 46 Chapter 3 Hardware Overview...
Страница 58: ...ES 2724 User s Guide 56 Chapter 4 The Web Configurator...
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Страница 82: ...ES 2724 User s Guide 80 Chapter 7 Basic Setting...
Страница 95: ...ES 2724 User s Guide Chapter 8 VLAN 93 Figure 39 Port Based VLAN Setup All Connected...
Страница 96: ...ES 2724 User s Guide 94 Chapter 8 VLAN Figure 40 Port Based VLAN Setup Port Isolation...
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Страница 126: ...ES 2724 User s Guide 124 Chapter 15 Link Aggregation...
Страница 132: ...ES 2724 User s Guide 130 Chapter 16 Port Authentication...
Страница 136: ...ES 2724 User s Guide 134 Chapter 17 Port Security...
Страница 142: ...ES 2724 User s Guide 140 Chapter 18 Classifier Figure 61 Classifier Example...
Страница 148: ...ES 2724 User s Guide 146 Chapter 19 Policy Rule Figure 64 Policy Example...
Страница 151: ...ES 2724 User s Guide Chapter 20 Queuing Method 149 Figure 65 Queuing Method...
Страница 158: ...ES 2724 User s Guide 156 Chapter 21 VLAN Stacking...
Страница 189: ...ES 2724 User s Guide Chapter 28 DHCP 187 Figure 93 DHCP Relay Configuration Example...
Страница 190: ...ES 2724 User s Guide 188 Chapter 28 DHCP...
Страница 210: ...ES 2724 User s Guide 208 Chapter 30 Access Control...
Страница 212: ...ES 2724 User s Guide 210 Chapter 31 Diagnostic...
Страница 216: ...ES 2724 User s Guide 214 Chapter 32 Syslog...
Страница 224: ...ES 2724 User s Guide 222 Chapter 33 Cluster Management...
Страница 232: ...ES 2724 User s Guide 230 Chapter 37 Routing Table...
Страница 268: ...ES 2724 User s Guide 266 Chapter 39 Introducing Commands...
Страница 276: ...ES 2724 User s Guide 274 Chapter 40 User and Enable Mode Commands...
Страница 290: ...ES 2724 User s Guide 288 Chapter 41 Configuration Mode Commands...
Страница 306: ...ES 2724 User s Guide 304 Chapter 43 IEEE 802 1Q Tagged VLAN Commands...
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Страница 326: ...ES 2724 User s Guide 324 Appendix A Product Specifications...