
GS-2724 User’s Guide
173
C
H A P T E R
26
Differentiated Services
This chapter shows you how to configure Differentiated Services (DiffServ) on the Switch.
26.1 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.
26.1.1 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 79
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.
26.1.2 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)
Summary of Contents for GS-2724
Page 1: ...www zyxel com GS 2724 Ethernet Switch User s Guide Version 3 70 4 2007 Edition 1 ...
Page 2: ......
Page 7: ...Safety Warnings GS 2724 User s Guide 7 ...
Page 8: ...Safety Warnings GS 2724 User s Guide 8 ...
Page 22: ...Table of Contents GS 2724 User s Guide 22 ...
Page 30: ...List of Tables GS 2724 User s Guide 30 ...
Page 32: ...32 ...
Page 36: ...Chapter 1 Getting to Know Your Switch GS 2724 User s Guide 36 ...
Page 40: ...Chapter 2 Hardware Installation and Connection GS 2724 User s Guide 40 ...
Page 46: ...Chapter 3 Hardware Overview GS 2724 User s Guide 46 ...
Page 48: ...48 ...
Page 58: ...Chapter 4 The Web Configurator GS 2724 User s Guide 58 ...
Page 64: ...Chapter 5 Initial Setup Example GS 2724 User s Guide 64 ...
Page 70: ...Chapter 6 System Status and Port Statistics GS 2724 User s Guide 70 ...
Page 84: ...84 ...
Page 94: ...Chapter 8 VLAN GS 2724 User s Guide 94 Figure 36 Port Based VLAN Setup All connected ...
Page 126: ...Chapter 16 Port Authentication GS 2724 User s Guide 126 ...
Page 130: ...Chapter 17 Port Security GS 2724 User s Guide 130 ...
Page 136: ...Chapter 18 Classifier GS 2724 User s Guide 136 Figure 58 Classifier Example ...
Page 139: ...Chapter 19 Policy Rule GS 2724 User s Guide 139 Figure 59 Policy ...
Page 145: ...Chapter 20 Queuing Method GS 2724 User s Guide 145 ...
Page 146: ...Chapter 20 Queuing Method GS 2724 User s Guide 146 ...
Page 152: ...Chapter 21 VLAN Stacking GS 2724 User s Guide 152 ...
Page 166: ...166 ...
Page 183: ...Chapter 27 DHCP GS 2724 User s Guide 183 Figure 89 DHCP Relay Configuration Example ...
Page 184: ...Chapter 27 DHCP GS 2724 User s Guide 184 ...
Page 186: ...186 ...
Page 210: ...Chapter 31 Syslog GS 2724 User s Guide 210 ...
Page 224: ...Chapter 36 Routing Table GS 2724 User s Guide 224 ...
Page 228: ...228 ...
Page 262: ...Chapter 38 Introducing Commands GS 2724 User s Guide 262 ...
Page 296: ...Chapter 42 IEEE 802 1Q Tagged VLAN Commands GS 2724 User s Guide 296 ...
Page 300: ...Chapter 44 Routing Domain Command Examples GS 2724 User s Guide 300 ...
Page 304: ...304 ...
Page 312: ...Appendix B Changing a Fuse GS 2724 User s Guide 312 ...
Page 332: ...Appendix E Common Services GS 2724 User s Guide 332 ...
Page 336: ...Appendix F Legal Information GS 2724 User s Guide 336 ...
Page 348: ...Index GS 2724 User s Guide 348 ...