Chapter 14: Quality of Service
164
Section II: Advanced Operations
Packet Processing
You can use the switch’s QoS tools to perform any combination of the
following functions on a packet flow:
Limiting bandwidth
Prioritizing packets to determine the level of precedence the switch will
give to the packet for processing
Replacing the VLAN tag User Priority to enable the next switch in the
network to process the packet correctly
Replacing the TOS precedence or DSCP value to enable the next
switch in the network to process the packet correctly.
Bandwidth Allocation
Bandwidth limiting is configured at the level of traffic classes, and
encompasses the flow groups contained in the traffic class. Traffic classes
can be assigned maximum bandwidths, specified in kbps, Mbps, or Gbps.
Packet Prioritization
The switch has eight Class of Service (CoS) egress queues, numbered
from 0 to 7. Queue 7 has the highest priority. When the switch becomes
congested, it gives high priority queues precedence over lower-priority
queues. When the switch has information about a packet’s priority, it
sends the packet to the appropriate queue. You can specify the queue
where the switch sends traffic, how much precedence each queue has,
and whether priority remapping is written into the packet’s header for the
next hop to use.
Prioritizing packets cannot improve your network’s performance when
bandwidth is over-subscribed to the point that egress queues are always
full. If one type of traffic is causing the congestion, you can limit its
bandwidth. Other solutions are to increase bandwidth or decrease traffic.
You can set a packet’s priority by configuring a priority in the flow group or
traffic class to which the packet belongs. The packet is put in the
appropriate CoS queue for that priority. If the flow group and traffic class
do not include a priority, the switch can determine the priority from the
VLAN tag User Priority field of incoming tagged packets. The packet is put
in the appropriate CoS queue for its VLAN tag User Priority field. If neither
the traffic class / flow group priority nor the VLAN tag User Priority is set,
the packet is sent to the default queue, queue 1.
Содержание AT-S63
Страница 14: ...Figures 14 ...
Страница 18: ...Tables 18 ...
Страница 28: ...28 Section I Basic Operations ...
Страница 58: ...Chapter 1 Overview 58 ...
Страница 76: ...Chapter 2 AT 9400Ts Stacks 76 Section I Basic Operations ...
Страница 96: ...Chapter 5 MAC Address Table 96 Section I Basic Operations ...
Страница 114: ...Chapter 8 Port Mirror 114 Section I Basic Operations ...
Страница 116: ...116 Section II Advanced Operations ...
Страница 146: ...Chapter 12 Access Control Lists 146 Section II Advanced Operations ...
Страница 176: ...Chapter 14 Quality of Service 176 Section II Advanced Operations ...
Страница 196: ...196 Section III Snooping Protocols ...
Страница 204: ...Chapter 18 Multicast Listener Discovery Snooping 204 Section III Snooping Protocols ...
Страница 216: ...Chapter 20 Ethernet Protection Switching Ring Snooping 216 Section III Snooping Protocols ...
Страница 218: ...218 Section IV SNMPv3 ...
Страница 234: ...234 Section V Spanning Tree Protocols ...
Страница 268: ...268 Section VI Virtual LANs ...
Страница 306: ...Chapter 27 Protected Ports VLANs 306 Section VI Virtual LANs ...
Страница 320: ...320 Section VII Internet Protocol Routing ...
Страница 360: ...Chapter 30 BOOTP Relay Agent 360 Section VII Routing ...
Страница 370: ...Chapter 31 Virtual Router Redundancy Protocol 370 Section VII Routing ...
Страница 372: ...372 Section VIII Port Security ...
Страница 402: ...Chapter 33 802 1x Port based Network Access Control 402 Section VIII Port Security ...
Страница 404: ...404 Section IX Management Security ...
Страница 436: ...Chapter 36 PKI Certificates and SSL 436 Section IX Management Security ...
Страница 454: ...Chapter 38 TACACS and RADIUS Protocols 454 Section IX Management Security ...
Страница 462: ...Chapter 39 Management Access Control List 462 Section IX Management Security ...
Страница 504: ...Appendix B SNMPv3 Configuration Examples 504 Security Model Security Level Storage Type SNMPv3 Parameters Continued ...
Страница 532: ...Appendix D MIB Objects 532 ...