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HP 5500 Ei 5500 Si Switch Series Configuration Guide

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    							 38 
Figure 10 GTS 
 
 
For example, in Figure 11, Device B performs traffic policing on packets from Device A and drops packets 
exceeding the limit. To avoid packet loss, you can pe rform traffic shaping on the outgoing interface of 
Device A so packets exceeding the limit are cached in Device A. Once resources are released, traffic 
shaping takes out the cached packets and sends them out.  
Figure 11  GTS application 
 
 
Line rate 
Line rate supports rate-limiting the outbound traffic.  
The line rate of a physical interface specifies the ma ximum rate for forwarding packets (including critical 
packets). 
Line rate also uses token buckets for traffic control. With line rate configured on an interface, all packets 
to be sent through the interface are handled by the toke n bucket at line rate. If enough tokens are in the 
token bucket, packets can be forwarded. Otherwise, packets are put into QoS queues for congestion 
management. In this way, the traffic passing the physical interface is controlled.
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    							 39 
Figure 12 Line rate implementation 
 
 
The token bucket mechanism limits traffic rate when accommodating bursts. It allows bursty traffic to be 
transmitted if enough tokens are available. If toke ns are scarce, packets cannot be transmitted until 
efficient tokens are generated in the token bucket. It restricts the traffic rate to the rate for generating 
tokens. 
Line rate can only limit traffic rate  on a physical interface, and traffic policing can limit the rate of a flow 
on an interface. To limit the rate of all the pac kets on interfaces, using line rate is easier.  
Configuring traffic policing 
Configuration restrictions and guidelines 
In a traffic behavior, do not configure traffic policing with any priority marking action (including local 
precedence, drop precedence, 802.1p priority, DSCP value, and IP precedence marking actions) in the 
same traffic behavior. Otherwise, you will fail to apply the QoS policy successfully.  
Configuration procedure 
To configure traffic policing:  
Step Command Remarks 
1.  Enter system view. 
system-view N/A 
2.  Create a class and enter class 
view.  traffic classifier
 tcl-name  [ operator  { and  
|  or  } ]   N/A 
3.
  Configure match criteria. 
if-match match-criteria   N/A 
4.  Return to system view. 
quit  N/A 
5.  Create a behavior and enter 
behavior view.  traffic behavior 
behavior-name N/A
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    							 40 
Step Command Remarks 
6.  Configure a traffic policing 
action.  car cir 
committed-information-rate  [ cbs 
committed-burst-size  [ ebs 
excess-burst-size  ] ] [ pir 
peak-information-rate ] [ green  action  ] 
[ yellow  action  ] [ red action  ]   N/A  
7.
  Return to system view. 
quit  N/A 
8.  Create a policy and enter 
policy view.  qos policy
 policy-name   N/A 
9.  Associate the class with the 
traffic behavior in the QoS 
policy.  classifier 
tcl-name behavior 
behavior-name   N/A 
10.
 Return to system view. 
quit  N/A 
11. Apply the QoS policy. 
• Applying the QoS policy to an 
interface 
• Applying the QoS policy to online 
users 
• Applying the QoS policy to a VLAN 
• Applying the QoS policy globally 
• Applying the QoS policy to the 
control plane  Choose one application 
destination as needed.  
 
Configuring GTS 
The Switch Series supports queue-based GTS, which shapes traffic of a specific queue.  
To  c o n fig u re  GTS :  
 
Step Command Remarks 
1.
  Enter system view. 
system-view N/A 
2.  Enter interface view or port 
group view. 
• Enter interface view: 
interface  interface-type 
interface-number 
•  Enter port group view: 
port-group manual 
port-group-name  Use either command. 
Settings in interface view take effect on 
the current interface. Settings in port 
group view take effect on all ports in the 
port group.  
3.
  Configure GTS for a queue.  qos gts 
queue queue-number  cir 
committed-information-rate  [ cbs 
committed-burst-size ]  N/A
 
 
Configuring the line rate 
The line rate of a physical interface specifies the maximum rate of outgoing packets. 
To configure the line rate:
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    							 41 
Step Command Remarks 
1.  Enter system view. 
system-view  N/A 
2.  Enter interface view 
or port group view. 
• Enter interface view: 
interface  interface-type 
interface-number 
•  Enter port group view: 
port-group manual 
port-group-name  Use either command. 
Settings in interface view take effect on the 
current interface. Settings in port group view 
take effect on all ports in the port group. 
3.
  Configure the line 
rate for the interface 
or port group.  qos lr outbound cir 
committed-information-rate
 
[  cbs  committed-burst-size  ] N/A 
 
Displaying and maintaining traffic policing, GTS, 
and line rate 
On the 5500 EI and 5500 SI Switch Series, you can configure traffic policing in MQC approach. For 
more information about the displayi
ng and maintaining commands, see  Displaying and maintaining 
QoS po

licies . 
 
Task Command Remarks 
Display interface GTS 
configuration information.
 display qos gts interface 
[ interface-type  interface-number  ] 
[ |  { begin |  exclude | include } regular-expression  ] Available in any 
view
 
Display interface line rate 
configuration information.
 display
 qos lr interface  [ interface-type  interface-number  ] 
[ |  { begin |  exclude | include } regular-expression  ] Available in any 
view
 
 
Traffic policing configuration example 
Network requirements 
As shown in  Figure 13: 
•   G
igabitEthernet 1/0/3 of Device A is connected to GigabitEthernet1/0/1 of Device B.  
•   Server, Host A, and Host B can access the Internet through Device A and Device B.  
Perform traffic control on GigabitEthernet 1/0/1 of Device A for traffic received from Server and Host A, 
respectively, to satisfy the following requirements: 
•   Limit the rate of traffic from Server to 1024 kbps: transmit the conforming traffic normally, and mark 
the excess traffic with DSCP value 0 and then transmit the traffic.  
•   Limit the rate of traffic from Host A to 256 kbps: transmit the conforming traffic normally, and drop 
the excess traffic.  
Perform traffic control on GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 of Device B to satisfy the 
following requirements: 
•   Limit the total incoming traffic rate of GigabitEthernet 1/0/1 to 2048 kbps, and drop the excess 
traffic.
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    							 42 
•  Limit the outgoing HTTP traffic (traffic accessing the Internet) rate of GigabitEthernet 1/0/2 to 1024 
kbps, and drop the excess traffic.  
Figure 13  Network diagram 
 
 
Configuration procedures 
1. Configure Device A: 
# Configure ACL 2001 and ACL 2002 to match traffic from Server and Host A, respectively.  
 system-view 
[DeviceA] acl number 2001 
[DeviceA-acl-basic-2001] rule permit source 1.1.1.1 0 
[DeviceA-acl-basic-2001] quit 
[DeviceA] acl number 2002 
[DeviceA-acl-basic-2002] rule permit source 1.1.1.2 0 
[DeviceA-acl-basic-2002] quit 
# Create a class named server , and use ACL 2001 as the match cr iterion. Create a class named 
host , and use ACL 2002 as the match criterion.  
[DeviceA] traffic classifier server 
[DeviceA-classifier-server] if-match acl 2001 
[DeviceA-classifier-server] quit 
[DeviceA] traffic classifier host 
[DeviceA-classifier-host] if-match acl 2002 
[DeviceA-classifier-host] quit 
# Create a behavior named  server, and configure the CAR action for the behavior as follows: set 
the CIR to 1024 kbps, and mark the excess packets (red packets) with DSCP value 0 and transmit 
them.  
[DeviceA] traffic behavior server 
[DeviceA-behavior-server] car cir 1024 red remark-dscp-pass 0 
[DeviceA-behavior-server] quit 
# Create a behavior named  host, and configure the CAR action for  the behavior as follows: set the 
CIR to 256 kbps.  
[DeviceA] traffic behavior host 
[DeviceA-behavior-host] car cir 256 
[DeviceA-behavior-host] quit 
# Create a QoS policy named  car, and associate class server with behavior server  and class host 
with behavior  host.  
[DeviceA] qos policy car
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    							 43 
[DeviceA-qospolicy-car] classifier server behavior server 
[DeviceA-qospolicy-car] classifier host behavior host 
[DeviceA-qospolicy-car] quit 
# Apply QoS policy car to the incoming traffic of port GigabitEthernet 1/0/1.  
[DeviceA] interface GigabitEthernet 1/0/1 
[DeviceA-GigabitEthernet1/0/1] qos apply policy car inbound 
2. Configure Device B: 
# Configure advanced ACL 3001 to match HTTP traffic.  
 system-view 
[DeviceB] acl number 3001 
[DeviceB-acl-adv-3001] rule permit tcp destination-port eq 80 
[DeviceB-acl-adv-3001] quit 
# Create a class named  http, and use ACL 3001 as the match criterion.  
[DeviceB] traffic classifier http 
[DeviceB-classifier-http] if-match acl 3001 
[DeviceB-classifier-http] quit 
# Create a class named  class, and configure the class to match all packets.  
[DeviceB] traffic classifier class 
[DeviceB-classifier-class] if-match any 
[DeviceB-classifier-class] quit 
# Create a behavior named  car_inbound, and configure the CAR action for the behavior as 
follows: set the CIR to 2048 kbps.  
[DeviceB] traffic behavior car_inbound 
[DeviceB-behavior-car_inbound] car cir 2048 
[DeviceB-behavior-car_inbound] quit 
# Create a behavior named  car_outbound, and configure a CAR action for the behavior as 
follows: set the CIR to 1024 kbps.  
[DeviceB] traffic behavior car_outbound 
[DeviceB-behavior-car_outbound] car cir 1024 
[DeviceB-behavior-car_outbound] quit 
# Create a QoS policy named  car_inbound, and associate class  class with traffic behavior 
car_inbound in the QoS policy.  
[DeviceB] qos policy car_inbound 
[DeviceB-qospolicy-car_inbound] classifier class behavior car_inbound 
[DeviceB-qospolicy-car_inbound] quit 
# Create a QoS policy named  car_outbound, and associate class  http with traffic behavior 
car_outbound  in the QoS policy.  
[DeviceB] qos policy car_outbound 
[DeviceB-qospolicy-car_outbound] classifier http behavior car_outbound 
[DeviceB-qospolicy-car_outbound] quit 
# Apply QoS policy  car_inbound to the incoming traffic of port GigabitEthernet 1/0/1.  
[DeviceB] interface GigabitEthernet 1/0/1 
[DeviceB-GigabitEthernet1/0/1] qos apply policy car_inbound inbound 
# Apply QoS policy  car_outbound to the outgoing traffic of  port GigabitEthernet 1/0/2.  
[DeviceB] interface GigabitEthernet 1/0/2 
[DeviceB-GigabitEthernet1/0/2] qos apply policy car_outbound outbound
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    							 44 
Configuring congestion management 
Both bridge mode (Layer 2) and route mode (Layer 3) Ethernet ports support the congestion management 
function. The term interface i n thi s  chapter  c ol le ctively refers  to  these  t ypes  of  por ts. You  c an use  the  port 
link-mode  command to set an Ethernet port to operate in bridge or route mode (see  Layer 2—LAN 
Switching Configuration Guide ). 
The 5500 SI Switch Series does not support Layer 3 Ethernet ports.  
Overview 
Network congestion degrades service quality on a tr aditional network. Congestion is a situation where 
the forwarding rate decreases due to insufficient resources, resulting in extra delay. 
Congestion is more likely to occur in complex packet switching circumstances.  Figure 14 sh
 ows two 
common cases: 
Figure 14  Traffic congestion causes 
 
 
Congestion can bring the following negative results: 
•  Increased delay and jitter during packet transmission 
•   Decreased network throughput and resource use efficiency 
•   Network resource (memory, in particular) exhaustion and system breakdown 
Congestion is unavoidable in switched networks and multi-user application environments. To improve the 
service performance of your network, you must take proper measures to address the congestion issues. 
The key to congestion management is defining a dis patching policy for resources to decide the order of 
forwarding packets when congestion occurs. 
Congestion management techniques 
Congestion management uses queuing and scheduling  algorithms to classify and sort traffic leaving a 
port. Each queuing algorithm addresses a particular ne twork traffic problem, and has a different impact 
on bandwidth resource assignment, delay, and jitter. 
Queue scheduling processes packets by their priorities, preferentially forwarding high-priority packets. 
The following section describes Strict Priority (SP) queuing, Weighted Fair Queuing (WFQ), Weighted 
Round Robin (WRR) queuing, SP+WRR queuing, and SP+WFQ queuing.
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    							 45 
SP queuing 
SP queuing is designed for mission-critical applications that require preferential service to reduce the 
response delay when congestion occurs. 
Figure 15  SP queuing 
 
 
In Figure 15 , SP queuing classifies eight queues on a port into eight classes, numbered 7 to 0 in 
descending priority order. 
SP queuing schedules the eight queues in the descendi ng order of priority. SP queuing sends packets in 
the queue with the highest priority first. When the queue with the highest priority is empty, it sends 
packets in the queue with the second highest priority, and so on. You can assign mission-critical packets 
to the high priority queue to make sure that they are always served first, and assign common service 
packets to the low priority queues and transmitted when the high priority queues are empty. 
The disadvantage of SP queuing is that packets in  the lower priority queues cannot be transmitted if 
packets exist in the higher priority queues. This ma y cause lower priority traffic to starve to death. 
WRR queuing 
WRR queuing schedules all the queues in turn to ensure every queue is served for a certain time, as 
shown in Figure 16.
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    							 46 
Figure 16 WRR queuing 
 
 
Assume a port provides eight output queues. WRR assigns each queue a weight value (represented by 
w7, w6, w5, w4, w3, w2, w1, or w0) to decide the proportion of resources assigned to the queue.  
•  T h e  55 0 0  S I  sw i t c h  s u p p o r t s  b y t e - c o u n t  w e i g h t,  w h i c h  d e t e r m i n e s  t h e  w e i g h t  b y  t h e  n u m b e r  o f  b y t e s  
scheduled in a cycle. 
•   T h e  55 0 0  E I  s w i t c h  s u p p o r t s  b y t e - c o u n t  w e i g h t  ( w h i c h  d e t e r m i n e s  t h e  w e i g h t  b y  t h e  n u m b e r  o f  b y t e s  
scheduled in a cycle) or packet-based weight (which determines the weight by the number of 
packets scheduled in a cycle).  
Take the byte-count weight as an example. On a 1000 Mbps port, you can configure the weight values 
of WRR queuing to 5, 5, 3, 3, 1, 1, 1, and 1 (corresponding to w7, w6, w5, w4, w3, w2, w1, and w0, 
respectively). In this way, the queue with the lowest priority can get a minimum of 50 Mbps of bandwidth. 
WRR avoids the disadvantage of SP queuing, where packe ts  in l ow - priori t y queues  can fai l  to  be  ser ve d 
for a long time. 
Another advantage of WRR queuing is that when the queues are scheduled in turn, the service time for 
each queue is not fixed. If a queue is empty, the ne xt queue will be scheduled immediately. This improves 
bandwidth resource use efficiency.
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    							 47 
WFQ queuing 
Figure 17 WFQ queuing 
 
 
WFQ is similar to WRR. You can use WFQ as an alternative to WRR.  
Compared with WRR, WFQ can work with the minimum guaranteed bandwidth as follows: 
•  By setting the minimum guaranteed bandwidth, you can make sure that each WFQ queue is 
assured of certain bandwidth. 
•   The assignable bandwidth is allocated based on the priority of each queue (assignable bandwidth 
= total bandwidth – the sum of minimum guaranteed bandwidth of each queue).  
For example, assume the total bandwidth of a port is 10 Mbps, and the port has five flows, with the 
precedence being 0, 1, 2, 3, and 4 and the minimum guaranteed bandwidth being 128 kbps, 128 kbps, 
128 kbps, 64 kbps, and 64 kbps, respectively.  
•   The assignable bandwidth = 10 Mbps – (128 kbps + 128 kbps + 128 kbps + 64 kbps + and 64 
kbps) = 9.5 Mbps. 
•   The total assignable bandwidth quota is the sum of all the (precedence value + 1)s, 1 + 2 + 3 + 4 
+ 5 = 15.  
•   The bandwidth percentage assigned to each flow is (precedence value of the flow + 1)/total 
assignable bandwidth quota. The bandwidth percentages for the flows are 1/15, 2/15, 3/15, 
4/15, and 5/15, respectively.  
•   The bandwidth assigned to a queue = the minimum guaranteed bandwidth + the bandwidth 
allocated to the queue from the assignable bandwidth. 
SP+WRR queuing 
Yo u  c a n  a s s i g n  s o m e  q u e u e s  o n  a  p o r t  t o  t h e  S P  s c heduling group and the others to the WRR scheduling 
group (group 1) to implement SP + WRR queue sche duling. The switch schedules packets in the SP 
scheduling group preferentially, and  when the SP scheduling group is empty, schedules the packets in the 
WRR scheduling group. Queues in the SP scheduling  group are scheduled with the SP queue scheduling 
algorithm. Queues in the WRR scheduling group are scheduled with WRR.
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