本文转自：http://kanghestef.blog.51cto.com/77886/191164

shape peak、shape average和police
以下是相关配置：
    环境：Dynamips、FlashFXP、IOS 12.4T
!
ftp-server enable
ftp-server topdir disk0:
!
……..
!
class-map match-all shape
match access-group 100
!
!
policy-map shape
class shape
police cir 80000 bc 15000 be 30000
conform-action transmit
exceed-action drop
!
…..
access-list 100 permit tcp any host 192.168.1.200
access-list 100 deny   tcp any any
R1#sh run int f0/0
Building configuration…
Current configuration : 166 bytes
!
interface FastEthernet0/0
ip address 192.168.1.221 255.255.255.0
duplex full
rmon native
rmon collection stats 1 owner config
service-policy output shape
end
R1#
R1#sh policy-map int f0/0
FastEthernet0/0
  Service-policy output: shape
    Class-map: shape (match-all)
7593 packets, 10691055 bytes
5 minute offered rate 36000 bps, drop rate 3000 bps
Match: access-group 100
police:
cir 80000 bps, bc 15000 bytes
conformed 2683 packets, 3636183 bytes; actions:
transmit
exceeded 232 packets, 349392 bytes; actions:
drop
conformed 34000 bps, exceed 3000 bps
    Class-map: class-default (match-any)
3388 packets, 4241610 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any

R1#

由于police是采用即时丢包机制，所以流量图呈锯齿状。
police bps [burst-normal] [burst-max] conform-action action exceed-action action
[violate-action action]
CISCO建议 burst-normal=configured rate/8*1.5, burst-max=burst-normal*2,这样限速的效果基本跟configured rate 持平
如下面的例子，在police命令中不使用这两个参数，而由系统自动生产，结果速度才4K左右，没有达到预期（8K）的目的
R1(config-pmap-c)#police 80000 con tr ex drop
R1(config-pmap-c-police)#
R1(config-pmap-c-police)#do sh policy-map int f0/0
FastEthernet0/0
  Service-policy output: shape
    Class-map: shape (match-all)
8779 packets, 12044939 bytes
5 minute offered rate 54000 bps, drop rate 10000 bps
Match: access-group 100
police:
cir 80000 bps, bc 2500 bytes
        conformed 3789 packets, 4873835 bytes; actions:
transmit
exceeded 312 packets, 465624 bytes; actions:
drop
conformed 49000 bps, exceed 10000 bps
    Class-map: class-default (match-any)
3420 packets, 4244403 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
R1(config-pmap-c-police)#
  shape average 命令跟接口模式下的shape命令效果一样。
 shape 采用队列缓存机制，除非队列排满否则不会出现丢包现象，从图中可知经过shape的流量图平缓了许多
R1(config-pmap-c)#shape average 80000
R1(config-pmap-c)#do sh policy-map int f0/0
FastEthernet0/0
  Service-policy output: shape
    Class-map: shape (match-all)
12047 packets, 16315383 bytes
5 minute offered rate 76000 bps, drop rate 0 bps
Match: access-group 100
Traffic Shaping
Target/Average   Byte   Sustain   Excess    Interval  Increment
Rate           Limit  bits/int  bits/int  (ms)      (bytes)
80000/80000     2000   8000      8000      100       1000
        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping
Active Depth                         Delayed   Delayed   Active
–      8         49        62683     41        54625     yes
    Class-map: class-default (match-any)
3542 packets, 4254941 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
R1(config-pmap-c)#
shape peak 80000 命令比shape average 80000 命令又不一样，流量大了一倍，因为默认情况下be ＝bc
R1(config-pmap-c)#shape peak 80000
R1(config-pmap-c)#do sh policy-map int f0/0
FastEthernet0/0
  Service-policy output: shape
    Class-map: shape (match-all)
13665 packets, 18675267 bytes
5 minute offered rate 82000 bps, drop rate 0 bps
Match: access-group 100
Traffic Shaping
Target/Average   Byte   Sustain   Excess    Interval  Increment
Rate           Limit  bits/int  bits/int  (ms)      (bytes)
160000/80000     2000   8000      8000      100       2000
        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping
Active Depth                         Delayed   Delayed   Active
–      14        1661      2413531   1653      2405473   yes
    Class-map: class-default (match-any)
3583 packets, 4258565 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
R1(config-pmap-c)#
对于shape来说，Tc 越小，流量图越平缓，Be越大，当拥塞发生时第一个Tc能传送的流量就越大。
一些笔记：
When policing traffic with CAR, Cisco
recommends the following values for the normal and extended burst parameters:
normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
extended burst = 2 * normal burst
If the burst values are too low, then the achieved rate is often much lower than the configured rate.
在连接到ISP的接口上要使用Traffic Shape，比如使用100M接口以10M的速度接入城域网，否则流量将在ISP端被限制，不利于本端qos策略的实施。
虽然rate－limit 可以使用input、output关键字，而traffic shape 不使用，但这不能说shape就不能shape input流量，可通过扩展acl来实施，如以下例子：
Listing 3-21 Shaping Traffic to 128 Kbps Using GTS
interface serial 0
traffic-shape group 101 128000
interface ethernet 0
traffic-shape group 102 128000
access-list 101 permit ip host 200.200.200.1 any
access-list 102 permit ip any host 200.200.200.1
traffic shape rate 跟 traffic shape group 是不能同时使用的