CCIE实验笔记之第3章 WAN协议（帧中继）之四
[size=2][color=#000000][font=Arial][size=10.5pt]3.5[/size][/font][font=宋体][size=10.5pt]帧中继流量整形[/size][/font][/color][/size][font=宋体][size=10.5pt][/size][/font][size=2][font=宋体]我们先看一个网络模型，图[/font][font=Times New Roman]3-5[/font][font=宋体]这个模型中有几百个远端站点需要访问授权中心，假设在主站点到授权中心的链路出现问题，很快恢复了，在主站点到授权中心会出现许多[/font][font=Times New Roman]TCP[/font][font=宋体]连接请求，出现大量数据，由于主站到授权中心的链路速率为[/font][font=Times New Roman]64Kbit/s[/font][font=宋体]，产生拥塞，远端站点仍以[/font][font=Times New Roman]T1[/font][font=宋体]的速率进行传输，并不知道主站到授权中心的链路只是[/font][font=Times New Roman]64Kbit/s[/font][font=宋体]。[/font][font=Times New Roman]Frame-relay Traffic Shaping[/font][font=宋体]（帧中继流量整形）就是为解决这类问题。[/font][/size]
[size=2][font=宋体]图[/font][font=Times New Roman]3-5 [/font][font=宋体]帧中继网络模型[/font][/size]
[size=2][font=宋体][img=550,318]http://www.cnfan.net/cisco/uploadfile/200707/20070703105320306.jpg[/img][/font][/size]
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[/size]
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[b][size=2][font=宋体]再看几个术语：[/font][/size][/b]
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[/size][/font][b][font=宋体]承诺速率计算间隔（[/font][font=Times New Roman]Tc[/font][/b][b][font=宋体]） [/font][/b][font=宋体] ＜[/font][font=Times New Roman]125ms[/font][font=宋体]，[/font][font=Times New Roman]Tc=Bc/CIR[/font][font=宋体]。 [/font][/size]
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[/size][/font][b][font=宋体]承诺信息速率（[/font][font=Times New Roman]CIR[/font][/b][b][font=宋体]）[/font][/b][font=宋体] 期望平均速率，和物理接口一致。 [/font][/size]
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[/size][/font][b][font=宋体]承诺突发量（[/font][font=Times New Roman]Bc[/font][/b][b][font=宋体]）[/font][/b][font=宋体] 每个[/font][font=Times New Roman]Tc[/font][font=宋体]时段时传送的数据量，通常为[/font][font=Times New Roman]CIR1/8[/font][font=宋体]，单位[/font][font=Times New Roman]bit/s[/font][font=宋体]。[/font][/size]
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[/size][/font][b][font=宋体]过量突发量（[/font][font=Times New Roman]Be[/font][/b][b][font=宋体]）[/font][/b][font=宋体] 试图传输超过[/font][font=Times New Roman]CIR[/font][font=宋体]的那部分数据量，单位[/font][font=Times New Roman]bit/s[/font][font=宋体]。实际由供应商决定。[/font][/size]
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[/size][/font][b][font=宋体]最小承诺信息速率（[/font][font=Times New Roman]MinCIR[/font][/b][b][font=宋体]）[/font][/b][font=宋体] 信道拥挤时能够传送的最小数据量。[/font][/size]
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[/size][/font][b][font=宋体]传输字节（[/font][font=Times New Roman]Byte increment[/font][/b][b][font=宋体]）[/font][/b][font=宋体] [/font][font=Times New Roman]=Bc/8[/font][font=宋体]，每个时段里传输的数据量。[/font][/size]
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[/size][/font][b][font=宋体]前向显式拥塞通告（[/font][font=Times New Roman]FECN[/font][/b][b][font=宋体]） [/font][/b][font=宋体] 当帧中继交换机察觉到发生拥塞，即向目的设备发送一个[/font][font=Times New Roman]FECN[/font][font=宋体]数据包，指示有拥塞。[/font][/size]
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[/size][/font][b][font=宋体]后向显式拥塞通告（[/font][font=Times New Roman]BECN[/font][/b][b][font=宋体]） [/font][/b][font=宋体] 当帧中继交换机察觉到发生拥塞，即向源设备发送一个[/font][font=Times New Roman]BECN[/font][font=宋体]数据包，指示降低发送数据包的速率。[/font][font=Times New Roman]IOS 11.2 or later version supported BECN[/font][font=宋体]。[/font][/size]
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[/size][/font][b][font=宋体]可丢弃指示符（[/font][font=Times New Roman]De[/font][/b][b][font=宋体]） [/font][/b][font=宋体]当网络发生拥塞时，有[/font][font=Times New Roman]De[/font][font=宋体]编织物设置的数据包将被丢弃。[/font][/size]
[b][font=宋体][size=2] [/size][/font][/b]
[size=2][font=宋体]启动流量整形后，[/font][font=Times New Roman]router[/font][font=宋体]在发送[/font][font=Times New Roman]packet[/font][font=宋体]前会检查是否有可用的令牌桶[/font][font=Times New Roman]or[/font][font=宋体]标志，事先定义令牌桶的容量，存有以一定速率放进去的令牌。任何时[/font][font=Times New Roman]router[/font][font=宋体]发送的速率大小要和令牌桶一致。在数据送出接口之前都要通过为[/font][font=Times New Roman]VC[/font][font=宋体]而建立的队列。[/font][/size]
[size=2][b][font=Times New Roman]BECN[/font][/b][b][font=宋体]响应模式：[/font][/b][font=宋体]如果[/font][font=Times New Roman]router[/font][font=宋体]收到[/font][font=Times New Roman]BECN[/font][font=宋体]，则速率降低[/font][font=Times New Roman]25%[/font][font=宋体]，在接下来每个[/font][font=Times New Roman]Tc[/font][font=宋体]间隔后都再降低[/font][font=Times New Roman]25%[/font][font=宋体]，起到降低到[/font][font=Times New Roman]MinCIR[/font][font=宋体]为止。如果有[/font][font=Times New Roman]16[/font][font=宋体]个[/font][font=Times New Roman]Tc[/font][font=宋体]间隔没有再收到[/font][font=Times New Roman]BECN[/font][font=宋体]，速率则以每次（[/font][font=Times New Roman]Be+Bc[/font][font=宋体]）[/font][font=Times New Roman]/16[/font][font=宋体]增加。配置帧中继流量整形步骤：[/font][/size]
[size=2][font=宋体]第[/font][font=Times New Roman]1[/font][font=宋体]步 允许[/font][font=Times New Roman]FRTS[/font][font=宋体] [/font][font=Times New Roman]router(config-if)#frame-relay traffic-shaping[/font][font=宋体]。[/font][/size]
[size=2][font=宋体]第[/font][font=Times New Roman]2[/font][font=宋体]步 创建映射类，[/font][font=Times New Roman]router(config-if)#frame-relay class [i]calss_name_l [/i][ in | out ][/font][font=宋体]，[/font][/size]
[size=2][font=Times New Roman]router(config)#map-class frame-relay class_name_l[/font][font=宋体]。前者可以多个[/font][font=Times New Roman]VC[/font][font=宋体]使用同一个映射类。[/font][/size]
[size=2][font=宋体]第[/font][font=Times New Roman]3[/font][font=宋体]步 在映射类配置中设置选项：[/font][/size]
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[/font][font=Times New Roman]Frame-relay adaptive-shaping [ becn | foresinght ]
[/font][font=宋体]使用[/font][font=Times New Roman]BECN[/font][/size]
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[/font][font=Times New Roman]Frame-relay cir [ in | out ][i]bit/s[/i][/font][font=宋体] 将[/font][font=Times New Roman]CIR[/font][font=宋体]设置为物理接口速率[/font][/size]
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[/font][font=Times New Roman]Frame-relay bc [ in | out ][i]bit/s[/i][/font][font=宋体] 合适的设置为远端设备的[/font][font=Times New Roman]1/8CIR[/font][font=宋体]。[/font][/size]
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[/font][font=Times New Roman]Frame-relay be out [i]bit/s [/i]
[/font][font=宋体] 不应超过接口速率。[/font][/size]
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[/font][font=Times New Roman]Frame-relay mincir [ in | out ][i]bit/s[/i][/font][font=宋体] 设为和供应商提供的[/font][font=Times New Roman]CIR[/font][font=宋体]值。[/font][/size]
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[/font][font=Times New Roman]Frame-relay traffic-rate [i]cir peak_speed [/i]
[/font][font=宋体]可选，不应超过接口速率，[/font][/size]
[size=2][font=宋体]第[/font][font=Times New Roman]4[/font][font=宋体]步 可选将队列应用于映射类，默认是[/font][font=Times New Roman]FIFO[/font][font=宋体]。[/font][/size]
[size=2][color=#000000][size=10.5pt][font=Times New Roman]3.5.1 [/font][/size][font=宋体][size=10.5pt]实例：帧中继流量整形的配置[/size][/font][/color][/size]
[size=10.5pt][/size][size=2][font=宋体]图[/font][font=Times New Roman]3-6 [/font][font=宋体]为一个帧中继点对点网络。[/font][/size]
[size=2][font=宋体]该实例中为防止[/font][font=Times New Roman]R5[/font][font=宋体]发送大量数据到[/font][font=Times New Roman]R2[/font][font=宋体]的[/font][font=Times New Roman]PVC[/font][font=宋体]，同时还要对传送到[/font][font=Times New Roman]R3[/font][font=宋体]的流量整形，假设[/font][font=Times New Roman]R5[/font][font=宋体]和[/font][font=Times New Roman]R3[/font][font=宋体]的接口速率为[/font][font=Times New Roman]1.544Mbit/s[/font][font=宋体]，[/font][font=Times New Roman]R2[/font][font=宋体]则是[/font][font=Times New Roman]64Kbit/s[/font][font=宋体]。[/font][font=Times New Roman]R5[/font][font=宋体]和[/font][font=Times New Roman]R2[/font][font=宋体]之间的[/font][font=Times New Roman]PVC[/font][font=宋体]的[/font][font=Times New Roman]CIR[/font][font=宋体]供应商设定为[/font][font=Times New Roman]32kbit/s[/font][font=宋体]，[/font][font=Times New Roman]R5[/font][font=宋体]和[/font][font=Times New Roman]R3[/font][font=宋体]之间的[/font][font=Times New Roman]PVC[/font][font=宋体]的[/font][font=Times New Roman]CIR[/font][font=宋体]为[/font][font=Times New Roman]512Kbit/s[/font][font=宋体]。[/font][/size]
[size=2][font=宋体]图[/font][font=Times New Roman]3-6[/font][/size]
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[/size]
[size=2][font=宋体]例[/font][font=Times New Roman]3-10 R5 FRTS:[/font][font=宋体]配置[/font][/size]
[size=2][font=宋体][img=550,346]http://www.cnfan.net/cisco/uploadfile/200707/20070703105337601.jpg[/img][/font][/size]
[font=Times New Roman][size=2]R5(config)#int s1/0[/size][/font]
[size=2][font=Times New Roman]R5(config-if)#frame-relay traffic-shaping [/font][font=宋体] [color=red]＜－[/color][/font][font=Times New Roman][color=red]enable FRTS[/color][/font][/size]
[font=Times New Roman][size=2]R5(config-if)#exit [/size][/font]
[font=Times New Roman][size=2]R5(config)#int s1/0.1[/size][/font]
[font=Times New Roman][size=2]R5(config-subif)#frame[/size][/font]
[size=2][font=Times New Roman]R5(config-subif)#frame-relay class 64kb
[/font][color=red][font=宋体]＜－[/font][/color][color=red][font=Times New Roman]set map class[/font][/color][/size]
[font=Times New Roman][size=2]R5(config-subif)#exit[/size][/font]
[font=Times New Roman][size=2]R5(config)#int s1/0.2[/size][/font]
[font=Times New Roman][size=2]R5(config-subif)#frame-relay class t1[/size][/font]
[font=Times New Roman][size=2]R5(config-subif)#[/size][/font]
[font=Times New Roman][size=2][/size][/font]
[size=2][font=宋体]例[/font][font=Times New Roman]3-11[/font][font=宋体]配置映射类[/font][/size]
[font=Times New Roman][size=2][/size][/font]
[size=2][font=Times New Roman]R5(config)#map-class frame-relay 64kb[/font][font=宋体] [color=red]＜－建立映射类[/color][/font][/size]
[size=2][font=Times New Roman]R5(config-map-class)#frame-relay adaptive-shaping becn[/font][font=宋体] [color=red]＜－[/color][/font][font=Times New Roman][color=red]Eable BENC response[/color][/font][/size]
[size=2][font=Times New Roman]R5(config-map-class)#frame-relay cir 1544000
[/font][color=red][font=宋体]＜－设置为物理端口速率[/font][/color][/size]
[size=2][font=Times New Roman]R5(config-map-class)#frame-relay bc 8000[/font][font=宋体] [color=red]＜－设置为远端端口速率的[/color][/font][font=Times New Roman][color=red]1/8[/color][/font][/size]
[size=2][font=Times New Roman]R5(config-map-class)#frame-relay be 64000[/font][font=宋体] [color=red]＜－[/color][/font][font=Times New Roman][color=red]Initail burst[/color][/font][/size]
[size=2][font=Times New Roman]R5(config-map-class)#frame-relay mincir 32000
[/font][color=red][font=宋体]＜－[/font][/color][color=red][font=Times New Roman]Carrier enforced CIR[/font][/color][/size]
[font=Times New Roman][size=2]R5(config-map-class)#exit[/size][/font]
[font=Times New Roman][size=2]R5(config)#map-class frame-relay t1[/size][/font]
[font=Times New Roman][size=2]R5(config-map-class)#frame-relay adaptive-shaping becn[/size][/font]
[font=Times New Roman][size=2]R5(config-map-class)#frame-relay cir 1544000[/size][/font]
[font=Times New Roman][size=2]R5(config-map-class)#frame-relay bc 8000[/size][/font]
[font=Times New Roman][size=2]R5(config-map-class)#frame-relay be 64000[/size][/font]
[font=Times New Roman][size=2]R5(config-map-class)#frame-relay mincir 512000[/size][/font]
[font=Times New Roman][size=2]R5(config-map-class)#[/size][/font]
[size=2][font=宋体]使用[/font][font=Times New Roman]show traffic-shape[/font][font=宋体]和[/font][font=Times New Roman]show frame-relay pvc[i] dlci_number[/i][/font][font=宋体]命令验证[/font][font=Times New Roman]FRTS[/font][font=宋体]配置，例[/font][font=Times New Roman]3-12[/font][font=宋体]列出两条命令所显示的信息：[/font][/size]
[size=2][font=宋体]例[/font][font=Times New Roman]3-12 show traffic-shape and show frame-relay pvc [/font][font=宋体]命令显示信息[/font][/size]
[font=Times New Roman][size=2]R5#show traffic-shape [/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2]Interface
Se1/0.1[/size][/font]
[font=Times New Roman][size=2]
Access Target
Byte
Sustain
Excess
Interval
Increment Adapt[/size][/font]
[font=Times New Roman][size=2]VC
List
Rate
Limit
bits/int
bits/int
(ms)
(bytes)
Active[/size][/font]
[font=Times New Roman][size=2]503
1544000
9930
15440
64000
10
1930
BECN[/size][/font]
[font=Times New Roman][size=2]502
1544000
9930
15440
64000
10
1930
BECN[/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2]Interface
Se1/0.2[/size][/font]
[font=Times New Roman][size=2]
Access Target
Byte
Sustain
Excess
Interval
Increment Adapt[/size][/font]
[font=Times New Roman][size=2]VC
List
Rate
Limit
bits/int
bits/int
(ms)
(bytes)
Active[/size][/font]
[font=Times New Roman][size=2]504
1544000
9930
15440
64000
10
1930
BECN[/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2]R5#show frame-relay pvc 502[/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2]PVC Statistics for interface Serial1/0 (Frame Relay DTE)[/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2]DLCI = 502, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1/0.1[/size][/font]
[font=Times New Roman][size=2][/size][/font]
[font=Times New Roman][size=2]
input pkts 365
output pkts 205
in bytes 37862
[/size][/font]
[font=Times New Roman][size=2]
out bytes 17038
dropped pkts 0
in FECN pkts 0
[/size][/font]
[font=Times New Roman][size=2]
in BECN pkts 0
out FECN pkts 0
out BECN pkts 0
[/size][/font]
[font=Times New Roman][size=2]
in DE pkts 0
out DE pkts 0
[/size][/font]
[font=Times New Roman][size=2]
out bcast pkts 188
out bcast bytes 15294
[/size][/font]
[font=Times New Roman][size=2]
5 minute input rate 0 bits/sec, 0 packets/sec[/size][/font]
[font=Times New Roman][size=2]
5 minute output rate 0 bits/sec, 0 packets/sec[/size][/font]
[font=Times New Roman][size=2]
Shaping adapts to BECN[/size][/font]
[font=Times New Roman][size=2]
pvc create time 04:11:05, last time pvc status changed 04:11:05[/size][/font]
[font=Times New Roman][size=2]
cir 1544000
bc 15440
be 64000
byte limit 9930
interval 10
[/size][/font]
[font=Times New Roman][size=2]
mincir 32000
byte increment 1930
Adaptive Shaping BECN[/size][/font]
[font=Times New Roman][size=2]
pkts 13
bytes 1014
pkts delayed 0
bytes delayed 0
[/size][/font]
[font=Times New Roman][size=2]
shaping inactive
[/size][/font]
[font=Times New Roman][size=2]
traffic shaping drops 0[/size][/font]
[font=Times New Roman][size=2]
Queueing strategy: fifo[/size][/font]
[font=Times New Roman][size=2]
Output queue 0/40, 0 drop, 0 dequeued[/size][/font]
[font=Times New Roman][size=2]R5#[/size][/font]
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