Cisco IOS IP Service Level Agreementv (IP SLA)
(配置命令以IOS Version 12.1(22)E1为例)
Responder and Control Protocol
1.Responder
内嵌在思科目标路由器中的一个组件，用来对IP SLA请求包做应答，通过对应达包添加时间戳属性，以提高测量计算的准确性。只有Cisco厂家的路由器才能作为Cisco IP Sla的Responder。
2.Control Protocol
Cisco IP Sla 利用Control message通知Responder需要监听指定端口。一旦Responder收到带有指定端口属性的Control message，它将立即对指定的本地端口进行监听，直到接受到IP LSA探测报文或超时定时器过期之后，Responder将会停止对该端口的listening。可以配置MD5认证来增强Control message的安全性。
IP SLA与Responder的交互过程：
1.用户初始化IP SLA，指定需要进行探测的目标地址、协议、端口等信息
2.Source向Responder发送带有初始化信息的Control message
3.如果配置了MD5认证，Control message将携带MD5信息一同发送
4.Responser收到Control message,如果开启MD5认证，Responder检查MD5认证，如果MD5认证失败，Responder返回失败信息
5.如果source没有收到Responder的反馈信息，它会继续重传，直到重传超时
6.当Responder收到Control message,它会对Control message进行处理，开始对指定的端口进行listening，并返回ok消息，如果无法处理则返回error消息。(Responder可以在同一个指定端口上处理来自不同source的IP SLA操作)
7.如果source收到Responder的ok响应，则开始发送测试包。(show ip sla statistics可以看到响应代码)
8.当Responder对IP SLA经行了响应或超时之后，将停止对指定端口的listening
RTT(Round Trip Time)计算方法
RTT = T4-△-T1
MD5认证配置范例(source和responder需要同时配置)：
R1(config)#key chain sla //定义key chain
R1(config-keychain)#key 1
R1(config-keychain-key)#key-string 2008pj.cn //定义密钥
R1(config-keychain-key)#exit
R1(config-keychain)#exit
R1(config)#ip sla key-chain sla //SLA调用key chain
验证命令：
show ip sla application //查看支持哪些应用
show ip sla configuration
show ip sla statistics [details]
UDP Echo Operation
用于测量Cisco路由和和路由器之间，或者Cisco路由器和任何IP设备之间的响应时间。如果目标设备是Cisco路由器，并且作为responder，那么Responder可以监听默认UDP Echo端口(7)或者用户自定义端口。
如果目标设备是非Cisco路由器，那么它只能监听默认UDP Echo端口(7)
备注：
UDP echo server 默认端口是7，而且思科路由器在Release 11.2之后默认关闭该服务。如果Responder(目标路由器)开启echo service，并且IP SLA echo option指定测量端口为7，由于port 7已经被echo server 占用，那么会导致IP SLA测量失败。
配置示例：
R1(config)#ip sla 1
R1(config-ip-sla)#udp-echo 2.2.2.2 500
R1(config-ip-sla-udp)#frequency 30
R1(config-ip-sla-udp)#threshold 150
R1(config-ip-sla-udp)# *** 其他可选配置
R1(config)#ip sla schedule 1 life 600 start-time now
验证命令：
R1#show ip sla statistics 1
Round Trip Time (RTT) for Index 1
Latest RTT: 71 milliseconds
Latest operation start time: *13:45:45.440 UTC Fri Mar 1 2002
Latest operation return code: OK
Number of successes: 6
Number of failures: 0
Operation time to live: 0
R1#show ip sla statistics 1 details
Round Trip Time (RTT) for Index 1
Latest RTT: 71 milliseconds
Latest operation start time: *13:45:45.440 UTC Fri Mar 1 2002
Latest operation return code: OK
Over thresholds occurred: FALSE
Number of successes: 6
Number of failures: 0
Operation time to live: 0
Operational state of entry: Inactive
Last time this entry was reset: Never
UDP Jitter Operation
Jitter, 代表交互数据包的延迟变量。例如Source连续的间隔10ms向目标发送探测报，在理想情况下，也会间隔10ms收到目标地址的应答包。如果网络出现延迟，在12ms之后收到应打包，那么 jitter为2(positive value)；如果在8ms之后收到应答包，jitter为-2(negative value)；理想情况下,jitter应该为0。
UDP Jitter Option支持的测量结果类型：
1. Per-direction jitter(单向jitter)
2. Per-direction packet-loss(单向丢包)
3. Per-direction delay(单向延迟,需要配置NTP来让时间同步)
4. Round-trip delay (average round-trip time)
测量出的单向结果可以明显的显示在哪个方向出现了拥塞或者瓶颈，这样对网络质量可以有个很好的评定。
默认情况下，IP SLA间隔F执行一组探测操作。每组操作中，连续共发送N个UDP数据包，每个数据包负载为S bytes,间隔T ms发送一次。
| Parameter | Default Value | Configured Command |
| Number of packet(N) | 10 packets | num-packets x |
| Playload size per packet(S) | 32 bytes | request-data-size x |
| Time between packets, in milliseconds(T) | 20 ms | interval x |
| Repeat interval (F) | 60 s | frequency x |
| Time out | 5000 ms | time-out x |
如果做Per-direction delay，需要source和destination时间同步(配置NTP)，如果时间不同步，返回值为0。Per-direction jitter和packet loss不需要时间同步。
配置示例：
R1(config)#ip sla 1
R1(config-ip-sla)#udp-jitter 2.2.2.2 222 source-ip 1.1.1.1 source-port 111 num-packets 5 interval 1000 //N=5，T=1s
R1(config-ip-sla-jitter)#timeout 10000 //time out=10s
R1(config-ip-sla-jitter)#frequency 10 //F=10s
R1(config)#ip sla schedule 1 life 11 start-time now
上述配置中，life为11s,frequency为10，刚好超过1s，而不到5s(发送5个包的时间为5)，但是IP SLA仍然会执行第二组操作(共花掉15s)，总共发送10个UDP包和2个control message(默认开启)。
R1#show ip sla statistics 1 details
Round Trip Time (RTT) for Index 1
Latest RTT: 61 milliseconds
Latest operation start time: *01:45:41.307 UTC Fri Mar 1 2002
Latest operation return code: OK
Over thresholds occurred: FALSE
RTT Values:
Number Of RTT: 5 RTT Min/Avg/Max: 56/61/76 milliseconds
Latency one-way time:
Number of Latency one-way Samples: 0
Source to Destination Latency one way Min/Avg/Max: 0/0/0 milliseconds
Destination to Source Latency one way Min/Avg/Max: 0/0/0 milliseconds
Source to Destination Latency one way Sum/Sum2: 0/0
Destination to Source Latency one way Sum/Sum2: 0/0
Jitter Time:
Number of Jitter Samples: 4
Source to Destination Jitter Min/Avg/Max: 1/7/12 milliseconds
Destination to Source Jitter Min/Avg/Max: 1/6/12 milliseconds
Source to destination positive jitter Min/Avg/Max: 4/4/4 milliseconds
Source to destination positive jitter Number/Sum/Sum2: 1/4/16
Source to destination negative jitter Min/Avg/Max: 1/8/12 milliseconds
Source to destination negative jitter Number/Sum/Sum2: 3/24/266
Destination to Source positive jitter Min/Avg/Max: 12/12/12 milliseconds
Destination to Source positive jitter Number/Sum/Sum2: 1/12/144
Destination to Source negative jitter Min/Avg/Max: 1/4/7 milliseconds
Destination to Source negative jitter Number/Sum/Sum2: 3/12/66
Interarrival jitterout: 0 Interarrival jitterin: 0
Packet Loss Values:
Loss Source to Destination: 0 Loss Destination to Source: 0
Out Of Sequence: 0 Tail Drop: 0 Packet Late Arrival: 0
Voice Score Values:
Calculated Planning Impairment Factor (ICPIF): 0
Mean Opinion Score (MOS): 0
Number of successes: 2
Number of failures: 0
Operation time to live: 0
Operational state of entry: Inactive
Last time this entry was reset: Never
| statistic 描述 | |
| Number Of RTT | 成功往返数据包 |
| Out Of Sequence | 无序数据包 |
| Tail Drop | 无法确定丢失原因的数据包(可能是尾丢弃) |
| Packet Late Arrival | 超时之后到达的数据包 |
UDP Jitter Operation for VoIP
UDP Jitter Operation 可以用作VOIP性能测试。支持的语音编码类型：g711alaw, g711ulaw, g729a 三种。
测量结果有一下两种衡量方式：
1.ICPIF(The Calculated Planning Impairment Factor)：障碍因子。范围为1到55，值越小，表明网络性能越好。
| Upper Limit for ICPIF | Speech Communication Quality |
| 5 | very good(最佳) |
| 10 | Good(很好) |
| 20 | Adequate(偏好) |
| 30 | Limiting case(一般) |
| 45 | Exceptional limiting case(差) |
| 55 | 极差 |
2.MOS(Mean Opinion Scores):平均意见评分。范围为1到5，值越大，表明语音传输性能越好。
| Score | Quality |
| 5 | Excellent |
| 4 | Good |
| 3 | Fair |
| 2 | Poor |
| 1 | Bad |
配置示例：
R1(config)#ip sla 2
R1(config-ip-sla)udp-jitter 2.2.2.2 222 codec g711alaw
R1(config)#ip sla schedule 2 life 60 start-time now
其他属性采用默认配置
R1#show ip sla statistics 2 details
Round Trip Time (RTT) for Index 2
Latest RTT: 46 milliseconds
Latest operation start time: *02:22:08.807 UTC Fri Mar 1 2002
Latest operation return code: OK
Over thresholds occurred: FALSE
RTT Values:
Number Of RTT: 893 RTT Min/Avg/Max: 4/52/425 milliseconds
Latency one-way time:
Number of Latency one-way Samples: 0
Source to Destination Latency one way Min/Avg/Max: 0/0/0 milliseconds
Destination to Source Latency one way Min/Avg/Max: 0/0/0 milliseconds
Source to Destination Latency one way Sum/Sum2: 0/0
Destination to Source Latency one way Sum/Sum2: 0/0
Jitter Time:
Number of Jitter Samples: 892
Source to Destination Jitter Min/Avg/Max: 1/15/51 milliseconds
Destination to Source Jitter Min/Avg/Max: 1/19/385 milliseconds
Source to destination positive jitter Min/Avg/Max: 1/17/51 milliseconds
Source to destination positive jitter Number/Sum/Sum2: 535/9142/196352
Source to destination negative jitter Min/Avg/Max: 1/13/51 milliseconds
Source to destination negative jitter Number/Sum/Sum2: 350/4726/90074
Destination to Source positive jitter Min/Avg/Max: 1/33/385 milliseconds
Destination to Source positive jitter Number/Sum/Sum2: 185/6282/712336
Destination to Source negative jitter Min/Avg/Max: 1/15/52 milliseconds
Destination to Source negative jitter Number/Sum/Sum2: 680/10424/210344
Interarrival jitterout: 0 Interarrival jitterin: 0
Packet Loss Values:
Loss Source to Destination: 0 Loss Destination to Source: 0
Out Of Sequence: 0 Tail Drop: 107 Packet Late Arrival: 0
Voice Score Values:
Calculated Planning Impairment Factor (ICPIF): 1
MOS score: 4.34 // mean opinion score(平均意见得分)
Number of successes: 1
Number of failures: 0
Operation time to live: 0
Operational state of entry: Inactive
Last time this entry was reset: Never
ICMP Echo Operation
通过ICMP echo request和ICMP echo reply来测量源和目标之间的响应时间，也可以通过设置DSCP值来测量QoS。ICMP packet size为request-size加上36byte的和(如果request-size为28byte，那么ICMP packet size为28+36=64byte)
配置示例：
R1(config)#no ip sla 1
R1(config-ip-sla)#icmp-echo 2.2.2.2
R1(config-ip-sla-echo)#request-data-size 30
R1(config)#ip sla schedule 1 life 60 start-time now
R1#show ip sla statistics 1 details
Round Trip Time (RTT) for Index 1
Latest RTT: 56 milliseconds
Latest operation start time: *05:43:11.446 UTC Fri Mar 1 2002
Latest operation return code: OK
Over thresholds occurred: FALSE
Number of successes: 1
Number of failures: 0
Operation time to live: 0
Operational state of entry: Inactive
Last time this entry was reset: Never
ICMP Path Echo Operation
ICMP Path Echo Operation，如同traceroute命令，测量到每一个中间节点的响应时间
配置示例：
R1(config)#ip sla 1
R1(config-ip-sla)#path-echo 3.3.3.3 source-ip 1.1.1.1
R1(config-ip-sla-pathEcho)#timeout 2
R1(config-ip-sla-pathEcho)#frequency 1
R1(config)#ip sla schedule 2 life 60 start-time now
TCP Connect Operation
用于测量虚应用程序到服务器的可用性、稳定性。例如telnet, SQL, http, ftp等。如果目标是被是非Cisco路由器，那么需要其开启知名端口服务
配置示例：
R1(config)#ip sla 1
R1(config-ip-sla)#tcp-connect 3.3.3.3 23
R1(config-ip-sla-tcp)#timeout 3
R1(config-ip-sla-tcp)#frequency 1
R1(config)#ip sla schedule 1 life 60 start-time now
DNS Operation
测量DNS的响应时间
配置示例:
R1(config)#ip sla 3
R1(config-ip-sla)#dns www.baidu.com name-server 8.8.8.8
HTTP Operation
http响应时间有3部分构成。
1. 域名查找
2. TCP connect to HTTP Server
3. 发送请求，获取数据
配置示例：
R1(config)#ip sl 3
R1(config-ip-sla)#http get http://www.2008pj.cn
R1(config)#ip sl schedule 3 life 6 start-time now
R1#show ip sla statistics 3 details
Round Trip Time (RTT) for Index 3
Latest RTT: 512 milliseconds
Latest operation start time: *00:45:17.935 UTC Fri Mar 1 2002
Latest operation return code: OK
Over thresholds occurred: FALSE
Latest DNS RTT: 263 ms
Latest TCP Connection RTT: 120 ms
Latest HTTP time to first byte: 248 ms
Latest HTTP Transaction RTT: 129 ms
Latest HTTP Status: 400
Latest HTTP Message Size: 168
Latest HTTP Entity-Body size: 39
Number of successes: 1
Number of failures: 0
Operation time to live: 0
Operational state of entry: Inactive
Last time this entry was reset: Never
SLA触发操作
当SLA检测结果超过指定阈值之后，可以出发其他操作。触发条件在reaction-configuration命令下配置，触发动作在reaction-trigger命令下配置。
配置示例：
R1(config)#ip sla 1
R1(config-ip-sla)#udp-echo 2.2.2.2 222
R1(config-ip-sla-udp)#timeout 5
R1(config-ip-sla-udp)#frequency 1
R1(config)#ip sla 2
R1(config-ip-sla)#icmp-echo 2.2.2.2
R1(config-ip-sla-echo)#timeout 5
R1(config-ip-sla-echo)#frequency 1
R1(config)#ip sla schedule 2 life 5 start-time pending //将调度挂起，等待其他被其他调度唤醒
R1(config)#ip sla reaction-configuration 1 react connectionLoss action-type action-type trapandTrigger threshold-type immediate //当检测到连接丢失之后采取的动作是向SNMP发送trap消息，并且启动触发操作(SLA 2)
R1(config)#ip sla reaction-trigger 1 2 //SLA 1检测结果违反规则之后唤醒SLA 2
R1(config)#ip sla logging traps
R1(config)#snmp-server enable traps
当目标地址2.2.2.2，端口222连接丢失之后，在本地路由器上产生如下log:
%RTT-4-OPER_CLOSS: condition occurred, entry number = 1
并向SNMP server发送如下SNMP trap信息(1.1.1.1是trap信息源地址，R1(config)#snmp-server trap-source Loopback0)：
IP SLA的应用
IP SLA与track相互协作引用的最广。比如利用IP SLA来跟踪下一跳IP的可达性，从而动态的改变静态路由的下一条。
范例：
在R1上配置默认路由到R2，R1优先选着192.168.1.x的网络，当该条链路不可达的时候，R1自动选则192.168.2.x的链路
R1配置：
| !ip route 0.0.0.0 0.0.0.0 192.168.1.2 10 track 1 //修改了默认AD为10ip route 0.0.0.0 0.0.0.0 192.168.2.2 20 track 2 //修改了默认AD为20!ip sla 1
icmp-echo 192.168.1.2 timeout 1000 frequency 1 ip sla schedule 1 life forever start-time now ip sla 2 icmp-echo 192.168.2.2 timeout 1000 frequency 1 ip sla schedule 2 life forever start-time now ! |
正常情况下，两条链路都可达时，一些验证命令：
| R1#show ip routeC 1.1.1.1 is directly connected, Loopback0C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, FastEthernet0/1S* 0.0.0.0/0 [10/0] via 192.168.1.2 |
| R1#show ip route track-table ip route 0.0.0.0 0.0.0.0 192.168.1.2 10 track 1 state is [up] ip route 0.0.0.0 0.0.0.0 192.168.2.2 20 track 2 state is [up] |
当主链路不可达时(R2上shutdown直连接口192.168.1.2),并在R1上开启debug track和debug ip routing，可以看到
| *Mar 1 01:03:51.975: Track: 1 Change #8 rtr 1, state Up->Down*Mar 1 01:03:51.975: RT: del 0.0.0.0 via 192.168.1.2, static metric [10/0]*Mar 1 01:03:51.975: RT: delete network route to 0.0.0.0*Mar 1 01:03:51.979: RT: NET-RED 0.0.0.0/0*Mar 1 01:03:51.979: RT: NET-RED 0.0.0.0/0
*Mar 1 01:03:51.979: RT: SET_LAST_RDB for 0.0.0.0/0 NEW rdb: via 192.168.2.2 *Mar 1 01:03:51.983: RT: add 0.0.0.0/0 via 192.168.2.2, static metric [20/0] *Mar 1 01:03:51.983: RT: NET-RED 0.0.0.0/0 *Mar 1 01:03:51.987: RT: default path is now 0.0.0.0 via 192.168.2.2 *Mar 1 01:03:51.987: RT: new default network 0.0.0.0 *Mar 1 01:03:51.987: RT: NET-RED 0.0.0.0/0 R1# *Mar 1 01:04:10.619: RT: NET-RED 0.0.0.0/0 |
| R1#show ip routeC 1.1.1.1 is directly connected, Loopback0C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, FastEthernet0/1S* 0.0.0.0/0 [20/0] via 192.168.2.2 |
| R1#show ip route track-table ip route 0.0.0.0 0.0.0.0 192.168.1.2 10 track 1 state is [down] ip route 0.0.0.0 0.0.0.0 192.168.2.2 20 track 2 state is [up] |