QoS（quality of service）是cisco的叫法，类似的叫法，在Juniper为CoS（class of service）。
CoS在外企的Juniper设备上配置比较多，在国内用户的设备上见到很少。

CoS基本都是一个AS里面都关联起来的，可以用node 形容单台设备，CoS是由classification，policing ，queuing/scheduling,shaping,remarking组成，最少可以只配置分类和队列；其它都是可选。

通过show class-of-service forwarding-class，show class-of-service classifier，show class-of-service interface等可以看到Juniper的默认配置。默认Forwarding class为 best-effort，expedited-forwarding，assured-forwarding，network-control；对应的queue 分别为0，1,2,3。设备支持的Queues跟设备的硬件和软件平台都是有关。默认所有IPV4流量都放在队列0中，除非ToS位被设置为110或111，在这种情况下，流量被放在队列3中,路由协议控制流量使用这些设置。 所有MPLS流量都放在队列0中。在缓冲分配中，队列0获得95%的缓冲总量，队列3获得5%的缓冲总量.在带宽分配中，队列0 获得95%的带宽总量，队列3 获得5%的带宽总量
classification：中一般用到字段是dscp，tos（inet-precedenc）；RFC 791中定义的IP包头说明了ToS字段的位置；DSCP字段是在RFC 2474和2475中定义的，其目的是代替ToS字段。前六位用来分类，后两位目前没有使用。还有用到的字段是二层中的ieee-802.1和ieee-802.1ad，mpls 里面的exp，IPV6中的dscp-ipv6。
classification 的配置分为三种：BA（Behavior aggregate），根据cos标记；MF（multifield）根据数据包头部字节；或是两种的混合模式。当MF和BA的配置有重合的部分时，以MF为准。classification是关联在物理接口上的，为policing和schedulers服务的，决定数据包在congestion的情况下的丢弃优先级。

policing：管制的配置较简单，出发条件为bandwidth（和其它的触发条件类似，具体带宽或百分比）和burst size突发流量大小一般配置为接口的mtu的10倍，例如MTU=1500，则burst size配置为15K。如果配置具体带宽可以使用K，M，G代表具体数值，只有两种触发都达到阈值，才可以触发管制动作，管制动作有硬管制discard直接丢弃超出的流量，并不发送icmp不可达信息；软管制，提高PLP包丢弃优先级，或是将流量分配到优先级较低的forwarding-class里面。

Queuing/Scheduling :配置主要由transmission-rate，priority，buffer-size，drop-profile-map，shaping-rate。其中shaping-rate和transmission-rate类似policer里面，可以配置为百分比，具体带宽，remainder。priority有strict-high，high，medium-high，medium-low，low。其中strict-high是做带宽保证用的，决定保证。drop-profile-map可以为线性或是跳跃性。buffer-size可以配置percent，temporal（时间，单位为ms），reminder。shaping-rate可以配置percent或是具体数值。
Shaping暂时只在schedulers里面配置过，通过help apropos shaping看到也可以在interfaces和class-of-service traffic-control-profiles中使用，后续我查查KB，看看具体的使用案例。
Remarking的配置跟classification比较类似，针对的流量出接口分配的优先级，code-point。

参考day one 做的配置，
classification：
BA：
set class-of-service classifiers dscp dscp-test forwarding-class voice loss-priority low code-points ef
set class-of-service classifiers dscp dscp-test forwarding-class data loss-priority low code-points cs4
set class-of-service classifiers dscp dscp-test forwarding-class data loss-priority low code-points cs3
set class-of-service classifiers dscp dscp-test forwarding-class data loss-priority low code-points af41
set class-of-service classifiers dscp dscp-test forwarding-class video loss-priority low code-points af21
set class-of-service classifiers dscp dscp-test forwarding-class video loss-priority high code-points cs2
set class-of-service classifiers dscp dscp-test forwarding-class nc loss-priority low code-points cs6
set class-of-service classifiers dscp dscp-test forwarding-class nc loss-priority low code-points cs7
set class-of-service forwarding-classes queue 0 video
set class-of-service forwarding-classes queue 2 voice
set class-of-service forwarding-classes queue 3 nc
set class-of-service forwarding-classes queue 6 data
set class-of-service interfaces ge- unit classifiers dscp dscp-test

MF：
set firewall family inet filter mf-classifier term voice from protocol udp
set firewall family inet filter mf-classifier term voice from port 16384-32767
set firewall family inet filter mf-classifier term voice then loss-priority low
set firewall family inet filter mf-classifier term voice then forwarding-class voice
set firewall family inet filter mf-classifier term voice then accept
set firewall family inet filter mf-classifier term interactive-video from protocol udp
set firewall family inet filter mf-classifier term interactive-video from protocol tcp
set firewall family inet filter mf-classifier term interactive-video from port 6060-6061
set firewall family inet filter mf-classifier term interactive-video then loss-priority low
set firewall family inet filter mf-classifier term interactive-video then forwarding-class video
set firewall family inet filter mf-classifier term interactive-video then accept
set firewall family inet filter mf-classifier term call-sgnaling from protocol tcp
set firewall family inet filter mf-classifier term call-sgnaling from port 1720
set firewall family inet filter mf-classifier term call-sgnaling then loss-priority high
set firewall family inet filter mf-classifier term call-sgnaling then forwarding-class video
set firewall family inet filter mf-classifier term call-sgnaling then accept
set firewall family inet filter mf-classifier term ssh-telnet from protocol tcp
set firewall family inet filter mf-classifier term ssh-telnet from port telnet
set firewall family inet filter mf-classifier term ssh-telnet from port ssh
set firewall family inet filter mf-classifier term ssh-telnet then loss-priority high
set firewall family inet filter mf-classifier term ssh-telnet then forwarding-class nc
set firewall family inet filter mf-classifier term ssh-telnet then accept
set firewall family inet filter mf-classifier term imcp-police from protocol icmp
set firewall family inet filter mf-classifier term imcp-police from protocol icmp6
set firewall family inet filter mf-classifier term imcp-police then policer icmp-5m-limit
set firewall family inet filter mf-classifier term imcp-police then forwarding-class data
set firewall family inet filter mf-classifier term imcp-police then accept
set firewall family inet filter mf-classifier term be-intranet from protocol tcp
set firewall family inet filter mf-classifier term be-intranet from port 8080
set firewall family inet filter mf-classifier term be-intranet then policer fc-250m-be-limit
set firewall family inet filter mf-classifier term be-intranet then forwarding-class data
set firewall family inet filter mf-classifier term be-intranet then accept
set firewall family inet filter mf-classifier term be-traffic from protocol tcp
set firewall family inet filter mf-classifier term be-traffic from port ftp
set firewall family inet filter mf-classifier term be-traffic from port ftp-data
set firewall family inet filter mf-classifier term be-traffic from port http
set firewall family inet filter mf-classifier term be-traffic from port https
set firewall family inet filter mf-classifier term be-traffic then loss-priority high
set firewall family inet filter mf-classifier term be-traffic then forwarding-class data
set firewall family inet filter mf-classifier term be-traffic then accept
set firewall family inet filter mf-classifier term all-else then accept
set firewall policer icmp-5m-limit if-exceeding bandwidth-limit 5m
set firewall policer icmp-5m-limit if-exceeding burst-size-limit 15k
set firewall policer icmp-5m-limit then discard
set firewall policer fc-250m-be-limit if-exceeding bandwidth-limit 250m
set firewall policer fc-250m-be-limit if-exceeding burst-size-limit 625k
set firewall policer fc-250m-be-limit then loss-priority low
set firewall policer fc-250m-be-limit then forwarding-class data
set interfaces ge-0/0/2 unit 0 family inet filter input mf-classifier

Queuing/Scheduling：
set class-of-service drop-profiles wred-moderate-interpolate interpolate fill-level 75
set class-of-service drop-profiles wred-moderate-interpolate interpolate fill-level 85
set class-of-service drop-profiles wred-moderate-interpolate interpolate fill-level 95
set class-of-service drop-profiles wred-moderate-interpolate interpolate fill-level 100
set class-of-service drop-profiles wred-moderate-interpolate interpolate drop-probability 20
set class-of-service drop-profiles wred-moderate-interpolate interpolate drop-probability 35
set class-of-service drop-profiles wred-moderate-interpolate interpolate drop-probability 50
set class-of-service drop-profiles wred-moderate-interpolate interpolate drop-probability 100
set class-of-service drop-profiles wred-aggressive fill-level 50 drop-probability 10
set class-of-service drop-profiles wred-aggressive fill-level 70 drop-probability 40
set class-of-service drop-profiles wred-aggressive fill-level 85 drop-probability 75
set class-of-service drop-profiles wred-aggressive fill-level 100 drop-probability 100
set class-of-service scheduler-maps scheduler-map-a forwarding-class voice scheduler voice-scheduler
set class-of-service scheduler-maps scheduler-map-a forwarding-class video scheduler video-scheduler
set class-of-service scheduler-maps scheduler-map-a forwarding-class data scheduler data-scheduler
set class-of-service scheduler-maps scheduler-map-a forwarding-class nc scheduler nc-scheduler
set class-of-service schedulers voice-scheduler transmit-rate percent 10
set class-of-service schedulers voice-scheduler buffer-size percent 5
set class-of-service schedulers voice-scheduler priority high
set class-of-service schedulers video-scheduler transmit-rate remainder
set class-of-service schedulers video-scheduler buffer-size remainder
set class-of-service schedulers video-scheduler priority medium-high
set class-of-service schedulers video-scheduler drop-profile-map loss-priority low protocol any drop-profile wred-aggressive
set class-of-service schedulers nc-scheduler transmit-rate percent 5
set class-of-service schedulers nc-scheduler buffer-size percent 5
set class-of-service schedulers nc-scheduler priority high
set class-of-service schedulers data-scheduler transmit-rate percent 40
set class-of-service schedulers data-scheduler buffer-size percent 25
set class-of-service schedulers data-scheduler priority medium-low
set class-of-service schedulers data-scheduler drop-profile-map loss-priority low protocol any drop-profile wred-moderate-interpolate
set class-of-service interfaces ge-* scheduler-map scheduler-map-a
set class-of-service interfaces ge-0/0/1 scheduler-map scheduler-map-a
set class-of-service interfaces ge-0/0/1 unit 0 shaping-rate 800m

Remarking：
set class-of-service rewrite-rules dscp dscp-remarking forwarding-class voice loss-priority low code-point 000000
set class-of-service rewrite-rules dscp dscp-remarking forwarding-class data loss-priority low code-point 000000
set class-of-service rewrite-rules dscp dscp-remarking forwarding-class video loss-priority low code-point 000000
set class-of-service rewrite-rules dscp dscp-remarking forwarding-class video loss-priority high code-point 000000
set class-of-service rewrite-rules dscp dscp-remarking forwarding-class nc loss-priority low code-point 000000
set class-of-service interfaces ge- unit rewrite-rules dscp dscp-remarking