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diff --git a/src/vnet/policer/policer.rst b/src/vnet/policer/policer.rst new file mode 100644 index 00000000000..0e7369e373b --- /dev/null +++ b/src/vnet/policer/policer.rst @@ -0,0 +1,217 @@ +.. _policer: + +Policing +======== + +VPP implements several policer types, that don't always conform +to the related RFCs [#rfc2697]_ [#rfc2698]_ [#rfc4115]_. +Only policers implemented in VPP will be presented, along with +the differences they have compared to RFCs. + +.. contents:: :local: + :depth: 1 + + +1 rate 2 color (1r2c) +--------------------- + +This is the most straightforward policer. There is no RFC describing it, +however we can found its description in many documentation [#juniper]_ [#cisco]_ . + +A 1r2c policer is great to classify incoming packets into two categories: +conforming packets (said green), and violating ones (said red). + +Parameters +~~~~~~~~~~ + +To set-up such a policer, only two parameters are needed: + +Committed Information Rate (CIR) + Given in bytes per second, this parameter is the average + throughput allowed by the policer. + + It sets the limit between conforming arriving packets (those making the + traffic fall below the CIR), and violating arriving packets + (those making the traffic exceed the CIR). + +Committed Burst Size (CBS) + It represents the size (in bytes) of a token bucket used to allow + some burstiness from the incoming traffic. + +.. figure:: /_images/policer-1r2c-bucket.png + :align: center + :scale: 25% + + Figure 1: 1r2c bucket filling logic + +The committed token bucket (C) is filling up at CIR tokens (bytes) +per second, up to CBS tokens. All overflowing tokens are lost. + +Color-Blind algorithm +~~~~~~~~~~~~~~~~~~~~~ + +.. image:: /_images/policer-1r2c-blind.png + :align: center + :scale: 75% + +| + +Color-Aware algorithm +~~~~~~~~~~~~~~~~~~~~~ + +In online documentation, there is no trace of a color-aware 1r2c policer. +However, VPP implementation allows such a thing. + +.. image:: /_images/policer-1r2c-aware.png + :align: center + :scale: 75% + +| + + +1 rate 3 color (1r3c) RFC 2697 [#rfc2697]_ +------------------------------------------ + +As for the `1 rate 2 color (1r2c)`_ policer, only one rate parameters is required +to setup a 1r3c policer. However, such a policer adds another kind of packet category: +exceeding ones (said yellow). + +Parameters +~~~~~~~~~~ + +To set-up such a policer, three parameters are needed: + +Committed Information Rate (CIR) + As in the `1 rate 2 color (1r2c)`_ policer. + +Committed Burst Size (CBS) + As in the `1 rate 2 color (1r2c)`_ policer. + +Excess Burst Size (EBS) + It represents the size (in bytes) of a second token bucket used + to allow an additional burstiness from the incoming traffic, when + traffic as been below the CIR for some time. + +.. figure:: /_images/policer-1r3c-bucket.png + :align: center + :scale: 25% + + Figure 2: 1r3c buckets filling logic + +The committed token bucket (C) is filling up at CIR tokens (bytes) +per second, up to CBS tokens. When C is full, tokens are overflowing +into the excess token bucket (E), up to EBS tokens. Only overflowing +tokens from E are lost. + +Color-Blind algorithm +~~~~~~~~~~~~~~~~~~~~~ + +.. image:: /_images/policer-1r3c-blind.png + :align: center + :scale: 75% + +| + +Color-Aware algorithm +~~~~~~~~~~~~~~~~~~~~~ + +.. image:: /_images/policer-1r3c-aware.png + :align: center + :scale: 75% + +| + +Notes +~~~~~ + +In the RFC 2697 [#rfc2697]_ describing the 1r3c policer, conforming (green) packets +only consume tokens from the token bucket C. Whereas, in VPP, they also consume tokens from E. + +One way to stick to the RFC is then to set the EBS parameter to be superior to CBS, so that +EBS - CBS corresponds to the EBS from the RFC. + +However, VPP does not enforce setting EBS > CBS, which could result in undesired behavior. + +2 rate 3 color (2r3c) RFC 2698 [#rfc2698]_ +------------------------------------------ + +Instead of setting the limit between yellow and red packets in terms of bursts, +as it is done by `1 rate 3 color (1r3c) RFC 2697`_ policers, two rate policers introduce +another rate parameter to discriminate between those two kinds of packets. + +Parameters +~~~~~~~~~~ + +To set-up such a policer, four parameters are needed: + +Committed Information Rate (CIR) + As in the `1 rate 2 color (1r2c)`_ policer. + +Committed Burst Size (CBS) + As in the `1 rate 2 color (1r2c)`_ policer. + +Peak Information Rate (PIR) + Given in bytes per second, this parameter is the average + throughput allowed by the policer when there is a peak in + traffic. + + It sets a second limit between exceeding arriving packets + (those making the traffic fall below the PIR, but above CIR), + and violating arriving packets (those making the traffic exceed the PIR). + +Peak Burst Size (PBS) + It represents the size (in bytes) of a second token bucket used + to allow an additional peak traffic. + +.. figure:: /_images/policer-2r3c-bucket.png + :align: center + :scale: 25% + + Figure 2: 2r3c-rfc2698 buckets filling logic + +The committed token bucket (C) is filling up at CIR tokens (bytes) +per second, up to CBS tokens. In the meantime, the peak token bucket (P) +is filling up at PIR tokens per second, up to PBS. All overflowing tokens +from C and P are lost. + +Color-Blind algorithm +~~~~~~~~~~~~~~~~~~~~~ + +.. image:: /_images/policer-2r3c-blind.png + :align: center + :scale: 75% + +| + +Color-Aware algorithm +~~~~~~~~~~~~~~~~~~~~~ + +.. image:: /_images/policer-2r3c-aware.png + :align: center + :scale: 50% + +| + +Notes +~~~~~ + +To have a working policer, the condition PIR >= CIR needs to hold. +Indeed, since we assume that peak traffic should have a greater +rate than committed ones. + + +2 rate 3 color (2r3c) RFC 4115 [#rfc4115]_ +------------------------------------------ + +The 2r3c-RFC4115 is an allowed choice by VPP. However, there is currently +no implementation of such a policer. Hence, the only two rate policer VPP +implements is the `2 rate 3 color (2r3c) RFC 2698`_ policer. + + +.. rubric:: References: + +.. [#juniper] https://www.juniper.net/documentation/us/en/software/junos/traffic-mgmt-nfx/routing-policy/topics/concept/tcm-overview-cos-qfx-series-understanding.html +.. [#cisco] https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_mqc/configuration/xe-16-8/qos-mqc-xe-16-8-book/qos-pkt-policing.html +.. [#rfc2697] https://www.rfc-editor.org/rfc/rfc2697.html +.. [#rfc2698] https://www.rfc-editor.org/rfc/rfc2698.html +.. [#rfc4115] https://www.rfc-editor.org/rfc/rfc4115.html |