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.. _qos:
***********************
QoS and Traffic Control
***********************
The generic name of Quality of Service or Traffic Control involves
things like shaping, scheduling, policing or dropping traffic, which are
the kind of things you may want to play with when you have, for
instance, a bandwidth bottleneck in a link and you want to somehow
prioritize some type of traffic over another.
tc_ is a powerful tool for Traffic Control found at the Linux kernel.
However, its configuration is often considered a cumbersome task.
Fortunately, VyOS eases the job through its CLI, while using ``tc`` as
backend.
How to make it work
===================
In order to have VyOS Traffic Control working you need to follow 2
steps:
1. Create a traffic policy.
2. Apply the traffic policy to an interface ingress or egress.
(You can only apply one policy per interface and direction.)
But before learning to configure your policy, we will quickly warn you
about the different units you can use and also show you what *classes*
are and how they work, as some policies may require you to configure
them.
Units
=====
When configuring your traffic policy, you will have to set data rate
values, watch out the units you are managing, it is easy to get confused
with the different prefixes and suffixes you can use. VyOS will always
show you the different units you can use.
Prefixes
--------
They can be **decimal** prefixes.
.. code-block:: none
kbit (10^3) kilobit per second
mbit (10^6) megabit per second
gbit (10^9) gigabit per second
tbit (10^12) terabit per second
kbps (8*10^3) kilobyte per second
mbps (8*10^6) megabyte per second
gbps (8*10^9) gigabyte per second
tbps (8*10^12) terabyte per second
Or **binary** prefixes.
.. code-block:: none
kibit (2^10 = 1024) kibibit per second
mibit (2^20 = 1024^2) mebibit per second
gibit (2^30 = 1024^3) gibibit per second
tbit (2^40 = 1024^4) tebibit per second
kibps (1024*8) kibibyte (KiB) per second
mibps (1024^2*8) mebibyte (MiB) per second
gibps (1024^3*8) gibibyte (GiB) per second
tibps (1024^4*8) tebibyte (TiB) per second
Suffixes
--------
A *bit* is written as **bit**.
.. code-block:: none
kbit (kilobits per second)
mbit (megabits per second)
gbit (gigabits per second)
tbit (terabits per second)
While a *byte* is written as a single **b**.
.. code-block:: none
kbps (kilobytes per second)
mbps (megabytes per second)
gbps (gigabytes per second)
.. _classes:
Classes
=======
In the subsection :ref:`creating_a_traffic_policy` you will see that
some of the policies use *classes*. Those policies let you distribute
traffic into different classes according to different parameters you can
choose. So, a class is just a specific type of traffic you select.
The ultimate goal of classifying traffic is to give each class a
different treatment.
Matching traffic
----------------
In order to define which traffic goes to which class, you define filters
(that is, matching criteria). Packets go through these matching rules
(as in the rules of a firewall) and, if a packet matches the filter, it
is assigned to that class.
In VyOS, a class is identified by a number you can choose when
configuring it.
.. note:: When configuring a class, some policies just need a
meaningless number to identify that class (Class ID), but in other
policies, like Priority Queue, the number of the class defines its
priority.
.. code-block:: none
set traffic-policy <policy> <policy-name> class <class-ID> match <class-matching-rule-name>
In the command above, we set the type of policy we are going to
work with and the name we choose for it; a class (so that we can
differentiate some traffic) and an identifiable number for that class;
then we configure a matching rule (or filter) and a name for it.
A class can have multiple match filters:
.. code-block:: none
set traffic-policy shaper MY-SHAPER class 30 match HTTP
set traffic-policy shaper MY-SHAPER class 30 match HTTPs
A match filter can contain multiple criteria and will match traffic if
all those criteria are true.
For example:
.. code-block:: none
set traffic-policy shaper MY-SHAPER class 30 match HTTP ip protocol tcp
set traffic-policy shaper MY-SHAPER class 30 match HTTP ip source port 80
This will match TCP traffic with source port 80.
There are many parameters you will be able to use in order to match the
traffic you want for a class:
- **Ethernet (protocol, destination address or source address)**
- **Interface name**
- **IPv4 (DSCP value, maximum packet length, protocol, source address,**
**destination address, source port, destination port or TCP flags)**
- **IPv6 (DSCP value, maximum payload length, protocol, source address,**
**destination address, source port, destination port or TCP flags)**
- **Firewall mark**
- **VLAN ID**
When configuring your filter, you can use the ``Tab`` key to see the many
different parameters you can configure.
.. code-block:: none
vyos@vyos# set traffic-policy shaper MY-SHAPER class 30 match MY-FIRST-FILTER
Possible completions:
description Description for this match
> ether Ethernet header match
interface Interface name for this match
> ip Match IP protocol header
> ipv6 Match IPV6 header
mark Match on mark applied by firewall
vif Virtual Local Area Network (VLAN) ID for this match
You can also write a description for a filter:
.. code-block:: none
set traffic-policy shaper MY-SHAPER class 30 match MY-FIRST-FILTER description "My filter description"
.. note:: An IPv4 TCP filter will only match packets with an IPv4 header length of
20 bytes (which is the majority of IPv4 packets anyway).
.. note:: IPv6 TCP filters will only match IPv6 packets with no header extension, see
https://en.wikipedia.org/wiki/IPv6_packet#Extension_headers
Default
-------
Often you will also have to configure what you want to do with traffic
called *default*, in the same way you do with a class. *Default* is just
any traffic which is not matching any of the classes you configured. It
is a class without filters.
Class treatment
---------------
Once a class has a filter configured, you will also have to define what
you want to do with the traffic of that class, what specific
Traffic-Control treatment you want to give it. You will have different
possibilities depending on the Traffic Policy you are configuring, you
will know about them in the :ref:`creating_a_traffic_policy` subsection.
.. code-block:: none
vyos@vyos# set traffic-policy shaper MY-SHAPER class 30
Possible completions:
bandwidth Bandwidth used for this class
burst Burst size for this class (default: 15kb)
ceiling Bandwidth limit for this class
codel-quantum
fq-codel - Number of bytes used as 'deficit' (default 1514)
description Description for this traffic class
flows fq-codel - Number of flows (default 1024)
interval fq-codel - Interval (milliseconds) used to measure the delay (default 100)
+> match Class matching rule name
priority Priority for usage of excess bandwidth
queue-limit Maximum queue size (packets)
queue-type Queue type for this class
set-dscp Change the Differentiated Services (DiffServ) field in the IP header
target fq-codel - Acceptable minimum queue delay (milliseconds)
Sometimes, you will want to embed_ a new policy into one class. In the
example above VyOS also shows the possibility to configure FQ-CoDel
settings into one of the classes of a Shaper policy.
.. _embed:
Embedding one policy into another one
-------------------------------------
Very often we will want to embed one policy into another.
For instance, you might want to apply different policies to the
different classes of a a Round-Robin policy you have configured.
Some policies, in order to be effective, they need to be applied to an
interface that is directly connected to the link where the bottleneck
is. If your router is is not directly connected to the bottleneck, but
some hop before it, you might want to embed your non-shaping policy into
a classful shaping one so that the bottleneck bandwidth is emulated and
your non-shaping policy takes effect.
You can configure a policy in a class through the ``queue-type``
setting.
.. code-block:: none
set traffic-policy shaper SHAPER_FOR_FQ-CODEL bandwidth 900mbit
set traffic-policy shaper SHAPER_FOR_FQ-CODEL default bandwidth 100%
set traffic-policy shaper SHAPER_FOR_FQ-CODEL default queue-type fq-codel
As shown in the last command of the example above, `queue-type` is the
esponsible for allowing these combinations, you will be able to use it
in many policies.
.. _creating_a_traffic_policy:
Creating a traffic policy
=========================
VyOS lets you control traffic in many different ways, here we will cover
every possibility. You can configure as many policies as you want, but
you will only be able to apply one policy per interface and direction
(inbound or outbound).
Some policies can be combined, you will be able to embed_ a different
policy that will be applied to a subqueue of the main policy.
.. hint:: If you are looking for a policy for your outbound traffic but
you do not know what policy you need, you might want to give a try to
FQ-CoDel_ as your multipurpose nearly-no-configuration fair-queue and
low-delay policy; or you might want to try Shaper_ if you don't need
to guarantee low delay but you want to manually allocate bandwidth
shares to specific traffic; or, if you want to manually allocate
bandwidth shares to specific traffic while guaranteeing low delay,
and you are not afraid of setting a complex configuration, you
might want to give Shaper-HFSC_ a go.
Drop Tail
---------
| **Queueing discipline:** PFIFO (Packet First In First Out).
| **Applies to:** Outbound traffic.
This the simplest queue possible you can apply to your traffic. Traffic
must go through a finite queue before it is actually sent. You must
define how many packets that queue can contain.
When a packet is to be sent, it will have to go through that queue, so
the packet will be placed at the tail of it. When the packet completely
goes through it, it will be dequeued emptying its place in the queue and
being eventually handed to the NIC to be actually sent out.
Despite the Drop-Tail policy does not slow down packets, if many packets
are to be sent, they could get dropped when trying to get enqueued at
the tail. This can happen if the queue has still not been able to
release enough packets from its head.
Very likely you do not need this simple policy as you cannot get much
from it. Sometimes it is used just to enable logging.
.. cfgcmd:: set traffic-policy drop-tail <policy-name> queue-limit <number-of-packets>
Use this command to configure a drop-tail policy (PFIFO). Choose a
unique name for this policy and the size of the queue by setting the
number of packets it can contain (maximum 4294967295).
Fair Queue
----------
| **Queueing discipline:** SFQ (Stochastic Fairness Queuing).
| **Applies to:** Outbound traffic.
Fair Queue is a work-conserving scheduler which schedules the
transmission of packets based on flows, trying to ensure fairness so
that each flow is able to send data in turn, preventing any single one
from drowning out the rest.
.. cfgcmd:: set traffic-policy fair-queue <policy-name>
Use this command to create a Fair-Queue policy, which is based on the
Stochastic Fairness Queueing and can be applied to outbound traffic.
The algorithm enqueues packets to hash buckets based on source address,
destination address and source port. Each of these buckets should
represent a unique flow. Because multiple flows may get hashed to the
same bucket, the hashing algorithm is perturbed at configurable
intervals so that the unfairness lasts only for a short while.
Perturbation may however cause some inadvertent packet reordering to
occur. An advisable value could be 10 seconds.
One of the uses of Fair Queue might be the mitigation of Denial of
Service attacks.
.. cfgcmd:: set traffic-policy fair-queue <policy-name> hash-interval <seconds>`
Use this command to define a Fair-Queue policy, based on the
Stochastic Fairness Queueing, and set the number of seconds at which
a new queue algorithm perturbation will occur (maximum 4294967295).
When dequeuing, each hash-bucket with data is queried in a round robin
fashion. You can configure the length of the queue.
.. cfgcmd:: set traffic-policy fair-queue <policy-name> queue-limit <limit>
Use this command to define a Fair-Queue policy, based on the
Stochastic Fairness Queueing, and set the number of maximum packets
allowed to wait in the queue. Any other packet will be dropped.
.. note:: Fair Queue is a non-shaping (work-conserving) policy, so it
will only be useful if your outgoing interface is really full. If it
is not, VyOS will not own the queue and Fair Queue will have no
effect. If there is bandwidth available on the physical link, you can
embed_ Fair-Queue into a classful shaping policy to make sure it owns
the queue.
.. _FQ-CoDel
FQ-CoDel
--------
| **Queueing discipline** Fair/Flow Queue CoDel.
| **Applies to:** Outbound Traffic.
The FQ-CoDel policy cuts things up into 1024 FIFO queues and tries to
provide good service between all of them. It also tries to keep the
length of all the queues short.
FQ-CoDel fights bufferbloat and reduces latency without the need of
complex configurations. It has become the new default Queueing
Discipline for the interfaces of some GNU/Linux distributions.
It uses a stochastic model to classify incoming packets into
different flows and is used to provide a fair share of the bandwidth to
all the flows using the queue. Each such flow is managed by the CoDel
queuing discipline. Reordering within a flow is avoided since Codel
internally uses a FIFO queue.
FQ-CoDel is based on a modified Deficit Round Robin (DRR_) queue
scheduler with the CoDel Active Queue Management (AQM) algorithm
operating on each queue.
.. note:: FQ-Codel is a non-shaping (work-conserving) policy, so it
will only be useful if your outgoing interface is really full. If it
is not, VyOS will not own the queue and FQ-Codel will have no
effect. If there is bandwidth available on the physical link, you can
embed_ FQ-Codel into a classful shaping policy to make sure it owns
the queue.
FQ-CoDel is tuned to run ok with its default parameters at 10Gbit
speeds. It might work ok too at other speeds without configuring
anything, but here we will explain some cases when you might want to
tune its parameters.
When running it at 1Gbit and lower, you may want to reduce the
`queue-limit` to 1000 packets or less. In rates like 10Mbit, you may
want to set it to 600 packets.
If you are using FQ-CoDel embedded into Shaper_ and you have large rates
(100Mbit and above), you may consider increasing `quantum` to 8000 or
higher so that the scheduler saves CPU.
On low rates (below 40Mbit) you may want to tune `quantum` down to
something like 300.
At very low rates (below 3Mbit), besides tuning `quantum` (300 keeps
being ok) you may also want to increase `target` to something like 15ms
and increase `interval` to something around 150ms.
.. cfgcmd:: set traffic-policy fq-codel <policy name> codel-quantum <bytes>
Use this command to configure an fq-codel policy, set its name and
the maximum number of bytes (default: 1514) to be dequeued from a
queue at once.
.. cfgcmd:: set traffic-policy fq-codel <policy name> flows <number-of-flows>
Use this command to configure an fq-codel policy, set its name and
the number of sub-queues (default: 1024) into which packets are
classified.
.. cfgcmd:: set traffic-policy fq-codel <policy name> interval <miliseconds>
Use this command to configure an fq-codel policy, set its name and
the time period used by the control loop of CoDel to detect when a
persistent queue is developing, ensuring that the measured minimum
delay does not become too stale (default: 100ms).
.. cfgcmd:: set traffic-policy fq-codel <policy-name> queue-limit <number-of-packets>`
Use this command to configure an fq-codel policy, set its name, and
define a hard limit on the real queue size. When this limit is
reached, new packets are dropped (default: 10240 packets).
.. cfgcmd:: set traffic-policy fq-codel <policy-name> target <miliseconds>`
Use this command to configure an fq-codel policy, set its name, and
define the acceptable minimum standing/persistent queue delay. This
minimum delay is identified by tracking the local minimum queue delay
that packets experience (default: 5ms).
Limiter
-------
| **Queueing discipline:** Ingress policer.
| **Applies to:** Inbound traffic.
Limiter is one of those policies that uses classes_. (Ingress qdisc is
actually classless but filters do work with it.)
The limiter performs basic ingress policing of traffic flows. Multiple
classes of traffic can be defined and traffic limits can be applied to
each class. Although the policer uses a token bucket mechanism
internally, it does not have the capability to delay a packet as a
shaping mechanism does. Traffic exceeding the defined bandwidth limits
is directly dropped. A maximum allowed burst can be configured too.
You can configure classes (up to 4090) with different settings and a
default policy which will be applied to any traffic not matching any of
the configured classes.
.. note:: In the case you want to apply some kind of **shaping** to your
**inbound** traffic, check the ingress-shaping_ section.
.. cfgcmd:: set traffic-policy limiter <policy-name> class <class ID> match <match-name> description <description>
Use this command to configure an Ingress Policer, defining its name,
a class identifier (1-4090), a class matching rule name and its
description.
Once the matching rules are set for a class, you can start configuring
how you want matching traffic to behave.
.. cfgcmd:: set traffic-policy limiter <policy-name> class <class-ID> bandwidth <rate>
Use this command to configure an Ingress Policer, defining its name,
a class identifier (1-4090) and the maximum allowed bandwidth for
this class.
.. cfgcmd:: set traffic-policy limiter <policy-name> class <class-ID> burst <burst-size>
Use this command to configure an Ingress Policer, defining its name,
a class identifier (1-4090) and the burst size in bytes for this
class (default: 15).
.. cfgcmd:: set traffic-policy limiter <policy-name> default bandwidth <rate>
Use this command to configure an Ingress Policer, defining its name
and the maximum allowed bandwidth for its default policy.
.. cfgcmd:: set traffic-policy limiter <policy-name> default burst <burst-size>
Use this command to configure an Ingress Policer, defining its name
and the burst size in bytes (default: 15) for its default policy.
.. cfgcmd:: set traffic-policy limiter <policy-name> class <class ID> priority <value>
Use this command to configure an Ingress Policer, defining its name,
a class identifier (1-4090), and the priority (0-20, default 20) in
which the rule is evaluated (the lower the number, the higher the
priority).
Network emulator
----------------
| **Queueing discipline:** netem (Network Emulator) + TBF (Token Bucket Filter).
| **Applies to:** Outbound traffic.
VyOS Network Emulator policy emulates the conditions you can suffer in a
real network. You will be able to configure things like rate, burst,
delay, packet loss, packet corruption or packet reordering.
This could be helpful if you want to test how an application behaves
under certain network conditions.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> bandwidth <rate>
Use this command to configure the maximum rate at which traffic will
be shaped in a Network Emulator policy. Define the name of the policy
and the rate.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> burst <burst-size>
Use this command to configure the burst size of the traffic in a
Network Emulator policy. Define the name of the Network Emulator
policy and its traffic burst size. It will only take effect if you
have configured its bandwidth too.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> network-delay <delay>
Use this command to configure a Network Emulator policy defining its
name and the fixed amount of time you want to add to all packet going
out of the interface. You can use secs, ms and us. Default: ms.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> packet-corruption
<percent>`
Use this command to emulate noise in a Network Emulator policy. Set
the policy name and the percentage of corrupted packets you want. A
random error will be introduced in a random position for the chosen
percent of packets.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> packet-loss
<percent>`
Use this command to emulate packet-loss conditions in a Network
Emulator policy. Set the policy name and the percentage of loss
packets your traffic will suffer.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> packet-reordering
<percent>`
Use this command to emulate packet-reordering conditions in a Network
Emulator policy. Set the policy name and the percentage of reordered
packets your traffic will suffer.
.. cfgcmd:: set traffic-policy network-emulator <policy-name> queue-limit <limit>
Use this command to define the length of the queue of your Network
Emulator policy. Set the policy name and the maximum number of
packets (1-4294967295) the queue may hold queued at a time.
Priority queue
--------------
| **Queueing discipline:** PRIO.
| **Applies to:** Outbound traffic.
The Priority Queue is a classful scheduling policy. It does not delay
packets, it simply dequeues packets according to their priority.
.. note:: Priority Queue, as other non-shaping policies, is only useful
if your outgoing interface is really full. If it is not, VyOS will
not own the queue and Priority Queue will have no effect. If there is
bandwidth available on the physical link, you can embed_ Priority
Queue into a classful shaping policy to make sure it owns the queue.
In that case packets can be prioritized based on DSCP.
Up to seven queues -defined as classes_ with different priorities- can
be configured. Packets are placed into queues based on associated match
criteria. Packets are transmitted from the queues in priority order. If
classes with a higher priority are being filled with packets
continuously, packets from lower priority classes will only be
transmitted after traffic volume from higher priority classes decreases.
.. note:: In Priority Queue we do not define clases with a meaningless
class ID number but with a class priority number (1-7). The lower the
number, the higher the priority.
As with other policies, you can define different type of matching rules
for your classes:
.. code-block:: none
vyos@vyos# set traffic-policy priority-queue MY-PRIO class 3 match MY-MATCH-RULE
Possible completions:
description Description for this match
> ether Ethernet header match
interface Interface name for this match
> ip Match IP protocol header
> ipv6 Match IPV6 header
mark Match on mark applied by firewall
vif Virtual Local Area Network (VLAN) ID for this match
As with other policies, you can embed_ other policies into the classes
(and default) of your Priority Queue policy through the ``queue-type``
setting:
.. code-block:: none
vyos@vyos# set traffic-policy priority-queue MY-PRIO class 3 queue-type
Possible completions:
fq-codel Fair Queue Codel
fair-queue Stochastic Fair Queue (SFQ)
drop-tail First-In-First-Out (FIFO)
priority Priority queueing based on DSCP
random-detect
Random Early Detection (RED)
.. cfgcmd:: set traffic-policy priority-queue <policy-name> class
<class-ID> queue-limit <limit>`
Use this command to configure a Priority Queue policy, set its name,
set a class with a priority from 1 to 7 and define a hard limit on
the real queue size. When this limit is reached, new packets are
dropped.
.. _Random-Detect:
Random-Detect
-------------
| **Queueing discipline:** Generalized Random Early Drop.
| **Applies to:** Outbound traffic.
A simple Random Early Detection (RED) policy would start randomly
dropping packets from a queue before it reaches its queue limit thus
avoiding congestion. That would be also beneficial for TCP connections
as the gradual dropping of packets acts as a signal for the sender to
decrease its transmission rate, avoiding global TCP synchronisation.
In contrast to simple RED, the Weighted Random Early Detect policy
found at VyOS provides different virtual queues based on the IP
Precedence value so that some virtual queues can drop more packets than
others.
This is achieved by using the first three bits of the ToS (Type of
Service) field to categorize data streams and, in accordance with the
defined precedence parameters, a decision is made.
IP precedence as defined in :rfc:`791`:
+------------+----------------------+
| Precedence | Priority |
+============+======================+
| 7 | Network Control |
+------------+----------------------+
| 6 | Internetwork Control |
+------------+----------------------+
| 5 | CRITIC/ECP |
+------------+----------------------+
| 4 | Flash Override |
+------------+----------------------+
| 3 | Flash |
+------------+----------------------+
| 2 | Immediate |
+------------+----------------------+
| 1 | Priority |
+------------+----------------------+
| 0 | Routine |
+------------+----------------------+
.. cfgcmd:: set traffic-policy random-detect <policy-name> bandwidth <bandwidth>
Use this command to configure a Random-Detect policy, set its name
and set the available bandwidth for this policy.
.. cfgcmd:: set traffic-policy random-detect <policy-name> precedence <IP-precedence-value> average-packet <bytes>
Use this command to configure a Random-Detect policy and set its
name, then name the IP Precedence for the virtual queue you are
configuring and what the size of its average-packet should be
(in bytes, default: 1024).
.. note:: When configuring a Random-Detect policy, remember: the higher
the precedence number, the higher the priority.
.. cfgcmd:: set traffic-policy random-detect <policy-name> precedence <IP-precedence-value> mark-probability <value>
Use this command to configure a Random-Detect policy and set its
name, then name the IP Precedence for the virtual queue you are
configuring and what its mark (drop) probability will be. Set the
probability by giving the N value of the fraction 1/N (default: 10).
.. cfgcmd:: set traffic-policy random-detect <policy-name> precedence <IP-precedence-value> maximum-threshold <packets>
Use this command to configure a Random-Detect policy and set its
name, then name the IP Precedence for the virtual queue you are
configuring and what its maximum threshold for random detection will
be (from 0 to 4096 packets, default: 18). At this size, the marking
(drop) probability is maximal.
.. cfgcmd:: set traffic-policy random-detect <policy-name> precedence <IP-precedence-value> minimum-threshold <packets>
Use this command to configure a Random-Detect policy and set its
name, then name the IP Precedence for the virtual queue you are
configuring and what its minimum threshold for random detection will
be (from 0 to 4096 packets). If this value is exceeded, packets
start being eligible for being dropped.
The default values for the minimum-threshold depend on IP precedence:
+------------+-----------------------+
| Precedence | default min-threshold |
+============+=======================+
| 7 | 16 |
+------------+-----------------------+
| 6 | 15 |
+------------+-----------------------+
| 5 | 14 |
+------------+-----------------------+
| 4 | 13 |
+------------+-----------------------+
| 3 | 12 |
+------------+-----------------------+
| 2 | 11 |
+------------+-----------------------+
| 1 | 10 |
+------------+-----------------------+
| 0 | 9 |
+------------+-----------------------+
.. cfgcmd:: set traffic-policy random-detect <policy-name> precedence <IP-precedence-value> queue-limit <packets>
Use this command to configure a Random-Detect policy and set its
name, then name the IP Precedence for the virtual queue you are
configuring and what the maximum size of its queue will be (from 1 to
1-4294967295 packets). Packets are dropped when the current queue
length reaches this value.
If the average queue size is lower than the :code:`min-threshold`, an
arriving packet is placed in the queue. If the average queue size is
between :code:`min-threshold` and :code:`max-threshold` an arriving
packet is either dropped or placed in the queue depending on the defined
:code:`mark-probability`. In case the average queue size is larger than
:code:`max-threshold`, packets are dropped. If the current queue size is
larger than :code:`queue-limit`, packets are dropped. The average queue
size depends on its former average size and its current size. If
:code:`max-threshold` is set but :code:`min-threshold` is not, then
:code:`min-threshold` is scaled to 50% of :code:`max-threshold`. In
principle, values must be :code:`min-threshold` < :code:`max-threshold`
< :code:`queue-limit`.
One use of this algorithm might be to prevent a backbone overload.
Rate control
------------
| **Queueing discipline:** Tocken Bucket Filter.
| **Applies to:** Outbound traffic.
Rate-Control is a classless policy that limits the packet flow to a set
rate. It is a pure shaper, it does not schedule traffic. Traffic is
filtered based on the expenditure of tokens. Tokens roughly correspond
to bytes.
Short bursts can be allowed to exceed the limit. On creation, the
Rate-Control traffic is stocked with tokens which correspond to the
amount of traffic that can be burst in one go. Tokens arrive at a steady
rate, until the bucket is full.
.. cfgcmd:: set traffic-policy rate-control <policy-name> bandwidth <rate>
Use this command to configure a Rate-Control policy, set its name
and the rate limit you want to have.
.. cfgcmd:: set traffic-policy rate-control <policy-name> burst <burst-size>
Use this command to configure a Rate-Control policy, set its name
and the size of the bucket in bytes which will be available for
burst.
As a reference: for 10mbit/s on Intel, you might need at least 10kbyte
buffer if you want to reach your configured rate.
A too small buffer will soon start dropping packets.
.. cfgcmd:: set traffic-policy rate-control <policy-name> latency
Use this command to configure a Rate-Control policy, set its name
and the maximum amount of time a packet can be queued (default: 50
ms.
Rate-Control is a CPU-friendly policy. You might consider using it when
you just simply want to slow traffic down.
.. _DRR:
Round robin (DRR)
-----------------
| **Queueing discipline:** Deficit Round Robin.
| **Applies to:** Outbound traffic.
The round-robin policy is a classful scheduler that divides traffic in
different classes_ you can configure (up to 4096). You can embed_ a
new policy into each of those classes (the default one included).
Each class is assigned a deficit counter (the number of bytes that a
flow is allowed to transmit when it is its turn) initialized to quantum.
Quantum is a parameter you configure which acts like a credit of fix
bytes the counter receives on each round. Then the Round-Robin policy
starts moving its Round Robin pointer through the queues. If the deficit
counter is greater than the packet's size at the head of the queue, this
packet will be sent and the value of the counter will be decremented by
the packet size. Then, the size of the next packet will be compared to
the counter value again, repeating the process. Once the queue is empty
or the value of the counter is insufficient, the Round-Robin pointer
will move to the next queue. If the queue is empty, the value of the
deficit counter is reset to 0.
At every round, the deficit counter adds the quantum so that even large
packets will have their opportunity to be dequeued.
.. cfgcmd:: set traffic-policy round-robin <policy name> class
<class-ID> quantum <packets>
Use this command to configure a Round-Robin policy, set its name, set
a class ID, and the quantum for that class. The deficit counter will
add that value each round.
.. cfgcmd:: set traffic-policy round-robin <policy name> class
<class ID> queue-limit <packets>
Use this command to configure a Round-Robin policy, set its name, set
a class ID, and the queue size in packets.
As with other policies, Round-Robin can embed_ another policy into a
class through the ``queue-type`` setting and then configure its
parameters.
.. code-block:: none
vyos@vyos# set traffic-policy round-robin DRR class 10 queue-type
Possible completions:
fq-codel Fair Queue Codel
fair-queue Stochastic Fair Queue (SFQ)
drop-tail First-In-First-Out (FIFO)
priority Priority queueing based on DSCP
.. code-block:: none
vyos@vyos# set traffic-policy round-robin DRR class 10
Possible completions:
codel-quantum
fq-codel - Number of bytes used as 'deficit' (default 1514)
description Description for this traffic class
flows fq-codel - Number of flows (default 1024)
interval fq-codel - Interval (milliseconds) used to measure the delay (default 100)
+> match Class matching rule name
quantum Packet scheduling quantum
queue-limit Maximum queue size (packets)
queue-type Queue type for this class
target fq-codel - Acceptable minimum queue delay (milliseconds)
.. _Shaper:
Traffic shaper
--------------
| **Queueing discipline:** Hierarchical Token Bucket.
| **Applies to:** Outbound traffic.
The Shaper policy does not guarantee a low delay, but it does guarantee
bandwidth to different traffic classes and lets you choose how to
allocate more traffic once the guarantees are met.
Each class can use a guaranteed part of the total bandwidth defined for
the whole policy, so all those shares together should not be higher
than the policy's whole bandwidth.
If guaranteed traffic in a class is met and there is room for more
traffic, the ceiling parameter can be used to set how much more
bandwidth can be used. If guaranteed traffic is met and there are
several classes willing to use their ceilings, the priority parameter
will establish the order in which that additional traffic will be
allocated. Priority can be any number from 0 to 7. The lower the number,
the higher the priority.
DEFAULT PRIORITY: 0
DEFAULT CEILING: SAME AS BANDWIDTH (so no borrowing)
.. cfgcmd:: set traffic-policy shaper <policy-name> bandwidth <rate>
Use this command to configure a Shaper policy, set its name
and the maximum bandwidth for all combined traffic.
.. cfgcmd:: set traffic-policy shaper <policy-name> class <class-ID> bandwidth <rate>
Use this command to configure a Shaper policy, set its name, define
a class and set the guaranteed traffic you want to allocate to that
class.
.. cfgcmd:: set traffic-policy shaper <policy-name> class <class-ID> burst <bytes>
Use this command to configure a Shaper policy, set its name, define
a class and set the size of the bucket. Shaper will dequeue its burst
bytes before awaiting the arrival of more tokens.
.. cfgcmd:: set traffic-policy shaper <policy-name> class <class-ID> ceiling <bandwidth>
Use this command to configure a Shaper policy, set its name, define
a class and set the maximum speed possible for this class. The
default ceiling value is the same as bandwidth, so no borrowing.
.. cfgcmd:: set traffic-policy shaper <policy-name> class <class-ID> priority <0-7>
Use this command to configure a Shaper policy, set its name, define
a class and set the priority for usage of available bandwidth once
guarantees have been met. The lower the priority number, the higher
the priority. The default priority value is 0, the highest priority.
As with other policies, Shaper can embed_ other policies into its
classes through the ``queue-type`` setting and then configure their
parameters.
.. :code-block:: none
vyos@vyos# set traffic-policy shaper HTB class 10 queue-type
Possible completions:
fq-codel Fair Queue Codel
fair-queue Stochastic Fair Queue (SFQ)
drop-tail First-In-First-Out (FIFO)
priority Priority queueing based on DSCP
random-detect
Random Early Detection (RED)
.. :code-block:: none
vyos@vyos# set traffic-policy shaper HTB class 10
Possible completions:
bandwidth Bandwidth used for this class
burst Burst size for this class (default: 15kb)
ceiling Bandwidth limit for this class
codel-quantum
fq-codel - Number of bytes used as 'deficit' (default 1514)
description Description for this traffic class
flows fq-codel - Number of flows (default 1024)
interval fq-codel - Interval (milliseconds) used to measure the delay (default 100)
+> match Class matching rule name
priority Priority for usage of excess bandwidth
queue-limit Maximum queue size (packets)
queue-type Queue type for this class
set-dscp Change the Differentiated Services (DiffServ) field in the IP header
target fq-codel - Acceptable minimum queue delay (milliseconds)
Available commands:
* Define a shaper policy:
:code:`set traffic-policy shaper <policy-name>`
* Add a description:
:code:`set traffic-policy shaper <policy-name> description <description>`
* Set the available bandwidth for all combined traffic of this policy in kbit/s,
default 100%:
:code:`set traffic-policy shaper <policy-name> bandwidth <rate>`
Available suffixes:
* % (percentage of total bandwidth)
* kbit (kilobits per second)
* mbit (megabits per second)
* gbit (gigabits per second)
* kbps (kilobytes per second)
* mbps (megabytes per second)
* gbps (gigabytes per second)
Traffic classes
"""""""""""""""
* Define a traffic class for a shaper policy, range for class ID is 2...4095:
:code:`set traffic-policy shaper <policy-name> class <class ID>`
* Add a class description:
:code:`set traffic-policy shaper <policy name> class <class ID> description
<description>`
* Specify a bandwidth limit for a class, in kbit/s:
:code:`set traffic-policy shaper <policy-name> class <class ID> bandwidth <rate>`
Available suffixes:
* kbit (kilobits per second, default)
* mbit (megabits per second)
* gbit (gigabits per second)
* kbps (kilobytes per second)
* mbps (megabytes per second)
* gbps (gigabytes per second)
* Set a burst size for a class, the maximum amount of traffic that can be sent,
in bytes:
:code:`set traffic-policy shaper <policy-name> class <class ID>
burst <burst-size>`
Available suffixes:
* kb (kilobytes)
* mb (megabytes)
* gb (gigabytes)
* Set a bandwidth ceiling for a class in kbit/s:
:code:`set traffic-policy shaper <policy-name> class <class ID> ceiling <rate>`
Available suffixes:
* % (percentage of total bandwidth)
* kbit (kilobits per second)
* mbit (megabits per second)
* gbit (gigabits per second)
* Set the priority of a class for allocation of additional bandwidth, if unused
bandwidth is available. You can set any number from 0 to 7. The lower
the number, the higher the priority. If no value is set for a classs,
it will be internally configured as 0, the highest priority.
:code:`set traffic-policy shaper <policy-name> class <class ID>
priority <priority>`
* Set a queue length limit in packets:
:code:`set traffic-policy shaper <policy name> class <class ID> queue-limit
<limit>`
* Specify a queue type for a traffic class, default fair-queue. Available
queue types:
* drop-tail
* fair-queue
* random-detect
* priority
:code:`set traffic-policy shaper <policy name> class <class ID> queue-type <type>`
* Modify DSCP field; the DSCP field value of packets in a class can be
rewritten to change the forwarding behaviour and allow for traffic
conditioning:
:code:`set traffic-policy shaper <policy name> class <class ID> set-dscp <value>`
DSCP values as per :rfc:`2474` and :rfc:`4595`:
+---------+------------+--------+------------------------------+
| Binary | Configured | Drop | Description |
| value | value | rate | |
+=========+============+========+==============================+
| 101110 | 46 | - | Expedited forwarding (EF) |
+---------+------------+--------+------------------------------+
| 000000 | 0 | - | Best effort traffic, default |
+---------+------------+--------+------------------------------+
| 001010 | 10 | Low | Assured Forwarding(AF) 11 |
+---------+------------+--------+------------------------------+
| 001100 | 12 | Medium | Assured Forwarding(AF) 12 |
+---------+------------+--------+------------------------------+
| 001110 | 14 | High | Assured Forwarding(AF) 13 |
+---------+------------+--------+------------------------------+
| 010010 | 18 | Low | Assured Forwarding(AF) 21 |
+---------+------------+--------+------------------------------+
| 010100 | 20 | Medium | Assured Forwarding(AF) 22 |
+---------+------------+--------+------------------------------+
| 010110 | 22 | High | Assured Forwarding(AF) 23 |
+---------+------------+--------+------------------------------+
| 011010 | 26 | Low | Assured Forwarding(AF) 31 |
+---------+------------+--------+------------------------------+
| 011100 | 28 | Medium | Assured Forwarding(AF) 32 |
+---------+------------+--------+------------------------------+
| 011110 | 30 | High | Assured Forwarding(AF) 33 |
+---------+------------+--------+------------------------------+
| 100010 | 34 | Low | Assured Forwarding(AF) 41 |
+---------+------------+--------+------------------------------+
| 100100 | 36 | Medium | Assured Forwarding(AF) 42 |
+---------+------------+--------+------------------------------+
| 100110 | 38 | High | Assured Forwarding(AF) 43 |
+---------+------------+--------+------------------------------+
Matching rules
""""""""""""""
* Define a class matching rule:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name>`
* Add a match rule description:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> description <description>`
* Specify a match criterion based on a **destination MAC address**
(format: xx:xx:xx:xx:xx:xx):
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ether destination <MAC address>`
* Specify a match criterion based on a **source MAC address**
(format: xx:xx:xx:xx:xx:xx):
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ether source <MAC address>`
* Specify a match criterion based on **packet type/protocol**, range 0...65535:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ether protocol <number>`
* Specify a match criterion based on **ingress interface**:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> interface <interface>`
* Specify a match criterion based on the **fwmark field**, range 0....4294967295:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> mark <fwmark>`
* Specify a match criterion based on **VLAN ID**, range 1...4096:
:code:`set traffic-policy round-robin <policy name> class <class ID> match
<match name> vif <VLAN ID>`
**IPv4**
* Specify a match criterion based on **destination IPv4 address and/or port**,
port may be specified as number or service name (i.e. ssh):
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ip destination <IPv4 address|port>`
* Specify a match criterion based on **source IPv4 address and/or port**, port
may be specified as number or service name (i.e. ssh):
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ip source <IPv4 address|port>`
* Specify a match criterion based on **DSCP (Differentiated Services Code Point)
value**, DSCP value may be specified as decimal or hexadecimal number:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ip dscp <DSCP value>`
* Specify a match criterion based on **IPv4 protocol**, protocol may be
specified by name (i.e. icmp) or IANA-assigned number:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ip protocol <proto>`
**IPv6**
* Specify a match criterion based on **destination IPv6 address and/or port**,
port may be specified as number or service name (i.e. ssh):
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ipv6 destination <IPv6 address|port>`
* Specify a match criterion based on **source IPv6 address and/or port**,
port may be specified as number or service name (i.e. ssh):
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ipv6 source <IPv6 address|port>`
* Specify a match criterion based on **DSCP (Differentiated Services Code Point)
value**, DSCP value may be specified as decimal or hexadecimal number:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ipv6 dscp <DSCP value>`
* Specify a match criterion based on **IPv6 protocol**, protocol may be
specified by name (i.e. icmp) or IANA-assigned number:
:code:`set traffic-policy shaper <policy name> class <class ID> match
<match name> ipv6 protocol <proto>`
.. _Shaper-HFSC:
shaper-hfsc (HFSC_ + sfq)
-------------------------
| **Queueing discipline:**
| **Applies to:**
TBD
.. _ingress-shaping:
The case of ingress shaping
===========================
| **Applies to:** Inbound traffic.
Only a **limiter** policy can be applied directly
for ingress traffic on an interface. It is possible though to use what is
called an Intermediate Functional Block (IFB_) to allow the usage of any policy
on the ingress traffic.
Let's assume eth0 is your WAN link. You created two traffic-policies: `WAN-IN`
and `WAN-OUT`.
Steps to do:
* First, create the IFB:
:code:`set interfaces input ifb0 description "WAN Input"`
* Apply the `WAN-IN` traffic-policy to ifb0 input.
:code:`set interfaces input ifb0 traffic-policy out WAN-IN`
* Redirect traffic from eth0 to ifb0
:code:`set interfaces ethernet eth0 redirect ifb0`
Applying a traffic policy
=========================
Once a traffic-policy is created, you can apply it to an interface:
.. code-block:: none
set interfaces etherhet eth0 traffic-policy out WAN-OUT
You can have serveral policies running at the same time:
.. code-block:: none
set interfaces ethernet eth0 traffic-policy in WAN-IN
set interfaces etherhet eth0 traffic-policy out WAN-OUT
set interfaces ethernet eth1 traffic-policy out LAN-OUT
A Real-World Example
====================
This policy sets download and upload bandwidth maximums (roughly 90% of the speeds possible), then divvies
up the traffic into buckets of importance, giving guaranteed bandwidth chunks to types of
traffic that are necessary for general interactive internet use, like web browsing, streaming, or gaming.
After identifying and prioritizing that traffic, it drops the remaining traffic into a general-priority
bucket, which it gives a lower priority than what is required for real-time use. If there is no real-time
traffic that needs the bandwidth, the lower-priority traffic can use most of the connection. This ensures
that the connection can be used fully by whatever wants it, without suffocating real-time traffic or
throttling background traffic too much.
.. code-block:: none
set traffic-policy shaper download bandwidth '175mbit'
set traffic-policy shaper download class 10 bandwidth '10%'
set traffic-policy shaper download class 10 burst '15k'
set traffic-policy shaper download class 10 ceiling '100%'
set traffic-policy shaper download class 10 match dns ip source port '53'
set traffic-policy shaper download class 10 match icmp ip protocol 'icmp'
set traffic-policy shaper download class 10 match ssh ip source port '22'
set traffic-policy shaper download class 10 priority '5'
set traffic-policy shaper download class 10 queue-type 'fair-queue'
set traffic-policy shaper download class 20 bandwidth '10%'
set traffic-policy shaper download class 20 burst '15k'
set traffic-policy shaper download class 20 ceiling '100%'
set traffic-policy shaper download class 20 match http ip source port '80'
set traffic-policy shaper download class 20 match https ip source port '443'
set traffic-policy shaper download class 20 priority '4'
set traffic-policy shaper download class 20 queue-type 'fair-queue'
set traffic-policy shaper download default bandwidth '70%'
set traffic-policy shaper download default burst '15k'
set traffic-policy shaper download default ceiling '100%'
set traffic-policy shaper download default priority '3'
set traffic-policy shaper download default queue-type 'fair-queue'
set traffic-policy shaper upload bandwidth '18mbit'
set traffic-policy shaper upload class 2 bandwidth '10%'
set traffic-policy shaper upload class 2 burst '15k'
set traffic-policy shaper upload class 2 ceiling '100%'
set traffic-policy shaper upload class 2 match ack ip tcp ack
set traffic-policy shaper upload class 2 match dns ip destination port '53'
set traffic-policy shaper upload class 2 match icmp ip protocol 'icmp'
set traffic-policy shaper upload class 2 match ssh ip destination port '22'
set traffic-policy shaper upload class 2 match syn ip tcp syn
set traffic-policy shaper upload class 2 priority '5'
set traffic-policy shaper upload class 2 queue-limit '16'
set traffic-policy shaper upload class 2 queue-type 'fair-queue'
set traffic-policy shaper upload class 5 bandwidth '10%'
set traffic-policy shaper upload class 5 burst '15k'
set traffic-policy shaper upload class 5 ceiling '100%'
set traffic-policy shaper upload class 5 match http ip destination port '80'
set traffic-policy shaper upload class 5 match https ip destination port '443'
set traffic-policy shaper upload class 5 priority '4'
set traffic-policy shaper upload class 5 queue-type 'fair-queue'
set traffic-policy shaper upload default bandwidth '60%'
set traffic-policy shaper upload default burst '15k'
set traffic-policy shaper upload default ceiling '100%'
set traffic-policy shaper upload default priority '3'
set traffic-policy shaper upload default queue-type 'fair-queue'
.. _tc: https://en.wikipedia.org/wiki/Tc_(Linux)
.. _TBF: https://en.wikipedia.org/wiki/Token_bucket
.. _HFSC: https://en.wikipedia.org/wiki/Hierarchical_fair-service_curve
.. _IFB: https://www.linuxfoundation.org/collaborate/workgroups/networking/ifb
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