Provided by: shorewall_5.2.3.4-1_all 
NAME
tcclasses - Shorewall file to define HTB and HFSC classes
SYNOPSIS
/etc/shorewall[6]/tcclasses
DESCRIPTION
A note on the rate/bandwidth definitions used in this file:
• don't use a space between the integer value and the unit: 30kbit is valid while 30 kbit is NOT.
• you can use one of the following units:
kpbs
Kilobytes per second.
mbps
Megabytes per second.
kbit
Kilobits per second.
mbit
Megabits per second.
bps or number
Bytes per second.
• if you want the values to be calculated for you depending on the output bandwidth setting defined for
an interface in tcdevices, you can use expressions like the following:
full/3
causes the bandwidth to be calculated as 1/3 of the full outgoing speed that is defined.
full*9/10
will set this bandwidth to 9/10 of the full bandwidth
Note that in a sub-class (a class that has a specified parent class), full refers to the RATE or CEIL
of the parent class rather than to the OUT-BANDWIDTH of the device.
DO NOT add a unit to the rate if it is calculated !
The columns in the file are as follows.
INTERFACE - interface[[:parent]:class]
Name of interface.
You may specify the interface number rather than the interface name. If the classify option is given
for the interface in shorewall-tcdevices[1](5), then you must also specify an interface class (an
integer that must be unique within classes associated with this interface). If the classify option is
not given, you may still specify a class or you may have Shorewall generate a class number from the
MARK value. Interface numbers and class numbers are always assumed to be specified in hex and class
number 1 is reserved as the root class of the queuing discipline.
You may NOT specify wildcards here, e.g. if you have multiple ppp interfaces, you need to put them
all in here!
Please note that you can only use interface names in here that have a bandwidth defined in the
shorewall-tcdevices[1](5) file.
Normally, all classes defined here are sub-classes of a root class that is implicitly defined from
the entry in shorewall-tcdevices[1](5). You can establish a class hierarchy by specifying a parent
class -- the number of a class that you have previously defined. The sub-class may borrow unused
bandwidth from its parent.
MARK - {-|value[:priority]}
The mark value which is an integer in the range 1-255. You set mark values in the
shorewall-mangle[2](5) file, marking the traffic you want to fit in the classes defined in here. You
can use the same marks for different interfaces.
The priority, if specified, is an integer in the range 1-65535 and determines the relative order in
which the tc mark classification filter for this class is to be applied to packets being sent on the
interface. Filters are applied in ascending numerical order. If not supplied, the value is derived
from the class priority (PRIORITY column value below): (class priority << 8) | 20.
RATE - {-|rate[:dmax[:umax]]}
The minimum bandwidth this class should get, when the traffic load rises. If the sum of the rates in
this column exceeds the INTERFACE's OUT-BANDWIDTH, then the OUT-BANDWIDTH limit may not be honored.
Similarly, if the sum of the rates of sub-classes of a class exceed the CEIL of the parent class,
things don't work well.
When using the HFSC queuing discipline, this column specify the real-time (RT) service curve. leaf
classes may specify dmax, the maximum delay in milliseconds that the first queued packet for this
class should experience. May be expressed as an integer, optionally followed by 'ms' with no
intervening white-space (e.g., 10ms).
HFSC leaf classes may also specify umax, the largest packet expected in this class. May be expressed
as an integer. The unit of measure is bytes and the integer may be optionally followed by 'b' with no
intervening white-space (e.g., 800b). umax may only be given if dmax is also given.
Beginning with Shorewall 4.5.6, HFSC classes may omit this column (e.g, '-' in the column), provided
that an lsrate is specified (see CEIL below). These rates are used to arbitrate between classes of
the same priority.
CEIL - [lsrate:]rate
The maximum bandwidth this class is allowed to use when the link is idle. Useful if you have traffic
which can get full speed when more needed services (e.g. ssh) are not used.
You can use the value full in here for setting the maximum bandwidth to the RATE of the parent class,
or the OUT-BANDWIDTH of the device if there is no parent class.
Beginning with Shorewall 4.5.6, you can also specify an lsrate (link sharing rate).
PRIORITY - priority
For HTB: The priority in which classes will be serviced by the packet shaping scheduler and also the
priority in which bandwidth in excess of the rate will be given to each class.
Higher priority classes will experience less delay since they are serviced first. Priority values are
serviced in ascending order (e.g. 0 is higher priority than 1).
Classes may be set to the same priority, in which case they will be serviced as equals. For both HTB
and HFSC, the priority is used to calculate the priority of following Shorewall-generated
classification filters that refer to the class:
• Packet MARK
• tcp-ack and the tos options (see below)
The rules for classes with lower numeric priorities will appear before those with higher numeric
priorities.
Beginning with Shorewall 4.5.8, the PRIORITY may be omitted from an HFSC class if you do not use the
MARK column or the tcp-ack or tos options. If you use any of those features and omit the PRIORITY,
then you must specify a priority along with the MARK or option.
OPTIONS (Optional) - [option[,option]...]
A comma-separated list of options including the following:
default
This is the default class for that interface where all traffic should go, that is not classified
otherwise.
Note
You must define default for exactly one class per interface.
tos=0xvalue[/0xmask][:priority] (mask defaults to 0xff)
This lets you define a classifier for the given value/mask combination of the IP packet's
TOS/Precedence/DiffSrv octet (aka the TOS byte).
Beginning with Shorewall 4.5.8, the value/mask may be followed by a colon (":") and a priority.
This priority determines the order in which filter rules are processed during packet
classification. If not specified, the value (class priority << 8) | 15) is used.
tos-tosname[:priority]
Aliases for the following TOS octet value and mask encodings. TOS encodings of the "TOS byte"
have been deprecated in favor of diffserve classes, but programs like ssh, rlogin, and ftp still
use them.
Beginning with Shorewall 4.5.8, the tos-name may be followed by a colon (":") and a priority.
This priority determines the order in which filter rules are processed during packet
classification. If not specified, the value (class priority << 8) | 15) is used.
tos-minimize-delay 0x10/0x10
tos-maximize-throughput 0x08/0x08
tos-maximize-reliability 0x04/0x04
tos-minimize-cost 0x02/0x02
tos-normal-service 0x00/0x1e
Note
Each of these options is only valid for ONE class per interface.
tcp-ack[:priority]
If defined, causes a tc filter to be created that puts all tcp ack packets on that interface that
have a size of <=64 Bytes to go in this class. This is useful for speeding up downloads. Please
note that the size of the ack packets is limited to 64 bytes because we want only packets WITHOUT
payload to match.
Beginning with Shorewall 4.5.8, the tcp-ack may be followed by a colon (":") and a priority. This
priority determines the order in which filter rules are processed during packet classification.
If not specified, the value (class priority << 8) | 10) is used.
Note
This option is only valid for ONE class per interface.
occurs=number
Typically used with an IPMARK entry in tcrules. Causes the rule to be replicated for a total of
number rules. Each rule has a successively class number and mark value.
When 'occurs' is used:
• The associated device may not have the 'classify' option.
• The class may not be the default class.
• The class may not have any 'tos=' options (including 'tcp-ack').
• The class should not specify a MARK value. If one is specified, it will be ignored with a
warning message.
The 'RATE' and 'CEIL' parameters apply to each instance of the class. So the total RATE
represented by an entry with 'occurs' will be the listed RATE multiplied by number. For
additional information, see shorewall-tcrules[3] (5).
flow=keys
Shorewall attaches an SFQ queuing discipline to each leaf HTB class. SFQ ensures that each flow
gets equal access to the interface. The default definition of a flow corresponds roughly to a
Netfilter connection. So if one internal system is running BitTorrent, for example, it can have
lots of 'flows' and can thus take up a larger share of the bandwidth than a system having only a
single active connection. The flow classifier (module cls_flow) works around this by letting you
define what a 'flow' is. The classifier must be used carefully or it can block off all traffic on
an interface! The flow option can be specified for an HTB leaf class (one that has no
sub-classes). We recommend that you use the following:
Shaping internet-bound traffic:
flow=nfct-src
Shaping traffic bound for your local net:
flow=dst
These will cause a 'flow' to consists of the traffic to/from each internal system.
When more than one key is give, they must be enclosed in parenthesis and separated by commas.
To see a list of the possible flow keys, run this command: tc filter add flow help Those that
begin with "nfct-" are Netfilter connection tracking fields. As shown above, we recommend
flow=nfct-src; that means that we want to use the source IP address before NAT as the key.
pfifo
When specified for a leaf class, the pfifo queuing discipline is applied to the class rather than
the sfq queuing discipline.
limit=number
Added in Shorewall 4.4.3. When specified for a leaf class, determines the maximum number of
packets that may be queued within the class. The number must be > 2 and <=128. If not specified,
the value 127 is assumed.
red=(redoption=value, ...)
Added in Shorewall 4.5.6. When specified on a leaf class, causes the class to use the RED (Random
Early Detection) queuing discipline rather than SFQ. See tc-red (8) for additional information.
Allowable redoptions are:
min min
Average queue size at which marking becomes a possibility.
max max
At this average queue size, the marking probability is maximal. Must be at least twice min to
prevent synchronous retransmits, higher for low min.
probability probability
Maximum probability for marking, specified as a floating point number from 0.0 to 1.0.
Suggested values are 0.01 or 0.02 (1 or 2%, respectively).
limit limit
Hard limit on the real (not average) queue size in bytes. Further packets are dropped. Should
be set higher than max+burst. It is advised to set this a few times higher than max.
Shorewall requires that limit be at least twice min.
burst burst
Used for determining how fast the average queue size is influenced by the real queue size.
Larger values make the calculation more sluggish, allowing longer bursts of traffic before
marking starts. Real life experiments support the following guide‐line:
(min+min+max)/(3*avpkt).
avpkt avpkt
Optional. Specified in bytes. Used with burst to determine the time constant for average
queue size calculations. 1000 is a good value and is the Shorewall default.
bandwidth bandwidth
Optional. This rate is used for calculating the average queue size after some idle time.
Should be set to the bandwidth of your interface. Does not mean that RED will shape for you!
ecn
RED can either 'mark' or 'drop'. Explicit Congestion Notification allows RED to notify remote
hosts that their rate exceeds the amount of bandwidth available. Non-ECN capable hosts can
only be notified by dropping a packet. If this parameter is specified, packets which indicate
that their hosts honor ECN will only be marked and not dropped, unless the queue size hits
limit bytes. Recommended.
fq_codel[=(codeloption=value, ...)]
Added in Shorewall 4.5.12. When specified for a leaf class, causes the class to use the FQ_CODEL
(Fair-queuing Controlled Delay) queuing discipline rather than SFQ. See tc-fq_codel (8) for
additional information.
Allowable codeloptions are:
limit
hard limit on the real queue size. When this limit is reached, incoming packets are dropped.
If the value is lowered, packets are dropped so that the new limit is met. Default is 1000
packets.
flows
is the number of flows into which the incoming packets are classified. Due to the stochastic
nature of hashing, multiple flows may end up being hashed into the same slot. Newer flows
have priority over older ones. This parameter can be set only at load time since memory has
to be allocated for the hash table. Default value is 1024.
target
is the acceptable minimum standing/persistent queue delay. This minimum delay is identified
by tracking the local minimum queue delay that packets experience. Default and recommended
value is 5ms.
interval
is used to ensure that the measured minimum delay does not become too stale. The minimum
delay must be experienced in the last epoch of length interval. It should be set on the order
of the worst-case RTT through the bottleneck to give endpoints sufficient time to react.
Default value is 100ms.
quantum
is the number of bytes used as 'deficit' in the fair queuing algorithm. Default is set to
1514 bytes which corresponds to the Ethernet MTU plus the hardware header length of 14 bytes.
ecn | noecn
can be used to mark packets instead of dropping them. If ecn has been enabled, noecn can be
used to turn it off and vice-versa. By default, ecn is enabled.
EXAMPLES
Example 1:
Suppose you are using PPP over Ethernet (DSL) and ppp0 is the interface for this. You have 4 classes
here, the first you can use for voice over IP traffic, the second interactive traffic (e.g.
ssh/telnet but not scp), the third will be for all unclassified traffic, and the forth is for low
priority traffic (e.g. peer-to-peer).
The voice traffic in the first class will be guaranteed a minimum of 100kbps and always be serviced
first (because of the low priority number, giving less delay) and will be granted excess bandwidth
(up to 180kbps, the class ceiling) first, before any other traffic. A single VoIP stream, depending
upon codecs, after encapsulation, can take up to 80kbps on a PPPoE/DSL link, so we pad a little bit
just in case. (TOS byte values 0xb8 and 0x68 are DiffServ classes EF and AFF3-1 respectively and are
often used by VOIP devices).
Interactive traffic (tos-minimum-delay) and TCP acks (and ICMP echo traffic if you use the example in
tcrules) and any packet with a mark of 2 will be guaranteed 1/4 of the link bandwidth, and may extend
up to full speed of the link.
Unclassified traffic and packets marked as 3 will be guaranteed 1/4th of the link bandwidth, and may
extend to the full speed of the link.
Packets marked with 4 will be treated as low priority packets. (The tcrules example marks p2p traffic
as such.) If the link is congested, they're only guaranteed 1/8th of the speed, and even if the link
is empty, can only expand to 80% of link bandwidth just as a precaution in case there are upstream
queues we didn't account for. This is the last class to get additional bandwidth and the last to get
serviced by the scheduler because of the low priority.
#INTERFACE MARK RATE CEIL PRIORITY OPTIONS
ppp0 1 100kbit 180kbit 1 tos=0x68/0xfc,tos=0xb8/0xfc
ppp0 2 full/4 full 2 tcp-ack,tos-minimize-delay
ppp0 3 full/4 full 3 default
ppp0 4 full/8 full*8/10 4
FILES
/etc/shorewall/tcclasses
/etc/shorewall6/tcclasses
SEE ALSO
http://www.shorewall.net/traffic_shaping.htm[4]
http://www.shorewall.net/configuration_file_basics.htm#Pairs[5]
tc-hfsc(7)
tc-red(8)
shorewall(8)
NOTES
1. shorewall-tcdevices
http://www.shorewall.org/manpages/shorewall-tcdevices.html
2. shorewall-mangle
http://www.shorewall.org/manpages/shorewall-mangle.html
3. shorewall-tcrules
http://www.shorewall.org/manpages/shorewall-tcrules.html
4. http://www.shorewall.net/traffic_shaping.htm
http://www.shorewall.org/traffic_shaping.htm
5. http://www.shorewall.net/configuration_file_basics.htm#Pairs
http://www.shorewall.org/configuration_file_basics.htm#Pairs
Configuration Files 04/11/2019 SHOREWALL-TCCLASSES(5)