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