Name

tcclasses — Shorewall file to define HTB classes

Synopsis

/etc/shorewall/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

    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. Each interface may be listed only once in this file. You may NOT specify the name of an alias (e.g., eth0:0) here; see http://www.shorewall.net/FAQ.htm#faq18

You may specify the interface number rather than the interface name. If the classify option is given for the interface in shorewall-tcdevices(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.

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(5) file.

Normally, all classes defined here are sub-classes of a root class that is implicitly defined from the entry in shorewall-tcdevices(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}

The mark value which is an integer in the range 1-255. You set mark values in the shorewall-tcrules(5) file, marking the traffic you want to fit in the classes defined in here. Must be specified as '-' if the classify option is given for the interface in shorewall-tcdevices(5)

You can use the same marks for different interfaces.

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, 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.

CEIL - 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 defined output bandwidth of that interface.

PRIORITY - priority

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.

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] (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).

tos-tosname

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.

        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

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.

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 tcrules (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 clasifier 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.

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 PPOE/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

See ALSO

http://shorewall.net/traffic_shaping.htm

shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-hosts(5), shorewall-interfaces(5), shorewall-ipsec(5), shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5), shorewall-netmap(5), shorewall-params(5), shorewall-policy(5), shorewall-providers(5), shorewall-proxyarp(5), shorewall-route_rules(5), shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)