ALTQ.CONF(5)

File Formats Manual

ALTQ.CONF(5)

NAME

altq.conf — ALTQ configuration file

DESCRIPTION

The altq.conf file contains a number of lines specifying the behavior of queueing disciplines. Comments start with a # and extend to the end of the line.

The altqd(8) program reads /etc/altq.conf at startup and sets up queueing disciplines. BLUE, CBQ (Class-Based Queueing), FIFOQ (First-In First-Out Queue), HFSC (Hierarchical Fair Service Curve), PRIQ (Priority Queueing), RED (Random Early Detection), RIO (RED with IN/OUT), WFQ (Weighted Fair Queueing), JoBS (Joint Buffer Management and Scheduling) and CDNR (Diffserv Traffic Conditioner) can be configured in this file.

Interface Commands

The interface command specifies a network interface to be under control of ALTQ. One interface specification is provided for each network interface under control of ALTQ. A system configured as a router may have multiple interface specifications.

Class Command

The class command specifies a packet scheduling class for CBQ, HFSC, JoBS or PRIQ. A class specifier must be provided for each packet scheduling class.

Filter Commands

The filter command specifies a filter to classify packets into a scheduling class. A filter specifier determines any statically-defined packet classification rules.

filter_values should be in the following format:

Here dst_addr and src_addr are dotted-decimal addresses of the destination and the source respectively. An address may be followed by netmask keyword. dport and sport are port numbers of the destination and the source respectively. proto is a protocol number defined for IP packets (e.g. 6 for TCP). tos keyword can be used to specify the type of service field value. gpi keyword can be used to specify the Security Parameter Index value for IPsec.

When filter value 0 is used, it is taken as a wildcard.

The filter6 command is for IPv6. filter6_value should be in the following format:

Here dst_addr and src_addr are IPv6 addresses of the destination and the source respectively. An address may be followed by an optional address prefix length. dport and sport are port numbers of the destination and the source respectively. proto is a protocol number defined for IPv6 packets (e.g. 6 for TCP). flowlabel keyword can be used to specify the flowlabel field value. tclass keyword can be used to specify the traffic class field value. gpi keyword can be used to specify the Security Parameter Index value for IPsec.

When filter value 0 is used, it is taken as a wildcard.

CBQ Commands

CBQ (Class Based Queueing) achieves both partitioning and sharing of link bandwidth by hierarchically structured classes. Each class has its own queue and is assigned its share of bandwidth. A child class can borrow bandwidth from its parent class as long as excess bandwidth is available.

The class command specifies a CBQ class. The classes are organized as a hierarchy, and every class, except for the root class, has a parent.

sched_type: must be cbq for a CBQ class.
if_name: Interface name. Must correspond to name in interface specification.
class_name: Arbitrary name for this class. Must be unique within the class hierarchy for this interface. The name ctl_class is a reserved class name.
parent_name: The name of the parent class for this class or NULL if this is the root class. Parent class must have been previously defined.
admission: The type of admission control and QoS type. cntlload is controlled load service for RSVP, otherwise, it should be none. The default is none.
priority: High numbers are higher priority. Max value is 7 and Min value is 0. Default is 1.
pbandwidth: The percentage of the interface bandwidth allocated to this class. Generally should add up to 100 percent at each level of the class hierarchy, although other amounts can be specified for purposes of experimentation.
exactbandwidth: Specify the bandwidth in bits-per-second instead of pbandwidth. Note that the bandwidth allocation of CBQ is not so precise but this is just a way to pass a parameter to CBQ; the user is supposed to know the detailed internals of CBQ. pbandwidth is a preferred way to specify the bandwidth of a class.
borrow: The class can borrow bandwidth from its parent class when this class is overlimit. If this keyword is not present, then no borrowing is done, and the packet is delayed or dropped when the class is overlimit.
default: Specify the default class. When this keyword is present, all packets that do not match some classification criteria are assigned to this class. Must be exactly one class on each interface defined as the default class.
control: Specify the control class. When this keyword is present, the predefined control class packets (RSVP, IGMP, and ICMP) are assigned to this class. Note that when the control class is not specified by the time the default class is created, one is automatically created with default parameters. Thus, if the control class is specified, it must be listed before the default class. Must be exactly one class on each interface defined as the control class.
maxburst: The maximum burst of back-to-back packets allowed in this class. Default is 16 but the default value is automatically reduced to 4 when the class bandwidth is small (about less than 1Mbps).
minburst: The minimum burst is used to obtain the steady state burst size. It's the parameter to help compute offtime for the class. Offtime is the amount of time a class is to wait between packets. Default is 2.
maxdelay: The maxdelay is specified in milliseconds and used to obtain the max queue size of the class. If not specified, the default max queue size (30 packets) is used.
packetsize: The average packet size in bytes to be used in CBQ over-/under-limit computations. Default value is MTU of the interface.
maxpacketsize: The maximum packet size in bytes for the class. Default value is MTU of the interface.
red: enables RED on this class queue.
rio: enables RIO on this class queue.
ecn: enables RED/ECN on this class queue.
flowvalve: enables RED/flow-valve (a.k.a. red-penalty-box) on this class queue.
cleardscp: clears diffserv codepoint in the IP header.

HFSC Commands

HFSC (Hierarchical Fair Service Curve) supports both link-sharing and guaranteed real-time services. H-FSC employs a service curve based QoS model, and its unique feature is an ability to decouple delay and bandwidth allocation. HFSC has 2 independent scheduling mechanisms. Real-time scheduling is used to guarantee the delay and the bandwidth allocation at the same time. Hierarchical link-sharing is used to distribute the excess bandwidth. When dequeueing a packet, HFSC always tries real-time scheduling first. If no packet is eligible for real-time scheduling, link-sharing scheduling is performed. HFSC does not use class hierarchy for real-time scheduling. Additionally, an upper-limit service curve can be specified for link-sharing to set the upper limit allowed for the class.

The class command specifies a HFSC class. The classes are organized as a hierarchy, and every class, except for the root class, has a parent.

Each HFSC class has 2 service curves, the real-time service curve and the link-sharing service curve. Service curves are specified by [type m1 d m2]. type should be either sc, rt, ls, or ul. sc (service curve) is used to set the same values to both real-time and link-sharing service curves. rt (real-time) is used to specify the real-time service curve. ls (link-sharing) is used to specify the link-sharing service curve. ul (upper-limit) is used to specify the upper-limit service curve for link-sharing. m1 is the slope of the first segment specified in bits-per-second. d is the x-projection of the intersection point of the 2 segments specified in milliseconds. m2 is the slope of the second segment specified in bits-per-second.

PRIQ Commands

PRIQ (Priority Queueing) implements a simple priority-based queueing. A higher priority class is always served first. Up to 16 priorities can be used with PRIQ.

WFQ Commands

WFQ (Weighted Fair Queueing) implements a weighted-round robin scheduler for a set of queue. A weight can be assigned to each queue to give a different proportion of the link capacity. A hash function is used to map a flow to one of a set of queues, and thus, it is possible for two different flows to be mapped into the same queue.

FIFOQ Commands

FIFOQ (First-In First-Out Queueing) is a simple tail-drop FIFO queue. FIFOQ is the simplest possible implementation of a queueing discipline in ALTQ, and can be used to compare with other queueing disciplines. FIFOQ can be also used as a template for those who want to write their own queueing disciplines.

RED Commands

RED (Random Early Detection) is an implicit congestion notification mechanism that exercises packet dropping or packet marking stochastically according to the average queue length. RED can be viewed as a buffer management mechanism and can be integrated into other packet scheduling schemes.

The red command sets the default RED parameters. min_th and max_th are the minimum and the maximum threshold values. inv_pmax is the inverse (reciprocal) of the maximum drop probability. For example, 10 means the maximum drop probability of 1/10.

RIO Commands

ALTQ/RIO has 3 drop precedence levels defined for the Assured Forwarding of DiffServ (RFC2597). Since adaptive flows are likely to stay under the medium drop precedence level under congestion, the medium drop precedence would protect adaptive flows from unadaptive flows.

The original RIO has 2 sets of RED parameters; one for in-profile packets and the other for out-of-profile packets. At the ingress of the network, profile meters tag packets as IN or OUT based on contracted profiles for customers. Inside the network, IN packets receive preferential treatment by the RIO dropper. It is possible to provision the network not to drop IN packets at all by providing enough capacity for the total volume of IN packets. Thus, RIO can be used to provide a service that statistically assures capacity allocated for users. This mechanism can be extended to support an arbitrary number of drop precedence levels. ALTQ supports 3 drop precedence levels.

The rio command sets the default RIO parameters. The parameters are RED parameters for 3 (low, medium, high) drop precedence.

BLUE Commands

CDNR Commands

The conditioner command specifies a diffserv traffic conditioner. A traffic conditioner is not a queueing discipline but a component to meter, mark or drop incoming packets according to some rules.

As opposed to a queueing discipline, a traffic conditioner handles incoming packets at an input interface. If no queueing discipline (e.g., CBQ) is used for the interface, a null interface command should be used to specify an input network interface.

The conditioner command has the following syntax.

An action can be a recursively defined action. The following actions are defined.

JoBS Commands

JoBS (Joint Buffer Management and Scheduling) is a queuing discipline that can enforce any feasible mix of absolute and proportional guarantees on packet losses, packet delays, and throughput, for classes of traffic, on a per-hop basis. No admission control is performed, thus if the set of service guarantees becomes infeasible, some service guarantees may be relaxed.

EXAMPLES

CBQ Example

# 
# cbq configuration for vx0 (10Mbps ether) 
# give at least 40% to TCP 
# limit HTTP from network 133.138.1.0 up to 10%, use RED. 
# other traffic goes into default class 
# 
interface vx0 bandwidth 10M cbq 
# 
class cbq vx0 root_class NULL priority 0 pbandwidth 100 
class cbq vx0 def_class root_class borrow pbandwidth 95 default 
class cbq vx0 tcp_class def_class borrow pbandwidth  40 
        filter vx0 tcp_class 0 0 0 0 6 
class cbq vx0 csl_class tcp_class pbandwidth  10   red 
        filter vx0 csl_class 0 0 133.138.1.0 netmask 0xffffff00 80 6 
        filter vx0 csl_class 133.138.1.0 netmask 0xffffff00 0 0 80 6 
# 
# sample filter6 command 
# 
                filter6 vx0 csl_class ::0 0 d000:a:0:123::/64 80 6

HFSC Example

# 
# hfsc configuration for hierarchical sharing 
# 
interface pvc0 bandwidth 45M hfsc 
# 
# (10% of the bandwidth share goes to the default class) 
class hfsc pvc0 def_class root pshare 10 default 
# 
#          bandwidth share    guaranteed rate 
#    CMU:       45%             15Mbps 
#    PITT:      45%             15Mbps 
# 
class hfsc pvc0 cmu  root pshare 45 grate 15M 
class hfsc pvc0 pitt root pshare 45 grate 15M 
# 
# CMU      bandwidth share    guaranteed rate 
#    CS:        20%             10Mbps 
#    other:     20%              5Mbps 
# 
class hfsc pvc0 cmu_other cmu  pshare 20 grate 10M 
        filter pvc0 cmu_other   0 0 128.2.0.0   netmask 0xffff0000 0 0 
class hfsc pvc0 cmu_cs    cmu  pshare 20 grate  5M 
        filter pvc0 cmu_cs      0 0 128.2.242.0 netmask 0xffffff00 0 0 
# 
# PITT     bandwidth share    guaranteed rate 
#    CS:        20%             10Mbps 
#    other:     20%              5Mbps 
# 
class hfsc pvc0 pitt_other pitt  pshare 20 grate 10M 
        filter pvc0 pitt_other  0 0 136.142.0.0  netmask 0xffff0000 0 0 
class hfsc pvc0 pitt_cs    pitt  pshare 20 grate  5M 
        filter pvc0 pitt_cs     0 0 136.142.79.0 netmask 0xffffff00 0 0

HFSC Example (simpler one with ulimit)

# 
interface fxp0 bandwidth 90M hfsc 
# reserve 20% for default class 
class hfsc fxp0 def_class root pshare 20 default 
# shared class for TCP and UDP 
class hfsc fxp0 shared_class root bandwidth 72M 
# shared class for all TCP 
class hfsc fxp0 tcp_shared shared_class bandwidth 40M ulimit 60M 
# generic tcp 
class hfsc fxp0 tcp_class tcp_shared bandwidth 15M ulimit 50M 
	filter fxp0 tcp_class 0 0 0 0 6 
# http 
class hfsc fxp0 http_class tcp_shared bandwidth 25M ulimit 40M 
	filter fxp0 http_class 0 80 0 0 6 
	filter fxp0 http_class 0 0 0 80 6 
# udp 
class hfsc fxp0 udp_class shared_class bandwidth 15M ulimit 20M 
	filter fxp0 udp_class 0 0 0 0 17

PRIQ Example

# 
# priq configuration for fxp0 (100Mbps ether) 
#     icmp: high priority 
#     tcp:  medium priority 
#     others: low priority 
# 
interface fxp0 bandwidth 100M priq 
# 
class priq fxp0 high_class NULL priority 2 
        filter fxp0 high_class 0 0 0 0 1 
class priq fxp0 med_class NULL priority 1 
        filter fxp0 med_class 0 0 0 0 6 
class priq fxp0 low_class NULL priority 0 default

WFQ Example

interface pvc0 bandwidth 134000000 wfq

FIFOQ Example

interface rl0 bandwidth 10M fifoq

Conditioner Example

# 
interface fxp0 
# 
# a simple dropper 
# discard all packets from 192.168.0.83 
# 
conditioner fxp0 dropper <drop> 
        filter fxp0 dropper 0 0 192.168.0.83 0 0 
 
# 
# EF conditioner 
# mark EF to all packets from 192.168.0.117 
# 
conditioner pvc1 ef_cdnr <tbmeter 6M 64K <mark 0xb8><drop>> 
        filter fxp0 ef_cdnr 0 0 192.168.0.117 0 0 
 
# 
# AF1x conditioner 
# mark AF1x to packets from 192.168.0.178 
#       AF11 (low drop precedence):    less than 3Mbps 
#       AF12 (medium drop precedence): more than 3Mbps and less than 10Mbps 
#       AF13 (high drop precedence):   more than 10Mbps 
# 
conditioner fxp0 af1x_cdnr <trtcm 3M 32K 10M 64K <mark 0x28><mark 0x30><mark 0x38>> 
        filter fxp0 af1x_cdnr 0 0 192.168.0.178 0 0

BUGS

This man page is incomplete. For more information read the source.

September 10, 2008

NetBSD 6.1