QOS(7)								   Miscellaneous							    QOS(7)

NAME

       qos - Quality of Service specification

DESCRIPTION

       The  text2qos and qos2text functions use the format described in this man page. Because all standard ATM tools on Linux use those functions
       to convert to or from the textual representation of QOS specifications, they expect them in the same format too.

       The most fundamental parameters are the traffic class and the AAL (ATM Adaption Layer) type. If	the  connection  is  bi-directional,  both
       directions have the same traffic class and the same AAL type. The traffic class and the AAL type are the first elements (in any order) in a
       QOS specification. The traffic class is the only required element. If the AAL type is omitted,  the  application  will  provide	a  default
       value. The following traffic classes are recognized:

       ubr    Unassigned Bit Rate

       cbr    Constant Bit Rate

       abr    Available Bit Rate

       The following AAL types are recognized:

       aal0   ("raw ATM")

       aal5

       If both, the traffic class and the AAL type are specified, they are separated by a comma.

       If  more  parameters are supplied, the traffic class and AAL type must be followed by a colon. Traffic parameters can be specified indepen-
       dently for the transmit and the receive direction. Their parameter lists are prefixed with tx: and rx:,	respectively.  If  both  parameter
       lists are present, the tx: list must precede the rx: list. If a parameter is equal for both directions, it can be placed in a common param-
       eter list (without prefix). The general format is as follows:

       class_and_aal:common_list,tx:list,rx:list

       Each list consists of elements specifying a parameter. Elements can appear in any order and they are separated with commas.  The  following
       elements are recognized:

       pcr=rate
	      is a synonym for max_pcr=rate

       max_pcr=rate
	      The upper limit for the peak cell rate to assign. If omitted, any rate up to link speed may be chosen.

       min_pcr=rate
	      The lower limit for the peak cell rate to assign. If omitted, any rate above zero can be chosen.

       sdu=size
	      is a synonym for max_sdu=size

       max_sdu=size
	      The size of the largest packet that may be sent or received. If omitted, a context-dependent default value is used.

       Values are specified as follows:

       rate   The  (decimal)  rate, optionally followed by a unit. The unit may be prefixed with one of the multipliers k, M, or G, meaning 1'000,
	      1'000'000, or 1'000'000'000, respectively. The units cps (cells per second) and bps (bits per second) are recognized. If	multiplier
	      and  unit  are omitted, cells per second are assumed. Note that the rate is always converted to cells per second, so rounding errors
	      may occur when specifying the rate in bits per second. Rates measured in bits per second are considered to be user data rates,  i.e.
	      one  cell  corresponds  to 384 bits. The rate can be a fractional value, e.g.  1.3Mbps.  It is an error to specify only a multiplier
	      without a unit. Link speed can be indicated by using the keyword max as the rate.

       size   The (decimal) number of bytes.

       The tx: or rx: lists may also just contain the single element none, which indicates that the corresponding direction is not used.  It is an
       error to specify none for both direction.

       Note  that  commas must never follow colons or other commas. Also, whitespace is not allowed inside a QOS specification. QOS specifications
       are case-insensitive.

EXAMPLES

       Each of the following lines contains a valid QOS specification:

	 ubr
	 ubr:pcr=100kbps
	 cbr,aal0:pcr=64kbps
	 CBR:max_pcr=11Mbps,min_pcr=10mbps,sdu=8192
	 aal5,ubr:tx:none
	 cbr:tx:pcr=30000,rx:none

       The following specificiations are equivalent:

	 CBR,AAL5:PCR=48Mbps
	 cbr,aal5:max_pcr=125000
	 cbr,aal5:tx:pcr=125kcps,rx:pcr=125kcps

AUTHOR

       Werner Almesberger, EPFL LRC/ICA <werner.almesberger@epfl.ch>

Linux								  April 20, 2000							    QOS(7)