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 independently 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 parameter 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>