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>

Linux                                            April 20, 2000                                           QOS(7)