1QOS(7) Miscellaneous QOS(7)
2
6 qos - Quality of Service specification
7
9 The text2qos and qos2text functions use the format described in this
10 man page. Because all standard ATM tools on Linux use those functions
11 to convert to or from the textual representation of QOS specifications,
12 they expect them in the same format too.
13 The most fundamental parameters are the traffic class and the AAL (ATM
15 Adaption Layer) type. If the connection is bi-directional, both direc‐
16 tions have the same traffic class and the same AAL type. The traffic
17 class and the AAL type are the first elements (in any order) in a QOS
18 specification. The traffic class is the only required element. If the
19 AAL type is omitted, the application will provide a default value. The
20 following traffic classes are recognized:
21 ubr Unassigned Bit Rate
23 cbr Constant Bit Rate
25 abr Available Bit Rate
27 The following AAL types are recognized:
29 aal0 ("raw ATM")
31 aal5
33 If both, the traffic class and the AAL type are specified, they are
35 separated by a comma.
36 If more parameters are supplied, the traffic class and AAL type must be
38 followed by a colon. Traffic parameters can be specified independently
39 for the transmit and the receive direction. Their parameter lists are
40 prefixed with tx: and rx:, respectively. If both parameter lists are
41 present, the tx: list must precede the rx: list. If a parameter is
42 equal for both directions, it can be placed in a common parameter list
43 (without prefix). The general format is as follows:
44 class_and_aal:common_list,tx:list,rx:list
46 Each list consists of elements specifying a parameter. Elements can
48 appear in any order and they are separated with commas. The following
49 elements are recognized:
50 pcr=rate
52 is a synonym for max_pcr=rate
53 max_pcr=rate
55 The upper limit for the peak cell rate to assign. If omitted,
56 any rate up to link speed may be chosen.
57 min_pcr=rate
59 The lower limit for the peak cell rate to assign. If omitted,
60 any rate above zero can be chosen.
61 sdu=size
63 is a synonym for max_sdu=size
64 max_sdu=size
66 The size of the largest packet that may be sent or received. If
67 omitted, a context-dependent default value is used.
68 Values are specified as follows:
70 rate The (decimal) rate, optionally followed by a unit. The unit may
72 be prefixed with one of the multipliers k, M, or G, meaning
73 1'000, 1'000'000, or 1'000'000'000, respectively. The units cps
74 (cells per second) and bps (bits per second) are recognized. If
75 multiplier and unit are omitted, cells per second are assumed.
76 Note that the rate is always converted to cells per second, so
77 rounding errors may occur when specifying the rate in bits per
78 second. Rates measured in bits per second are considered to be
79 user data rates, i.e. one cell corresponds to 384 bits. The rate
80 can be a fractional value, e.g. 1.3Mbps. It is an error to
81 specify only a multiplier without a unit. Link speed can be
82 indicated by using the keyword max as the rate.
83 size The (decimal) number of bytes.
85 The tx: or rx: lists may also just contain the single element none,
87 which indicates that the corresponding direction is not used. It is an
88 error to specify none for both direction.
89 Note that commas must never follow colons or other commas. Also, white‐
91 space is not allowed inside a QOS specification. QOS specifications are
92 case-insensitive.
93
95 Each of the following lines contains a valid QOS specification:
96 ubr
98 ubr:pcr=100kbps
99 cbr,aal0:pcr=64kbps
100 CBR:max_pcr=11Mbps,min_pcr=10mbps,sdu=8192
101 aal5,ubr:tx:none
102 cbr:tx:pcr=30000,rx:none
103 The following specificiations are equivalent:
105 CBR,AAL5:PCR=48Mbps
107 cbr,aal5:max_pcr=125000
108 cbr,aal5:tx:pcr=125kcps,rx:pcr=125kcps
109
112 Werner Almesberger, EPFL LRC/ICA <werner.almesberger@epfl.ch>
113Linux April 20, 2000 QOS(7)