The purpose of the Bearer capability information element is to indicate a requested Recommendation I.231 [6] bearer service to be provided by the network. It contains only information which maybe used by the network (see Annex I). The use of the Bearer capability information element in relation to compatibility checking is described in Annex B.
The Bearer capability information element is coded as shown in Figure 4-11 and Table 4-6.
No default bearer capability may be assumed by the absence of this information element.
The maximum length of this information element is 12 octets.
Note - Future extensions to the codings of the Bearer capability information element should not be in conflict with the initially defined coding of the Low layer compatibility information element.See 4.5.19.
Bits |
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8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Octets |
Bearer capability Information element identifier |
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0 |
0 |
0 |
0 |
0 |
1 |
0 |
0 |
1 |
Length of the bearer capability contents |
2 |
|||||||
1 ext. |
Coding standard |
Information transfer capability |
3 |
|||||
1 ext. |
Transfer mode |
Information transfer rate |
4 |
|||||
1 ext. |
Rate multiplier |
4.1* |
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0/1 ext. |
Layer 1 ident. |
User information layer 1 protocol |
5* |
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0 |
1 |
|||||||
0/1 ext. |
Synch./ asynch |
Negot. |
User rate |
5a* |
||||
0/1 ext. |
Intermediate rate |
NIC on Tx |
NIC on Rx |
Flow control on Tx |
Flow control on Rx |
Spare |
5b* |
|
0/1 ext. |
Hdr/ no Hdr |
Multi frame |
Mode |
LLI negot. |
Assignor/ee |
In-band neg. |
Spare |
5b* |
0/1 ext. |
Number of stop bits |
Number of data bits |
Parity |
5c* |
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1 ext. |
Duplex mode |
Modem type |
5d* |
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1 ext. |
Layer 2 ident. |
User information layer 2 protocol |
6* |
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1 |
0 |
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0/1 ext. |
Layer 3 ident. |
User information layer 3 protocol |
7* |
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1 |
1 |
|||||||
0/1 ext. |
Spare |
Additional layer 3 protocol information (most significant bits) |
7a* |
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0 |
0 |
0 |
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1 ext. |
Spare |
Additional layer 3 protocol information (most significant bits) |
7b* |
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0 |
0 |
0 |
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NOTES 1. This octet is required if octet 4 indicates multirate (64 kbit/s base rate). Otherwise, it shall not be present. 2. This octet may be present if octet 3 indicates unrestricted digital information and octet 5 indicates either of the CCITT standardized rate adaptions V.110 and X.30 or V.120 [9]. It may also be present if octet 3 indicates 3.1 kHz audio and octet 5 indicates G.711. 3. This structure of octet 5b only applies if octet 5 indicates ITU-T standardized rate adaption (see Recommendations V.110 [7], I.460 [15] and X.30 [8]). 4. This structure of octet 5b only applies if octet 5 indicates ITU-T standardized rate adaption (see Recommendation V.120 [9]). 5. This octet may be included if octet 7 indicates ISO/IEC TR 9577 (Protocol Identification in the network layer). |
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Bearer capability information element
Bearer capability information element
Coding standard (octet 3) |
||
Bits |
||
7 6 |
||
0 0 |
CCITT standardized coding as described below |
|
0 1 |
ISO/IEC standard (Note 1) |
|
1 0 |
National standard (Note 1) |
|
1 1 |
Standard defined for the network (either public or private) present on the network side of the interface (Note 1) |
|
Note 1 - These other coding standards should be used only when the desired bearer capability cannot be represented with the CCITT-standardized coding. |
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Information transfer capability (octet 3) |
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Bits |
||
5 4 3 2 1 |
||
0 0 0 0 0 |
Speech |
|
0 1 0 0 0 |
Unrestricted digital information |
|
0 1 0 0 1 |
Restricted digital information |
|
1 0 0 0 0 |
3.1 kHz audio |
|
1 0 0 0 1 |
Unrestricted digital information with tones/announcements (Note 2) |
|
1 1 0 0 0 |
Video |
|
All other values are reserved. |
||
Note 2 - Unrestricted digital information with tones/announcements (UDI-TA) is the new information transfer attribute value that had previously been named "7 kHz audio" in Recommendation Q.931 (1988). |
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Transfer mode (octet 4) |
||
Bits |
||
7 6 |
||
0 0 |
Circuit mode |
|
1 0 |
Packet mode |
|
All other values are reserved. |
||
Information transfer rate (octets 4 , bits 5 to 1) |
||
Bits |
|
|
5 4 3 2 1 |
Circuit mode |
Paquet-mode |
0 0 0 0 0 |
- |
This code shall be used for packet mode calls |
1 0 0 0 0 |
64 kbit/s |
- |
1 0 0 0 1 |
2×64 kbit/s |
- |
1 0 0 1 1 |
384 kbit/s |
- |
1 0 1 0 1 |
1536 kbit/s |
- |
1 0 1 1 1 |
1920 kbit/s |
- |
1 1 0 0 0 |
Multirate (64 kbit/s base rate) |
|
All other values are reserved. |
||
Note 3 - When the information transfer rate 2×64 kbit/s is used, the coding of octets 3 and 4 refer to both 64 kbit/s channels. Note 4 - Additional attributes are defined in Table 4-7. |
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Rate mutiplier (octet 4.1) |
||
Note 5 - Coded as a binary representation of the multiplier to the base rate. The multiplier can take any value from 2 up to the maximum number of B-channels available on the interface. |
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User information layer 1 protocol (octet 5) |
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Bits |
||
5 4 3 2 1 |
||
0 0 0 0 1 |
CCITT standardized rate adaption V.110 and X.30. This implies the presence of octet 5a and optionally octets 5b, 5c and 5d as defined below. |
|
0 0 0 1 0 |
Recommendation G.711 [10] µ-law |
|
0 0 0 1 1 |
Recommendation G.711 A-law |
|
0 0 1 0 0 |
Recommendation G.721 [11] 32 kbit/s ADPCM and Recommendation I.460. |
|
0 0 1 0 1 |
Recommendations H.221 and H.242 |
|
0 0 1 1 0 |
||
0 0 1 1 1 |
Non-CCITT standardized rate adaption. This implies the presence of octet 5a and, optionally, octets 5b, 5c and 5d. The use of this code point indicates that the user rate specified in octet 5a is defined by the user. Additionally, octets 5b, 5c and 5d, if present, are defined consistent with the user specified rate adaption. |
|
0 1 0 0 0 |
ITU-T standardized rate adaption V.120 [9]. This implies the presence of octets 5a and 5b as defined below, and optionally octets 5c and 5d. |
|
0 1 0 0 1 |
ITU-T standardized rate adaption X.31 [14] HDLC flag stuffing. |
|
0 1 0 1 0 |
Recommendation G.728 [98] LD-CELP (Note 7) |
|
0 1 0 1 1 |
Recommendation G.729 [99] CS-ACELP (Note 7) |
|
All other values are reserved. |
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Note 6 - If the transfer mode is "circuit mode", and if the information transfer capability is "unrestricted digital information" or "restricted digital information"; and if the user information layer 1 protocol is to be identified only to the addressed entity octet 5 shall be omitted. If the transfer mode is packet mode, octet 5 may be omitted. Otherwise, octet 5 shall be present. Note 7 - These codings can only be used in ISUP [100] User Service Information Parameter. |
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Synchronous/Asynchronous (octet 5a) |
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Bit |
||
7 |
||
0 |
Synchronous data |
|
1 |
Asynchronous data |
|
Note 8 - Octets 5b - 5d may be omitted in the case of synchronous user rates. |
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Negotiation (octet 5a) |
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Bits |
||
6 |
||
0 |
In-band negotiation not possible |
|
1 |
In-band negotiation not possible |
|
Note 9 - See Recommendations V.110 [7], I.460 [15] and X.30 [8] or modem type recommendation. |
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User rate (octet 5a) |
||
Bits |
||
5 4 3 2 1 |
||
0 0 0 0 0 |
For I.460 [15], rate is specified by bits 7, 6 of octet 5b, intermediate rate. |
|
0 0 0 0 1 |
0.6 kbit/s Recommendations X.1 [17] |
|
0 0 0 1 0 |
1.2 kbit/s |
|
0 0 0 1 1 |
2.4 kbit/s Recommendations X.1 |
|
0 0 1 0 0 |
3.6 kbit/s |
|
0 0 1 0 1 |
4.8 kbit/s Recommendations X.1 |
|
0 0 1 1 0 |
7.2 kbit/s |
|
0 0 1 1 1 |
8 kbit/s Recommendation I.460 |
|
0 1 0 0 0 |
9.6 kbit/s Recommendations X.1 |
|
0 1 0 0 1 |
14.4 kbit/s |
|
0 1 0 1 0 |
16 kbit/s Recommendation I.460 |
|
0 1 0 1 1 |
19.2 kbit/s |
|
0 1 1 0 0 |
32 kbit/s Recommendation I.460 |
|
0 1 1 0 1 |
38 kbit/s Recommendation V.110 [87] |
|
0 1 1 1 0 |
48 kbit/s Recommendations X.1 |
|
0 1 1 1 1 |
56 kbit/s |
|
1 0 0 1 0 |
57.6 kbit/s Recommendation V.14 extended [88] |
|
1 0 0 1 1 |
28.8 kbit/s Recommendation V.110 [89] |
|
1 0 1 0 0 |
24 kbit/s Recommendation V.110 [89] |
|
1 0 1 0 1 |
0.1345 kbit/s Recommendation X.1 |
|
1 0 1 1 0 |
0.100 kbit/s Recommendation X.1 |
|
1 0 1 1 1 |
0.075/1.2 kbit/s Recommendations X.1 (Note 10) |
|
1 1 0 0 0 |
1.2/0.075 kbit/s Recommendations X.1 (Note 10) |
|
1 1 0 0 1 |
0.050 kbit/s Recommendations X.1 |
|
1 1 0 1 0 |
0.075 kbit/s Recommendations X.1 |
|
1 1 0 1 1 |
0.110 kbit/s Recommendations X.1 |
|
1 1 1 0 0 |
0.150 kbit/s Recommendations X.1 |
|
1 1 1 0 1 |
0.200 kbit/s Recommendations X.1 |
|
1 1 1 1 0 |
0.300 kbit/s Recommendation X.1 |
|
1 1 1 1 1 |
12 kbit/s |
|
All other values are reserved. |
||
Note 10 - The first rate is the transmit rate in the forward direction of the call. The second rate is the transmit rate in the backward direction of the call. |
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Octet 5b for V.110, I.460 and X.30 rate adaption |
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Intermediate rate (octet 5b) |
||
Bits |
||
7 6 |
||
0 0 |
Not used |
|
0 1 |
8 kbit/s |
|
1 0 |
16 kbit/s |
|
1 1 |
32 kbit/s |
|
Network independent clock (NIC) on transmission (Tx) (octet 5b) (Note 11) |
||
Bit |
||
5 |
||
0 |
Not required to send data with network independent clock |
|
1 |
Required to send data with network independent clock |
|
Note 11 - Refers to transmission in the forward direction of the call. Note 12 - See Recommendations V.110 [7], I.460 [15] and X.30 [8]. |
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Network independent clock (NIC) on reception (Rx) (octet 5b) (Note 13) |
||
Bit |
||
4 |
||
0 |
Cannot accept data with network independent clock (i.e. sender does not support this optional procedure) |
|
1 |
Can accept data with network independent clock (i.e. sender does support this optional procedure) |
|
Note 13 - Refers to transmission in the backward direction of the call. Note 14 - See Recommendations V.110 [7], I.460 [15] and X.30 [8]. |
||
Flow control on transmission (Tx) (octet 5b) (Note 15) |
||
Bit |
||
3 |
|
|
0 |
Not required to send data with flow control mechanism |
|
1 |
Required to send data with flow control mechanism |
|
Note 15 - Refers to transmission in the forward direction of the call. Note 16 - See Recommendations V.110, I.460 and X.30. |
||
Flow control on reception (Rx) (octet 5b) (Note 17) |
||
Bit |
||
2 |
||
0 |
Cannot accept data with flow control mechanism (i.e. sender does not support this optional procedure) |
|
1 |
Can accept data with flow control mechanism (i.e. sender does support this optional procedure) |
|
Note 17 - Refers to transmission in the backward direction of the call Note 18 - See Recommendations V.110, I.460 and X.30. |
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Octet 5b for V.120 [9] rate adaption |
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Rate adaption header/no header (octet 5b) |
||
Bit |
||
7 |
||
0 |
Rate adaption header not included |
|
1 |
Rate adaption header included |
|
Multiple frame establishment support in data link (octet 5b) |
||
Bit |
||
6 |
||
0 |
Multiple frame establishment not supported. Only UI frames allowed |
|
1 |
Multiple frame establishment supported |
|
Mode of operation (octet 5b) |
||
Bit |
||
5 |
||
0 |
Bit transparent mode of operation |
|
1 |
Protocol sensitive mode of operation |
|
Logical link identifier negotiation (octet 5b) |
||
Bit |
||
4 |
||
0 |
Default, LLI = 256 only |
|
1 |
Full protocol negotiation (Note 19) |
|
Note 19 - A connection over which protocol negotiation will be executed is indicated in bit 2 of octet 5b. |
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Assignor/assignee (octet 5b) |
||
Bit |
||
3 |
||
0 |
Message originator is "Default assignee" |
|
1 |
Message originator is "Assignor only" |
|
In-band/out-band negotiation (octet 5b) |
||
Bit |
||
2 |
|
|
0 |
Negotiation is done with USER INFORMATION messages on a temporary signalling connection |
|
1 |
Negotiation is done in-band using logical link zero |
|
Number of stop bits (octet 5c) |
||
Bits |
||
7 6 |
||
0 0 |
Not used |
|
0 1 |
1 bit |
|
1 0 |
1.5 bits |
|
1 1 |
2 bits |
|
Number of data bits excluding parity Bit if present (octet 5c) |
||
Bits |
||
5 4 |
||
0 0 |
Not used |
|
0 1 |
5 bits |
|
1 0 |
7 bits |
|
1 1 |
8 bits |
|
Parity information (Octet 5c) |
||
Bits |
||
3 2 1 |
||
0 0 0 |
Odd |
|
0 1 0 |
Even |
|
0 1 1 |
None |
|
1 0 0 |
Forced to 0 |
|
1 0 1 |
Forced to 1 |
|
All other values are reserved. |
||
Mode duplex (octet 5d) |
||
Bit |
||
7 |
||
0 |
Half duplex |
|
1 |
Full duplex |
|
Modem type (octet 5d) |
||
Bits |
||
6 5 4 3 2 1 |
||
0 0 0 0 0 0 |
national use |
|
0 1 0 0 0 1 |
Recommendation V.21 [55] |
|
0 1 0 0 1 0 |
Recommendation V.22 [56] |
|
0 1 0 0 1 1 |
Recommendation V.22 bis [57] |
|
0 1 0 1 0 0 |
Recommendation V.23 [58] |
|
0 1 0 1 0 1 |
Recommendation V.26 [59] |
|
0 1 0 1 1 0 |
Recommendation V.26 bis [60] |
|
0 1 0 1 1 1 |
Recommendation V.26 ter [61] |
|
0 1 1 0 0 0 |
RecommendationV.27 [62] |
|
0 1 1 0 0 1 |
Recommendation V.27 bis [63] |
|
0 1 1 0 1 0 |
Recommendation V.27 ter [64] |
|
0 1 1 0 1 1 |
Recommendation V.29 [65] |
|
0 1 1 1 0 0 |
Recommendation V.32 [66] |
|
0 1 1 1 1 0 |
Recommendation V.34 [99] |
|
1 0 0 0 0 0 |
national use |
|
1 1 0 0 0 0 |
user specified |
|
All other values reserved. |
||
User information layer 2 protocol (octet 6) |
||
Bits |
||
5 4 3 2 1 |
||
0 0 0 1 0 |
Recommendation Q.921/I.441 [3] |
|
0 0 1 1 0 |
Recommendation X.25 [5], link layer |
|
0 1 1 0 0 |
LAN logical link control (ISO/IEC 8802-2) (Note 24) |
|
All other values are reserved. |
||
Note 20 - If the transfer mode is "packet mode", octet 6 shall be present. For other cases, if the user layer 2 protocol is to be identified to the network, then octet 6 shall be present; otherwise octet 6 shall be omitted. |
||
User information layer 3 protocol (octet 7) |
||
Bits |
||
5 4 3 2 1 |
||
0 0 0 1 0 |
Recommendation Q.931/I.451 |
|
0 0 1 1 0 |
Recommendation X.25, packet layer |
|
0 1 0 1 1 |
ISO/IEC TR 9577 [82] (Protocol identification in the network layer) (Notes 22 and 24) |
|
All other values are reserved. |
||
Note 21 - If the user information layer 3 protocol is to be identified to the network, octet 7 shall be present; otherwise octet 7 shall be omitted. |
||
Note 22 – If the user information layer 3 protocol indicates "Network layer protocol identification", octet 7a and 7b may be included to identify the actual user information layer 3 protocol to the network. |
||
Octets 7a and 7b (Notes 22 and 23) |
||
Bit 8 (ext.) set to 0 in octet 7a and set to 1 in octet 7b. |
||
Bits 7 to 5 are spare (set to 0) in both octets. |
||
7a |
7b |
|
Bits |
Bits |
|
4 3 2 1 |
4 3 2 1 |
|
1 1 0 0 |
1 1 0 0 |
Internet Protocol (RFC 791) (ISO/IEC TR 9577 [82]) |
1 1 0 0 |
1 1 1 1 |
Point-to-point Protocol (RFC 1548) |
Note 23 – If the user information layer 3 protocol indicates "Network layer protocol Identification", octet 7a and 7b may be included to identify the actual user information layer 3 protocol to the network. These codepoints are assigned consistently with ISO/IEC TR 9577 [82]. Note 24 – These codings can only be used where transfer mode is "circuit mode". |
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Bearer capability attributes
BC Attributes |
|||||
Additional Attributes |
|||||
Transfer mode |
Information transfer capability |
Structure |
Configuration |
Establishment |
Symmetry |
Circuit |
Speech |
8 kHz integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
Circuit |
Unrestricted data |
8 kHz integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
Circuit |
Restricted data |
8 kHz integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
Circuit |
3,1 kHz audio |
8 kHz integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
Circuit |
Unrestricted data with tones/announcements |
8 kHz integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
Circuit |
Video |
8 kHz integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
Packet |
Unrestricted data |
Service data unit integrity |
Point-to-point |
Demand |
Bi-directional symmetric |
NOTES 1 When the information transfer rate 2 × 64 kbit/s is used, 8 kHz integrity with Restricted Differential Time Delay (RDTD) is offered. 2 When multirate (64 kbit/s base rate) is indicated as the information transfer rate, Time Slot Sequence integrity shall be provided. |
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