Bits

8

7

6

5

4

3

2

1

Octets

Channel identification information element identifier

0

0

0

1

1

0

0

0

1

Length of channel identification contents

2

1 ext.

Int. id. present

Int. type

0
spare

Pref./Excl.

D-channel
ind.

Info. channel
selection

3

0/1
ext.

Interface identifier

3.1*, etc.
(Note 1)

1 ext.

Coding standard

Number/ Map

Channel type/Map element type

3.2*
(Note 2)
(Note 5)

Channel number/Slot map (Note 3)

3.3*
(Note 2)
(Note 4)
(Note 5)

NOTES

1. When the "interface identifier present" field in octet 3 indicates "interface implicitly identified" octet 3.1 is omitted. When octet 3.1 is present it may be extended by using the extension bit (bit 8).

2. When the "interface type" field in octet 3 indicates "basic interface", octets 3.2 and 3.3 are functionally replaced by the "information channel selection" field in octet 3, and thus omitted.

3. When channel number is used and a single channel is indicated bit 8 shall be set to "1". When channel number is used and multiple channels are indicated, bit 8 shall be used as an extension bit to indicate an extension to subsequent channels and coded according to the rules specified in 4.5.1.

4. When channel number is used, this octet may be repeated to indicate multiple channels.

5. These octets shall be omitted when the entire interface is to be identified.

Interface identifier present (octet 3)

Bit

7

0

Interface implicitly identified (Note 1)

1

Interface explicitly identified in one or more octets, beginning with octet 3.1.

Note 1 - The interface which includes the D-channel carrying this information element is indicated.

Interface type (octet 3)

Bit

6

0

Basic interface

1

Other interface e.g. primary rate (Note 2)

Note 2 - The type of interface should be understood because the interface is identified by the "interface identifier present" field (octet 3, bit 7) and the interface identifier field (octet 3.1), if any.

Preferred/Exclusive (octet 3)

Bit

4

0

Indicated channel is preferred

1

Exclusive; only the indicated channel is acceptable

Note 3 - Preferred/exclusive has significance only for B-channel selection.

D-channel indicator (octet 3)

Bit

3

0

The channel identified is not the D-channel

1

The channel identified is the D-channel

Note 4 - D-channel indication has significance in D-channel use. No other information affects D-channel use.

Information channel selection (octet 3) (Note 5)

Basic interface

Other interfaces

Bits

2 1

0 0

No channel

No channel

0 1

B1 channel

As indicated in following octets

1 0

B2 channel

Reserved

1 1

Any channel (Note 6)

Any channel

Note 5 - The information channel selection does not apply to the D-channel.

Note 6 - This value shall be used on a basic access when both B-channels are to be identified, e.g. multirate (64 kbit/s base rate). This shall not be used for restart procedures.

Interface identifier (octet 3.1)

Binary code assigned to the interface at subscription time. At subscription time, the binary code for the interface will specify the number of octets to be used and the content of each octet.

Note 7 – When the 'information channel selection' field of octet 3 (bit 2-1) indicates 'any channel', if present the interface 'identifier' field is set to all '0'.

Coding standard (octet 3.2)

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 8 - These other coding standards should only be used when the desired call states cannot be represented by ITU-T-standardized coding.

Number/map (octet 3.2)

Bit

5

0

Channel is indicated by the number in the following octet.

1

Channel is indicated by the slot map (Map) in the following octet(s).

Note 9 - When the information transfer rate is 64 kbit/s the channel number shall be used unless there exists a bilateral agreement between the user and the network to use the slot map.

Note 10 - Slot map shall be used when supporting the multirate (64 kbit/s base rate) bearer capability on a primary rate access.

Channel type/map element type (octet 3.2)

Bits

4 3 2 1

0 0 1 1

B-channel units(Note 4)

0 1 1 0

H0-channel units

1 0 0 0

H11-channel units

1 0 0 1

H12-channel units

All other values are reserved.

Note 11 - This value shall be used for multirate (64 kbit/s base rate) bearer capability.

Channel number (octet 3.3)

Binary number assigned to the channel. For B-channels, the channel number equals the time slot number. See Recommendation I.431 [27].

Note 12 - Either "Channel Number" or "Slot map" is used exclusively, depending on the "Number/Map" information.

Slot map (octet 3.3)

Bit position(s) in slot map corresponding to time slot(s) used by the channel is set to 1, see Figure 4-19. The remaining bits are set to 0.

Note 13 - The length of the slot-map (in bits) is defined by the capacity of the interface type (e.g. 1534 kbit/s or 2048 kbit/s for a primary rate interface) divided by the capacity of the channel type/map-element type (e.g. 64 kbit/s for a B-channel). The length of the slot map is the smallest number of complete octets that contain the length in bits.

Bits

8

7

6

5

4

3

2

1

Octets

24

23

22

21

20

19

18

17

3.3.1

16

15

14

13

12

11

10

9

3.3.2

8

7

6

5

4

3

2

1

3.3.3

1544 kbit/s

Bits

8

7

6

5

4

3

2

1

Octets

31

30

29

28

27

26

25

24

3.3.1

23

22

21

20

19

18

17

16

3.3.2

15

14

13

12

11

10

9

8

3.3.3

7

6

5

4

3

2

1

0

3.3.4

2048 kbit/s

Bits

8

7

6

5

4

3

2

1

Octets

d(4)

c(3)

b(2)

a(1)

3.3

1544 kbit/s

Bits

8

7

6

5

4

3

2

1

Octets

e(5)

d(4)

c(3)

b(2)

a(1)

3.3

2048 kbit/s

Bits

8

7

6

5

4

3

2

1

Octet

H11(1)

3.3

1544 kbit/s

Bits

8

7

6

5

4

3

2

1

Octet

H12(1)

3.3

2048 kbit/s