This message is sent by the user or the network to indicate that the equipment sending the message has disconnected the channel (if any) and intends to release the channel and the call reference, and that the receiving equipment should release the channel and prepare to release the call reference after sending RELEASE COMPLETE. The RELEASE message is sent by the network to the user to indicate that the access connection is awarded on either the D‑channel or an existing channel and that the network intends to release the call reference. See Table 3-29.
RELEASE message content
Message type: RELEASE |
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Information element |
Reference |
Direction |
Type |
Length |
Protocol discriminator |
Both |
M |
1 |
|
Call reference |
Both |
M |
2-* |
|
Message type |
Both |
M |
1 |
|
Cause |
Both |
O (Note 2) |
2-32 |
|
Display |
n ® u |
O (Note 3) |
(Note 4) |
|
User-user |
u ® n |
O (Note 5) |
(Note 6) |
|
NOTES 1. This message has local significance; however, it may carry information of global significance when used as the first call clearing message. 2. Mandatory in the first clearing message, including when the RELEASE message is sent as a result of an error handling condition. 3. Included if the network provides information that can be presented to the user. 4. The minimum length is 2 octets; the maximum length is network dependent and is either 34 or 82 octets. 5. User-user information may be sent if RELEASE is the first clearing message and the access connection has not yet reached the active state and Q.931/X.25 mapping service is provided by the network. However, user-user information is not sent if the access connection has reached the active state since X.25 procedures would be used for this information transfer. 6. The minimum length is 2 octets; the standard default maximum length is 131 octets. |
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