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please check this link
ieeexplore.ieee.org/iel5/6648/17837/00824460.pdf?arnumber=824460 -
Posted by waqasahmad
For details:
www.protocols.com/pbook/v5.htm
en.wikipedia.org/wiki/V5_interface
Posted by sagitraz
The signalling protocol specification and layer multiplexing PSTN protocol on the V5-interface is basically a stimulus protocol. It does not control the call procedures in the AN, but rather transfers information about the analogue line state over the V5 interface. The V5 PSTN protocol is used in conjunction with the national protocol entity in the LE. The national protocol entity in the LE, which is used for customer lines which are connected directly to the LE, is also used to control calls on customer lines which are connected via the V5-interface. For time critical sequences it is also required to extract certain signalling sequences (e.g., compelled sequences) from the national protocol entity into an "AN part" of the national prot oc ol entity. However, the V5-PSTN protocol has a relatively small functional part which is concerned with path setup, release of the path on the V5 interface, call collision resolution on the V5 interface and handling of new calls in case of overload conditions in the LE. The majority of line signals are not interpreted by the V5-PSTN protocol, but simply transferred transparently between the user port in the AN and national protocol entity in the LE.
The structure of PSTN is shown below:
Format Octet
Protocol discriminator 1
Layer 3 address 2
Layer 3 address (cont.) 3
Message type 4
Other Information Elements etc.
Protocol discriminator
Distinguishes between messages corresponding to one of the V5 protocols. The value of the protocol discriminator for PSTN is 01001000.
Layer 3 address
Identifies the layer 3 entity, within the V5.2 interface, to which the transmitted or received message applies.
Message type
Identifies the function of the message being sent or received. Message types for PSTN may be as follows:
• ESTABLISH
• ESTABLISH ACK
• SIGNAL
• SIGNAL ACK
• STATUS
• STATUS ENQUIRY
• DISCONNECT
• DISCONNECT COMPLETE
• PROTOCOL PARAMETER
Other Information Elements
For PSTN the following Information Elements may appear:
Single Octet IEs:
• Pulse-notification
• Line-information
• State
• Autonomous-signaling-sequence
• Sequence-response
Variable Length IEs
• Sequence-number
• Cadenced-ringing
• Pulsed-signal
• Steady-signal
• Digit-signal
• Recognition-time
• Enable-autonomous-acknowledge
• Disable-autonomous-acknowledge
• Cause
Posted by agustinhammond
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