The Link Access Procedure – D Channel (LAPD) portable software product provides the LAPD link level protocol, supports the ITU-T and other variants of the protocol and reliably sends and receives information over the physical transmission media. LAPD detects errors and is able to recover from lost, errored or duplicated information. The LAPD software:

  • Establishes multiple data link connections on a single physical link
  • Releases data link connections
  • Transfers acknowledged data on established link level connections
  • Transfers unacknowledged data outside of link level connections
  • Maintains flow control of the transfer of data
  • Reinitializes data link connections upon detection of an error

Trillium LAPD software enables telecom equipment manufacturers of soft switches, signaling gateways, signal transfer points, service control points, media gateway controllers or other products to:

  • Accelerate time to market
  • Reduce development costs
  • Reduce project risk of internally developed LAPD applications

Product deliverables consist of C source software, documentation, training, a warranty and technical support.

FEATURES + BENEFITS

The LAPD software supports the following 1988 CCITT recommendation Q.920 and Q.921 link level features:

  • Link Access Procedure – D Channel (LAPD).
  • Both acknowledged (multiple frame operation) and unacknowledged modes supported.
  • Modulo 128 frame sequencing.
  • Link window size of 1 to 127 for modulo 128 sequencing.
  • Broadcast data link connection.
  • Supports three standard SAPI values (Q.930, X.25, and management) with extension capabilities up to 64 SAPIs.
  • Acts as a Terminal Equipment (TE).
  • Acts as an Exchange Termination/NT2 (ET).
  • Supports both the user and the network.
  • Supports both TEI static and dynamic assignments.
  • Provides the layer manager for TEI assignment and removal, including the ASP code in the network side. Only the TEI management option provides this feature.
  • Supports one or more TEIs per SAP.
  • Supports XID frame.
  • Provides “piggy-backed” acknowledgment of frames to increase throughout on the link.
  • Conforms to Trillium Advanced Portability Architecture (TAPA)
  • Benefits of licensing Trillium software from Continuous Computing

EXTENDED FEATURES

  • Modulo 8 frame sequencing.
  • Link window size of 1 to 7 for modulo 8 sequencing.
  • XID frames can be used by the layer manager or by any other program.
  • Each SAP can be configured to support only one TEI (in this case, only one data link connection is supported per SAP). Also, a SAP can be configured to support multiple TEIs (in this case, more than one data link connection can be supported by one SAP).
  • Each individual SAP (on the same physical link) can be configured to support non-automatic TEIs or to support automatic TEIs. Support of automatic TEIs requires the TEI management option.

PRODUCT INTERWORKING

Trillium LAPD software may be used with Trillium Q.930/Q.931, X.25/X.75 Packet Level Protocol, ISAC-S, SCC, 68302, 68360 and MTSS software products.

CONFORMANCE

Trillium LAPD software conforms to the following standard. Refer to the LAPD Functional Specification for detailed implementation.

  • ITU-T specification Q.920/Q.921 – ISDN User/Network Interface – Data Link Layer Specification (03/93)