SIST ETS 300 123 E1:2003

SIST ETS 300 123 E1:2003 is the Slovenian adoption of ETS 300 123 Edition 1 from ETSI. It specifies attachment requirements for Data Terminal Equipment (DTE) that connect to Packet Switched Public Data Networks (PSPDN) using the CCITT Recommendation X.25 (1984) interface. The document focuses on DTEs that use Link Access Procedure Balanced (LAPB) extended (modulo 128) operation.

What does SIST ETS 300 123 E1:2003 specify?

SIST ETS 300 123 E1:2003 specifies the extra attachment requirements for packet mode DTEs that subscribe to the optional LAPB extended operation. It is intended to be used together with NET 2, and the foreword says its text may be used as Annex H to NET 2.

The document is organized into a foreword, normative references, definitions, symbols and abbreviations, Clause 4 on LAPB extended (Modulo 128) operation, and a history note. In practice, that means the standard is a focused add-on: it tells you how to adapt the base NET 2 approval tests for extended LAPB behavior.

What are the key requirements of SIST ETS 300 123 E1:2003?

Clause 4.1 says that all tests from section 9 of NET 2 apply, but with specific changes for LAPB extended operation. For implementers, this means the base approval test set stays in place, but the link-layer behavior must be exercised in extended mode.

• Clause 4.1 replaces SABM with SABME. In practice, the DTE must support the extended balanced mode setup command during testing and operation.
• Clause 4.1 requires the control field for frames with sequence numbers to follow the X.25 format for extended operation. This matters because sequence numbering and frame parsing must work correctly at the interface.
• Clause 4.1 requires the FRMR frame information field to use the X.25 format for extended operation. This is important for error reporting when the link rejects an invalid frame.
• Clause 4.1 says Test 9.3 of NET 2 is performed with the tester transmitting an I frame 128 times. That checks that the DTE handles the extended modulo operation across a full sequence range.
• Clause 4.2.1 adds a link set-up mode establishment collision test. The DTE is placed in Disconnected Mode (DM), then the tester applies the listed frame sequence so labs can verify how the equipment responds to competing setup and disconnect signaling.
• Clause 4.2.1 allows DISC to be transmitted. In practice, that gives the implementation some flexibility during the collision case while still testing the same link-setup situation.

What terms does SIST ETS 300 123 E1:2003 define?

• Data Terminal Equipment (DTE) - the terminal equipment that attaches to the packet network interface.
• Packet Switched Public Data Networks (PSPDN) - the public packet networks the DTE connects to.
• Link Access Procedure Balanced (LAPB) - the balanced link procedure whose extended mode is covered here.
• Set Asynchronous Balanced Mode Extended (SABME) - the command used instead of SABM for extended operation.
• Frame Reject (FRMR) - the reject frame whose information field format is specified for this mode.
• Disconnected Mode (DM) - the link state used in the collision test.
• Disconnect (DISC) - the disconnect frame that may be used in the collision case.

Who uses SIST ETS 300 123 E1:2003?

SIST ETS 300 123 E1:2003 is used by DTE designers, interface engineers, conformance test labs, and approval bodies working with packet data equipment. It is also relevant to buyers and technical evaluators who need to check whether a DTE supports X.25 attachment with LAPB extended operation.

In practice, these users apply the standard when designing the interface behavior, setting up test plans, running approval tests, and documenting support for the optional extended LAPB mode. It is most relevant in telecommunications and packet data communications work where X.25 interoperability still matters.

Which standards are used with SIST ETS 300 123 E1:2003?

• NET 2 - provides the main approval requirements for DTE attachment to PSPDN and the section 9 tests that Clause 4 modifies.
• CCITT Recommendation X.25 (1984) - provides the interface definition and the frame formats used for extended LAPB operation.

What does the SIST ETS 300 123 E1:2003 document contain?

The document contains a short foreword, the normative references that anchor it to NET 2 and X.25, and a small technical core in Clause 4. Clause 4.1 explains how to adapt the NET 2 test set for LAPB extended operation, including the command used, the extended frame formats, and the repeated I-frame test. Clause 4.2.1 gives a specific collision scenario for link set-up mode establishment while the DTE is in DM.

The contents also show the document structure clearly: definitions, symbols and abbreviations, then the operational and test requirements, followed by history. The history identifies it as the first edition and notes its PDF conversion date.