信息技术 系统间远程通信和信息交换 X.25DTE一致性测试 第2部分:数据链路层一致性测试套

[中文适用范围]： ISOIIEC 8882 的这一部分定义了一个抽象测试套件，用于测试 IUT 数据链路层与 ISOllEC 7776 (1986,1995) 或 ITU-T 建议 X.25 (1980,1984,1988,1993) 的一致性。 使用测试仪和 DTE 之间的专用电路来测试数据终端设备 (DTE) 是否符合上述 IS0 国际标准或 ITU-T 建议书。 需要注意的是，ITU-T建议书X.25（1980）、X.25（1984）、X.25（1988）和X.25（1993）是从DCE的角度编写的，因此没有明确规定DTE 操作。 在这种情况下，由于需要与 X.25 DCE 通信，因此假定暗示包含 DTE 的推荐操作。 ISOIIEC 8882 的这一部分不包括对 ITU-T 建议书中给出的 LAP 程序的测试。 注：根据 ISOIIEC 7776，扩展模式操作（模 128）、多链路程序和 DTE-DTE 操作的测试用例有待进一步研究。 在 ISOIIEC 8882 本部分的其余部分中，术语“X.25 标准”是指所有四个 ITU-T 建议书 X.25 (1980)、X.25 (1984)、X.25 (1988)、X.25 (1993) 以及国际标准 ISOIIEC 7776 (1995) 和 ISOIIEC 7776 (1986)，除非另有说明。 [外文原描述]： This part of ISO/IEC 8882 defines an abstract test suite for testing the conformance of the Data Link Layer of an IUT with respect to ISO/IEC 7776 (1986, 1995) or the ITU-T Recommendation X.25 (1980, 1984, 1988, 1993). Conformance of a Data Terminal Equipment (DTE) to the above ISO International Standard or ITU-T Recommendations is tested using a dedicated circuit between the tester and the DTE. It is noted that ITU-T Recommendations X.25 (1980), X.25 (1984), X.25 (1988) and X.25 (1993) are written from the perspective of a DCE and therefore do not always explicitly specify the DTE's operation. In such cases it is assumed that recommended operation of a DTE is included by implication because of the need to communicate with X.25 DCE's. This part of ISO/IEC 8882 excludes the testing of the LAP procedures given in the ITU-T Recommendations. NOTE Test cases for extended mode operation (Modulo 128), multilink procedure and DTE-DTE operation as per ISO/IEC 7776 are for further study. The tests in this part of ISO/IEC 8882 are designed for six possible interworking situations, shown in Figure 1. This part specifies tests for all six cases shown in Figure 1, but recognizes that not every test may apply to a particular DTE. A test selection procedure has to be performed to determine the applicability of a test to a particular DTE. Such selection will be based on the PICS and the PIXIT. Figure 1 — Testing X.25-DTE/DCE and X.25-DTE/DTE Interworking In the rest of this part of ISO/IEC 8882, the term "X.25 standards" means all four of ITU-T Recommendations X.25 (1980), X.25 (1984), X.25 (1988), X.25 (1993), and International Standards ISO/IEC 7776 (1995) and ISO/IEC 7776 (1986), unless stated otherwise.