Purpose: To verify that the SUT signals the correct duration of the Link Confidence Test due to various conditions.

References:

• SMT 6.2 sections 7.2.2, 9.4.6, and 9.6.3
• SMT 7.3 sections 7.2.2, 9.4.6, and 9.6.3

Resource Requirements:

• Testing Station to establish connections signalling any port type, to change its port type and connection policy, to transmit link errors during both LCT and when active, and to transmit SIF-Configuration Requests. When the Testing Station is not transmitting, it becomes a passive node allowing ring traffic through unmodified.
• Passive Monitor to capture line states and SIF-Configuration frames.

Discussion: The duration of the LCT when there is no recent history of excessive link errors shall be Short. The duration of the LCT following the failure of the LCT shall be Medium. The duration of the LCT after the rejection of a link due to an excessive Link Error Rate shall be Long. The duration of the LCT used to withhold a connection shall be Extended. Stations implementing SMT 7.3, may optionally signal a longer LCT duration than is specified. For this reason, the first section only applies to stations implementing SMT 6.2.

Test Setup: Configure a ring with the Testing Station, the SUT and the Monitor (see figure). The Monitor is set up to capture line state changes and SIF-Configuration frames.

No recent history of excessive link errors

Procedure: The Testing Station attempts a connection with the SUT. Repeat for each port on the SUT.

Observable Results: On the Monitor, verify that for stations implementing SMT 6.2, the SUT signals a Short LCT.

Link Errors during LCT

Procedure: The Testing Station attempts a connection with the SUT, transmitting a large number of link errors during the LCT so that the SUT signals LCT failure (on the Monitor, SIGNAL, n=7 = HLS). The Testing Station attempts another connection with the SUT without transmitting link errors during LCT. Repeat for each port on the SUT.

Observable Results: On the Monitor, verify that for stations implementing SMT 6.2, the SUT signals a Medium LCT. Verify that for stations implementing SMT 7.3, the SUT signals at least a Medium LCT.

Link Errors while active

Procedure:The TestingStation transmits a large number of link errors. Verify that the SUT rejects the link. The Testing Station attempts a connection with the SUT. Repeat for each port on the SUT.

Observable Results: On the Monitor, verify that for stations implementing SMT 6.2, the SUT signals a Long LCT. For stations implementing SMT 7.3, verify that the SUT signals at least a Long LCT.

Withholding a connection

Procedure: The Testing Station transmits a SIF-Configuration Request with FC=X'41' and DA=MAC address of SUT. On the Monitor, look at the SIF-Configuration Response from the SUT and note the SUT's ConnectionPolicy found in parameter X'0005', Station Policies. The Testing Station attempts a connection with the SUT, signalling a port type that is not compatible with that of the SUT based on the SUT's ConnectionPolicy. If no such port exists, this part cannot be performed. The Testing Station also signals that the port types are not compatible (SIGNAL, n=3 = MLS).

Observable Results: On the Monitor, verify that the SUT signals an Extended LCT.

Possible Problems: If the SUT does not fail LCT due to receiving link errors during LCT, part 2 cannot be performed. Also, the Link Error Rate (LER) is based on a statistical relationship between the number of errors observed in a given interval and the current Link Error Rate. The size of the interval is not defined in the standard. For this reason, it is not clear how long the link errors must be sent in order to cause the SUT to remove the link in part 3.