Paradyne 3615, 3616 manual Local Loopback, DTE Loopback, Remote Digital Loopback

COMSPHERE DualFlow Data Service Units

NOTE

To abort a loopback on the tributary DSU from the NMS, establish a dial connection with the control DSU, then issue a subnetwork abort command from the NMS to the control.

Local Loopback

Only available to a DSU, Local Loopback (LL) is session-disruptive; that is, performing the test will disrupt data. It permits the DTE or router to run a test to determine whether the DTE or router connection to the DSU and the DSU itself are functioning properly. The DSU must be connected to the DTE or router, but the network connection to the DSU is not required.

While the DSU is in Local Loopback, any data transmission by the DTE or router is returned as received data. An operator can send a test pattern and verify correct reception of the test. The DSU does not monitor this testing.

NOTE

If the NMS is to abort the Local Loopback, the tributary's DBM must be in Standby mode. If in Dial Backup mode and the NMS issues the Abort command, the command will not be recognized. The loopback will have to be aborted from the DSU's control panel.

DTE Loopback

DTE Loopback (DTE) loops back the data path at the DTE interface without affecting operation of the other port. This loopback is used to verify that the DTE or router connection and the cable are good.

Digital Loopback

Digital Loopback (DL) allows manual testing of the remote end of the circuit. Data coming in is immediately transmitted back. For example, a Digital Loopback may be required in order to complete an external bit error rate test (BERT) from the remote DSU. The local DSU receives test data, loops it back to the transmitter before the DSU's DTE interface, and returns it to the network.

Digital Loopback can also be initiated by receiving a V.54 pattern to go into Digital Loopback. Enable configuration options V.54 Lpbk (V.54 Loopback) in the DSU option set, and RespondRDL (Respond to Remote Digital Loopback).

Remote Digital Loopback

Only available to the DBM, the Remote Digital Loopback (RL), sometimes referred to as RDL, typically supports testing using an external device, like a protocol analyzer that is connected to the local DSU's DTE interface. A test message from the external device is looped back from the receiver to the transmitter in the remote DBM and returned to the local DBM.

In Remote Digital Loopback, the local DBM (control or tributary) puts the remote DBM into Digital Loopback.

DTE

(ROUTER)

		DL or	DL or
		RL on	RL on a
DTE	LL	Aggregate	Port
DSU		NETWORK	DSU

DTE

(ROUTER)

496-14493a

Figure 4-3. Loopbacks

4-10 December 1996 3615-A2-GB20-20