Ldm Test Screen (Delt) - ZyXEL Communications MSC1024G Series User Manual

Chapter 8 Diagnostic Screens
• MEP port - has the ability to send pro-active connectivity check (CC) packets and get
other MEP ports information from the CC packets of neighboring switches within an
MA.
• MIP port - only forwards the CC packets.
CFM provides two tests to discover connectivity faults.
• Loopback test - similar to "pinging" a computer. A loopback test checks if the MEP port
receives its LBR (Loop Back Response) from its target after it sends the LBM (Loop
Back Message). If no response is received, there might be a connectivity fault between
them.
• Link trace test - similar to the "traceroute" function. A link trace test provides additional
connectivity fault analysis to obtain more information on where the fault is. In the link
trace test, MIP ports also send a LTR (Link Trace Response) in response to the source
MEP port's LTM (Link Trace Message). If an MIP or MEP port does not respond to the
source MEP, this may indicate a fault. Administrators can take further action to check and
resume services from the fault according to the line connectivity status report.
An example is shown next. A user reports he cannot access the Internet. To check the problem,
the administrator starts the link trace test from the A which is an MEP port to the B which is
also an MEP port. Each aggregation MIP port between aggregated devices response the LTM
packets and also forwards them to the next port. A fault occurs in the port C. A discovers the
fault since it just gets the LTR packets from the ports flowing before the port C.
Figure 91 MIP and MEP Example

8.2 LDM Test Screen (DELT)

Click Diagnostic > LDM in the navigation panel to display this screen. Use this screen to
perform loop diagnostics (LDM stands for Loop Diagnostic Mode) on an ADSL2, ADSL2+ or
VDSL port. This is a Dual End Loop Test (DELT) that acts on a per-tone basis. A DELT
provides details about the line condition. The subscriber device must also support DELT in
order to perform this. See ITU-T G933.2 for more information. This feature is applicable for
ALC line cards only.
176
B (port 8, MEP)
C
(port 17, MIP)
(port 18, MIP)
A
(port 2, MEP)
MSC1000G/1024G/1224G Series User's Guide