Chapter 22 Diagnostic
P-660HN-FxZ Series User’s Guide
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The following table describes the fields in this screen.
Table 125
Maintenance > Diagnostic > DSL Line
LABEL
DESCRIPTION
ATM Status
Click this to view your DSL connection’s Asynchronous Transfer Mode (ATM)
statistics. ATM is a networking technology that provides high-speed data transfer.
ATM uses fixed-size packets of information called cells. With ATM, a high QoS
(Quality of Service) can be guaranteed.
The (Segmentation and Reassembly) SAR driver translates packets into ATM cells.
It also receives ATM cells and reassembles them into packets.
These counters are set back to zero whenever the device starts up.
inPkts
is the number of good ATM cells that have been received.
inDiscards
is the number of received ATM cells that were rejected.
outPkts
is the number of ATM cells that have been sent.
outDiscards
is the number of ATM cells sent that were rejected.
inF4Pkts
is the number of ATM Operations, Administration, and Management
(OAM) F4 cells that have been received. See ITU recommendation I.610 for more
on OAM for ATM.
outF4Pkts
is the number of ATM OAM F4 cells that have been sent.
inF5Pkts
is the number of ATM OAM F5 cells that have been received.
outF5Pkts
is the number of ATM OAM F5 cells that have been sent.
openChan
is the number of times that the ZyXEL Device has opened a logical DSL
channel.
closeChan
is the number of times that the ZyXEL Device has closed a logical DSL
channel.
txRate
is the number of bytes transmitted per second.
rxRate
is the number of bytes received per second.
ATM Loopback
Test
Click this to start the ATM loopback test. Make sure you have configured at least
one PVC with proper VPIs/VCIs before you begin this test. The ZyXEL Device
sends an OAM F5 packet to the DSLAM/ATM switch and then returns it (loops it
back) to the ZyXEL Device. The ATM loopback test is useful for troubleshooting
problems with the DSLAM and ATM network.
DSL Line Status
Click this to view statistics about the DSL connections.
noise margin downstream
is the signal to noise ratio for the downstream part of
the connection (coming into the ZyXEL Device from the ISP). It is measured in
decibels. The higher the number the more signal and less noise there is.
output power upstream
is the amount of power (in decibels) that the ZyXEL
Device is using to transmit to the ISP.
attenuation downstream
is the reduction in amplitude (in decibels) of the DSL
signal coming into the ZyXEL Device from the ISP.
Discrete Multi-Tone (DMT) modulation divides up a line’s bandwidth into sub-
carriers (sub-channels) of 4.3125 KHz each called tones. The rest of the display is
the line’s bit allocation. This is displayed as the number (in hexadecimal format) of
bits transmitted for each tone. This can be used to determine the quality of the
connection, whether a given sub-carrier loop has sufficient margins to support
certain ADSL transmission rates, and possibly to determine whether particular
specific types of interference or line attenuation exist. Refer to the ITU-T G.992.1
recommendation for more information on DMT.
The better (or shorter) the line, the higher the number of bits transmitted for a DMT
tone. The maximum number of bits that can be transmitted per DMT tone is 15.
There will be some tones without any bits as there has to be space between the
upstream and downstream channels.
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