Chapter 25 xDSL Statistics
VMG1312-B Series User’s Guide
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The following t able describes t he labels in t his screen.
Table 97 Status > xDSL St at istics
LABEL DESCRIPTION
Refr esh I nter val Select the tim e int erval for refreshing statist ics.
Line Select which DSL line’s st at istics you want t o display.
xDSL Training
St atus
This displays the current state of sett ing up t he DSL connection.
Mode This displays t he I TU st andard used for this connect ion.
Traffic Type This displays the t ype of traffic the DSL port is sending and receiving. I na ct ive displays if
the DSL port is not currently sending or receiving t raffic.
Link Uptim e This displays how long t he port has been running (or connected) since the last time it was
st arted.
xDSL Port Det ails
Upstream These are t he stat istics for t he traffic direction going out from the por t to t he service
provider.
Downstream These are t he statist ics for t he traffic direction com ing int o the port from the service
provider.
Line Rate These are the data transfer rates at which t he port is sending and receiving data.
Actual Net Data
Rat e
These are t he rat es at which the port is sending and receiving t he payload data without
transport layer pr ot ocol headers and traffic.
Trellis Coding This displays whether or not t he port is using Trellis coding for traffic it is sending and
receiving. Trellis coding helps to reduce t he noise in ADSL transm issions. Trellis m ay reduce
t hroughput but it m akes t he connection m ore stable.
SNR Margin This is t he upstream and downstream Signal- t o- Noise Rat io m argin ( in dB). A DMT sub-
carrier’s SNR is the ratio bet w een the r eceived signal power and t he received noise pow er.
The signal-t o- noise ratio m argin is the m axim um t hat t he r eceived noise power could
increase with the system still being able to m eet its transm ission t arget s.
Actual Delay This is t he upstream and downstream int erleave delay. I t is the wait (in m illiseconds) t hat
determ ines t he size of a single block of dat a t o be int erleaved ( assem bled) and t hen
t ransm itt ed. I nterleave delay is used when t ransm ission error correction (Reed- Solom on)
is necessary due to a less t han ideal telephone line. The bigger t he delay, t he bigger t he
data block size, allowing bet t er error correction to be perform ed.
Transm it Power This is the upst ream and downstream far end act ual aggregate t ransm it power (in dBm ) .
Upstream is how m uch power the port is using to t ransm it t o the service provider.
Downst r eam is how m uch port the ser vice provider is using to t ransm it to t he port.
Receive Power Upstream is how m uch power the service pr ovider is receiving fr om t he port . Downst ream
is how m uch power t he port is receiving from the service provider.
Actual I NP Sudden spikes in the line’s level of external noise ( im pulse noise) can cause er rors and
result in lost packet s. This could especially im pact t he quality of m ultim edia t raffic such as
voice or video. I m pulse noise protect ion ( I NP) pr ovides a buffer to allow for correction of
errors caused by err or correct ion to deal with t his. The num ber of DMT ( Discrete Multi-
Tone) sym bols shows the lev el of im pulse noise protection for the upst ream and
downstream traffic. A higher sym bol value prov ides higher error correction capability, but it
causes overhead and higher delay which m ay increase error rates in received m ultim edia
data.
Tot al Attenuation This is the upst ream and downstream line att enuation, m easured in decibels ( dB). This
att enuation is t he difference between t he power t ransm it t ed at the near-end and the pow er
received at t he far- end. Attenuation is affect ed by the channel characteristics ( wire gauge,
qualit y, condition and length of t he physical line).
At t ainable Net
Data Rat e
These are t he highest theoretically possible t ransfer rates at which the port could send and
receive payload dat a wit hout t ransport layer protocol header s and traffic.
xDSL Counters
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