The Volpe Firm, Inc

The Volpe Firm, Inc.

Advanced Troubleshooting in a DOCSIS 3.0 Plant

Brady Volpe Walter MillerJDSU

Advanced Field TroubleshootingWhy is DOCSIS 3 Troubleshooting Different?

Multiple Bonded Channels• Downstream

– Not that different. – The channels are constant carrier– Multiple downstream channels have been around forever

• Upstream– Still most vulnerable portion of plant– The modem is no longer limited to a single upstream transmit path– In some ways this is actually easier with DOCSIS 3.0

Partial Service One or more upstream or downstream channels become unusable Partial service does not necessarily impact subscriber Can be viewed as an advantage from a network operations POV Hard to detect after CM registration

If the channel is down when the modem registers:– Will not cause performance issues, unless US is at maximum utilization– The errors for the “down” channel(s) are reported to the CMTS in the REG-ACK– D3.0 test equipment will show fewer channels bonded that expected

If the channel is down after the modem registers:– Data loss until CMTS realizes that Ch is unusable (~1 min – 15xT3 timeouts)– T4 Timeout > CMTS stops granting transmit opportunities – CMTS vendors handle re-acquisition differently (it is a SHOULD requirement)

Impaired Service One or more channels are experiencing RF channel impairments

– Presence of codeword errors is one way to identify an impaired channel

Channel impaired when ranging ok, but data becomes corrupted What would we say about impaired service:

– Impaired service impacts subscriber performance and quality of experience (QoE)– It is easy to detect impaired service– Throughput can be a good test for this, but not in all cases– High volume Packetloss is the most effective test to detect impaired service

Customer complaints likely to generate a ticket:– VoIP issues (robo-voice, dropped words, dialing issues, dropped calls, etc.)– VOD – cannot retrieve movie, cannot interact with Guide– Gaming issues – latency, interactivity issues– VPN issues – calling, two-way video, desktop sharing, VPN dropping, etc.– File Sharing/Transfer/FTP Upstream – very slow upstream transfers

Advanced Field TroubleshootingEvaluating the Downstream Quality

Use traditional PHY attributes• MER• BER• DQI

Use traditional Service Layer attributes• PacketLoss• Throughput

Advanced Field TroubleshootingEvaluating the Upstream Quality

To troubleshoot the field, look in

the headend!

Partial Service Troubleshooting

Partial Service manifests as missing channels. Does not demonstrate Packetloss or Throughput

Impaired Service TroubleshootingAn impaired service may or may not exhibit codeword errors and packetloss

When troubleshooting impaired service, it is critical to view the performance of the individual upstream channels.

Impaired Service Troubleshooting

Impaired Service Troubleshooting

Impaired Service Troubleshooting

Impaired Service Troubleshooting

Impaired Service Troubleshooting

Obviously there is an issue with the channel at 19 MHz

Utilize this method to traverse the network and find the impairment causing this issue

Summary Partial Service

• Tremendous Operational Advantage• Can go unnoticed

Impaired Service• Can be difficult to troubleshoot without the right tools

Many Impairments not detectable with• Packetloss• Throughput

Best Practice• Utilize tools that allow the simultaneous testing of bonded

upstream channels at a PHY layer

Q&A