The Volpe Firm, Inc.
Advanced Troubleshooting in a
DOCSIS 3.0 Plant
Brady Volpe Walter MillerJDSU
Advanced Field Troubleshooting
Why 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 Troubleshooting
Evaluating the Downstream QualityUse traditional PHY attributes
• MER• BER• DQI
Use traditional Service Layer attributes• PacketLoss• Throughput
Advanced Field Troubleshooting
Evaluating 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
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