FOT Topic: How to debug problems in GPON/EPON

When facing Bandwidth fluctuation in connection of PON

How to debug problems in PON

How to debug problems in PON

  Hello, can somebody help that why sometimes we face Bandwidth fluctuation in 100Mb connection of PON?

Methods 1: Ensure  that  all connections are clean and correct

Ensure that all connections are cleaned as standard for FOI guidelines. Any foreign bodies or grease from hands will cause laser and therefore bandwidth fluctuations. Ensure that FON is tested including splitter outputs. If network is thoroughly tested then check the OLT port output.

Methods 2: Collect as much diagnosing data as possible

Throughput issues are difficult to diagnose. Have you gone into your OLT’s EMS statistics pages? What about the edge router CLI? Home router/gateway? Are you seeing large queue depths? High packet drop rates? Large numbers of CRC errors and/or uncorrected FEC errors? Is the problem load sensitive? Do upstream and downstream load factor correlate?
If a simple investigation doesn’t yield an obvious cause, you’ll need expert help.

Methods 3: Check the uplink if is under-dimensioned or in heavy bandwidth

Good point.
Another reason may be that the uplink is under-dimensioned and when many users start using heavy bandwidth, they start experiencing speed fluctuations.

Methods 4: Try check the buffer bloat or interactions between TCP and the OLT’s upstream scheduler

You’re talking about TCP ACK issues. The rule of thumb for asymmetrical links is normalized bandwidth ratio no greater than 8:1. See the overview in RFC 3819, and RFC 3449 for deep analysis and mitigation techniques. This is not a diagnosis that I’d consider likely. Other TCP related issues, particularly buffer bloat or interactions between TCP and the OLT’s upstream scheduler, seem more likely.

Methods 5: Hints and different debugging way from another expert.

I would think the first thing to do is give a bit more information about the situation. If this is a lab exercise, things like diagnosing optical issues is probably of lower priority. If this is a field situation, it might be more so.
There could be a completely properly operating way for this to happen. DBA. It is not clear whether you have over-subscribed ODN. Another example could be PC problems at endpoints (spyware for example) which can cause temporary bandwidth issues. Heck it could be an ONT bug for all any of us know from the information you have given.
Those are just 2 of hundreds of things that I have seen. That is why more specificity about the situation you are talking about.

Methods 6: Comparing other premises (PON users) to debug

number of thing can affect speed … very first thing you should check all hardware which are installed in your premises and check only you are getting same problem or other users with same plan ….

Methods 7: Try configure CBR profile

you can configure CBR profile for access bandwidth at OLT

Methods 8: Losses on fiber can also effect bandwidth

losses on fiber can also effect bandwidth….If bandwidth is over utilized you may face this problem as well…. ensure QoS is properly defined at your end…… ensure proper service profile 100 mbps is defined on access and core side….There might be more parameters to check that why bandwidth is fluctuated

Methods 9: Check for macro and micro bending on your routes, even it can  be minimised…

In adition to the above comments check for macro and micro bending on your routes. Even a tie strap pulled to tightly or a fiber coiled beyond the bending radius in the splice closures etc. Also make sure you have the right fiber cables for the right applications. There really is a number of reasons but they can be minimised.

Methods 10: Consider that what Splitting ratio you are using

One more thing to be consider that what Splitting ratio are you using for 100 MB link your PON port should not be splitted more than 16 times …or may say better to use 1:2 at exchange end and at FDH end 2:8 splitter to be used for better bandwidth….

Methods 11: Are you facing high BER?

Are you facing high BER? Have you checked the speed with different packet sizes or with the same? what size of packets you used on the test? What QoS buffering techniques and token sizes are you adopting?

Methods 12: Detail of bandwidth fluctuation

How do you test your fluctuation of your bandwidth, what is your primary ( equipment side) and what is your secondary ( are you in OSP or ISP side)

Methods 13: Same issue with another GPON network case

I’m facing the same issue with our GPON network, for 10Mb and 20Mb duplex packages, the speed is within range for Upstream and Downstream. When it get to the 50Mb package, the Downstream is within the range of 48-56Mbps but Upstream is just 10% of the Downstream Maximum I can get when i carryout speed tests is 8Mb for Upstream.
What could be the possible explanation for this?

Methods 14: T-CONT Value

do you define any TCONT value …………………..
–>I created Traffic table with defined CIR, PIR, CBS and PBS values.

Methods 15: The very first thing you need to check is the FON

The very first thing you need to check is the FON. Check the OTDR test results from the handover from implementation and see if you have any bad connectors, splices, microbends. The higher the BW the greater the affects of any of the fluctuations. Ensure all connectors are cleaned before testing to eliminate cross contamination. The very easy way to check is with the OPM if it fluctuates on the dBm settings then you need to look at the FOC.

Methods 16: Rather than PHY or OTN issues, try check GTC, Ethernet/VLAN, IP and TCP issues

With those symptoms, I would be looking at GTC, Ethernet/VLAN, IP and TCP issues, rather than PHY or OTN issues. Particularly since the problem only seems to manifest at 100 Mb/s. Start by looking into the EMS for clues. Use a tool like Wireshark to capture and analyze at the TCP, IP and Ethernet layers. I’d particularly look at TCP for clues.
Collecting OLT Data

Collecting OLT Data

  –More discussions, welcome to share your ideas…

1 Comment
  1. Dear Team,

    I am using GPON HGU device on Huawei MA5603T GPON OLT. Is this device compatible with Huawei OLT? I tried by best but not able to make it operational. Is there any support that I can get it from here.

    Thanks and Regards.

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