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ESMC - extended QL TLV

asked 2020-01-10 10:04:06 +0000

Argus gravatar image


According G.8264/Y.1364 if a clock in an option 1 network supports both the QL TLV and the extended QL TLV, it should set the SSM code and the enhanced SSM code according, and send both the QL TLV and the extended QL TLV. Both TLVs shall be sent in one ESMC PDU.

In wireshark QL TLV is ok. TLV Type, TLV length and SSM Code are as expected.

But I'm having a problem with extended QL TLV saying that Timestamp is invalid?!

Accoring to this table from G.8264 4. octat number of extended QL TLV should represent enhanced ssm code which is in this case 20, but as you can see from first picture that octate (and 3 more following) are assigned to Timestamp!?

Does someone knows is Wireshark supporting extended QL TLV, or the problem is in something else?

Link to a .pcap file:

Best regards

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The length is hard coded:


And looks like it has been a while since last worked on:

Chuckc gravatar imageChuckc ( 2020-01-10 17:39:56 +0000 )edit

Hello, can you please tell me what is the need for an enhanced SSM code?

lokesh.sharma gravatar imagelokesh.sharma ( 2021-12-08 07:54:03 +0000 )edit

The G.8264 standard has evolved to include a new set of more accurate reference clocks and the ESMC values needed to expand to include them. They have also added features to keep track of the chain of connection between the reference source: such as how many hops have been crossed, and what is the quality of those hops. This means that they added a TLV, which the dissector seems to get wrong.

Dennis at Cisco gravatar imageDennis at Cisco ( 2022-09-13 10:30:15 +0000 )edit

Hello Dennis, According to G.8264.1 the enhanced SSM code does not go into the selection process, still, the extended QL TLV has an SSM code. Second, what purpose does it really solve by having so many new parameters? 1. Hop count: I do agree. But if any device does not support extended QL TLV, hop-count will not work. Please let me know if I am wrong. 2. Quality of those hops: As far as I understood, the parameters can only provide you with the source quality level. I am waiting for your reply. thanks in advance.

lokesh.sharma gravatar imagelokesh.sharma ( 2022-10-03 07:10:58 +0000 )edit

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answered 2020-01-10 18:05:28 +0000

Jaap gravatar image

This warrants a bug report here. Please attach the capture file to the bug as well.

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Hi, this looks a bit old, but I've struck the same issue. I'll file a bug report.

Dennis at Cisco gravatar imageDennis at Cisco ( 2022-09-13 10:28:08 +0000 )edit

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Asked: 2020-01-10 10:04:06 +0000

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Last updated: Jan 10 '20