LND describegraph returns channels with null policies

Question

The describegraph command for lncli returns several channels that have at least one policy set to null. In many cases, they are both set to null, and last_update is set to 0, as shown in the following example.

{
    "channel_id": "754441998110162945",
    "chan_point": "cb9eb6ae3f285da7cd120a83db7ceca4fee2c19eb72513530646e1bd340e1663:1",
    "last_update": 0,
    "node1_pub": "0227e8baab7b4397a88ea2bb3976a7fc8f975aa4fc28ef9272a33b6a1291ffff63",
    "node2_pub": "03864ef025fde8fb587d989186ce6a4a186895ee44a926bfc370e2c366597a3f8f",
    "capacity": "480000",
    "node1_policy": null,
    "node2_policy": null
}

How is null supposed to be interpreted?

The channel above has a page on 1ML. It shows channel policies for both peers. Why do the results I get show null for both peers?

score 0 · Accepted Answer · answered Jan 25 '23 at 16:18

I cannot know for sure the reason for this behavior but given the inner workings of the Gossip Protocol there is a high likelihood that the following is the reason.

Channels are anounced via the channel_announcement message. These messages contain more or less the information that you saw in your output. The capacity is not part of the message but retrieved by looking at the bitcoin node for the chan_point which is the funding transaction id and the output of the funding tx of the channel.

Nodes then independently send out channel_updates that contain their own routing policies. So what can happen is that your lightning node is new and has already received the channel announcement but no channel_update yet. Another possibility is that 1ML shows some old values of a channel update which your newis node may not see. This could happen if the the peers of the channel have been offline for some time or not sending out channel_updates for some time as nodes on the lightning network will only gossip channel_updates that are younger than two weeks. So in case there was no channel update within the last 14 days you will only get to see the announcement. There could be many other reasons if you want to digg deeper I suggest to read either BOLT 07 of the spec or the gossip chapter of mastering the Lightning Network.

LND describegraph returns channels with null policies

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