metadata along with payment within LN

Question

Is it possible to send metadata along with a standard invoice payment within a Lightning network?

Trying to find out if it is possible to distribute some sort of tokens(side chain) while paying with satoshis.

Answer 1

Yes it is possible.

All lightning messages have a space dedicated to optional messages in tlv encoding format. There is much documentation on this and many optional lighting based protocols are built using this space in the message.

See sphinx chat, impervious.ai, amp, etc

For some existing explanations:

• Explanation on tlv extensions
• Available size in tlv extensions