In the Lightning Network protocol, Hashed Time Locked Contracts (HTLCS) are used in the construction of channels. A new HTLC is required per route that the channel is serving in.
In BOLT #2, this maximum number of HTLCs in a channel is hard limited to 483 as the maximum safe size to prevent the transaction from being too large to be valid. In common software implementations such as LND, this limit is set much lower to 12 HTLCS. This is because accepting a larger number of HTLCS makes it more difficult for transactions to confirm during congested periods as they must pay hire fees.
Therefore, similarly to how congestion control is handled for normal
transaction, lightning channel updates can be done across an
tree, allowing nodes to safely use many more HTLCS.
Because each HTLC can have its own relative time lock in the tree, this also improves the latency senstivity of the lightning protocol on contested channel close.