+ /// The number of blocks such that if:
+ /// `incoming_htlc.cltv_expiry < outgoing_htlc.cltv_expiry + cltv_expiry_delta`
+ /// then we need to fail the HTLC backwards. When forwarding an HTLC, cltv_expiry_delta determines
+ /// the outgoing HTLC's minimum cltv_expiry value -- so, if an incoming HTLC comes in with a
+ /// cltv_expiry of 100000, and the node we're forwarding to has a cltv_expiry_delta value of 10,
+ /// then we'll check that the outgoing HTLC's cltv_expiry value is at least 100010 before
+ /// forwarding. Note that the HTLC sender is the one who originally sets this value when
+ /// constructing the route.