# On-ledger Requests

Requests to the smart contract as transactions on the Tangle are called on-ledger requests. As they are simply posted by a transaction to the Tangle, they can be sent to any chain deployed on the Tangle without accessing a Wasp node. The IOTA Smart Contracts committee is actively monitoring the Tangle and will be aware of the request.

## Fees​

Fees charged by the IOTA Smart Contracts chain will be taken from this transaction, so be sure to send enough IOTAs to cover the fee, or the request will be rejected.

## Processing Order​

Requests are stored in the mempool and selected on a random batch selection. Because of this, the order of execution is not guaranteed. If a user needs a guaranteed sequence of processing, they should wait for a request to be processed before sending the following one.

## Fallback and Timelock Options​

By leveraging the ExtendedLockedOutput, it is possible to send requests with time constraints.

• fallback: By providing a deadline timestamp and a fallback address it is possible to post a request which, if not processed by the deadline, will not be picked-up by IOTA Smart Contracts, and the funds will be spendable by the fallback address.
• timelock: By providing a timelock timestamp it is possible to post a request which will not be picked up until the timelock timestamp is passed.