# External relays

The Asterizm Protocol has been designed to allow not only internal off-chain modules but also external services to act as [relays](/infrastructure/asterizm-relayer.md). These external relays can be trusted services that have undergone protocol audits and have set up the necessary infrastructure.

Each relay has the authority to establish its transfer fee in the native currency of the network. All relay data is stored on-chain, making this information accessible to everyone.

Every client is free to choose which relay they want to use for sending confirmations of their transfers (**`transferHash`**). To do this, the client should invoke the method <mark style="color:orange;">`setExternalRelay(address _externalRelay)`</mark> on their [client contract](/infrastructure/asterizm-connector/client-smart-contract-abstraction.md).&#x20;

{% hint style="warning" %}
IMPORTANT!&#x20;

A client can only set the address of an external relay once. If they attempt to call the method again, the contract will return an error.

Please exercise caution when configuring this parameter because once set, you cannot change it or revert to the "default" relay. You will need to redeploy contracts if you wish to make changes in this regard.
{% endhint %}


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