smom-dbis-138/docs/operations/integrations/CCIP_FEES.md

CCIP Fees

Overview

CCIP messages require LINK tokens to pay for cross-chain message delivery. This document explains how fees are calculated and managed.

Fee Calculation

CCIP fees are calculated based on:

1. Message Size: Larger messages cost more
2. Target Chain: Different chains have different fee rates
3. Gas Price: Current gas prices on target chain
4. Token Type: Native tokens vs LINK tokens

Calculating Fees

Use the calculateFee() function to get the required fee:

CCIPSender sender = CCIPSender(senderAddress);
uint256 fee = sender.calculateFee(targetChainSelector, messageData);

Fee Payment

Fees are paid when sending the message:

sender.sendOracleUpdate{value: fee}(targetChainSelector, receiverAddress, messageData);

Fee Estimation

Typical Fees (as of 2024)

• Small message (< 100 bytes): ~0.01-0.05 LINK
• Medium message (100-500 bytes): ~0.05-0.2 LINK
• Large message (> 500 bytes): ~0.2-1.0 LINK

Note: Fees vary by chain and network conditions

Managing LINK Balance

Check Balance

IERC20 linkToken = IERC20(LINK_TOKEN_ADDRESS);
uint256 balance = linkToken.balanceOf(address(this));

Transfer LINK

# Transfer LINK to sender contract
cast send $LINK_TOKEN "transfer(address,uint256)" $SENDER_CONTRACT $AMOUNT \
  --rpc-url $RPC_URL --private-key $PRIVATE_KEY

Approve Spending

IERC20 linkToken = IERC20(LINK_TOKEN_ADDRESS);
linkToken.approve(senderAddress, amount);

Fee Monitoring

Monitor fee consumption:

• Track total fees spent
• Monitor fee per message
• Alert on high fee usage
• Set fee budgets

Metrics

• ccip_fees_total: Total LINK spent on fees
• ccip_fees_per_message: Average fee per message
• ccip_fee_errors: Failed transactions due to insufficient fees

Cost Optimization

1. Minimize Message Size

• Use efficient encoding
• Remove unnecessary data
• Compress data when possible

2. Batch Updates

• Combine multiple updates into one message
• Reduce number of messages sent
• Lower total fee cost

3. Monitor Gas Prices

• Send during low gas price periods
• Use gas price oracles
• Schedule updates strategically

4. Use Native Tokens

• Some chains support native token payments
• May be cheaper than LINK in some cases

Fee Limits

Set maximum fee limits to prevent excessive spending:

uint256 constant MAX_FEE_PER_MESSAGE = 1 ether; // 1 LINK

require(fee <= MAX_FEE_PER_MESSAGE, "Fee too high");

Refunds

CCIP may refund unused fees if:

• Message fails to deliver
• Target chain is unavailable
• Message is rejected

Check refund status in transaction logs.

Troubleshooting

Insufficient LINK

Error: "Insufficient LINK balance"

Solution:

1. Check LINK balance
2. Transfer more LINK tokens
3. Verify token address is correct

Fee Too High

Error: "Fee exceeds limit"

Solution:

1. Reduce message size
2. Wait for lower gas prices
3. Increase fee limit (if appropriate)

Fee Calculation Failed

Error: "Failed to calculate fee"

Solution:

1. Verify CCIP Router is accessible
2. Check target chain selector is valid
3. Ensure router is properly configured

Best Practices

1. Maintain Buffer: Keep 2-3x expected fees in balance
2. Monitor Regularly: Check fee consumption daily
3. Set Alerts: Alert on low balance or high fees
4. Budget Planning: Plan for fee costs in operations budget
5. Test Fees: Test fee calculation in staging environment

References

• CCIP Integration Guide
• CCIP Router Setup
• Chainlink CCIP Fees