In Safire, error percentage is defined as the ratio between the sum of TCP retransmission and UDP loss and the total number of transmitted packets.
The TCP retransmission includes:
- TCP SYN retransmissions, indicating that the firewall fails to establish TCP connection before the request timeout occurs.
- TCP fast retransmissions, indicating that transmitted packets are not received by the receiver due to packet loss caused by the congested firewall.
- FIN retransmissions
- Out-of-order packets
- Duplicated ACKs