Cisco Systems, Inc. Networks may experience transmission bit errors due to various factors, such as poor fiber quality. This document describes extensions to IS-IS, OSPF, and BGP-LS to advertise the Bit Error Rate (BER) and Packet Error Rate (PER) metrics for the links that can be used for Traffic Engineering. Note that mechanisms for measuring bit errors or acting on that information, once advertised, are outside the scope of this document.