ce Affecting (SA) DS3 LOS/HBER DS3 Out-of-Frame DS3 AIS Received DS3 IDLE Received DS3 Equipment Failure-Non Service Affecting (NSA) Common Equipment Failure (NSA) Multiple DS1 LOS/HBER DS1 Equipment Failure (SA) Single DS1 LOS/HBER DS1 Equipment Failure (NSA) FEAC codes are shown in the output of the show controllers command. Framing Clear-Channel DS3 Framing Data links require the full capacity of the DS3 without any individual channels, as shown in Figure 21-4. Framing is still required, and either C-bit or M13 framing can be used to maintain clock synchronization between the two ends. The M12 and M23 steps are not needed, however, and nor are the overhead bits introduced by them. These bits are used for pure data. DS1 #01 11011 Channelized DS3 DS1 #01 11011 DS1 #02 10011 DS1 #02 10011 DS1 #27 11100 DS1 #27 11100 DS1 #28 00101 DS1 #28-00101 Clear-Channel DS3 11011 11011 Figure 21-4. Channelized versus clear-channel DS3 Because there's no multiplexing overhead, the amount of bandwidth available over a clear-channel DS3 is 44.2 Mbps. When using a DS3 for data links, C-bit framing should be used to gain the benefits of increased error reporting outlined previously. Line Coding DS-3 links support Alternate Mark Inversion (AMI), Bipolar Three Zero Substitution (B3ZS), and High-Density Bipolar Three (HDB3) line coding. AMI is the same as the AMI used on T1s, discussed in Chapter 20. B3ZS is similar to B8ZS, also discussed in Chapter 20, except that it replaces occurrences of three rather than eight consecutive zeros with a well-known bipolar violation. HDB3 is used primarily in Japan and Europe. The default line coding on Cisco DS3 interfaces is B3ZS. When using chan- nelized DS3s, the line coding may be AMI, depending on how the circuit was ordered. Usually B3ZS is preferred. Configuring DS3s Recall that there are two flavors of DS3: clear-channel and channelized. Typically, clear-channel DS3s are used for data links, and channelized DS3s are used for voice links. The configurations in this section assume an integr