This read-only enumerated attribute specifies whether this virtual channel connection is used to transport data(1) or voice(2). It tells an administrator the service class of a given VCC riding the OC-3 trunk, which matters for prioritizing troubleshooting of voice-carrying circuits. For example, an operator triaging a batch of VCC errors would prioritize investigating entries marked voice, since call quality issues are typically more time-sensitive than data throughput issues.