Introduction

Definition

DCC transmission through external clock ports is a DCN solution provided by Huawei. In this solution, DCC bytes are output through an external clock port to a specified E1 port. Third-party equipment transmits the signals as common E1 services.

There are two networking scenarios for the DCC transmission through external clock ports solution:

• Direct access mode

  An NE is directly connected to a third-party network using an external clock port.

  Figure 1 provides a networking example of the direct connection mode. In this example, the third-party network is a PDH network that provides E1 ports for the OptiX NEs on both sides. In this case, you can directly connect an E1 cable that connects to an external clock port to the third-party network. The third-party network then transmits the E1 service as an ordinary service. DCC bytes are transparently transmitted between the two NEs. A special application of the direct connection mode is to use an E1 cable to directly connect the external clock ports of two OptiX NEs.

  Figure 1 Networking example for DCC transmission through external clock ports (direct connection mode)
  
  

• Indirect connection mode

  An NE is connected to a third-party network using a service port.

  Figure 2 provides a networking example of the indirect connection mode. In this example, the third-party network is an SDH/PDH hybrid network. PDH signals are transmitted on the transmission path although the network provides SDH optical ports for the OptiX NEs on both sides. In this case, first use an E1 cable to connect the external clock port to an E1 port of an E1 tributary board, and then configure cross-connections between the E1 service and the line board. The E1 service is transmitted to the third-party network through an SDH port. The third-party network then transmits the E1 service as an ordinary service. In this manner, DCC bytes are transparently transmitted between the two NEs.

  Figure 2 Networking example for DCC transmission through external clock ports (indirect connection mode)
  
  

Purpose

DCC transmission through external clock ports is preferred as the DCN solution when the third-party network does not support the transmission of DCC bytes but supports the transmission of E1 services.