Introduction of CES Services on Huawei Optix OSN equipment

The circuit emulation service (CES) helps to solve the problem of insufficient optical fiber resources in the access ring and allows TDM services to be transparently transmitted across the pure packet mode.

At the physical layer on the UNI side, Huawei OptiX OSN equipment is interconnected with a CE through the following physical channels for accessing CES services:

• Channelized STM-1
• E1

Figure 1 Networking diagram of the CES 

As shown in Figure 1, the OptiX OSN equipment can gain access to CES services at emulation node 1, emulation node 2, or emulation node 3.

• At emulation node 1, the OptiX OSN 1500 transmits E1 services to the GE packet ring.
• At emulation node 2, the OptiX OSN 3500, OptiX OSN 7500 or OptiX OSN 7500 II transmits E1 signals that are received from the BTS through TDM STM-1/STM-4 ring to the 10GE packet ring.
• At emulation node 3, the OptiX OSN 3500, OptiX OSN 7500 or OptiX OSN 7500 II converts E1 CESs on the 10GE packet ring into STM-1 signals and then sends them to the BSC.

The OptiX OSN equipment supports both structure-aware TDM circuit emulation service over packet switched network (CESoPSN) and structure-agnostic TDM over packet (SAToP). Installation guide like OSN 3500 configuration guide can be found in the Hedex files.

In the case of CESoPSN, the features are as follows:

• The equipment is aware of frame structures, frame alignment modes, and timeslots in TDM circuits.
• The equipment processes the overheads in and extracts the payloads from the TDM frames. Then, the equipment loads timeslots to the packet payload in a specific sequence. As a result, the services in each timeslot are fixed and visible in packets.

In the case of SAToP, the features are as follows:

• The equipment is agnostic about the structures of the TDM signals. To be specific, the equipment treats TDM signals as constant bit-rate (CBR) flows, and emulates all the TDM signals in the same way.
• The overheads and payloads in TDM signals are transparently transmitted.