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Linkedin query on OSC/GCC/DCC...answered by me:-

Query on Linkedin:Wondering about the difference in use of the OSC and GCC in OTN+WDM systems

First thing I would like to share is that transport equipment typically contains integrated external DCN ports for standalone management. However, as the network infrastructure equipment continues growth with remote locations, it may not be feasible to have a local external DCN network at each and every remote site. Thus OSC/GCC/DCC can provide a cost-effective in-band/Outband data communications link back to a gateway NE (GNE) and back to a centralize network management stations for remote maintenance from customer NMS/OSS. 

Now brief on GCC. 
GCC are general Communication channel used in OTN. 

In OTN, the GCC0 is used on the OTU overhead while GCC1 and GCC2 are used from the ODU overhead. GCC0 provides terminal-regen and regen-regen communications. GCC1/GCC2 provides direct terminal-terminal communications.It allows an in-band management solution between various elements in network.As they are inband communication mechanism,bytes inside frame are responsible for the communication as different levels as in case of DCC in SDH/SONET. 

Now brief on OSC 

ITU-T G.692,defines OSC.As we donot have framing concept for DWDM rather it acts as a carrier we require some outband communication systems for maintenace and remote operation.OSC is generated from special supervisory cards that are capable to transmit communication information over bandwidth say 2Mbps,155Mbps etc.Bandwidth rate is vendor specific. 

Again question arises what is OSC? 

The OSC is carried on a separate wavelength, different from the wavelengths carrying the actual traffic.It is separated from the other wavelengths at each amplifier stage and received, processed, and retransmitted, 

The OSC provides an out-of-band, full-duplex communications channel for remote node management, monitoring and control similar to the Data Communications Channel (DCC) of SONET/SDH and the General Communications Channel (GCC) of OTN. The OSC optically segregates network management and control from user data, so even if the OSC is lost, data forwarding continues uninterrupted. 

For WDM systems operating in the C-band, the popular choices for the OSC wavelength include 1310 nm, 1480 nm, 1510 nm, or 1620 nm. Using the 1310 nm band for the OSC precludes the use of this band for carrying traffic. 

Both functionality/working principles are part of ITU-T standards. 


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