Disable the Control Word for Layer 2 Circuits

To emulate the VC encapsulation for Layer 2 circuits, a 4-byte control word is added between the Layer 2 PDU being transported and the VC label that is used for demultiplexing. Various networking formats (ATM, Frame Relay, Ethernet, and so on) use the control word in a variety of ways.

The JUNOS software supports the control word for Frame Relay. However, it does not support the control word for any other networking format, meaning that it is not fully compliant with the Internet draft in cases where the control word is mandatory. To be minimally compliant with the Internet draft, the JUNOS software supports a null control word (a control word of all zeros). If the JUNOS software receives a packet with a control word attached, the control word is discarded before the packet is forwarded to its destination.

The JUNOS software can typically determine whether a neighboring router supports the control word. However, if you want to explicitly disable its use on a specific interface, include the no-control-word statement:

no-control-word;

For a list of hierarchy levels at which you can configure this statement, see the statement summary section for this statement.