Option: Mapping Layer 2 Protocol Control Information into a Layer 2 Circuit
The control word is defined in Internet draft draft-martini-l2circuit-encap-mpls-07.txt Encapsulation Methods for Transport of Layer 2 Frames Over IP and MPLS Networks. It is a set of fields that carry Layer 2 control information across a Layer 2 circuit. The following control word support is available for PE routers:
Frame Relay—To carry Frame Relay FECN/BECN information in a Layer 2 circuit control word, include the
translate-fecn-and-becnstatement at the[edit interfaces interface-name encapsulation frame-relay-ccc unit unit-number encapsulation frame-relay-ccc family ccc]hierarchy level. To carry Frame Relay DE information in a Layer 2 circuit control word, include thetranslate-discard-eligiblestatement at the[edit interfaces interface-name encapsulation frame-relay-ccc unit unit-number encapsulation frame-relay-ccc family ccc]hierarchy level.[edit] interfaces {interface-name{ encapsulation frame-relay-ccc; unit 0 { encapsulation frame-relay-ccc; point-to-point; dlci 512; family ccc { translate-fecn-and-becn; translate-discard-eligible; } } } }ATM AAL5 mode—For ATM2 IQ interfaces, the ATM AAL5 control word contains bit fields to carry sequence numbers, ATM cell loss priority (CLP), and explicit forward congestion indication (EFCI) information. When you configure ATM Layer 2 circuits, the control word carries the sequence number, CLP, and EFCI information by default. No additional configuration is necessary.
ATM cell-relay mode—For ATM2 IQ interfaces, the ATM cell-relay control word supports sequence number processing only. Once you configure a cell-relay mode Layer 2 circuit, the sequence number information is carried by default. No additional configuration is necessary.