1. Pseudowire Control Word Negotiation Mechanism Analysis and Update draft-jin-pwe3-cbit-negotiation-01 1 PWE3 IETF79 Lizhong JinRaymond Key Thomas NadeauSimon Delord Vishwas Manral

2. Introduction This draft is an outcome from many face-to-face and email discussions with: –Stewart Bryant, Andrew Malis, Nick Del Regno, Sami Boutros, Luca Martini, Venkatesan Mahalingam, Alexander Vainshtein, Adrian Farrel, and etc. This draft describes the problem of control word negotiation mechanism specified in [RFC4447]. 2

3. Relations with other draft draft-delregno-pwe3-mandatory-control-word also solve the problem of control word negotiation, and briefly described in option 4 in this draft. 3

4. Problem Statement 4 CW: PREFERRED Label Map: Cbit=0 CW: NOT-PREFERRED Label Map: Cbit=0 CW: PREFERRED Label Map: Cbit=0 Configuration changed to Label Withdraw 1 According to the control word negotiation mechanism, the received label mapping on PE2 from PE1 indicates Cbit=0, therefore PE2 will still send label mapping with Cbit=0. 1 PW Negotiated Cbit=0 Wrong

5. Option 1: Control Word Re-Negotiation by Label Request 55 CW: PREFERRED Label Map: Cbit=0 CW: NOT-PREFERRED Label Map: Cbit=0 CW: PREFERRED Label Request Configuration changed to Label Withdraw PW Negotiated Cbit=0 PW Negotiated Cbit=1 Label Map: Cbit=1

6. Option 1: Control Word Re-Negotiation by Label Request When PE doing the CW changing operation, it should send label request to peer PE, even if it has already received the label mapping message. Request message processing for PW: –The request message should be processed in ordered mode in MS-PW case. –PE1 SHOULD send label mapping with locally configured CW parameter. Option1 is backward compatible. 6

7. Option 2: Make CW Non-Configurable –Default value is PREFERRED which can be degraded to NOT PREFERRED by negotiation automatically; –But: there is explicit requirement from service providers to allow control word to be configurable. 7

8. Option 3: Manual Configuration Process for CW 88 CW: PREFERRED Label Map: Cbit=1 CW: NOT-PREFERRED Label Map: Cbit=0 CW: PREFERRED Configuration changed to Label Withdraw PW Negotiated Cbit = 0 AND 1 = 0 PW Negotiated Cbit = 1 AND 1 = 1 Label Map: Cbit=1 1. Abandon the control word negotiation mechanism described in [RFC4447]; 2. Local PE should simply do “AND” operation between receiving CW with local configuration (PREFERRED or not-PREFERRED).

9. Option 4: Make CW Capability Mandatory –The PW will only be in operation UP when both PW end-points support control word capability. 9

10. Next steps Which option should be accepted? Need comments from work group Thank you 10