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Pseudowire freeze mechanism

Pseudowire freeze mechanism . draft-jin-pwe3-pw-freeze-00 Lizhong Jin Bhumip. Khasnabish. Requirements. Several PW high availability mechanism Pseudowire redundancy mechanism PSN tunnel protection technology

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Pseudowire freeze mechanism

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  1. Pseudowire freeze mechanism draft-jin-pwe3-pw-freeze-00 Lizhong Jin Bhumip. Khasnabish

  2. Requirements • Several PW high availability mechanism • Pseudowire redundancy mechanism • PSN tunnel protection technology • For the PW control plane failure, using above high availability methods will bring: • Additional resources to backup • High provisioning cost • For the case when many PWs are down due to signaling failure which is coursed by sharing same fate of signaling session: • It is a burden or pressure for the network to switch all affected PWs to the backup at the same time. • MPLS-TP is required that the data and control planes are both logically and physically separated.

  3. T-LDP Session Router CE1 PE1 PE2 CE2 AC AC TE-Tunnel PW Problem statement (I) • In some network of deploying PW, the signaling path is different from the data transmission path. • See the figure above, T-LDP session has different path with TE-Tunnel path (setup by strict ERO). • In this case, the failure of T-LDP session should not influence the pseudowire data traffic.

  4. Problem statement (II) • Problem statement • According to the LDP procedure [RFC5036], if the T-LDP session is DOWN, the corresponding traffic is interrupted. • When graceful restart [RFC3478] is enabled on this T-LDP session, PE will not interrupt the PW traffic for a time within the time of "reconnect time“. • The maximum value of "reconnect time" is 4294967.295 seconds, or 49.7 days, not infinite. • Sometimes, operators need more flexible configuration, and only want some of the PWs not to be influenced by T-LDP session status, so as to provide different availability level of service.

  5. Problem statement (III) • The PW freeze mechanism aims to: • Provide a function for PW not to be influenced by the turbulence of control plane. • When the PW supports “freeze" function and is operational UP: • It will not be influenced by the turbulence of control plane.

  6. PW freeze status encoding • PW freeze status is encoded in PW status TLV: 0x00000080 (to be assigned by IANA). • When the PW freeze bit is set, • it indicates that the PW supports "freeze" function, and will be in "freezed" state. • When the PW freeze bit is cleared, • it indicates that the PW will be in "unfreeze" state. • When the PW is configured as "freeze“, PE SHOULD advertise the capability when: • Sending label mapping message carrying the PW status TLV with "PW freeze bit" set • Sending LDP notification message carrying the PW status TLV with "PW freeze bit" set.

  7. PW freeze status signaling • When one of the PW endpoint signals PW status with PW freeze bit cleared • both of the two endpoints should unfreeze the PW. • When PW is already in "freeze" state • the PW status should be transmitted through G-ACH, as defined in [I-D. draft-ietf-pwe3-static-pw-status-00].

  8. PE operation • If PW supports "freeze" function through negotiation: • When PW is operational UP • PW will enter into the freezed state. • The PE should locally store the PW information that received from the peer node, including PW type, PW label and etc. • When T-LDP session is DOWN, the PE should continue the PW data forwarding.

  9. Next steps • Need comments from work group Thank you

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