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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

Pseudowire freeze mechanism

draft-jin-pwe3-pw-freeze-00

Lizhong Jin

Bhumip. Khasnabish

requirements
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.
problem statement i

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.
problem statement ii
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.
problem statement iii
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.
pw freeze status encoding
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.
pw freeze status signaling
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].
pe operation
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.
next steps
Next steps
  • Need comments from work group

Thank you