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LDP Graceful Restart for Pseudowire

LDP Graceful Restart for Pseudowire. draft-jiang-pwe3-ldp-gr-01.txt. Kan. Hu Jian. Luo Bo. Wu ZTE Corporation. Introduction. LDP graceful restart mechanism defined in [RFC 3478] can be applied to pseudowire graceful restart.

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LDP Graceful Restart for Pseudowire

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  1. LDP Graceful Restart for Pseudowire draft-jiang-pwe3-ldp-gr-01.txt Kan. Hu Jian. Luo Bo. Wu ZTE Corporation

  2. Introduction • LDP graceful restart mechanism defined in [RFC 3478] can be applied to pseudowire graceful restart. • Pseudowire graceful restart (GR) mechanism can be optimized by extending capability negotiation in [RFC 3478] .

  3. Problem statement (I) Pseudowire • PE1 support both LSP-FEC and PW-FEC graceful restart. • PE2 only support graceful restart for LSP-FEC. • Through Fault Tolerant (FT) Session TLV in the LDP Initialization message, negotiated result is: • PE1 will assume PE2 also supports graceful restart for both LSP-FEC and PW-FEC. • PE2 will assume PE1 only supports graceful restart for LSP-FEC. AC AC CE1 CE2 PE1 PE2

  4. Problem statement (II) Pseudowire • PE2 restarts its control plane. • PE1 detects that its LDP session with a neighbor went down. • PE1 retains the LSP-FEC and PW-FEC label bindings, and continue traffic forwarding. • PE2 will not retain PW-FEC in the data plane, and remove the label and PW-FEC binding. • The traffic black hole will be caused on PE1 until recovery time out AC AC CE1 CE2 PE1 PE2 LSP&PW GR LSP GR

  5. Problem statement (III) Pseudowire Black hole time = PE1 LDP session established time + Minimum {FT Recovery Time, Maximum Recovery Time} AC AC CE1 CE2 PE1 PE2 LSP&PW GR LSP GR

  6. LDP graceful restart capability encoding • FT FEC type TLV 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0| FT FEC type TLV (tbd) | Length (= 4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F| Reserved | FEC Element | Reserved | | | Flag | Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ • This draft defines FT FEC type TLV to indicate the FEC element type that support graceful restart. • FEC element type: One octet FEC Element Type that specifies the FEC Element Type that supports graceful restart. Please see section 3.4.1 of RFC5036, and RFC4447.

  7. LDP graceful restart capability encoding • Several FT FEC type TLVs can be appended behind FT Session TLV • Each FT FEC type TLV will carry a FEC element type which indicates the FEC that support graceful restart. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0| FT Session TLV (0x0503) | Length (= 12) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FT Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FT Reconnect Timeout (in milliseconds) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Recovery Time (in milliseconds) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0| FT FEC type TLV (tbd) | Length (= 4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F| Reserved | FEC Element | Reserved | | | Flag | Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ................. | ~ ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0| FT FEC type TLV (tbd) | Length (= 4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F| Reserved | FEC Element | Reserved | | | Flag | Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  8. PE operation during restart with the extension Pseudowire • PE1 detects that its LDP session with PE2 went down. It already knew that the neighbor is only capable of preserving its LSP-FEC forwarding state across the restart By negotiating through FT FEC type TLV. • PE1 will delete the PW-FEC and label binding immediately, but it will retains the LSP-FEC and label bindings received via that session and marks them as "stale". • PE1 will notify CE1 that network side is down, and CE1 will not send traffic toPE1. AC AC CE1 CE2 PE1 PE2 LSP&PW GR LSP GR

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

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