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Introduction

Preferential Forwarding Status bit Definition draft-muley-dutta-pwe3-redundancy-bit-00.txt Praveen Muley, Pranjal K. Dutta, Mustapha Aïssaoui , Marc Lasserre, Matthew Bocci, Alcatel-Lucent Jonathan Newton, Cable & Wireless Olen Stokes, Extreme Networks Hamid Ould-Brahim, Nortel Networks.

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Introduction

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  1. Preferential Forwarding Status bit Definitiondraft-muley-dutta-pwe3-redundancy-bit-00.txtPraveen Muley, Pranjal K. Dutta, Mustapha Aïssaoui, Marc Lasserre, Matthew Bocci, Alcatel-LucentJonathan Newton, Cable & WirelessOlen Stokes, Extreme Networks Hamid Ould-Brahim, Nortel Networks

  2. Introduction • Two drafts described PW redundancy applications • draft-muley-pwe3-redundancy-00.txt • VPWS redundancy applications such as CE dual-homing and MS-PW redundancy • draft-pdutta-l2vpn-hvpls-standby-00.txt • VPLS redundancy applications such as MTU dual-homing in H-VPLS, inter-domain redundancy • Both proposed a solution based on signaling a new PW status bit referred to as ‘active/standby’ bit • Outcome of the discussion in IETF 67 was to: • combine VPWS and VPLS redundancy scenarios into a single draft (draft-muley-pwe3-redundancy-01.txt) • write a separate draft to specify the behavior of PE/T-PE nodes when sending or receiving the new status bit (this draft)

  3. Active state definition • A PW is considered to be in Active state when the PW labels are exchanged between its two terminating points in control plane and the corresponding data path is established • In this state data traffic can flow over the PW in both directions • A PW by default is always in Active state after it is set UP by signaling

  4. Standby state definition • A PW is considered to be in Standby state when the PW labels are exchanged between its two terminating points in the control plane but the data traffic is blocked at either or both the ends • In this state the blocked end(s) of the PW SHOULD NOT forward data traffic over the PW but MUST allow PW OAM packets, e.g, VCCV packets, to be sent and received

  5. Independent Mode of Operation • Synchronization of PW paths not mandatory • Asymmetric PW path forwarding is allowed • Each endpoint of the PW selects independently which PW to activate based on the specific application • endpoints advertise the resulting Active/Standby status over all PWs in the redundancy set using the new status bit • Each endpoint MUST select the PW which shows local Active and remote Active in preference to any other combination of local and remote forwarding states • If multiple PWs show Active/Active, then the PW to forward traffic to is a local endpoint decision • If not found, an endpoint MAY forward over a PW which shows other combination of forwarding states • However, the receiving end may discard the received packets • No error message is generated

  6. Independent Mode Use Case PE1 PE3 Standby PW Active Standby Standby AC CE 2 Active AC Active Standby CE 1 Standby PE2 Active Active PW PE4 Active AC Standby Standby AC Active Standby PW Dual-homing protocol

  7. Master/Slave Mode of Operation • Synchronization of PW paths mandatory • One PE/T-PE Master node and one or many PE/T-PE Slave nodes • Local configuration assigns Master/Slave roles • The Slave node SHOULD block forwarding over the PW when the Rx status bit transitions from Active to Standby • If it fails to block it, it does nothing • The Slave node MUST unblock forwarding over the PW when the Rx status bit transitions from Standby to Active • If it fails to unblock it, it generates a status bit of "PW not forwarding" back to the Master • Full state machine provided in the draft

  8. Master/Slave Mode Use Case • PE-rs nodes will replicate broadcast, multicast, and unicast unknown packets over active PW group only! PE1-rs (slave) PE3 Full Mesh VPLS Core Active PW Group MTU (master) Active Access PSN Standby PE2-rs (slave) PE4 Standby PW Group

  9. Interoperability with existing implementations • A T-PE/PE which does not implement the new active/standby status bit keeps a PW active as long as it is operationally up • It does not actively block forwarding over a PW • It does not act on active/standby status bit received from peers • For the operation of the VPWS and VPLS redundancy applications, all participating T-PE/PE nodes MUST implement the appropriate mode (independent or master/slave)

  10. Status Code for PW Preferential Forwarding Status • T-LDP Status Bit: 0x00000020 • When the bit is set, it indicates "PW forwarding standby" status • When the bit is cleared, it represents "PW forwarding active" status (default settings)

  11. Next Step • Authors would like to make this a WG document to request the new status bit allocation from IANA • Authors would like to request WG feedback on mailing list

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