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IETF 62, Minneapolis 03/08/2005

Handling (G)MPLS-TE control plane saturation draft-leroux-ccamp-ctrl-saturation-00.txt Jean-Louis Le Roux (France Telecom) Jean-Yves Mazeas (France Telecom) Jean-Philippe Vasseur (Cisco) Sami Boutros (Cisco). IETF 62, Minneapolis 03/08/2005.

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IETF 62, Minneapolis 03/08/2005

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  1. Handling (G)MPLS-TEcontrol plane saturation draft-leroux-ccamp-ctrl-saturation-00.txt Jean-Louis Le Roux (France Telecom)Jean-Yves Mazeas (France Telecom)Jean-Philippe Vasseur (Cisco) Sami Boutros (Cisco) IETF 62, Minneapolis 03/08/2005

  2. Background and Motivations • Some MPLS-TE deployments may generate a large number of TE-LSPs • E.g. a full mesh of 300 PEs => more than 20 k RSVP sessions per LSR • RSVP sessions are quite memory consuming • Unfortunately LSR memory is not infinite  • There may be cases where an LSR runs out of memory, or more generally out of a specific control plane resource, and cannot support a new TE-LSP • This document defines (G)MPLS-TE routing and signaling extensions for a proper handling of such control plane saturation

  3. Overview • An LSR is said saturated when it runs out of a specific control plane resource and cannot handle any new TE-LSP • Various reasons for such saturation • Memory shortage • CPU overaload • The maximum number of LSPs configured by the operator is reached • … • Signaling extension so that a saturated LSR can properly reject any new TE-LSP, and notify the reasons for the rejection • Routing extensions so that an LSR can advertise its control plane status (saturated or not) • Routing and signaling extensions are complementary • Used as a trigger for head-end LSRs to take appropriate actions

  4. Signaling extension • A new RSVP ERROR code : Saturation • Several error sub-codes, indicating the reasons for the saturation (memory shortage, max LSP number reached…) • On receipt of a Path message for a new LSP, a saturated LSR should reject the LSP, and send back a PathErr, with the Saturation Error code • Such notification will allow head-end LSR taking appropriate action • E.g. recompute a path avoiding the saturated node • …

  5. Routing extension • Light ISIS and OSPF routing extensions for the advertisement of LSR status • New Saturation TLV • To be carried within the ISIS CAP TLV or the OSPF Router Info LSA • A set of bit flags informing about the LSR control plane status • Currently one bit defined: S : Saturation • A Saturated LSR should set the Saturation bit • The Saturation bit must be carefully cleared to avoid the node being saturated again • An hysteresis approach could be used to avoid status oscillation • Allows head-end LSRs to take appropriate actions • Head-End LSRs detecting that an LSR has become saturated should not reroute already established LSP, but should avoid the LSR when computing a new path • Head-LSRs detecting that a node is no longer saturated may delay any reoptimization procedure, in order to avoid a signalling storm that may again saturate the node

  6. Next steps • Interest for this work ? • Consensus for a WG doc ? • Please send your comments to the list

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