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Inter-AS PCE discovery

This paper discusses how Inter-AS TE paths require PCE-to-PCE communication across AS for relaying path computation requests through PCECP. Dynamic discovery helps PCE to find suitable PCE for path computation across AS using MP-BGP with new AFI/SAFI extensions for information exchange. The interoperability between BGP and IGP is maintained for seamless PCE data propagation, utilizing specific PCE capabilities for diverse path computation requirements. This study highlights the role of BGP for enhanced PCE discovery in Inter-AS scenarios.

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Inter-AS PCE discovery

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  1. Inter-AS PCE discovery Authors: Vijayanand HCL technologies Somen Bhattacharya Prasanna Nagabhushan Avici Systems Avici Systems

  2. Motivation * Inter-AS TE paths require PCE to PCE communication across AS for relaying path computation requests through PCECP. * Dynamic discovery helps PCE to discover suitable PCE for PCECP across AS for the path computation. * Using MP-BGP new afi/safi extensions to facilitate the exchange of PCE information across AS domains. * BGP inherent protocol security, scalability, policy based filtering can be used for propagation of PCE information. * Interoperability between BGP and IGP by maintaining the same PCE TLV discovery structure defined in IGP. * Defined unused PCE TLV capability bits to specify new Inter AS specific PCE capabilities. Avici Systems

  3. MP BGP extensions * The PCE discovery TLV and PCE Status TLV will be carried in the MP-Reach NLRI of BGP update messages. BGP speakers shall encode this in a new <AFI,SAFI> value <TBD,TBD>. * The path computation capability PATH-COMP-CAP sub-TLV is carried in the PCE discovery TLV. This is used to advertise path computation specific capabilities of the PCE. 7 DRA bit: Capability to compute inter-area diverse paths 8 DAS bit: Capability to compute intra-AS diverse paths 9 DRS bit: Capability to compute inter-AS diverse paths 10 C bit : Capability to handle inter-AS policy constraints 11 T bit : Capability to handle diff-serv aware TE requests 9-31 : Reserved for future use. * The ALTERNATE-PCES sub-TLV specifies the set of PCEs as an alternate to a given primary PCE for path computation purposes. One or more alternate PCE can be selected when the given primary PCE fails. Avici Systems

  4. Use case scenario pce-igp-disc/ pce-mp-ibgp Inter-AS LSP pce-mp-ebgp AS 100 AS 200 PCE PCE ASBR ASBR PCC PCC ASBR • PCE stores discovery information and updates the received capability and congestion status to choose suitable PCE for setting up PCECP • Discovery information needs to traverse only few (neighboring ?) ASes, BGP Policy can be used to achieve this Avici Systems

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