Disjointed SRLG Routing for GMPLS Networks by Hierarchically Distributed PCE

Hiroshi MATSUURA  Naotaka MORITA  Tatsuro MURAKAMI  Kazumasa TAKAMI  

IEICE TRANSACTIONS on Communications   Vol.E90-B   No.1   pp.51-62
Publication Date: 2007/01/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.1.51
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Internet
SRLG,  GMPLS,  routing,  path computation server,  OSPF,  explicit route object,  RSVP,  

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Multilayered network interaction among various networks such as IP/MPLS packet networks and optical fiber networks are now achieved using generalized multiprotocol label switching (GMPLS) technology. One unique feature of GMPLS networks is that GMPLS packet-layer label switching paths (LSPs), such as IP/MPLS LSPs, sometimes tunnel through GMPLS lower layer LSPs such as optical fiber/lambda LSPs. One problem that occurs in this situation is protecting an important primary packet LSP by using a protection LSP that is physically separated from the primary LSP. The packet router has difficulty recognizing lower layer LSPs that are totally disjointed from the primary LSP. This is because, in a GMPLS's packet layer, a source router only differentiates one lower layer LSP from another, and does not check the disjointedness of segments through which the lower layer path passes. Sometimes, different lower LSPs pass through the same optical fiber, and a malfunction of one optical fiber sometimes causes many lower layer LSPs to malfunction at the same time. To solve this problem, a shared risk link group (SRLG) is introduced. Network links that belong to the same SRLG share a common physical resource. We apply this SRLG to the proposed hierarchically distributed path computation elements (HDPCEs) and achieve effective disjointed SRLG protection for important primary GMPLS packet paths.