See also my draft, draft-hummel-mpls-hierarchical-lsp-00.txt:
An hierarchical LSP (H-LSP) shall concatenate normal LSPs (and/or hierarchical LSPs of lower hierarchical level) just like an normal LSP concatenates
physical links. However, it takes some changes in CR-LDP signalling as to establish hierarchical LSPs:
Explicit Routing: the ingress of the H-LSP provides the complete sequence of sub H-LSPs to be concatenated (= change in ER-TLV).
Implicit Routing: the ingress (the transit) node of the H-LSP needs to send the LSP-ID of the first (the next) sub H-LSP to be concatenated (=new TLV).
The messages (LABEL-REQUEST, LABEL-MAPPING,...) have to be sent THRU "Control-Plane" sub H-LSPs (like thru tunnels) whose endpoints comply with the
endpoints of the to be concatenated "User Plane" sub H-LSPs.
The LSP-IDs of the involved "Control-Plane" sub H-LSPs should be derivable from the LSP-IDs of the involved "User-Plane" sub H-LSPs.
I stressed that, based on a small but contiguous partial mesh of LSPs an effective full mesh can be accomplished by building H-LSPs.
The N-square problem would completely disappear. Costs, i.e. work for the H-LSPs would only happen at the rim of the network. Indeed the network would not
even know that the H-LSPs exist, as all messages are tunnelled thru the "Control Plane" sub H-LSPs.
I would appreciate if more people supported this work on H-LSPs.
Von: Vinay Vernekar [mailto:email@example.com]
Gesendet: Dienstag, 16. April 2002 15:18
An: firstname.lastname@example.org; email@example.com
Betreff: Need for hierarchical SONET/SDH LSPs.