Here, the major contribution has come from the IETF??™s generalized
multiprotocol label switching (GMPLS) framework [7].
212 Chapter 8
GMPLS extends packet-based multiprotocol label switching (MPLS) by abstracting
labels to cover a range of Layer 1 entities??”TDM timeslots, wavelengths, bands, and
fibers. This solution defines key protocols for resource discovery, signaling, traffic engineering,
and link management. For example, resource discovery is done via extensions
to existing interior gateway protocols (IGP) such as open-shortest path first-traffic engineering
(OSPF-TE) and intermediate-system to intermediate-system (IS-IS). Namely,
routing updates provide state on wavelength/timeslot usages, protection/diversity, and
so on. Meanwhile GMPLS signaling extends the resource reservation-traffic engineering
(RSVP-TE) protocol for setup/takedown of lightpath (or SONET/SDH) circuits. In turn
RSVP-TE is driven by constraint-based routing (CBR), which performs advanced resource
engineering. Recently, there have also been many liaison efforts between the ITU-T and
IETF to streamline GMPLS protocols to be ASON-compliant. Overall, GMPLS increases
horizontal control plane integration (data-optical) and eliminates feature overlaps in
traditional multilayered setups, for example, addressing, signaling, routing, and so on.
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