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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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Furthermore, because the labels can be exchanged using LMP, an alternative<br />

local policy can further be imposed such that (with respect to the higher<br />

numbered node's label set) the higher numbered node can allocate labels from<br />

the high end of the label range while the lower numbered node allocates labels<br />

from the low end of the label range.<br />

This mechanism would augment any close packing algorithms that might be<br />

used for b<strong>and</strong>width (or wavelength) optimization. One special case that should<br />

be noted when using RSVP <strong>and</strong> supporting this approach is that the neighbor's<br />

node ID might not be known when sending an initial Path message. When this<br />

case occurs, a node should suggest a label chosen at r<strong>and</strong>om from the available<br />

label space.<br />

Addressing <strong>and</strong> routing<br />

GMPLS reuses <strong>IP</strong> routing <strong>and</strong> addressing models. A routing domain is made up<br />

of GMPLS enabled nodes.<br />

For scalability purposes, GMPLS implements two enhancements to addressing<br />

the links:<br />

► Unnumbered links: Logic links that carry TE properties but do not need an<br />

address.<br />

► Link bundling: A single logical link to represent a number of links (either<br />

physical or logical).<br />

Path computation allows proprietary algorithms for distributed <strong>and</strong> centralized<br />

computation. It is essentially a constraint-based routing problem. The routes are<br />

selected according to quality of service (QoS) requirements <strong>and</strong> the resource<br />

capability along the path.<br />

Routing protocols are usually extended from OSPF-TE <strong>and</strong> IS-IS-TE. They must<br />

allow the auto-discovery of network topology, advertise resource availability, <strong>and</strong><br />

accommodate unnumbered links or bundled links.<br />

A.4.7 GMPLS examples<br />

The Optical Internetworking Forum (OIF) is defining a User Network Interface<br />

(UNI) for the GMPLS specification. It is called the OIF UNI.<br />

► OIF UNI allows neighbor discovery <strong>and</strong> channel assignment at the<br />

Synchronous Digital Hierarchy or STS level.<br />

► The control interface can be an out-of-b<strong>and</strong> Ethernet interface or an in-b<strong>and</strong><br />

comm<strong>and</strong> carried in the SDH/Sonet processing charge.<br />

950 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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