ounter that where control protocols have been deployed to provision optical networks, they have been proprietary and have suffered from interoperability problems. With the modest success of MPLS in packet-switched IP networks, optical network providers have developed a process to generalize the applicability of MPLS to cover optical networks as well, the result of which is the set of Internet Drafts that are collectively referred to as GMPLS. These drafts extend the following:13 The MPLS data forwarding model, such that it includes current practice in optical networks The MPLS control protocols, so that they can be used as a standardized and interoperable way of provisioning optical networks Figure 7-11 lays out three approaches to optical routing. The top case depicts a fairly traditional approach. This approach is resource intensive because packet processing is needed at every node. The middle case shows an improved architecture, where optical bypass is supported at intermedi- ary nodes. The bottom case enables edge-to-edge optical routing.8 Some people have called this technology optical label switching (OLS). As men- tioned earlier, OLS enables packet switching in the optical domain. Packet forwarding is based on an optical header. The header is a subcarrier multi- plexed with the optical data. The label field in the optical header deter- mines packet forwarding. Data is delayed (in a fiber loop) while the header is examined; however, the data never leaves the optical domain. A control function will erase and reinsert the label in the optical header (for example, using an optical notch filter). All-Optical Networks IP over WDM Routing Strategies Figure 7-11 IP processing A. Client layer, no optical bypass scenarios for an optical network. B. Integrated layer, optical bypass allowed C. Transport layer, optical bypass optimized OLSR = Optical Label Switching Routing NE GMPLS protocols are analyzed in Chapter 8. Related work to standard- ize the management and configuration of optical networks is ongoing in the 