With different vendor equipments being deployed in the core and metro networks, automated end-to-end service provisioning across multi-vendor optical networks poses new challenges from an architectural and protocol standpoint. Traditionally, telecommunications networks have been managed in a proprietary fashion using centralized Network/Element Management Systems (NMS/EMS). The Telecommunications Management Forum (TMF) is standardizing NMS/EMS interaction with the aim of achieving multi-vendor equipment interoperability. This standardized management plane based end-to-end architecture appears to be the quickest path to short-term core and metro network interoperability (compared to a longer-term distributed control plane provisioning approach of GMPLS being developed at IETF). We consider the problem of routing end-to-end metro sub-rate circuits (STS-1/3/12) across the wavelength switched (STS-48/192) core under various NMS/EMS interaction and information exchange models. We propose an algorithm framework for efficient packing of sub-STS-48 paths onto STS-48/192 paths in the core network so as to improve capacity utilization and reduce blocking. At any given time, there will be a number of provisioned STS-48/192 paths in the core network that are partially used up and have available capacity. We call such paths "fragmented paths". The objective of efficient packing is to minimize the number of fragmented paths in the core network at any given time, while trying to minimize end-to-end path costs also. To achieve this, the portion of a sub-STS-48 circuit through the core network may be multiplexed within one or more provisioned STS-48/192 paths. The way these circuits are multiplexed depends on the grooming capability of the core and metro networks.