This paper describes recent standardization activities on optical networking and relevant issues which are conducted in ITU-T. The organization is first described, then, several recommendations both which are already recommended and expected to be completed in a couple of years.

Optical path technology that employs both WDM/FDM and wavelength routing will play a key role in supporting future high bandwidth transport networks. WP/VWP (Wavelength Path/Virtual Wavelength Path) technologies are very effective in realizing optical path networks. In these networks, since photonic wavelengths are scarce resources, the number of wavelengths required to construct the network must be minimized. However, the wavelength assignment problem, minimizing the number of wavelengths, is an NP-complete problem. Solving this problem heuristically is an important issue for designing large-scale WP/VWP based networks that are also practical. To realize optical path networks, we need to develop path accommodation design algorithms that heuristically solve the wavelength assignment problem. This paper proposes novel path accommodation design algorithms for WP/VWP networks that minimize the number of wavelengths required. We numerically elucidate that the numbers of wavelengths required for active WPs and VWPs are almost equal. When link failure restoration is considered, they are different; more wavelengths are needed with the WP scheme than with the VWP scheme. It is also demonstrated that the proposed algorithms are applicable to a large scale network design.

This paper proposes novel optical path accommodation design algorithms for networks wherein the number of wavelengths multiplexed into a fiber is restricted. This algorithm optimizes both optical path route and wavelength assignment in VWP/WP networks. It minimizes optical path cross-connect (OPXC) system scale in terms of incoming/outgoing fiber port numbers. A comparison in terms of required OPXC system scale between the WP and VWP schemes is demonstrated for the first time.

In order to transport an ever-increasing amount of IP traffic effectively, Photonic IP networks that employ wavelength routing and Layer 3 cut-through are very important. This paper proposes a new network design algorithm that minimizes the network cost considering IP traffic growth for multi-layered photonic IP networks that comprise electrical label switched paths (LSPs) and optical LSPs. We evaluate the network cost obtained from the developed network design algorithm that considers IP traffic growth and compare it to the results obtained from a static zero-based algorithm. The static zero-based algorithm does not take into account the history of progressive past IP traffic changes/growth until that time. The results show that our proposed algorithm is very effective; the cost increase from the cost obtained using the zero-based algorithm is marginal. The algorithm developed herein enables effective multi-layered photonic IP network design that can be applied to practical networks where IP traffic changes/increases progressively and that can be used for long term network provisioning.

This paper discusses global area optical transport ring networks using wavelength division multiplexing (WDM) technologies and proposes a novel optical add/drop multiplexer (OADM) architecture suitable for such an application field. Study on the requirements of a global area ring application elucidates the appropriate ring/protection architecture as the path switched bi-directional ring. The proposed OADM architecture has flexibility in terms of path provisioning and scalability. We conclude that the proposed OADM can effectively configure the large-scale path switched bi-directional rings.

This paper discusses global area optical transport ring networks using wavelength division multiplexing (WDM) technologies and proposes a novel optical add/drop multiplexer (OADM) architecture suitable for such an application field. Study on the requirements of a global area ring application elucidates the appropriate ring/protection architecture as the path switched bi-directional ring. The proposed OADM architecture has flexibility in terms of path provisioning and scalability. We conclude that the proposed OADM can effectively configure the large-scale path switched bi-directional rings.

The concept of an optical path layer has become increasingly attractive with the growth of traffic in the backbone network. The recent advances in optical switching technology support the deployment of optical cross-connect (OXC) nodes and the construction of large-scale optical path networks. This paper proposes a highly-reliable and fast pre-assigned restoration scheme for optical path networks. To achieve the pre-assigned restoration scheme, this paper investigates the extension of the Generalized Multi-Protocol Label Switching (GMPLS) protocol functionality considering the interoperability with GMPLS capable IP routers in the future. This paper also proposes a new network control architecture called the "partition model" through discussion of network architecture. We clarify that the M:N end-to-end restoration scheme achieves efficient resource usage and management of the network especially in the "partitioned model" network. With the finite design of the GMPLS protocol extension based on the M:N end-to-end restoration scheme, we successfully achieve an intelligent protocol that guarantees 100% recovery against single link failure and is capable of protection grade fast restoration of the optical path less than 50 msec. To our knowledge, this is the first demonstration of GMPLS-controlled protection grade fast optical path restoration.

Bolstering survivable backbone networks against multiple failures is becoming a common concern among telecom companies that need to continue services even when disasters occur. This paper presents a multiple-failure recovery scheme that considers the operation and management of optical paths. The presented scheme employs scheme escalation from pre-planned restoration to full rerouting. First, the survivability of this scheme against multiple failures is evaluated considering operational constraints such as route selection, resource allocation, and the recovery order of failed paths. The evaluation results show that scheme escalation provides a high level of survivability even under operational constraints, and this paper quantitatively clarifies the impact of these various operational constraints. In addition, the fundamental functions of the scheme escalation are implemented in the Generalized Multi-Protocol Label Switching control plane and verified in an optical-cross-connect-based network.