Key technology of GMPLS

1 Introduction

With the rapid development of Internet and optical fiber technology, the integration of IP and Optical network technology will become an important trend of network development in the future. How to solve the integration of IP layer and optical layer, GMPLS provides a good idea. Gmpls inherits almost all MPLS features and protocols, and is an extension of MPLS to optical network, it can use unified control plane to manage a variety of different technologies to build a network, so as to simplify the network structure, reduce network management costs and optimize network performance provides an important guarantee.

　Review of 2 Multi-Protocol label switching (MPLS) technology

MPLS is the foundation of GMPLS, it is located in the 2.5-layer network technology, for IP layer and link layer interaction provides a unified operating platform, has a strong adaptability and flexibility, can support the existing network layer and link layer of various protocols (such as the network layer support IPV4, IPV6, IPX, AppleTalk, etc., to support the link layer fr, ATM, PPP and so on. MPLS is a technology that can greatly improve the speed of routing forwarding, its architecture is divided into two separate components, namely forwarding components (also called data level) and control components (also called control level). The forwarding component uses the label forwarding database maintained by the label switch to perform data packet forwarding tasks based on the label carried by the packet. The control component is responsible for establishing and maintaining label forwarding information between a set of interconnected switches.

The simple work of MPLS is that when the data packet arrives at the entry LSR (label switch) of the MPLS network cloud, the portal LSR determines which FEC (forwarding equivalence class) the packet belongs to by analyzing the data packet header (FEC), which is a set of data streams with certain commonalities, The data is LSR in the same way during the forwarding process, and then the LIB (tag information base) is searched to add a label associated with the FEC to the data grouping. In subsequent LSR, you do not need to look up IP packet headers, just look up the Lib based on the label of the data packet to determine its forwarding exit, replace the old label with the new label before forwarding, and then forward to the next LSR. When the data packet arrives at the exit LSR, the export LSR removes the label from the data packet, and forwards the data packets according to the traditional IP forwarding mode. Among them, all of the FEC-bound label distribution and LSP are created by LDP (the label Distribution protocol).

Key Technology of 3 Gmpls

In order to adapt to the requirement of the future Intelligent Optical Network to provide network resources and transmission signaling dynamically, we need to extend and update the traditional MPLS. GMPLS is the product of the expansion of MPLS to optical network, it supports the traditional packet switching, time division switching, wavelength switching and optical fiber exchange, and also modifies and expands the original routing protocol and signaling protocol.

At present, the integration of IP layer and optical transport layer is mainly two directions of overlapping model and integration model, GMPLS should support both models.

The overlapping model is also called the client-server model, that is, the optical layer network as the server, the IP network layer as the customer layer, the two have independent control plane. Specifically, one in the core optical network, and the other in the customer layer, the focus is embodied in the User-network interface (UNI), the two do not Exchange routing information, independent selection of the road, with an independent topological structure. As a server, the core optical network provides wavelength service for customers at the edge of the network. Its advantage is that the optical network and IP network can develop independently, the disadvantage is that the network expansion performance is poor, there are N2 problems. In addition, there are two different address spaces at two levels that require complex address resolution.

The integration model is also called equivalent model or hybrid model, and its basic characteristic is that the control intelligence of the optical transport layer is transferred to the IP layer, and the End-to-end control is implemented by the IP layer. At this time, optical transport network and IP network to form an integrated network, unified control plane to maintain a single topology, optical switches and IP routers can freely exchange all information and run the same routing and signaling Protocol, to achieve integrated management and traffic engineering. But its shortcoming is also obvious, is must in the light layer and the IP layer interaction massive state and the control information.

3.1 gmpls label and label Interchange Path

GMPLS in order to control the optical network, it not only supports the traditional packet switching, but also supports time division switching, wavelength switching and optical fiber exchange, which determines that GMPLS and MPLS are very different, mainly in the following aspects:

· The label space of MPLS is very large, and the wavelength and time channel are very limited.

· The MPLS LSP can be allocated the bandwidth of the continuous value, while the optical channel and the time channel can only be allocated the bandwidth of the finite discrete value.

· If there are more than one parallel optical fiber between two nodes, GMPLS must also support fibre exchange.