Application of label switching technology in all-optical interconnection network

Absrtact: Firstly, this paper introduces the expansion of MPLS to optical network, secondly, this paper expounds the application of the traditional electric domain switching technology in the optical domain, and finally analyzes the all-optical Internet solution based on label switching: Multiprotocol wavelength label Switching (mplms), lobs switching based on label Optical burst switch, all optical label packet switching olps.

Key words: Multi-protocol wavelength label switching Mplms, lobs based on label optical burst switching, all optical label packet switching olps

1, the expansion of MPLS to optical network

Traditional IP network is "Do the best", in the traffic and network bandwidth management function is very weak, often lead to network congestion, difficult to meet the delay, jitter and transmission quality has special requirements of the application (such as voice and video services, etc.), at this time MPLS (Multiprotocol label Exchange) came into being, The implementation of the third layer of packet switching to the second layer of the packet exchange based on the "Multi-layer switching technology", you can use a variety of second-tier protocols, such as Frame Relay, ATM, PPP, Ethernet and so on. MPLS has fast forwarding based on tag and strong traffic engineering management function, can provide better QoS service guarantee, IP/MPLS over ATM This mature technology combination method has been widely applied to meet the telecom level QoS requirements backbone network.

With the development of optical communication technology, communication distance has been "dead", network transmission bandwidth bottleneck has become the past, the application of WDM technology in optical fiber has given an alternative scheme of IP/MPLS over ATM mode, that is ip/mpls over WDM, High-speed ATM switching routers from the backbone network to the edge of the network. In order to apply MPLS to optical network, it is necessary to construct an intelligent wavelength router/optical switch with MPLS routing protocol and signaling protocol and optical switch, and the traditional MPLS protocol will be extended and modified accordingly. At the same time, the IETF proposed the new concept of GMPLS, which is an inevitable product of the expansion of MPLS to optical network, with the rapid implementation of optical connection to intelligent Optical Network, the realization of dynamic service allocation and dynamic network resources in the optical layer, and the realization of end-to-end monitoring and protection and recovery functions. GMPLS can support a variety of exchange types, such as packet Exchange PSC, TIME division multiplexing Tdm﹑ wavelength switching LSC and fiber exchange FSC, resulting in the common label and LSP hierarchical nesting concept, which allows the system to scale with a forwarding layer, then the top of the label will be the FSC interface, followed by the LSC , TDM, and finally the PSC. GMPLS also expands the notion that MPLS logically separates the control plane from the data plane, allowing the existence of multiple physical control planes associated with the data plane.

2. The application of traditional electronic domain switching technology in optical domain

In the traditional voice and data Services network, we have used circuit switching and packet switching, these mature technologies, in contrast to the burst switching technology is little known, of course, from the exchange of granularity, switching mode (through or storage forwarding), network bandwidth resources, such as the reservation of the way to classify words there are many exchange technology, The most used is the above three kinds of exchange technology. According to their respective characteristics, there are three kinds of optical switching technologies in the optical domain:

1 Wavelength routing Switching (WRS): When using circuit switching technology in WDM networks, is realized in the form of wavelength exchange, in each link between adjacent nodes, one wavelength corresponds to an optical channel for exchange, providing end-to-end "virtual wavelength routing", in the edge of the network to establish a light path. The light path is created by reserving a dedicated wavelength channel along each link in the path. When transferring the data stream in the point-to-point optical path, the intermediate node does not need any processing, does not need any e/o and o/e transformations, and does not need buffering data. Wavelength-switched network is a form of traditional circuit-switched networks, which cannot be used to statistic multiplexing shared bandwidth resources, so the bandwidth utilization ratio is low.

2 optical packet Switching (OPS): the packet/packet switching in the domain is represented by the optical packet switching OPS in the optical domain, is based on the virtual Circuit and light time division multiplexing, fixed-length short packet format, generally based on TDM to use all the bandwidth in the optical fiber, the data net load in the form of light signal, the letterhead overhead can be light form, It can also be a form of electricity, by using the out-of-band wavelength or subcarrier multiplexing Transmission control overhead to separate it from the business data, the control overhead and the delay between the business data are realized by the optical fiber delay line (optical memory), and the variable length optical packet can be realized by the series fiber delay line. The main advantage of OPS is that the bandwidth utilization can be improved by using the statistic multiplexing network bandwidth, and the delay problem caused by the optical/electric conversion processing control information is more serious.

3 Optical Burst Switching (OBS): Combining the advantages of wavelength routing switching and optical packet switching, OBS technology can improve network utilization by reserving bandwidth in a limited time period. The basic exchange entity is a burst frame, which is a series of packets moving between the entry node, the intermediate node, and the exit node. The burst frame is mainly composed of the head control burst frame (controlling Burst) and the data burst frame (Burst), which are transmitted independently. The control burst frame is transmitted by the data burst frame to reserve the bandwidth along the path, then the data burst frame is transmitted along the same path as the bandwidth of the control burst frame, and there are three kinds of burst Exchange protocol tag (tell-and-go), IBT (In-band-terminator), RFD (reserve-a-fixed-duration) to coordinate the control of the collaboration between burst frames and burst frames (i.e., the time of sending offsets between them);

3. All-optical Internet solution based on label Exchange

The traditional MPLS technology and wavelength routing are exchanged, optical packet switching and optical burst switching combine to form the whole optical interconnection network technology based on label switching, and the corresponding all-optical Internet solutions include: Multiprotocol wavelength label switching, mplms switching lobs, all optical label packet switching olps.

3.1 Multi-Protocol wavelength label Switching (MPLMS) Optical Interconnection Network Technology

Mplms is an extension of the traditional MPLS in the optical domain, using OXC as LSR, wavelength as the label (shown in Figure 1), followed by the original MPLS framework, does not need to define new content. It directly uses the first layer (optical wavelength class) of the exchange to deal with the third layer of IP routing forwarding, the label and WDM wavelength channel, its discrete wavelength or fiber channel similar to the label, and through the Mplms signaling to refer to the optical channel. Thus greatly simplifies the network hierarchy, and has a more powerful business management, traffic engineering, QoS guarantee function. Mplms can also be viewed as a simplified MPLS without a tag stack or by packet forwarding, using IP routing protocol to discover topology, using MPLS signaling protocol to realize the automatic allocation of wavelength path, it provides the basic frame for real-time configuration of optical wavelength path, and the separation of routing and signaling is advantageous to the new algorithm of introducing new features flexibly. This approach enables routers on the business tier, the ATM switch or ADM dynamically requires the transmission network to provide the required wavelength, realizes the unified network control and the fast service supply, simplifies the integration of the IP layer and the optical layer and the network management of the layer, reduces the network operation and the business expansion cost, and is advantageous to the large-scale network laying. The integration of the IP layer with the optical layer is presenting an unprecedented prospect. Mplms is a new network management control platform, through which IP and other services can be seamless access to a large bandwidth of the fiber network, is to build a new network of future effective methods.

Figure 1 Mplms Network Architecture and label Exchange process