Lost Bursts OPTICAL BURST SWITCHING OBS

256 OPTICAL BURST SWITCHING 0x1A 0x1B 0x01 0x02 0x0E 0x03 0x0B 0x001F 0x001 0x000F 0x035 Domain 0xA Domain 0xB OBS top domain Figure 10.14 Address hierarchy. within these domains are allotted 12 bits. As an example, the address of the OBS node in domain 0x001F is: 0xB.0x001F.0x035.

10.3.4 The Routing Architecture

In the Jumpstart OBS architecture there is a clear separation between the control plane and the data plane. The data plane is all optical and is responsible for transporting bursts. The control plane is an electronic packet-switching network and is responsible for signaling, routing, and network management. In the Jumpstart prototype network, an OBS node consists of an OXC which is a 2D MEMS switch fabric and a control unit which is known as the JITPAC controller [JITPAC] . The JITPAC controllers communicated with each other via an ATM network. Figure 10.15 shows the control and data planes. OXC OXC OXC OXC OXC JITPAC JITPAC JITPAC JITPAC JITPAC Data plane Control plane Figure 10.15 The data and control planes in Jumpstart. THE JUMPSTART PROJECT 257 Because of the nature of OBS, the signaling messages are associated with bursts and they follow the same path as their bursts. For instance, a SETUP message precedes the transmission of each data burst and is responsible for setting up the path for the burst, while a RELEASE message is responsible for releasing the resources at each OXC after the end of a burst’s transmission. Other such signaling messages are the optional CONNECT message, which confirms the establishment of a path, and the FAILURE message, which is used to release network resources when a burst is dropped within the network. By definition, these messages have to go through all of the OBS nodes along the burst’s path, either in the forward direction i.e., the SETUP and RELEASE messages or the reverse direction i.e., the CONNECT and FAILURE messages. Unlike the signaling messages, there is no requirement for other control messages, such as those used to exchange routing information and report network failures to the network management system, to take the same path as data bursts. Below, we will refer to all of the messages except the signaling messages, as control messages. Jumpstart uses different routing architectures for control messages and data bursts. The routing for signaling messages was not considered, since they use the same routes as the data bursts. Each JITPAC maintains two forwarding tables, one for control messages, hereafter referred to as the control forwarding table, and one for data bursts, hereafter referred to as the burst forwarding table. This distinction is a logical one, and the two forwarding tables can be implemented as a single data structure. Also, two discrete path computation components have been defined; one for maintaining the control forwarding table, and the other for maintaining the burst forwarding table. Each path computation component uses its own routing protocol for topology discovery and link status updates, as well as its own routing algorithm for computing paths. The decision to support two different routing architectures, one for the data plane and one for the control plane, was motivated by several observations. As will be seen below, a transparent optical path which carries a data burst between two OBS nodes must satisfy a completely different set of requirements than the electrical or electro-optic path that carries control messages between the JITPACs. Similarly, the routing information needed to find appropriate optical paths is very different than that needed to route control messages. Therefore, implementing two sets of routing protocols and algorithms allows each set to be optimized for the specific requirements of a given plane data or control. As a result, any modifications or extensions to the data plane routing architecture will not affect the control plane, and vice versa. For instance, the network designer can upgrade the algorithm to compute optical data paths, or modify the link information collected for routing data bursts, without affecting the control plane routing infrastructure. The decoupling of control and data planes also reduces the overall complexity of the implementation, and makes it easier to debug and deploy the individual pieces of the routing architecture. Furthermore, this decoupling allows the use of existing routing protocols and algorithms whenever appropriate, especially within the control plane. Below, we describe the intra-domain routing architecture for control messages and data bursts. The routing architecture for control messages The control plane of the Jumpstart OBS network is implemented on an electrical packet- switching network. The primary routing goal in this plane is the computation of shortest