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Optical packet and circuit integrated (OPCI) networks provide both optical packet switching (OPS) and optical circuit switching (OCS) links on the same physical infrastructure using a wavelength multiplexing technique in order to deal with best-effort services and quality-guaranteed services. To immediately respond to changes in user demand for OPS and OCS links, OPCI networks should dynamically adjust the amount of wavelength resources for each link. We propose a resource-adjustable hybrid optical packet/circuit switch and transponder. We also verify that distributed control of resource adjustments can be applied to the OPCI ring network testbed we developed. In cooperation with the resource adjustment mechanism and the hybrid switch and transponder, we demonstrate that automatically allocating a shared resource and moving the wavelength resource boundary between OPS and OCS links can be successfully executed, depending on the number of optical paths in use.
© 2013 Optical Society of America
1. Introduction
Efficient energy consumption and the diversification of services are required for future networks [1]. Transparent optical switching technologies for various bit rates and formats without electrical processing can assist in large-capacity transmission using little power. In particular, an optical packet switching (OPS) scheme can allow efficient bandwidth use because of the fine granularity in the temporal domain. However, it is difficult to guarantee a deterministic data transfer rate due to packet congestion. Therefore, we have proposed an optical packet and circuit integrated (OPCI) network that offers both OPS links and optical circuit switching (OCS) links [2]. Figure 1 shows a conceptual diagram for our OPCI network. To diversify services, OPS links enable bandwidth-sharing and best-effort data transfer, while OCS links enable a fully occupied bandwidth and bandwidth-guaranteed data transmission.
Networks providing both packet-switching and circuit-switching have received a lot of attention and several works has been conducted [3–5]. The authors of [3] use the Openflow protocol in order to unify the packet- and circuit-switching control. However, they have not sufficiently developed optical switching devices, and thus their Openflow switch still relies on electrical processes, which limit the switching speed at a certain level of energy consumption. The authors of [4] have experimentally demonstrated a photonic switch supporting both packet- and circuit-switching. However, each input or output port of the photonic switch is used for either packet- or circuit-switching at the same moment. Thus, it will experience very low bandwidth utilization when only a tiny number of optical paths are established in a port. The authors of [5] have proposed a biologically-inspired wavelength allocation method that allocates wavelengths to path/packet integrated networks. In this work, the performance of this method has been evaluated by simulation method.
Recently, we developed an OPCI ring network testbed and confirmed the basic operation of an OPCI node such as add/drop, optical switching, and optical buffering for fourteen 10 Gbps optical paths and 100 Gbps optical packets [6,7]. In the OPCI network, different wavelength resources are allocated to OPS and OCS links. For efficient resource usage, the boundary between two resources is expected to be flexibly moved in response to user demand for best-effort or bandwidth-guaranteed services, as shown in the bottom of Fig. 1. The boundary movement between two resources is achieved by allocating a shared resource to the OPS or OCS links. Previously, we developed a distributed resource adjustment mechanism to autonomously move the boundary depending on the number of optical paths in use for each link at each node on the control plane (C-plane) [8].
In this paper, we newly propose a resource-adjustable hybrid optical packet/circuit switch and transponder in order to physically move the boundary between the resources for OPS and OCS links on the data plane (D-plane). We verify that distributed control of this resource adjustment can be applied to our OPCI ring network testbed as well as centralized control. We achieved the automatic configuration of the hybrid optical packet/circuit switch and transponder based on the resource adjustment mechanism and the dynamic movement of the boundary between two resources for the first time. Error-free data transmission using OPS and OCS links on a shared band was successfully executed before and after moving the boundary.
2. Controlling the resource boundary in an OPCI node
Figure 2 shows the resource adjustment mechanism and the architecture of the OPCI node for the moving boundary. Here, wavelength resources are divided into three wavebands, as shown in the upper part of Fig. 2(a). Each waveband has N wavelengths. Note that each waveband does not necessarily need to be the identical number of wavelengths. The OPS and OCS links occupy two wavebands. Another is used as a shared resource. We use a multi-wavelength optical packet, which consists of N wavelengths x 10 Gbps optical lanes. To move the boundary between the resources for the OPS and OCS links, the shared waveband is allocated to an OPS or OCS link (called a resource adjustment) according to predefined conditions. These conditions are determined based on the resource-control policy of the network operators.
Fig. 2 (a) Conceptual diagram for a wavelength resource adjustment mechanism and OPCI node architecture including an ideal hybrid optical packet/circuit transponder and switch. (b) Flowcharts of wavelength resource adjustment mechanism.
The flowchart of resource adjustment mechanism is shown in Fig. 2(b) [8]. Since an optical path is established by occupying part of the wavelength resources, users who request optical paths would pay a higher usage fee compared with users who request optical packets. In order to meet as many requests for optical paths as possible, the resource adjustment would be performed depending on how many optical paths are being used. In OPCI nodes, every time a signaling message is transferred, the number of optical paths in use (nc) is checked for each link interface. When an optical path is established and nc reaches N-1, the shared waveband is automatically allocated to the OCS links. Then, the wavelength resource for the OCS links increases from N to 2N. However, when an optical path is released and nc becomes lower than N-1 (and the number of paths in use in the shared waveband is zero), the shared waveband is automatically allocated to an OPS link. Then, the wavelength resources for OCS links decreases from 2N to N.
We propose the architecture of an OPCI node to adjust resources in the data plane (D-plane). One example of the architecture of an OPCI node is shown in the bottom of Fig. 2(a). An OPCI node mainly consists of a waveband multiplexer/demultiplexer (WB Mux/Demux), a dedicated OPS system, a dedicated OCS system, and a hybrid optical packet/circuit switch. In addition, one dedicated N-wavelength optical packet transponder [9], N dedicated optical path transponders, and one hybrid transponder are equipped. One optical packet transponder handles N wavelengths while one optical packet transponder handles one wavelength. Therefore, the number of dedicated transponders for OPS and OCS are different in Fig. 2(a). Note that the number of transponders for each waveband can be increased if more wavebands can be used. Ideally, the hybrid system includes OPS and OCS modes with a single device. If one of the two modes is chosen, the hybrid system performs the same function as a dedicated one. Based on the results of the resource adjustment in the C-plane, the OPS or OCS mode of the hybrid system is selected by a node controller. It is decided beforehand whether data coming from client networks (e.g., the Ethernet) will be carried by either OPS or OCS links. Via a layer-2 switch (L2SW) on the client network side, data is forwarded to the appropriate transponder. The Optical packets and optical paths from transponders are multiplexed by the Mux and sent to an OPCI ring network.
We propose a feasible hybrid system that consists of a combination of one OPS and one OCS system, as shown in Fig. 3. Wavelength selective switches (WSS) are used as WB Mux/Demux and optical circuit switches. These systems are connected using different ports of the WSS and L2SW. By switching data at L2SW and WSS, the data coming from client networks is forwarded to an OPS and OCS system in the hybrid system. Therefore, we can select an OPS or OCS mode and transmit either optical packets or optical paths on a shared waveband in an OPCI ring network.
In OPCI networks, autonomous distributed control for the resource adjustment is proposed as shown in Fig. 4 [8]. The resource adjustment mechanism is installed in each controller of the OPCI node. A signaling message is sent from an ingress node (Node 1) to an egress node (Node 6) in order to establish or release the optical paths. In each interface of the OPCI nodes connected by fiber, the resource adjustment is executed by the node controller when a change in the number of optical paths in use matches the predefined conditions as we explained in the flowchart in Fig. 2(b). However, an autonomous distributed resource adjustment was only executed in the C-plane on the OPCI ring network testbed.
Here, we newly verified the proper operation of the autonomous distributed resource adjustment for the D-plane on the OPCI ring network testbed. Figure 5(a) shows the experimental setup. We assumed an OPCI ring network built with two OPCI nodes and set two emulators in place of OPCI nodes. When one optical path was established by sending a signaling message from Host 1 to Host 2 and the number of optical paths matched the predefined condition, which was the same as the one shown in the bottom of Fig. 4, the shared waveband was automatically allocated to the OCS links by node controllers 1 and 2. In addition, node controllers 1 and 2 output messages to control the OPS and OCS modes of the hybrid system, as shown in Fig. 3. Namely, the output port of the L2SW and the input port of the WSS should be changed. Figure 5(b) shows one result of the control messages output from each node controller to establish a WSS. We confirmed that each node controller sent a control message to the corresponding OPCI node and received a success-message from each emulator in a distributed manner.
Fig. 5 (a) Experimental setup of distributed control for resource adjustment using OPCI node emulators. (b) Examples of control messages to switch WSS ports in node controller 1 and 2.
3. Demonstration of a dynamic moving boundary for wavelength resources between OPS and OCS links
We performed a demonstration of a dynamic moving boundary as proof of concept. Here, we handled 40 wavelengths (λ1 – λ40) of 1531.90–1563.05 nm with 100 GHz spacing. In the C-plane, we used 10 wavelengths as one waveband (N = 10). On the other hand, in the D-plane, we could not use 10 consecutive wavelengths as one waveband due to a shortage of devices. Here, a 10-wavelength group (λ13, λ16–λ19, λ31–λ33, λ37, λ40) was allocated to a shared waveband. A different 10-wavelength group (λ21–λ30) was allocated to an occupied waveband for OPS links. In addition, another 10-wavelength group (λ10–λ12, λ14, λ15, λ34–λ36, λ38, λ39) was allocated to an occupied waveband for OCS links. Figure 6 shows the setup for the OPCI ring network. OPCI node 1 had five 10 Gbps optical transport network (10G-OTN) path transponders of different wavelengths (λ10, λ11, λ12, λ14, λ15), a 100 Gbps optical packet (100G-OP) transponder with 10-wavelength 10 Gbps optical lanes (λ21–λ30), two wavelength-selective switches (WSS), an OPS system, some optical amplifiers, and a hybrid optical packet/circuit transponder and switch. The optical packet switch consisted of a semiconductor optical amplifier (SOA) switch and a switch controller [7]. WSS were used as both optical circuit switches and Add/Drop Mux/Demux. The hybrid transponder consisted of a 40 Gbps optical packet (40G-OP) transponder [9] with 4-wavelength 10 Gbps optical lanes (λ13, λ16, λ19, λ31), and one 10G-OTN transponder (λ13) and three laser diodes (LDs) (λ16, λ19, λ31). LDs were used as path transponders due to a shortage of 10G-OTN transponders. The client interface for all transponders was 10 Gigabit Ethernet (10GbE). The hybrid switch consisted of another optical packet switch and optical circuit switch (OPS 2 and OCS 2). Via a switch on the side of the client networks, data were forwarded to the proper transponder. By changing the data route with an L2-SW and WSS, the hybrid transponder and switch changed to OPS or OCS mode. In addition, eight LDs were used to launch 8-wavelength static optical paths (λ2-λ9) for stable operation. These static paths were not resource adjustment targets. OPCI node 2 had five different wavelength 10G-OTN path transponders (λ34, λ35, λ36, λ38, λ39), and a hybrid transponder that consisted of a 40G-OP transponder, one 10G-OTN transponder (λ37), and three LDs (λ17, λ18, λ40).
Each OPCI node controller had an autonomous distributed control mechanism for signaling, OCS routing, and resource adjustment. When Host 1 requests a path establishment or release to Host 2 via the OPCI ring network, it sends a signaling message to Host 2 via those controllers. In each node, every time a signaling message is transferred, each node controller controls the WSS (Add) and WSS (Drop) in order to set up or delete the optical connections in the switches. In addition, according to the number of optical paths in use, each node controller automatically increases or decreases the OCS link resources in the C-plane and changes the mode of the hybrid transponder and switch in the D-plane. Note that only a mode change in the hybrid transponders and switches is executed via the centralized control from Host 1 in this demonstration [10].
We will show the demonstration scenario and the results of the automatic allocation of a shared waveband from OPS to OCS links for boundary control in steps.
STEP 1) The shared waveband is allocated to the OPS links. In the occupied waveband for the OCS links, eight optical paths are established. Note that a one-way optical path is set using one wavelength due to the shortage of transponders in the D-plane, while a bidirectional path is established using the same wavelength in the C-plane. Figure 7(a) shows the spectrum of 10-wavelength and 4-wavelength optical packets using occupied and shared wavebands, and eight optical paths, respectively. Figure 7(d) shows the temporal waveform for an extracted optical lane (λ13) of 4-wavelength optical packets.
Fig. 7 (a)-(c) Spectrum waveforms for STEP 1–3. (d) Temporal waveform for one optical lane of the 4-wavelength optical packets. (e) Temporal waveform for one optical path (λ13). (f) Results of the Resource adjustment in the C-plane at node controller 1.
STEP 2) In the occupied waveband for the OCS links, a ninth optical path is established in the C-plane. Because the number of paths in use (nc) reached 9 ( = N-1), the shared waveband is allocated to the OCS links. The hybrid transponder and switch for each node is automatically changed to the OCS mode. Therefore, the 4-wavelength optical packets are extinguished. Figure 7(b) shows the spectrum of the deleted 4-wavelength optical packets using the shared wavebands.
STEP 3) In the occupied waveband for the OCS links, the tenth optical path is completely established. Then, using the shared waveband for the OCS links, four optical paths are also established. Figure 7(c) shows the spectrum of the additional four optical paths using the shared bandwidth. Figure 7(e) shows the temporal waveform of one optical path (λ13). The upper right figure is the extended one.
Figure 7(f) shows the results of resource adjustment at node controller 1 in STEP 2. The shared waveband was allocated to the OCS links and the number of wavelengths for OCS was increased from 10 to 20 wavelengths in the C-plane. Therefore, we confirmed that autonomous distributed control for resource adjustment could be realized. In addition, from the monitoring results of the temporal waveforms of one wavelength (λ13) as shown in Figs. 7(d) and 7(e), we can see that an OPS link was physically changed to OCS links in the shared waveband.
We measured the frame error rate of the transmitted 10GbE frame from OPCI nodes 1 to 2 via the OPS or OCS links in the shared waveband. The 1518 Byte-long frames were transmitted from Host 1 and encapsulated into optical packets or optical paths in each transponder. The optical packets or optical paths were forwarded to OPCI node 2. We measured the frame error rate for the 10GbE frames transmitted via 4-wavelength optical packets in STEP 1 or an optical path (λ13) in STEP 3. In both cases, frame error rates of less than 1 × 10−8 were achieved. This is sufficient quality because a frame error rate of less than 1 × 10−4 is regarded as high quality [11] and L2 error correction mechanisms can be used.
4. Conclusion
To immediately respond to changes in user demand for OPS and OCS links, we developed a distributed resource adjustment mechanism that autonomously allocates a shared resource to the OPS or OCS links on the control plane. We proposed a resource-adjustable hybrid optical packet/circuit switch and transponder to physically perform the resource adjustment on the data plane. In cooperation with the resource adjustment mechanism and the hybrid switch and transponder, we experimentally demonstrated that the automatic allocation of a shared resource and the movement of a boundary for wavelength resources between OPS and OCS links can be executed depending on the number of optical paths in use.
Acknowledgments
The authors would like to thank Wei Ping Ren, Ryo Mikami, and Takeshi Makino of the National Institute of Information and Communications Technology for their support in these experiments.
References and links
1. ITU-T, “Future networks: objectives and design goals,” Recommendation Y. 3001, 2011.
2. H. Harai, “Optical packet and circuit integrated network for future networks,” IEICE Trans. Commun. E95-B(3), 714–722 (2012). [CrossRef]
3. S. Das, G. Parulkar, N. McKeown, P. Singh, D. Getachew, and L. Ong, “Packet and circuit network convergence with OpenFlow,” in Proc. Optical Fiber Communications Conference (2010), no. OTuG1. [CrossRef]
4. H. Wang, A. S. Garg, K. Bergman, and M. Glick, “Design and demonstration of an all-optical hybrid packet and circuit switched network platform for next generation data centers, ” in Proc. of Optical Fiber Communications Conference (2010), no. OTuP3. [CrossRef]
5. S. Arakawa, N. Tsutsui, and M. Murata, “A biologically-inspired wavelength resource allocation for optical path/packet integrated networks,” in Proc. Optical Networking Design and Modeling (2011).
6. H. Furukawa, H. Harai, T. Miyazawa, S. Shinada, W. Kawasaki, and N. Wada, “Development of optical packet and circuit integrated ring network testbed,” Opt. Express 19(26), B242–B250 (2011). [CrossRef] [PubMed]
7. H. Furukawa, S. Shinada, T. Miyazawa, H. Harai, W. Kawasaki, T. Saito, K. Matsunaga, T. Toyozumi, and N. Wada, “A multi-ring optical packet and circuit integrated network with optical buffering,” Opt. Express 20(27), 28764–28771 (2012). [CrossRef] [PubMed]
8. T. Miyazawa, H. Furukawa, K. Fujikawa, N. Wada, and H. Harai, “Development of an autonomous distributed control system for optical packet and circuit integrated networks,” J. Opt. Commun. Netw. 4(1), 25–37 (2012). [CrossRef]
9. H. Furukawa, N. Wada, H. Harai, M. Naruse, H. Otsuki, K. Ikezawa, A. Toyama, N. Itou, H. Shimizu, H. Fujinuma, H. Iizuka, and T. Miyazaki, “Demonstration of 10 Gbit ethernet/optical-packet converter for IP over optical packet switching network,” J. Lightwave Technol. 27(13), 2379–2380 (2009). [CrossRef]
10. H. Furukawa, T. Miyazawa, N. Wada, and H. Harai, “Moving boundary between wavelength resources in optical packet and circuit integrated ring network,” in Proc. 39th European Conference and Exhibition on Optical Communication (2013), no. We.1.E.2.
11. ITU-T, “Network performance objectives for IP-based services,” Recommendation Y.1541.
