OpenFlow-based Dynamic Wavelength Path Control for ... - IEEE Xplore

OpenFlow-based Dynamic Wavelength Path Control for Future Photonic Networks (Invited Paper) Lei Liu*, Takehiro Tsuritani, and Itsuro Morita KDDI R&D Laboratories Inc., 2-1-15 Ohara Fujimino-shi, Saitama, Japan *[email protected] Abstract—OpenFlow, which allows operators to control the network using software running on an external controller, provides the maximum flexibility for operators, and matches the carrier's preferences given its centralized architecture, simplicity and manageability. In this paper, we present an OpenFlow-based approach for dynamic wavelength path control in future photonic networks, assessing its overall feasibility and efficiency through a field trial. Keywords-OpenFlow; unified control plane; photonic networks

I.

INTRODUCTION

In today’s commercial IP/optical multi-layer networks, different layers are separately operated without dynamic interaction, which leads to low network efficiency, high operational expenditure, as well as long processing latency for path provisioning and restoration. Despite a decade of development and standardization efforts, with three different interconnection models (i.e. peer, overlay, and border peer) proposed for a generalized multi-protocol label switching (GMPLS)-based unified control plane (UCP) in multi-layer optical networks, there are no commercial deployments of these models to date, and the debate for their practicability in a real operational scenario grows in intensity [1]. Due to its distributed nature, the number of protocols, and the interactions among different layers, the GMPLS-based UCP becomes overly complex. Moreover, since the GMPLS standardization significantly lags behind the product development, vendors make private protocol extensions to satisfy their own requirements. As a result, the interworking among GMPLS products from different vendors is very difficult [2], which seriously reduces flexibility in network construction. On the other hand, software defined networking (SDN), and in particular, the OpenFlow [3] architecture, which allows operators to control the network using software running on a network operating system (e.g. NOX [4]) within an external controller, provides the maximum flexibility for the operator to control a network, and matches the carrier’s preferences given its centralized architecture, simplicity and manageability. For these reasons, although the OpenFlow architecture was originally designed for Ethernet networks, several studies have recently considered such architecture in the context of optical networks [5-10]. However, despite massive progress, an OpenFlow-based UCP for future photonic networks is still at a starting stage since key issues, including dynamic cross-layer path creation, dynamic restoration, transponder control, and multivendor interoperability have not been addressed so far.

In light of this, in this paper, we present an OpenFlowbased approach for dynamic wavelength path creation and restoration in future photonic networks. We experimentally verify the overall feasibility and efficiency of the proposed approach through a field trial among Japan, China and Spain. II.

OPENFLOW-BASED DYNAMIC WAVELENGTH PATH CONTROL FOR FUTURE PHOTONIC NETWORKS

A. Brief Introduction to OpenFlow We briefly outline the main features of OpenFlow. A more detailed and exhaustive description is available in [3]. An OpenFlow-based network comprises at least one NOX, several OpenFlow switches, a secure channel that interconnects the NOX with the OpenFlow switch, and the OpenFlow protocol for signaling between the NOX and the switches. In an OpenFlow controlled network, packet forwarding is executed in the OpenFlow switch according to a flow table, and the NOX is responsible for the routing decision. When the OpenFlow switch receives a packet that does not match any entry in the flow table, it sends the packet to the NOX. The NOX may drop the packet or may add a new flow entry in the flow table, to force the OpenFlow switch to forward packets belonging to the same flow on a given path.

Figure 1. (a) OF-PXC; (b) OF-TPND.

B. OpenFlow-enabled Optical Switching Nodes We take the photonic cross-connect (PXC) as an example to illustrate how to use OpenFlow protocol to control an optical switching node. Fig.1(a) shows the structure of a PXC. We firstly introduce a virtual OpenFlow switch (VOFS) with virtual Ethernet interfaces (veths). These veths are virtualized from the physical interfaces of the PXC and each veth exactly corresponds to a physical interface of the PXC, as shown in Fig.1(a). By using this approach, the VOFS obtains a virtualized view of the physical structure of the PXC. The combination of an VOFS and the corresponding PXC is referred to as an OpenFlow-enabled PXC (OF-PXC), which is controlled by a NOX controller through the OpenFlow protocol,

as shown in Fig.1(a). Once the first IP packet of a new flow is received by the NOX, the NOX obtains the source and destination IP addresses of this flow and then performs routing and wavelength assignment (RWA) based on its knowledge of the whole network. After that, according to the results, the NOX inserts a new flow entry in the flow table of the VOFS. In turn, based on the flow entry, the VOFS automatically sends standard transaction language 1 (TL1) commands to crossconnect the corresponding ports of PXC through, for example, the transmission control protocol (TCP) interface to establish the lightpath, thanks to the same virtualized view of the PXC structure in the VOFS. This solution is fairly straightforward and cost-efficient, and more importantly, by using the proposed approach, all the network elements are virtualized as standard OpenFlow switches from the viewpoint of the NOX. In this case, the NOX can control and program the whole network by simply adding and deleting flow entries in the VOFS through the standard OpenFlow Flow Mod messages, which is beneficial for addressing the multivendor interoperability issue. C. OpenFlow-enabled Transponder The design of the OpenFlow-enabled transponders (OFTPDN) is shown in Fig.1(b). TPND groups are connected to an extended OpenFlow switch, which is able to trap the failure alarms from TPND and then convert the alarm into an extended OpenFlow Packet In message to notify the NOX. On the other hand, this OpenFlow switch receives specified Flow Mod messages from the NOX, and then translates them into TL1 to control TPNDs.

assigns the wavelength in the optical domain, and then adds a flow entry in all the nodes along the computed route in a sequential order, starting from the ingress router. In turn, according to the inserted flow entry, each VOFS within the optical nodes automatically controls the underlying hardware to cross-connect the corresponding ports, as shown in Fig.2(a). Moreover, upon a link failure, the OF-TPND detects the lossof-signal (LOS), and then forwards an alarm to the NOX to trigger the restoration path establishment, as shown in Fig.2(b). III.

FIELD TRIAL SETUP, RESULTS, AND DISCUSSIONS

The field trial setup is shown in Fig.3. An IP/optical multilayer network with the aforementioned extensions was constructed in Beijing (China), Tokyo (Japan), and Barcelona (Spain). For the OpenFlow-based UCP, a NOX was deployed in Japan, communicating with all the nodes by using the OpenFlow protocol through the public Internet. In the data plane, the hardware of OF-TPND1 and OF-ROADM1 (reconfigurable optical add/drop multiplexer) was emulated by using a commodity PC, which can emulate the failure alarm similar to a real transponder. The rest nodes were equipped with real hardware. The whole network is assumed to be operated by a single carrier in Japan, which is a scenario where a carrier rents network resources from other carriers in different countries to provide international services. In Fig.3, the number close to each network element is their identifier from the viewpoint of the NOX (i.e. data path ID in OpenFlow terminology). Each link was deployed with four wavelengths, as shown in Fig.3. The NOX was equipped with a 3.2GHz CPU (Core 2 duo) and 1GB of RAM memory.

Figure 3. Field trial setup.

Figure 2. (a) Procedure for end-to-end path creation; (b) Procedure for endto-end path restoration.

D. OpenFlow-based End-to-End Dynamic Path Creation and Restoration Once a new IP flow arrives at the ingress router (OF-R), the ingress router forwards the first packet (or a copy of the first packet) of this flow to the NOX. The NOX calculates the route,

We firstly verified the dynamic cross-layer path creation by setting up 4 paths, one by one, as summarized in Table 1. Considering that lightpaths are usually bi-directional in most operational scenarios, different wavelengths were selected for paths (1), (2), (3) and (4), due to the wavelength continuity constraint. We also used the passive approach presented in [8] to release these paths. In Table 1, the path setup/release latency in the control plane is shown, which comprises the OpenFlow message propagation time and NOX processing latency. The overall latency includes the aforementioned control plane processing latency, the interaction time between a VOFS and its controlled hardware, and the internal processing time of optical nodes/TPNDs. Since this internal processing time is difficult to measure and it varies depending on the hardware and vendor, for simplicity, we used a reference value of 10ms for all nodes/TPNDs. For the other latency contributors, we measured their average values by repeating the experiment more than 100 times. We observed that the processing time in

the NOX was relatively short and the key contributor to the path setup latency in the control plane was the OpenFlow message propagation time (i.e. Packet In and Flow Mod).

1s and 5s respectively. Fig.4 shows the CPU utilization of the NOX. It can be seen that, when the interval time of flows was 0s, the NOX was very busy and highly loaded. But when the time interval was slightly increased to 1s, the CPU load was sharply alleviated. However, in any case, considering the scalability issue of a centralized UCP, the introduction of a powerful path computation element (PCE) into the OpenFlowbased UCP is a one of the promising solutions to offload the NOX and thus enhance the network scalability [9, 10]. IV.

Figure 4. CPU utilization of the NOX.

We also evaluated the dynamic lightpath restoration, as summarized in Table 2. The control plane processing latency from the generation of a failure alarm to the insertion of new flow entries in every node along the restoration path ranged from 21 to 241ms, and the overall latency ranged from 269 to 487ms. Similar to the path setup/release latency, the major contributor to the restoration latency was also the OpenFlow message propagation time. When the nodes/TPNDs were geographically separated from the NOX, this latency increased significantly. To test the performance of an OpenFlow UCP in the case of high load, 1000 new flows at Client1 and Client3 were generated simultaneously, with the flow interval time 0s, TABLE I. No. (1) (2) (3) (4) TABLE II.

Src. Client1 Client2 Client2 Client4

Dest. Client2 Client3 Client4 Client1

Calculated Path

Wavelength

SL(CP)

SL(Overall)

RL(CP)

RL(Overall)

78797375010605 050601020708 050601023132 3231020175737978

W1 W2 W3 W4

~138 ms ~13 ms ~181 ms ~332 ms

~388 ms ~257 ms ~424 ms ~578 ms

~132 ms ~11ms ~170 ms ~321 ms

~257 ms ~131 ms ~290 ms ~445 ms

SUMMARY OF DYNAMIC END-TO-END RESTORATION (CPLR: CONTROL PLANE LATENCY DURING RESTORATION; OLR: OVERALL LATENCY DURING RESTORATION)

No.

Working Path

Failed Link

LOS Detection

Restoration Path

CPLR

OLR

1 2 3

Path (2) Path (1) Path (4)

OF-PXC5---OF-PXC6 OF-PXC1---OF-PXC2 OF-PXC5---OF-PXC6

OF-TPND3 OF-TPND2 OF-TPND1

05060104020708 787973717703010605 323104037771737978

~21 ms ~83 ms ~241 ms

~269 ms ~332 ms ~487 ms

ACKNOWLEDGMENT

REFERENCES [2]

[3] [4]

In this paper, we present an OpenFlow-based approach for dynamic wavelength path creation and restoration in future photonic networks. We propose a virtualization approach to extend OpenFlow to optical switching nodes, and for the first time, we evaluate the OpenFlow-based dynamic cross-layer path creation, restoration and transponder control. The results show that, in our tested scenario, the dynamic end-to-end cross-layer path creation and restoration can be achieved within 578ms and 487ms respectively, in which a major contributor is the OpenFlow message propagation time (i.e. Packet In and Flow Mod). The paper aims at providing an active contribution in support of the ongoing SDN/OpenFlow standardization activities and facilitating the industrial deployment of an UCP for IP/optical multi-layer networks in the near future.

SUMMARY OF PATHS (SL/RL(CP): PATH SETUP/RELEASE LATENCY IN THE CONTROL PLANE; SL/RL(OVERALL): OVERALL PATH SETUP/RELEASE LATENCY)

The authors would like to thank Mr. R. Vilalta, Dr. R. Casellas, Dr. R. Martínez, and Dr. R. Muñoz of the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Spain, and Mr. D. Zhang, Ms. L. Hong, Dr. H. Guo, and Prof. J. Wu of Beijing University of Posts and Telecommunications (BUPT), China, for their great support for this joint project and the field trial presented in this paper.

[1]

CONCLUSIONS

A. Farrel, “A unified control plane: dream or pipedream?” in Proc. IPOP 2010, keynote K-3, 2010. L. Liu, T. Tsuritani, I. Nishioka, S. Huang, S. Yoshida, K. Kubo and R. Hayashi, “Experimental demonstration of highly resilient wavelengthswitched optical networks with a multivendor interoperable GMPLS control plane,” IEEE/OSA Journal of Lightwave Technology, vol. 30, no. 5, pp. 704-712, 2012. OpenFlow, http://www.openflow.org/. NOX, http://www.noxrepo.org/.

[5]

S. Das, G. Parulkar, N. McKeown, P. Singh, D. Getachew, L. Ong, “Packet and circuit network convergence with OpenFlow,” in Proc. OFC/NFOEC 2010, paper OTuG1, 2010. [6] L. Liu, T. Tsuritani, I. Morita, H. Guo and J. Wu, “OpenFlow-based wavelength path control in transparent optical networks: a proof-ofconcept demonstration,” in Proc. ECOC 2011, paper Tu.5.K.2, 2011. [7] L. Liu, D. Zhang, T. Tsuritani, R. Vilalta, R. Casellas, L. Hong, I. Morita, H. Guo, J. Wu, R. Martínez and R. Muñoz, “First field trial of an OpenFlow-based unified control plane for multi-layer multi-granularity optical networks,” in Proc. OFC/NFOEC 2012, paper PDP5D.2, 2012. [8] L. Liu, T. Tsuritani, I. Morita, H. Guo and J. Wu, “Experimental validation and performance evaluation of OpenFlow-based wavelength path control in transparent optical networks,” Optics Express, vol. 19, no. 27, pp. 26578-26593, 2011. [9] L. Liu, R. Casellas, T. Tsuritani, I. Morita, R. Martínez and R. Muñoz, “Interworking between OpenFlow and PCE for dynamic wavelength path control in multi-domain WSON,” in Proc. OFC/NFOEC 2012, paper OM3G.2, 2012. [10] A. Giorgetti, F. Cugini, F. Paolucci and P. Castoldi, “OpenFlow and PCE architectures in wavelength switched optical networks,” in Proc. ONDM 2012, paper Tue3.7, 2012.