2022年软件定义光网络 .pdf

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1、OTh1H.3.pdfOFC/NFOEC Technical Digest?2013 OSASoftware Defined Optical Networks Technology and Infrastructure:Enabling Software-Defined Optical Network Operations D.Simeonidou,R.Nejabati,M.P.Channegowda High Performance Networks Laboratory,Merchant Venturers School of Engineering,University of Brist

2、ol,UK dimitra.simeonidoubristol.ac.ukAbstract:A control plane architecture based on OpenFlow for optical SDN is introduced.Requirements for its implementation are discussed considering emerging optical transport technologies.Two implementations of the architecture and results on their performance ar

3、e reported.OCIS codes:(060.4250)Networks;(060.4510)Optical Communications.1.Introduction Software defined networking or SDN is defined as a control framework that supports programmability of network functions and protocols by decoupling the data plane and the control plane,which are currently integr

4、ated vertically in most network equipment.The SDN technology allows the underlying infrastructure to be abstracted that can be used by applications and network services as a virtual entity.This allows network operators to define and manipulate logical maps of the network and therefore create multipl

5、e co-existing network slices(virtual networks)independent of underlying transport technology and network protocols 1.Furthermore,the separation of control plane and data plane makes the SDN a suitable candidate for an integrated control plane supporting multiple network domains and multiple transpor

6、t technologies.OpenFlow(OF)is an open standard,vendor and technology agnostic protocol that allows separation of data and control plane and therefore it is a suitable candidate for the realization of SDN.It is based on flow switching with the capability to execute software/user defined flow based ro

7、uting,control and management in a controller(i.e.OF controller)outside the data path.OF extensions to support optical networks can provide a new vendor agnostic framework for evolving carrier grade networks.Enabling SDN via OF at the optical layer can facilitate coordination and orchestration of ser

8、vices involving the optical layer together with higher network layers.This can be achieved by providing a unified control plane platform for integration of electronic packet and optical networks for access,metro and core network segments.In addition OF can support application specific network slicin

9、g at the optical layer.This paper introduces a control plane architecture based on OF for software defined optical networks.Subsequently the paper discusses technological considerations and requirements for OF protocol extensions to support optical transport networks.Furthermore,the paper describes

10、two technical implementations of the OF based SDN architecture and report on performance evaluation of the proposed approaches.2.A unified control plane based on OpenFlow for software defined optical network In order to enable SDN based unified control and management of an optical network the follow

11、ing challenges need to be addressed:Definition of a unified optical transport and switching granularity(e.g.optical flow)that can be generalized for different optical transport technologies(e.g.fixed DWDM,flexi DWDM,sub-wavelength switching,etc.)Design and implementation of an abstraction mechanism

12、that can hide the transport layer technology details and realize the aforementioned generalized switching entity definition Taking into account physical layer specific features of different optical transport technologies such as power,impairments,switching constraints,etc.Cross technology constraint

13、s for bandwidth allocation and traffic mapping in networks comprising heterogeneous technological domains e.g.packet over single or hybrid optical transport technologies Figure 1a shows the architectural block diagram of an OF based optical SDN control plane addressing the aforementioned challenges.

14、Central to the proposed architecture is an abstraction mechanism,realised by extended OF controller and the OF protocol.This mechanism enables generalization of flow switching concept for the underlying heterogeneous optical transport technologies as well as its integration with packet switched doma

15、ins.The control plane using the extended OF protocol and the controller are able to abstract the switching entity and transport format of each technological domain in the form of generic flows(figure 1c)and to configure network elements using technology specific flow tables (i.e.intra-domain flow ta

16、bles).In addition,the architecture utilizes 978-1-55752-962-6/13/$31.00?2013 Optical Society of America名师资料总结-精品资料欢迎下载-名师精心整理-第 1 页，共 3 页 -OTh1H.3.pdfOFC/NFOEC Technical Digest?2013 OSAan inter-domain flow table for enforcing cross technology constraints for bandwidth allocation when traffic travers

17、e from one technology domain to another(figure 1b,e.g.flexi DWDM to fixed WDMD,or packet to DWDM).In this architecture,an SDN application can obtain a unified and abstracted view of the underlying networks based on information gathered through OF protocol.It can also configure and control the networ

18、k by updating flow tables.3.Flow definition and OpenFlow extensions for supporting optical network Existing standard OF protocol extensions addressing optical domain consider SONET/SDH,Optical Cross Connects(OXCs),and Ethernet/TDM convergence as circuit switched technologies.The latest OF extensions

19、 supporting circuit switching is documented as addendum v0.3 2.It does not support optical network features like switching constraints and optical impairments.Furthermore it does not support advanced and emerging optical transport technologies such as flexible DWDM grid.To address the shortcomings o

20、f current OF extension on supporting optical network technologies,we have proposed a generic optical flow specification as shown in figure 1c.In the proposed definition,an optical flow can be identified by a flow identifier comprising port,wavelength or center frequency(CF)of the optical carrier,ban

21、dwidth associated with the wavelength or CF,signal type(e.g.optical transport format:sub-wavelength switching header information,time slot,bitrate,protocol,modulation format)associated with a specific optical transport and switching technology,and constraints specific to the physical layer(e.g.sensi

22、tivity to impairments and power range).This definition is generic enough to allow applying the concept of optical flow to both existing and emerging optical transport technologies.To enable OF protocol to support the proposed flow definition,we have extended the Switch_Feature and CFlow_Mod messages

23、 of the OF protocol.The Switch_Feature extension supports optical network elements(NE)capabilities including:central frequency,spectrum range and bandwidth granularity of transponders and switches;number of ports and wavelength channels of switches;peering connectivity inside and across multiple dom

24、ains;signal types;NE optical constraints e.g.attenuation;etc.We have also extended the CFlow_Mod messages for configuring NEs i.e.transponders and switching/cross connect nodes for both fixed and flexible grid DWDM compatible NEs based on the ITU-T G.694.1 recommendation 3.The equation 193.1+n 0.006

25、25(THz)is used to calculate the central frequency of a frequency slot,while 12.5 GHz m yields the slot width where n is an integer and m is a positive integer.Based on the aforementioned flow definition and OF protocol extensions,we introduce two methods for implementation of the proposed control pl

26、ane architecture:1-integrated GMPLS and OpenFlow;and 2-stand-alone OpenFlow.In the integrated GMPLS-OpenFlow approach(Figure 2a),the OF controller receives information regarding the topology and resources using extended OF protocol.However,path computation,lightpath establishment and teardown are pe

27、rformed utilizing the GMPLS control plane.Extended OF controller and associated SDN applications are developed considering loose and explicit lightpath establishment.In the former Figure 1.(a)Architecture of a SDN enabled optical network control plane based on OpenFlow,(b)example of cross technology

28、 flow routing/mapping constraints(c)generic optical flow identifier(b)(c)(a)名师资料总结-精品资料欢迎下载-名师精心整理-第 2 页，共 3 页 -OTh1H.3.pdfOFC/NFOEC Technical Digest?2013 OSAcase only ingress and egress NEs and ports are specified and the GMPLS control plane handles the path computation and establishment in the int

29、ernal optical cloud.In other words,the OF controller exploits GMPLS in order to compute flow tables and consequently to establish and verify the lightpaths.In the latter case(Figure 2b),the controller is able to specify the full details of the lightpath(i.e.,address all the switches and ports along

30、the lightpath),to verify the feasibility of the lightpath and perform its establishment.In this approach,in order to implement the proposed architecture we have developed an OF agent for each NE.Our agent utilizes an internal API to communicate with the NEs,and the proposed extended OF protocol and

31、flow definition to communicate with the extended OF controller.In this approach the controller utilizes the Switch_Feature messages to construct the network topology and CFlow_Mod message to control optical transponders and switches.The extended OF controller unlike the earlier approach relies on th

32、e SDN application for computing flow tables in the controller and consequently for establishing and verifying end-to-end lightpaths.4.Experimental evaluation We have evaluated and compared the proposed architecture and technical approaches in two test-beds.One test-bed deployed integrated GMPLS-Open

33、Flow on packet over fixed DWDM test-bed using NEC OF enabled packet switches and ADVA GMPLS enabled ROADMs(figure 2a).The other test-bed deployed stand-alone OpenFlow on packet over mixed flexi and fixed DWDM network and incorporated NEC OF enabled packet switches,ADVA OF enabled ROADMs and in-house

34、-build flexi OXC and transponders(figure 2b).We have evaluated the performance of both approaches in terms of path setup times using an SDN application to create network slices.Figure 2c shows path setup times for packet over the ADVA ROADMs domain(packet over fixed WDM domain only)using the integra

35、ted GMPLS-OpenFlow and standalone OpenFlow approaches for different path request load values indicating significantly faster path setup times for the stand-alone OpenFlow.Figure 2d illustrates the performance of the stand-alone OpenFlow for end-to-end path setup time(figure 2b test-bed)for different

36、 technology domains.Path setup times are compared for three different cases i.e.fixed DWDM domain only,flexi-fixed DWDM domains,packet over fixed-flexi DWDM domains.In addition,the comparing of results from the three test scenarios:multi domain,multi technology as presented in figure 2d;and the sing

37、le domain standalone OF presented in figure 2c show that the OF controller performance is stable for different network scenarios irrespective to the transport technology and the complexity of the network topology.5.Conclusion We have proposed a control plane architecture based on OpenFlow for enabli

38、ng SDN operations in optical networks.We discuss requirements and describe implementations of OpenFlow protocol extensions for transport optical networks incorporating commercial optical equipment as well as research prototypes of emerging optical transport technologies.Experimental validations and

39、performance analysis of the proposed architecture demonstrate improved path setup times and control stability when OpenFlow is applied directly to optical transport technologies.6.References 1 Software-Defined Networking:The New Norm for Networks,ONF white paper,Open Networking Foundation,April 2012

40、.2 S.Das,G.Parulkar,P.Singh,D.Getac hew,L.Ong,and N.McKeown,“Packet and circuit network convergence with OpenFlow,”in Optical Fiber Communication Conference 2010,paper OTuG1.3 ITU-T Recommendation G.694.1,Feb 2012.Figure 2:(a)and(b)test-beds setup,(c)and(d)performance evaluation results 名师资料总结-精品资料欢迎下载-名师精心整理-第 3 页，共 3 页 -