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GLASS (GMPLS Lightwave Agile Switching Simulator) A Scalable Discrete Event Network Simulator forGMPLS-based Optical InternetYoungtak Kim, Eunhyuk Lim, Chul Kim, Kwangil Lee, Douglas Montgomery,Oliver Borchert, Richard Rouil, David SuAdvanced Network Technologies Division (ANTD),National Institute of Standards and Technology (NIST)820 West Diamond Avenue, Gaithersburg, MD 20899, U.S.A.(Tel: 1-301-975-3613; Fax: 1-301-590-0932; E-mail ytkim@yu.ac.kr)MPLS LSP (Label Switched Path) among the core routers, thetraffic engineering has been more flexible and predictable. MPLSarchitecture, which had been basically designed upon packetswitching capability, recently has been generalized intoGeneralized MPLS (GMPLS) to include other switchingcapabilities, such as TDM circuit switching, fiber/lambdaswitching with generalized label [3]. The implementation of IPbased control plane for the next generation optical network withthe GMPLS control architecture has been received great interestsrecently; and it has been accepted by the optical networkequipment vendors and network operators. The DiffServtechnology has been developed to provide differentiated qualityof-service (QoS) according to the user’s requirements ornecessity [4]. Especially, the protocol structure of “DiffServaware-MPLS with GMPLS-based WDM Optical Network” hasbeen emphasized as a promising technical solution for NextGeneration Internet.These newly proposed and developed Internet networkingand traffic engineering technologies are currently standardizedindividually by IETF, ITU-T, OIF and other related forums. As aresult, the inter-operability, complexity, scalability andeffectiveness of the integrated operations with various newprotocol modules have become the major concerns of InternetService Providers (ISP) and network operators, as well as thesystem vendors.To test and evaluate the inter-operability and effectiveness ofthe newly proposed protocol functions, the implementation ofprototype systems and configuration of a trial test-bed network isone possible approach; but it usually takes long time and is costly.As a more practical approach, the network simulation with theconfigurable node protocol structure and the scalable network sizeis used in popular by many researchers and system developer.Network Simulator (ns) [6], JavaSim [7], SSFNet [8], and OPNET[9] are the most popularly used network simulators. But, thesenetwork simulators do not support the integrated simulation of“DiffServ-aware-MPLS” on the “GMPLS-based WDM OpticalNetwork” with OAM functions and fault restoration functions.Abstract – In this paper, we explain the design philosophyand the overall architecture of a scalable discrete event networksimulator for GMPLS-based Optical Internet, called GLASS(GMPLS Lightwave Agile Switching Simulator). GLASS hasbeen developed to support the R&D works in the area of NextGeneration Internet (NGI) networking with GMPLS-basedWDM optical network, and Internet traffic engineering withDiffServ-over-MPLS. It supports discrete-event simulations ofvarious DiffServ packet classification, per-hop-behavior (PHB)processing with class-based-queuing, MPLS traffic engineering,MPLS OAM functions that provide performance monitoring andfault notification, GMPLS-based signaling for WDM opticalnetwork, link/node failure model, and fast restoration from anoptical link failure.The NIST GLASS is implemented with Java programminglanguage on the SSFNet (Scalable Simulation FrameworkNetwork) simulation platform. It has been designed andimplemented with open interfaces to support future expansionsor replacements of protocol modules by users. It also providesDML description input file interface to support the users’flexible definition and modification of simulation parametersand configuration of protocol modules. The simulation outputsare generated in text file format that can be used by Excel toproduce various graph or charts. Recently, a GUI-basedtopology and simulation creator has been developed to support avisual environment from which one can configure and run thesimulator.Keywords – MPLS/GMPLS, WDM Optical Network,DiffServ, Network Simulation, Traffic EngineeringI. IntroductionA. MotivationIn order to manage the explosively increasing Internettraffic more effectively, various traffic engineering andnetworking technologies have been proposed, developed andimplemented. The physical link bandwidth has been expandedwith DWDM optical transmission technology and Optical AddDrop (OADM) & Optical Cross Connect (OXC) switchingtechnologies [1]. MPLS (Multi-Protocol Label Switching) hasbeen introduced to enhance the packet forwarding & switchingperformance by using faster fixed-label switching at layer 2.5[2]. By using the connection-oriented, bandwidth reservedB. Network Simulation for DiffServ-aware-MPLS on theGMPLS-based WDM Optical NetworkThe GLASS has been developed for the integratedsimulations of Next Generation Internet (NGI) networking withGMPLS-based WDM optical network, and Internet trafficengineering with DiffServ-over-MPLS [10]. It supports the1
optical network’s OXC-LSR is provided to the MPLS packetswitching capable (PSC) router (PSC-LSR) to be used in thecalculation of a routing decision.As shown in Figure 1(b), the MPLS layer network and opticallayer network can both have the same control plane functionsbased on the GMPLS-signaling architecture. This unified controlplane provides various advantages, such as various inter-workinginterface model across domains, integrated traffic engineering[19-29], and efficient integrated fault restoration.discrete-event simulations of various DiffServ packetclassification, per-hop-behavior (PHB) processing with classbased-queuing, MPLS traffic engineering, MPLA OAM forperformance monitoring and fault restoration, GMPLS-basedsignaling for WDM optical network, link/node failure model,and fast restoration from link or node failure.GLASS has been implemented on the SSFNet (ScalableSimulation Framework Network) simulation platform. It hasbeen designed and implemented with open interfaces to supportfuture expansion and replacement of protocol modules by users.It also provides DML description input file interface to supportthe users’ flexible definition/modification of simulationparameters and configuration of protocol modules.Recently, a GUI-based topology and simulation creator(GLASS-TSC) has been developed to support a visualenvironment from which one can configure and run thesimulator [10].The rest of this paper is organized as follows. Section IIdescribes the basic concept and the operations of “DiffServaware-MPLS Traffic Engineering”, and “GMPLS-based WDMOptical Networking.” Section III explains the target scalablenetwork simulation of the Internet networking and trafficengineering on the GMPLS-based optical network. Section IVdescribes the architecture of GLASS, and Section V summarizesthe paper.IP Layer networkGMPLS/PSC Layer networkIPRouterIPRouterGMPLS/OXC layer IPRouterIPRouterGMPLS PSC-LSRGMPLS OXC-LSR(a) Domain Interworking ModelInternet control & management protocols(RIP, OSPF, BGP, DVMRP, MOSPF)II. DiffServ-aware-MPLS traffic engineering andGeneralized Multi-Protocol Label Switching(GMPLS)Traffic engineering with fault management & performance managementfor Internet Transit NetworkApplicationGMPLS-Signaling OAM/LMPGMPLS-Signaling for optical networkTCP/UDPA. Networking Model of Next Generation InternetOne of the most important functional requirements of NextGeneration Internet is an efficient traffic engineering mechanismto manage the explosively increasing Internet traffic and toprovide QoS-guaranteed services to end users [11-14]. Also, inorder to provide the sufficient bandwidth required for themultimedia applications, the DWDM optical network has beendeveloped and deployed as the backbone transit network. ementations, the IP-based optical network control with theGMPLS (Generalized Multi-Protocol Label Switching) [15, 17,18] architecture has been designed and implemented recently.GMPLS-based control plane for the optical transport networkprovides great flexibility in the inter-networking of IP/MPLSnetwork and optical network.Figure 1(a) shows the domain Interworking model of nextgeneration Internet with IP layer network, MPLS layer networkand optical layer network. In GMPLS architecture, the MPLSlayer network and the optical layer network can beinterconnected in overlay model or peer-to-peer model. Inoverlay model, the MPLS layer network is the client of opticallayer network, and MPLS layer network sends requests of theoptical path setup through the O-UNI (optical user-networkinterface) signaling [16]. The routing information of the opticaldomain is not provided to the client MPLS layer network. Inpeer-to-peer model, the optical lambda channel is modeled asjust another LSP with generalized label (fiber ID and lambdaID) that has bigger bandwidth, and the routing information ofIPNICHost AIPNICO-NIC(WDM)IP RouterIPMPLSO-NIC O-NIC(WDM) SC-LSR(Optional Core)(b) Protocol Structure of GMPLSFigure 1. Networking model of Next Generation InternetB. Internet Traffic EngineeringA major goal of Internet traffic engineering is to facilitateefficient and reliable network operations while simultaneouslyoptimizing network resource utilization and maximizing trafficperformance [20-29]. The key performance objectives associatedwith traffic engineering (TE) are either traffic-oriented orresource-oriented. The traffic-oriented performance objectivesinclude the aspects that enhance the QoS of traffic stream, such asminimization of packet loss, minimization of delay, maximizationof throughput, and enforcement of service level agreements. Theresource-oriented performance objectives include the aspectspertaining to the optimization of resource utilization.In order to accomplish the objectives of traffic engineering,we must consider the service level specification/agreement, theInternet traffic engineering with DiffServ which manages themicro-flow of each service class, the DiffServ-aware-MPLStraffic engineering with traffic & QoS parameters that managesthe MPLS LSP for the aggregated flow of one or more DiffServclass-types. Figure 2 shows the overall traffic engineeringarchitecture.2
can define 64 different classes with distinct DiffServ Code Points(DSCP) [30]. In order to simplify the classification of DiffServ, aset of DiffServ classes is defined as a class-type where the classesin the same class-type possess common aggregate maximum andminimum bandwidth requirements to guarantee the requiredperformance level. Even though there is no maximum orminimum bandwidth requirement to be enforced at the level of anindividual class within the class-type, we can use the prioritypolices for classes within the same class-type in terms ofaccessing the class-type bandwidth (e.g. via the use of preemptionpriorities). Table 1 shows an example definition of class-type andtheir performance objectives.In service level specification, the objective QoS parametersof the requested service traffic flow should be specified, and thespecification must be agreed or contracted by both the serviceclient and the network service provider. ITU-T recommendationY.1541 provides a good example of the service levelspecification [22]. In order to guarantee the required QoS and toprovide better bandwidth utilization, DiffServ defines the PerHop-Behavior (PHB) at each IP/MPLS router node. The PHBincludes the class-based-queuing with specific metering/measuring and coloring, dropping policy, queuing, packetscheduling and optional traffic shaping.MPLS provides various attractive features of trafficengineering based on explicitly labeled & switched path. Theexplicitly labeled paths are not constrained by the destinationbased forwarding paradigm, but it can potentially be efficientlymanaged by their traffic parameters. The traffic trunk of anaggregation of traffic flows of the same class can be easilymapped onto LSPs, and a set of attributes can be associated withtraffic trunks that modulate their behavioral characteristics. Also,a set of attributes can be associated with resources that constrainthe placement of LSPs and traffic trunks across them. MPLSallows flexible traffic aggregation, and it is relatively easy tointegrate a constraint-based routing with lower overhead.To provide the traffic engineering capability, the existingsignaling and routing protocol modules must be expanded. Asrouting and signaling protocol with traffic engineeringextensions, OSPF-TE [23-26], RSVP-TE[17], IS-IS-TE[27],CR-LDP[18] are under standardization in IETF. To support theinter-domain traffic engineering, the TE extensions to BGP-4protocol have been proposed [44-48]. The signaling and routingprotocols with TE extensions basically provide mechanisms ofmaintaining the link state information database according to thespecified TE parameters, such as physical distance, availablebandwidth, allocated bandwidth, residual error rate, resourcecolor, shared risk link group (SRLG) identifier, etc.Table 1. Example of DiffServ Class-type and yNatureNCT1/ Minimized error RIP, OSPF, 100NCT0high priorityBGP-4msecJitter sensitive100EFreal-time highVoIPmsecinteractionJitter sensitiveVideo250AF4real-time highconference msecinteractionTerminalTransaction data250AF3sessioninteractivemsecCustom appData base250AF2 Transaction dataWebmsecLow loss bulkFTPAF11 secdataE-mailBest effortBEBest effortUserviceInternet Traffic Engineering with DiffServ or IntServIntServ-Guaranteed Service-Controlled service- Best effort serviceMPLS Traffic Engineering- LSP traffic/QoS parametersUserAISP 1ISP 2GMPLS NetworkGMPLS NetworkOXC/WDM OpticalBackbone NetworkOXC/WDM OpticalBackbone NetworkpacketBandwidthLossdefinitionRatioU10-3Peak rate10msec10-3Peak U10-3CommittedrateCommittedrateU10-3UThe mapping of DiffServ-class-types into MPLS LSP (LabelSwitched Path) can be implemented in either E-LSP (Expinferred-LSP) or L-LSP (Label-only-inferred LSPs) model. In ELSP model, LSPs can transport multiple class-types (orderedaggregates), and the EXP field of the MPLS shim header conveysthe PHB to be applied to the packet (conveying both informationabout the packet’s scheduling treatment and its drop precedence)at each LSR. In L-LSP model, each LSP only transports a singleclass-type, so the packet’s treatment is inferred exclusively fromthe packet’s label value, while the packet’s drop precedence isconveyed in the EXP field of the MPLS shim header.E-LSP model has merit of easier connection handling andprotection; the creation of a single LSP for end-to-end services fora customer is easier that the setting up, maintaining, administeringand monitoring multiple LSPs for each class-type. Also, E-LSPmodel requires reduced number of LSPs needed to deploy end-toend services in a network. The path protection and switchingmechanisms are more easily applied to a single LSP that a groupof related LSPs. Finally, the bandwidth borrowing among theclass-types of a customer is much easier.In MPLS networking, the guaranteed provisioning ofbandwidth is controlled by the per-LSP queue and the MPLSpacket scheduler. Several LSPs can be encapsulated by an outerLSP using the hierarchical LSP stacking, and this hierarchicalLSP stacking can be applied recursively. Each outer LSP is alsospecified with its own traffic parameters as explained above. IfService Level Agreement (SLA); Service Level Specification (SLS)Traffic Level Agreement (TLA); Traffic Level Specification(TLS)DiffServ-DiffServ Code Points (DSCPs)- PHB (Per-Hop Behavior)JitterUserBFigure 2. Internet traffic engineeringC. DiffServ-aware MPLS Traffic EngineeringDifferentiated Service (DiffServ) with Per-Hop-Behavior(PHB) has been developed to provide a QoS-guaranteed packettransmission [30-43]. According to the source/destinationaddress, service type, and protocol ID of IP packet header, we3
via O-UNI signaling, modify, delete or status enquiry of the lightpaths. For this light path handling, the control plane should havethe functional modules of signaling (such as CR-LDP [18] orRSVP [17], BGP[44-48]), routing (such as OSPF or ISIS), andwavelength assignment. Recently, Optical Internetworking Forum(OIF) generated the O-UNI 1.0 standard document [16] and IETFgenerated the LMP (Link Management Protocol) draft documentfor the control channel management and the link propertycorrelation [19].As shown in Figure 3, the protocol modules of control planefor OXC/OADM are IP-based; the interactions with its peer nodesare done through IP packet forwarding. Figure 4 shows the O-UNIbetween MPLS-LSR and OXC-LSR, and the O-NNI signalingamong OXC-LSRs.there is any available excess bandwidth in the outer LSP, theexcess bandwidth is allocated to the inner LSPs in proportion totheir weights in addition to their committed data rates. Since theLSP stacking is organized in recursive manner hierarchically,the available excess bandwidth in the outmost LSP should berecursively allocated to the inner LSPs according to the innerLSPs’ weights. By this reallocation of the excess bandwidth, wecan increase the utilization of network resources.D. GMPLS-based WDM Optical NetworkingThe major equipments for WDM optical networking areoptical cross-connect (OXC) with optical add-drop multiplexing(OADM), and the DWDM network interface card (DWDMNIC) for the client nodes (such as MPLS LSR or IP Router).OXC/OADM provides wavelength routing & switching,wavelength conversion, fiber/port switching, and wavebandswitching. The optical switching functions are implemented ineither all-optical switching architecture or with OpticalElectrical-Optical (O-E-O) architecture. According to thearchitecture and the modules, the lambda conversion and lambdaswitching may have different limitations, such as the number ofwavelength converters in a OXC and the range of wavelengthconversion. Through the add-drop ports of OXC/OADM, theoptical frames are delivered to the upper protocol layers, such asMPLS or IP layer. Figure 2 shows a typical optical domainmodel.E. Interworking Models of Optical InternetThe internetworking of IP/MPLS network and opticalnetwork can be considered in service model, interaction modeland routing approaches [13,14]. In service model, the IP layernetwork and optical layer network can operate in either clientserver service model or in integrated service model. In clientserver model, the optical network primarily provides a set ofbigger bandwidth pipes to the client IP/MPLS layer, while inintegrated service model, the IP layer network and the opticallayer networks are treated as a single network and there is nodistinction between the optical switches and the IP/MPLS routersas far as the control plane goes.In IP/MPLS-over-optical interaction model, three scenarioshave been suggested: overlay model, peer model and augmentedmodel [13, 14]. In overlay model, the optical network providespoint-to-point connection to the IP/MPLS domain. The IP/MPLSrouting protocols are independent of the routing and signalingprotocols of the optical layer. When the network operators of theIP/MPLS layer network and the optical layer network are different,this overlay model would be used in consideration of the privacyand security of network status information. In peer model, theoptical routers and optical switches act as peer nodes and there isonly one instance of a routing protocol running across the opticaldomain and the IP/MPLS domain. A common IGP like OSPF orIS-IS may be used to exchange topology information. OPSFopaque Link State Advertisement (LSA) and extended typelength-value (TLV) encoded fields may be used to in the case ofIS-IS. The assumption in this model is that all the o
overlay model, the MPLS layer network is the client of optical layer network, and MPLS layer network sends requests of the optical path setup through the O-UNI (optical user-network interface) signaling [16]. The routing information of the optical domain is not provided to the client MPLS layer network. In
Craft user sees whole network easily Circuit provisioning options Point and click from EMS Activated from EMS with explicit route - signaled using GMPLS Activated from EMS, computed route using GMPLS Circuit tracking with GMPLS Network element layer understands end to end circuit view Simplifies troubleshooting and alarm correlation ROADM
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