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Generalized MPLS - An OverviewDaniela Vieira Cunha, Graca BressanDepartment of Electrical Engineering - POL1

Escola Politkcnica, University of SZo Paulo (USP)S5o Paulo - Brazil

Emails: (dcunha, gbressanielarc.usp.br

Abstract: CMPLS, being developed by IETF and OIF, ha sbeen proposed to address traf l c engineering to n variety onenuoi-king technology, and tu sene in R variety of networksignaling layers. exrending capabilities beyond those networksthat ar e only packet-based. GMPL S is an extension o MPLSrind it provides a control plane for devices that swirch in rime,packe t, wavelength, and fiber doiliains. This coilinion controlpluiie promises to sirnpliJy network operatiori andmariagenient by automating end-to-erid provisioning ocoiinections, nianaging network resources, and providingQuS. One o th e main architecture enhancements proposed byGMPLS is th e cornplete separation of the control and dutaplanes, allowing high performance, i i i t e l l i pn networkingujliile sbiiplifiing networks by combining transport andrmrltiservice switching into a single layered rietwork.

Keywords: GMPLS, control plane, optical networks

I. INTRODUCTIONIn recent years, there has been a massive increase in datatraffic driven primarily by the explosive growth of the lnlernetas well as the propagation of VPNs (Virtual PrivateNetworks), pushing the bandwidth requirements for IP(Internet Protocol) data to limits that demand thereconstruction of the entire network architecture, and malungunprecedented chang es to the existing transport infrastructure.The amount of data traffic worldwide has alreadysurpassed voice traffic some years ago: for that reason,convergence of the IP and optical layers is expected to be thetheine in the next phase of Internet expansion. At the sametime, there is increasingly strong demand from customers tokeep the cost of networking down.The need to carry more traffic, combined with the need tominimize the cost of camying this traffic results in a situationwhere SP s (Service Providers) need solutions that enable them

to carry a large volume of traffic in the inost cost-efficientmanner.

The industry believes that optical networking is a ke ysolution to keep up with the growth. Substantial interest hasbeen focused on optical networking, which is being developedto increase network capacity and scalability. Thus,telecommunications equipment designers face a huge task inconverging the optical-networking and IP worlds to answercarrier demands for greater efficiency and improved cost-effectiveness.

However, to realize IP and optical networks greatestpotential benefits, IP services in particular will need to bemore intelligent, flexible and scalable. That will allowoperators and providers to offer IP services beyond the less-profitable com modity category, where they reside today [ ].

b c dFigure 1. Evolution toward the use of GMPLS

Typically, there are four layers in the current data networkarchitecture, as shown in Figure la: IP, ATM (AsynchronousTransfer Mode). SONETISDH (Synchronous OpticalNetworWSynchronous Digital Network), and opticalnetworWDWDM (D ense Wavelength Division Multiplexing).This multilayer architecture suffers from the bottleneck effectwhere any layer can limit the scalability of the entire network.It is a150 fairly cost-ineffective. Though ATM has theadvantages of providing QoS (Quality of Service)functionality. it is very inefficient in massive datatransportation because of its huge overhead. As a

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consequence, changes are forming for the next generationcarrier networks to bypass both ATM and SONETISDHlayers, thus building a two-layer network (F igure Id) using IPw d opricaVDWDM layers with GMPLS (Generalized MPLS)GMPLS is not ordinary MPLS (Multiprotocol LabelSwitching), it is the extension of the MPLS paradigm tooptical networks, supported by IETF (Internet EngineeringTask Force) and OIF (Optical Internetworking Forum), thataddresses the needs of the optical control plane.Initially, a brief overview of MPLS and its evolution toGMPLS is given in section 2 and 3 respectively. Next, insection 4, a summary of GMPLS characteristics, protocols,labels. hierarchy, model and outstanding issues are explored.At the end, some conclusions are presented.

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11. MPLS BACKGROUNDMPLS extended the suite of 1P protocols to expedite theforwarding scheme used by IP routers. Routers have usedcomplex and time-consuming route lookups and addressmatchiiig schemes to deterniine the next hop for a receivedpacket, primarily by examining the destination address in theheader of the packet. MPLS has greatly simplified thisoperation by basing the forwarding decision on a simple label(Figure 2) .

Figure 2. Simplified MPLS Forwarding

For each specific area service a table of FEC (ForwardingEquivalence Class) is created to represent a group of flowswith the same TE (Traffic Engineering) requirements. Aspecific label is then bound to an FEC. At the ingress of anMPLS network, incoming IP packets are examined andassigned a label by a LER (Label Edge Router). The labeledpackets are then forwarded along an LSP (Label SwitchedPath), where each LSR (Label Switching Router) makes aswitching decision based on the packet's label field. An LSRdoes not need to exam ine the IP headers of the packets to find

the next hop. An LSR simply strips off the existing label andapplies a new label for the next hop.Another major feature of MPL,S is its ability to place 1Ptraffic on a defined path through the network. This capabilitywas not previously possible w ith IF' traffic. In this way. MPLSprovides bandw idth guarantees and other differentiated servicefeatures for a specific user application.Signaling is done using a LDP (Label DistributionProtocol) that runs on every MPLS node. There is a number ofdifferent LDPs. The two most popular are RSVP-TE(Resource Reservation Protocol) and CR-LDP (Constrained-based Routing LDP). These protocols provide real-timecoordination of the current network topology, includingattributes of each link.MPLS extensions to routing protocols, OSPF (OpenShortest Path First) and IS-IS (Intermediate System toIntermediate System), allow nodes to not only exchangeinformation about network topology, but also resourceinformation and even policy information. This information isused to compute the optimal patlis for the LSPs through thenetwork and allow complex TE decisions to be madeautomatically when selecting routes through the network.

111. MPLS EVOLUTION TO GMPLSThe MPLS researches proved that a label could map to acolor in a spectrum and that MPLS packets could be linkeddirectly to an optical network. The y called this process MPXS(Multiprotocol Lambda Switching). As research continued, itwas found that in order to have a truly dynamic network, amethod for totally controlling a network intelligeiit opticalnetworking was born.Since MPLS offered network switching, provisioningcould be accomplished automatically in MPLS; this featurecould be carried onto the telecom n etworks and switches couldbe provisioned using MPLS swilch as 3 core. However, sinceMPLS was specific to IP networks, the protocols would haveto he modified in order to talk to the telecom equipm ent. Thegeneralizing of th e MPL S protocol led to the birth of GMPLS.The IETF has extended MPL S suite of protocols to includedevices that switch in time, wavelength, and space domainsvia GMPLS. Thus GMPLS nodss can have links with one ormore of the following switching capabilities: FSC (FiberSwitch Capable). LSC (Lambda Sw itch Capable), TS C (TDM

- Time Division Multiplexing - Switch Capable), and PSC(Packet Switch Capable).The basic challenge for an all-encompassing controlprotocol is the establishment. maintenance, and managementof TE paths to allow the data plane to efficiently trensport user

data from the source to the de:;tination. A user flow startingfrom its source is likely to travel several network span s.

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Generalized MPLS An Overview

hlPLSFucus on d m lanePSCLabel - 32-bilnumberBGP-4 wilh mullipmlocoland labelcarrying extensions to suppon VPNs

A. MPLS AND GMPLS DIFFERENCESMPLS and GMPLS might he familiar terms to manypeople. However, some people may still confuse the GMPLS

control plane with the MPLS data plane. Although GM PLS isan extension of MPLS, its usage i n the control is differentfrom MPLS operation in the data plane. Table I belowpresents some of the main differences between these twoapproaches.On e of the main differences between the original MPLSand GMPLS is their functional focus. The original MPLSmainly focuses on the data plane. On the other hand, GMPLSfocuses on the control plane that performs connectionmanagement for the data plane for both PSC interfaces andnowpac ket switched interfaces, which include TSC, LSC, andFSC.Another difference between M PLS and G MPL S is that th eoriginal MPLS requires the LSP to be set up between routersat both ends, while GMP LS extends the concept of LSP set upbeyond routers. The LSP in GMPLS can be set up betweenany similar types of LSRs at both ends.

GMPLSFocus on control planePSC, SC, SC,TSCLnbel- &ilrory lzngihBGP being extended furlher tosvppon optical VPNs

V;iriour extensions IO LDPICR-LDPatid RSVP-TEo suppon services More work u n d e w a y lo expand thrcapabilitiesmc h as Di f lServ with TELDP scs TCP, SVP Hellomessages intruduced. Io improvereliabil ity

As mentioned in Table 1 , GMPLS allows the differenttypes of interfaces to work toge ther by nesting one LS P insideanoth er. This capability allows the syst em to scale better byforming a forwarding hierarchy, also known as labelhierarchy.Furthermore, there are functions specific to opticalnetworks that GMPLS covers that are not in the originalMPLS, such as suggested label, label set and bi-directional

LSP setup.

LM P ha s been introduced 10 mtomatediscovery. control channelmaintenance, and fm l t nwnagemcnt

IV. GMPLSGMPLS was developed with the goal of creating a singlesuite of protocols that would he applicable to all service and

transport traffic. As a result, it provides the same enhancedforwarding schemes for TDM, WDM (Wavelength DivisionMultiplexing), and physical fib er as it does for an IP/ATM/FR(Frame Relay) flow. The support for the additional types ofswitching has driven GM PLS to extend certain base functionsof traditional MPLS and, in some cases, to add functionality.These chang es and additions impact basic L SP properties, howlabels are requested and communicated, the unidirectionalnature of LSPs, how errors are propagated, and informationprovided for synchronizing the ingress and egress LSR s.It is also defined a com mon co ntrol plane, which simplifiesoperations and management, reducing the cost of operations.Th e new intelligence that GM PLS brings to the control planealso helps with network management. With it, many of theadvanced intelligence resource-engineering conceptsdeveloped for IP networks, such as constrained-based routing

and TE, are finding their way into the optical arena. Inaddition, the wider universal con trol plane within GM PLS willallow providers and operators to create a much broader rangeof dynamic services.Generalized MPLS is a natural extension of MPLS to theoptical signaled model and uses an open platform for thedynamic interconnection of multiple client layers, includingIP. It s control architecture provides a simple and mature set ofprotocols.GMP LS will also address two of the key tasks i n networkoperations and growth p rovisioning and restoration IS]Generalized MPLS requires modifications to currentsigilaling and routing protocols. It has also triggered thedevelopment of a new protocol known as LMP (LinkManagement Protocol). GMPLS discovers its neighbors.

distributes link information, and provides topologymanagement. path m anagemen t, link protection and recovery.GMPLS allows for link management, topology discovery,routing, signaling and survivability across IP and opticalnetworks, centralized control, automatic provisioning, loadbalancing, provisioning bandwidth service, BO D (bandwidthon demand), and OV PN (OpticalVF") .

A. Generalized LabelTraditional MPLS is designed to carry L3 (Layer 3) IPtraffic using e stablished IP-based paths and associating thesepaths with arbitrarily assigned labels. A label is a short, fixedlength, locally significant identifier that is used to identify aFEC. These labels can be configured explicitly by a network

administrator, or be dynamically assigned by means of aprotocol such as LDP o r RSVP.

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GMPLS generalizes MPLS in that it defines labels forswitching types of LI (Layer l ) , L2 (Layer 21, or L 3 traffic.GMPLS nodes can have links with one or more switchingcapabilities (FSC, LSC, TSC, PSC) thus, to deal with thewidening scope of MPLS into the optical and time domain,several new forms of label are required. These new forms oflabel are collectively referred to as G-label (GeneralizedLabel).G-label extends the traditional label by allowing therepresentation of not only labels which travel in-band withassociated data packets, but also labels which identify time-slots, wavelengths, or space division multiplexed positions, asGMPLS extends MPLS from supporting PSC interfaces andswitching to include support of non-packet switching. In thefollowing, it is summarized the characteristics of G-label inGMPL S signaling specification:

Values used in G-label field only have significancebetween two neighbors, and the receiver may need to c onvertthe received value into a value that has local significance;A G-label does not identify the class to which thelabel belongs. This is implicit in the m ultiplexing capabilitiesof the link on which the label is used;A G-label only carries a single level of label, i.e., it isnon-hierarchical. W hen multiple levels of label a e required,each LSP m ust be established separately:Each G-label object carries a variable length labelparameters.

The information transmitted over a GM PLS netw ork musthe associated with a label type. There are five different labelsthe information can he associated to. Bellow it is a l ist ofthe mand their characteristics:. MPLS labelThis label represents a generic MPLS label, a FR label, or. Fiber LabelsA link between LSRs may consist of a bundle of opticalfibers. LSRs may choose to allocate a whole fiber to a datatlow and so simply need to agree on which fiber (within thebundle) to use. In this case, the label va lue is the number ofthe selected fiber w ithin th e bundle.

.

..

.

an AT M label.

. Wavelength LabelsWhere the bandwidth of an optical fiber is subdivided byWDM, an optical LSR may choose to allocate a singlewavelength to a requested data flow. In this case, the labelvalue is the wavelength of the selected wavelength.. Waveband LabelsIf consecutive wavelengths are grouped together into awaveband, so as all to he switched in the same way, the label

is a "waveband I D and a pair of numbers (channels IDS)indicating the lower and upper wavelengths of the selectedwaveband. In w aveband switching, the switching interface canrecognize and switch individual waveband within the link(without distinguishing lambda, chann els, or packets).

Time-slot LabelsWhere the bandwidth of an optical fiber is subdivided intotime slots by the TDM, an optical switch may satisfy aparticular data flow request by allocating one or more timeslots to that flow. The exact details of TDM labelrepresentation depend upon the TDM hierarchy in use. forexample SONET or SDH.

For all the types of GMPLS described, the label valuedirectly implies the bandwidth that is available for thecorresponding data flow, which means bandwidth allocation.This is quite different from the case for non-generalizedlabels, and is a fundamental reflection of the nature of opticalnetworks.

B. G M P L S HierarchyGMPLS allows the different types of interfaces to worktogether by nesting one G-LSP inside another. This capabilityallows the system to scale better by building a forwardinghierarchy (Figure 3) . Nesting of G-LSPs between interfacetypes increase flexibility in service definition and makes itpossible for service providers operating a GMPLS network todeliver both bundled and unbundled services.

mm ...- . ..

Figure 3. Forwarding hierarchy of Nested LSPs.

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Generalized M P L 5 An Overview

At the top of the hierarchy are FSC interfaces. Underneathar e LSC interfaces, followed by TSC interfaces, and finallyPSC interfaces. This way, an LSP that starts and ends on aPSC interface can be nested (together with other LSP s) into anLSP that starts and ends on a TS C interface. This LSP, in turn,can be nested into an LSP that starts and ends on an LS Cinterface, which in turn can be nested into an LSP that startsand end s on an F SC interface.

As shown in Figure 4, the flows that have MPLS shimheader are transferred through a packet LSP that originatesbetween two packet switches. The flows are aggregated inTDM switch such as SONET and S DH. The aggregated flowswith SONETISDH label are multiplexed inside a TDM t imeslot LSP between two TDM switches. Similarly, themultiplexed flows with new lambda label can be transferredinside a lambda LSP that originates between two lambdaswitches. Finally, the flows with new fiber label can betransferred inside a fiber L SP that originates between two fiberswitches. Reversely, these flows must he recovered in lowerswitching interface using label information.

LamMaLSPTlmcrlof Label .OM Time4at LSP

Figure 4. GMPLS Hierarchy

PSC Packet Switch CapablePSC interface can switch the received data on a packet-by-packet basis. This interface recognizes packetkell boundariesand can forward data based on the content of the packetkellheader. The label carried in the shim header is used in thisinterface. All kinds of label used in PSC interface are definedas MPLS label.Examples of such an interface include interfaces on routersthat forward data based on the co ntent of the IP header, AT Mswitches, FR switches that have been enabled w ith an MPLS

control plane. interfaces on routers that forward data based onthe content of the MPLS sh im header.

TSC - TDM Switch CapableTSC interface forwards data based on the data's time slot

i n a repeating cycle. This interface can multiplex ordemultiplex channels within a fram e such as SD H payload.Examples of such an interface are interfaces onSONET/SDH cross-connect, ADM (AddlDrop Multiplexer),Terminal Multiplexer (TM), and DXC (Digital Cross-Connect).

LSC ~ Lambda Switch C apableLSC interface forwards data based on the wavelength onwhich the data is received. Therefore, this interface canrecognize and switch individual lambdas within the interface.Examp le on such an interface include interfaces on a PX C(Photonic Cross-connect), OADM (Optical ADM), OXC(Optical C ross-connect) switch that can operate at the level ofan individual wav elength.

FS C - Fiber Switch CapableFSC interface forward data based on a position of the d atain the real world physical spaces. Therefore. this interface canswitch the entire contents to another interface (withoutdistinguishing lambdas, chan nels or packets). Fiber switchingsystem switches at the granularity of an entire interface, andcannot exact individual lambdas within the interface. Thisinterface uses porclfiber label.Examples of such an interface are interfaces on PXC or

OXC that opente only at the level of a single or multiplefibers, an automated optical patch panel, or a protectionswitch.

GMPLS first defines several new forms to label thegeneralized label objects. These objects include thegeneralized label request, the generalized label, the explicitlabel control, and the protection flag. Any of the objects mightbe removed or modified and new objects might also be addedi n the future

However, since an optical link may consist of a bundle offibers, and the switches may support more than one kind ofmultiplexing on those fibers, it is necessary for the upstreamLSR to specify the LSP encoding type that it wants for thedata flow being setup; this encoding type then determineswhether the agreed label will be timeslot or wavelength based,and of what kind. The choice of how to switch for any

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particular LSP is made when the LSP is setup. This increasesthe flexibility of how the netw ork resource s can be used.

C. GMPLS ProtocolsGMPLS requires modifications to curent signaling androuting protocols to provide control and managementinternetworking between photonic switches andopticalDWDM transmission systems. In addition to therouting and signaling protocols, GMPLS makes use of theLMP it defines for link managem ent.

Keep Alive i Link Verification

Figure 5.Rela t ionsh ip be tween Pro toco ls

Figure 5 shows th e interrelation between the routingand signaling protocols, and also the LM P.

Signa l ing E nhancemen tsThe signaling protocols are responsible for all theconnection management actions and, are used to setup,modify, remove and retrieve the T E LSP information. TheGMPL S signaling extends certain base functions of the RSVP -TE and CR-LDP signaling and, in some cases, addsfunctionality. These chang es and additions impact basic LSPproperties, how labels are requested and communicated, theunidirectional nature of LSPs, how errors are propagated, andinformation provided for synchronizing the ingress and egress.It is defined the following new building blocks on the topof MPLS-TE:* A new generic label request format;. abels for TSC, LSC and FSC interfaces (G-labels);

Waveband switching support;Bi-directional LS P establishment with contentionresolution;Rapid failure notification extensio ns;Protection information currently focusing on linkprotection;Explicit routing with explicit label control for a finedegree of control;Specific traffic parameters per technology;LSP administrative status handling.

R o u t i n g E n h a n c e m e n t sThe GMP LS routing extends certain base functions of theOSPF-TE and IS-IS-TE routin:: an d, in som e cases, addsfunctionality. They are used for the auto-discovery of network

topology, address the routing capability for signalingmessages, and advertise resource availa bility (e.g., bandwidthor protection type).The major enhancements are as follows:. upport for Unnumbered Links

An unnumbered link has to be a point-to-point link. AnLSR at each end of an unnumbered link assigns a 32-bitidentifier to that link. Support for unnum bered links in routingincludes carrying inform ation about the identifiers of that link.Specifically, when an LSR advertises an unnumbered TE link,the advertisement carries both the local and the remoteidentifiers of th e link.. ink Protection T ype . LF TLPT represents the protection capability that exists for

each link of an LSP. It is desirable to carry this information sothat it may be used by the path computation algorithm to setup LSPs with approp riate protection charac teristics. Protectioninformation also indicates if the LSP is a primary or asecondary LSP. A secondary LSP is a backup to a primaryLSP.Six link protection types are cumently defined asindividual flags and can be comhined:

Extra Traftic . edicated 1:l- Unprotected I Dedicated 1+1- Shared . nhanced- Shared Risk Link G roup (SRL G) InformationA set of links may constitute a SRLG if they share aresource whose failure may afFect all links in the set. A link

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Generalized M P L S An Overview

may belong to multiple SRLGs. Thus SRLG Informationdescribes a list of SRLG s that the link belongs to.If an LSR is required to have multiple diversely routed

LSPs to another LSR, the path com putation should attempt toroute the paths so that they do not have any links in common,and such that the path SRLG s are disjoint.. nterface Switching Capability DescriptorIn the context of GMPLS, interfaces may have differentswitching capabilities. Interfaces at each end of a l ink need nott o have the same switching capabilities. The sam e happens tointerfaces on the same node.The Interface Switching Capability Descriptor describesswitching capa bility, of an interface. For bi-directional link s,the sw itching capabilities of an interface are defined to be thesame either direction.

LM P ~ Link Management ProtocolTo enable communication between nodes for routing,signaling, and link management, control channels must beestablished between a node p air.Link management is a collection of useful proceduresbetween adjacent nodes that provide local services such ascontrol channel management, link connectivity verification,link property correlation, and fault managem ent. The L MP hasbeen defined to fulfill these operations.Briefly, LMP provides for the following:

* Control Channel ManagementLMP control channel managemen t is used to establish andmaintain control channels between nodes. Control channels

exist independently of TE links, and can be used to exchangecontrol-plane information such as signaling, routing , and l inkmanagement information. Each control channel individuallynegotiates its control channel parameters and maintainsconnectivity using a fas t Hello protocol.

1 Link Property C orrelationA link property correlation exchange is defined. Theexchange is used to aggregate multiple data link s into bundledlink and exchange, correlate, or change TE l ink parameters.The link property correlation exchange may de done at anytime a l i n k is up and not in the Verification process. It allowsadding component links to a link bundle, changing a linksprotection mechanism, change port identifiers, or changecomponent identifiers in a bundle.

. Link Connectivity VerificationLink connectivity verification is an optimal procedure thatmay be used to verify the physical connectivity of data links as

well as to exchange the link identifiers that are used in theGMPLS signaling. The use of this procedure is negotiated aspa n of the configuration exchange that takes place during thenegotiation phase of the H ello protocol. This procedure shouldbe done initially when a data link is first established

* Fault ManagementFault management is an important requirement from theoperational point of view. It includes usually: fault detection,fault localization and fault notification. When a failure occursand is detected, an operator needs to know exactly where ithappened and a source node may need to be notified in orderto take some actions. Note that fault localization can also beused to support some specific local protectionhestorationmechanisms.

D. GMPLS IssuesFor a control plane to be used for all of the networks typesmentioned, the following issues must be considered:m Data forwarding is not limited to that of merely packetforwarding. The general solution must be able to retain thesimplicity of forwarding using a label for a variety of devicesthat switch in time or wavelength, or space;. Not every type of network is capable of looking into thecontents oft he received d ata, and of extracting a label;- Scalability is an important issue in designing largenetworks to accomm odate changes in the network quickly andgracefully. The resources that must be managed in a TSC or

optical network are expected to be m uch larger in scope thanin a packet-based network. For optical networks it is expectedthat hundreds to thousands of wavelengths (lambdas) will betransporting user data on hundreds of fibers;. onfiguring the switching fabric in electronic or opticalswitches may be a time-consuming process. For instance, in aDXC that is capable of switching tens of thousands of digitalsignal (DS) identifying the connection between theinputloutput ports could be time-consuming as fewer portsbecome available to accommodate incoming user traffic.Latency in setting up an LSP within these types of networkscould have a cumulative delaying effect in setting up an end-to-end flow;. Networks have the inherent ability to perform a fastswitchover from a failed path to a working one. GMPLScontrol plane must be able to accommodate this and otherlevels of protection granularity. It also needs to provide

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restoration of failed paths via static (pre-allocated) or dynamicreroute, depending on the required C OS (Class of Service).Table 2 presents a summary of the issues in the control

plane approach.

lSSW GMPLSSolution

Table 2. Summary of Issues in a Control PlaneApproachProtocol Notes

SwitchingDivcraity

ForwardingDiversity

Configuration

G~la bei Signaling LSP s t s i t anden d on the sametype of deviceLogical or All Signaling an dphysical routing io travelrepantion of out-of-bandcontroi an d daw,Suggested label Signaling Expedite LSPBi-directionalLSP

setup

Lower linkadjacency database sizeSignalingLink bundling BandwidthScaIBbilityHierarchical

Reliability Protection and L M PrestomtionSRLF for pathdiversity

Routing

Efficienl use of Hierarchical Signalingnetwork LSPrcwurces RoutingU"""miJ:eredlinks

SimulateSONET bi-directional line-awitchednng( B U R ) andUPSRSave on exccssuse of scarce waddresses

V. CONCLUSIONSGMPLS provides a whole new way of optical networking.

It not only provides the possibility of multi-layer, multi-vendor control plane interoperahility, but also enables newtypes of services such as BOD nd O VPN . In addition, carrierscan enjoy automated TE and single-step connectionprovisioning, saving their valuable time, and avoiding errorswith a lower cost. The control plane also supports newrestoration schemes to provide additional protection forvarious network topologies that traditional transport systemscannot support efficiently.Service providers can integrate the signaling protocol inGMPLS to establish high capacity infrastructures forsupporting fast provision of connection services, and also

handle large volumes of traffic io a cost-effective way, speedup the services, and solve the bottleneck effect. GMPLS canreduce operation and managemem cost without affecting theQoS of the entire network. It can also raise revenueopportunities and increase the network performance.Furtherm ore, it has the function:$ of restoration and flexibleprotection to provide network survivability.GMPLS will be an integral part of deploying the nextgeneration of data and optical networks. It provides thenecessary bridges between the IP and photonic layers to allowfor interoperable and scalable parallel growth in the IP andphotonic dimensions. By streamlining support formultiplexing and switching in a hierarchical fashion andcombining the flexible intelligence of MPLS TE, the businessvalue of optical switching GMPLS will prove essential in anysolution that aims to enable large volumes of traffic in a cost-efficient manner for service providers.

R E F E R E N C E S[ I ] Banerjee, A.. Drake, J., Lang, J. , Tum er, B. , Awduche, D.,Berger, L., Kompella, K., Rekhter, Y., (2001)."Generalized Multiprotocol Label Switching: AnOverview of Signaling Enhancements and RecoveryTechniques". IEEE Communications Magazine, July.[21 Choi, I., Kang, M., Lee, G.. Um, J . , Lee, Y . , Kim, J.,(.2002), "Framework for GMPLS Label Encoding",Internet Draft, draft-choi-~:mpls-label-framework-OO.txt,October, expired date April 2003.[31 Chokesatean, P.. Y aemnoi, T., Sukcharoenkana, W ..Zhang, Y. , (2001). "Will GMPLS replace ATM andSONETISD H in the next few years?%141 International Engineering Consortium, "GeneralizedMultiprotocol Label Switching", www.iec.org .151 Kom pella, K., Rekhter, Y., (2002), "Routing Extensions,inSupport of Generalized MPLS", Internet Draft. draft-ietf-ccamp-gmpls-routing-05.txt, August, expired dateFebruary 2003.[61 Man nie, E., (20021, "Generalized Multiprotocol LabelSwitching (GMPLS) Architecture", Internet Draft, draft-ietf-ccamp-gmpls-architecture-03.tnt. August, expired dateFebruary 2003.

www.polarisnetworks.cond);mpls.[SI Saha, D., (2202) Tove rgin g Optical and IP: Can GMPLSTake Control?", Comm unication Systems Design,February.[91 White Rock Networks. (2002) "GMPLS: A New Way ofOptical Networking", January.

[7 ] GMPLS Resource Center, ~20021,

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