Network Working Group J.L. Le Roux
(France Telecom)(Ed.) Internet Draft D. Brungard (AT&T)France Telecom Category: Informational E. Oki (NTT)Expires: April 2007January 2008 D. Papadimitriou (Alcatel) K. Shiomoto (NTT) M. Vigoureux (Alcatel) October 2006(Ed.) Alcatel-Lucent Evaluation of existing GMPLS Protocols against Multi Layer and Multi Region Networks (MLN/MRN) draft-ietf-ccamp-gmpls-mln-eval-02.txtdraft-ietf-ccamp-gmpls-mln-eval-03.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document provides an evaluation of Generalized Multi-Protocol Label Switching (GMPLS) protocols and mechanisms against the requirements for Multi-Layer Networks (MLN) and Multi-Region Networks (MRN). In addition, this document identifies areas where additional protocol extensions or procedures are needed to satisfy these requirements, and provides guidelines for potential extensions. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119. Table of Contents 1. Terminology.................................................3 2.Introduction................................................3 3.2. MLN/MRN Requirements Overview...............................4 4.3. Analysis....................................................4 4.1. Multi-Layer Aspects.........................................4 126.96.36.199.1. Multi Layer Network Aspects.................................4 3.1.1. Support for Virtual Network Topology Reconfiguration........4 188.8.131.52.184.108.40.206. Control of FA-LSPs Setup/Release..........................5 220.127.116.11.18.104.22.168. Virtual TE-Links..........................................6 22.214.171.124.126.96.36.199. Traffic Disruption Minimization During FA Release.........8 188.8.131.52.Release.........7 184.108.40.206. Stability.................................................8 220.127.116.11.1.2. Support for FA-LSP Attributes Inheritance...................8 4.1.3. Support for Triggered Signaling.............................8 4.1.4. FA3.1.3. FA-LSP Connectivity Verification................................9 4.2. Multi-RegionVerification............................8 3.2. Specific Aspects...............................9 4.2.1.Aspects for Multi-Region Networks..................9 3.2.1. Support for Multi-Region Signaling..........................9 18.104.22.168.2.2. Advertisement of Internal Adaptation Capabilities..........10 5.Capabilities...........9 4. Evaluation Conclusion......................................12 6.5. Security Considerations....................................13Considerations....................................12 6. Acknowledgments............................................12 7. Acknowledgments............................................13 8.References.................................................13 22.214.171.124. Normative..................................................13 126.96.36.199. Informative................................................13 9. Authors'8. Editors' Addresses:........................................14 9. Contributors' Addresses:...................................14 10. Intellectual Property Statement............................15 1. Terminology This document uses terminologies defined in [RFC3945], [RFC4206], and [MLN-REQ]. 2.Introduction Generalized Multi-Protocol Label Switching (GMPLS) extends MPLS to handle multiple switching technologies: packet switching (PSC), layer-two switching (L2SC), TDM switching (TDM), wavelength switching (LSC) and fiber switching (FSC) (see [RFC 3945]). A data plane layer is a collection of network resources capable of terminating and/or switching data traffic of a particular format. For example, LSC, TDM VC-11 and TDM VC-4-64c representare three different layers. A network comprising transport nodes with different data plane switching layers controlled by a single GMPLS control plane instance is called a Multi-Layer Network (MLN). A GMPLS switching type (PSC, TDM, etc.) describes the ability of a node to forward data of a particular data plane technology, and uniquely identifies a control plane region. The notion of LSPLabel Switched Path (LSP) Region is defined in [RFC4206]. A network comprised of multiple switching types (e.g.(for example PSC and TDM) controlled by a single GMPLS control plane instance is called a Multi-Region Network (MRN). Note that the region is a control plane only concept. That is, layers of the same region share the same switching technology and, therefore, need the same set of technology specifictechnology-specific signaling objects. Note that a MRN is necessarily a MLN, but not vice versa, as a MLN may consist of a single region (control ofmultiple data plane layers within a region).of the same switching technology. Hence, in the following, we use the term layer"layer" if the mechanism discussed applies equally to layers and regions (e.g.(for example VNT, virtual TE-link, etc.), and we specifically use the term region"region" if the mechanism applies only for supportingto the support of a MRN. The objectives of this document are to evaluate existing GMPLS mechanisms and protocols ([RFC 3945], [RFC4202], [RFC3471])[RFC3471, [RFC3473]]) against the requirements for MLN and MRN, defined in [MLN-REQ]. From this evaluation, we identify several areas where additional protocol extensions and modifications are required to meet these requirements, and provide guidelines for potential extensions. An overviewA summary of MLN/MRN requirements is provided in section 3.2. Then section 43 evaluates for each of these requirements, whether current GMPLS protocols and mechanisms allow addressingmeet the requirements. When the requirements are not met,met by existing protocols, the document identifies whether the required mechanisms could rely on GMPLS protocols and procedure extensions or ifwhether it is entirely out of the scope of GMPLS protocols. Note that this document specifically addresses GMPLS control plane functionality for MLN/MRN in the context of a single administrative control plane partition. 3.Partitions of the control plane where separate layers are under distinct administrative control are for future study. This document uses terminologies defined in [RFC3945], [RFC4206], and [MLN-REQ]. 2. MLN/MRN Requirements Overview Section 5 of [MLN-REQ] lists a set of functional requirements for Multi Layer/Region Networks (MLN/MRN). These requirements are summarized below:below, and a mapping with sub-sections of [MLN-REQ] is provided. Here is the list of requirements that apply to MLN: - Support offor robust Virtual Network Topology (VNT) reconfiguration. This implies the following requirements: - Optimal control of FA-LSPForwarding Adjacency LSP (FA-LSP) setup and release;release (section 5.8.1 of [MLN-REQ]); - Support for virtual TE-links;TE-links (section 5.8.2 of [MLN- REQ]); - Traffic Disruption minimization during FA-LSP release (e.g. network reconfiguration events);(section 5.5 of [MLN-REQ]); - Stability;Stability (section 5.4 of [MLN-REQ]); - Support for FA-LSP attributes inheritance; - Support for Triggered Signaling;inheritance (section 5.6 of [MLN-REQ]); - Support for FA-LSP data plane connectivity verification;verification (section 5.9 of [MLN-REQ]); Here is the list of requirements that apply to MRN only: - Support for Multi-Region signaling;signaling (section 5.7 of [MLN-REQ]); - Advertisement of the adaptation capabilities and resources; 4.resources (section 5.2 of [MLN-REQ]); 3. Analysis 4.1. Multi-Layer3.1. Multi Layer Network Aspects 188.8.131.52.1.1. Support for Virtual Network Topology Reconfiguration A set of lower-layer FA-LSPs provides a Virtual Network Topology (VNT) to the upper-layer.upper-layer [MLN-REQ]. By reconfiguring the VNT (FA-LSP setup/release) according to traffic demands between source and destination node pairs ofwithin a layer, network performance factors such as maximum link utilization and residual capacity of the network can be optimized. Such optimal VNT reconfiguration implies several mechanisms that are analyzed in the following sections. Note that the VNT approach is just one possible approach among others,to perform inter-layer Traffic Engineering. 184.108.40.206.220.127.116.11. Control of FA-LSPs Setup/Release In a Multi-Layer Network, FA-LSPs are created, modified, released periodically according to the change of incoming traffic demands from the upper layer. This implies a TE mechanism that takes into account the demands matrix, the TE topology and potentially the current VNT, in order to compute and setup a new VNT. Several functional building blocks are required to support such TE mechanism: - Discovery of TE topology and available resources. - Collection of traffic demands of theupper layer.layer traffic demands. - Policing and scheduling of VNT resources policing/schedulingwith regardsregard to traffic demands and usage (i.e.(that is, decision to setup/release FAs);FA-LSPs); The functional component in charge of this function is called a VNT Manager (VNTM), it may be distributed on network elements or centralized on an external tool (see [VNTM]). It may also be partially centralized and distributed.(VNTM). - VNT PathPaths Computation according to TE topology, and potentially taking into account the old (existing) VNT (toto minimize changes);changes. The Functional component in charge of VNT computation may be distributed on network elements or may be centralized on an external tool (such as e.g.a PCE).Path Computation Element (PCE), [RFC4655]). - FA-LSP setup/release. GMPLS routing protocols supportprovide TE topology discovery. GMPLS signaling protocols allow setting up/releasing FA-LSPs. VNT Management functions (resources policing/scheduling, decision to setup/release FA, FAFA-LSPs, FA-LSP configuration) are out of the scope of GMPLS protocols. Such functionalities can be achieved directly on layer border LSRs, and/or onor through one or more external tools. When an external tool is used, an interface is required between the VNTM and the network elements so hasas to setup/releases FA-LSPs. This may rely on SNMP (TE MIB) or on proprietary interfaces.could use standard management interfaces such as [RFC4802]. The set of traffic demands of the upper layer is required for the VNT Manager to take decisions to setup/release FAs. This requires knowledge of the aggregated bandwidth reserved byFA-LSPs. Such traffic demands include satisfied demands, for which one or more upper layer LSPs established between any pair of border LSRs. Existing GMPLS routing allows for the collection of traffic demands of the upper region. It can be deduced from FA TE-link advertisements. The set of traffic demands can be inferred: - either directly, based on upper-layer FA TE-link advertisements. The traffic demands between two points correspond to the cumulated bandwidth reserved by upper-layer LSPs between these two points; - or indirectly, based on lower-layer FA TE-link advertisements. In this case a mechanism to infer the upper-layer traffic demand from the aggregated bandwidth reserved in lower-layer LSPs might be required,LSP have been successfully satisfied, as all pairs of border nodes may not be directly connected by a lower layer LSP. Collection of trafficwell as unsatisfied demands of anand future demands, for which no upper region may actually be achieved in several ways depending on the location of VNT Managers: - If a VNTM is distributed on borderlayer LSRs, then theLSP has been setup yet. The collection of traffic demands would rely on existing GMPLS routing, as per described above; - If a VNTMsuch information is centralized on an external tool, thenbeyond the collectionscope of traffic demandsGMPLS protocols, but may be achieved using existing GMPLS routing, provided that the tool relies onpartially inferred from parameters carried in GMPLS routing to discover TE link information,signaling or it may rely on another mechanism out of the scope ofadvertised in GMPLS protocols (e.g. SNMP TE-link MIB).routing. Finally, VNTthe computation of FA-LSPs that form the VNT can be performed directly on layer border LSRs or on an external tool (such as an external PCE)a Path Computation Element (PCE), [RFC4655]), and this independentlyis independent of the location of the VNTM. VNT computation is triggered by the VNTM (e.g.(for example, when the Pathpath computation is externalized on a PCE, the VNTM acts as PCC). HencePath Computation Client (PCC)). Hence, to summarize, no GMPLS protocol extensions are required to control FA-LSP setup/release. 18.104.22.168.22.214.171.124. Virtual TE-Links A Virtual TE-link is a TE-link between two nodes,upper layer nodes that is not actually associated towith a fully provisioned FA-LSP.FA-LSP in a lower layer. A Virtual TE-link represents the potentiality to setup a FA-LSP. There is no IGP adjacency associatedan FA- LSP in the lower layer to a Virtual TE-link.support the TE-link that has been advertised. A Virtual TE-link is advertised as any classicalTE-link, i.e.following the rules in [RFC4206] defined for fully provisioned TE-links. Particularly,In particular, the flooding scope of a Virtual TE-link is within an IGP area, as is the case for any TE- link. During its signalling, ifTE-link. If an upper-layer LSP makesattempts (through a signalling message) to make use of a Virtual TE-link, the underlying FA-LSP is immediately signalled and provisioned.provisioned in the process known as triggered signaling. The use of Virtual TE-links has two main advantages: - flexibility:Flexibility: allows to compute athe computation of an LSP path using TE-links and thiswithout takingneeding to take into account the actual provisioning status of the corresponding FA-LSP in the lower layer in terms of provisioning;layer; - stability:Stability: allows stability of TE-links in the upper layer, while avoiding wastage of bandwidth in the lower layer, as data plane connections are not established.established until they are actually needed. Virtual TE-links are setup/deleted/modified dynamically, according to the change of the (forecast) traffic demand, operator's policies for capacity utilization, and the available resources in the lower layer. The support of Virtual TE-links requires two main building blocks: - A TE mechanism for dynamic modification of Virtual TE-link Topology; - A signallingsignaling mechanism for the dynamic setup and deletion of virtual TE-links. Setting up a virtual TE-link requires a signallingsignaling mechanism allowing an end-to-end association between Virtual TE-link end points so as to exchange link identifiers as well as some TE parameters. The TE mechanism responsible for triggering/policing dynamic modification of Virtual TE-links is out of the scope of GMPLS protocols. Current GMPLS signalling does not allow setting up and releasing Virtual TE-links. Hence GMPLS signalling must be extended to support Virtual TE-links. We can distinguish two options for setting up Virtual TE-links: - The Soft FA approach,approach that consists of setting up the FA-LSP in the control plane without actually activating cross connections in the data plane. OneOn the one hand, this requires state maintenance on all transit LSRs (N square issue), but on the other hand this may allow for some admission control. Indeed, when a soft-FA is activated, therethe resources may be no longer available resourcesfor use by other soft- FAssoft-FAs that were sharinghave common links, theselinks. These soft-FA will be dynamically released and corresponding virtual TE-links are deleted. The soft-FA LSPs may be setup using procedures similar to those described in [GMPLS-RECOVERY][RFC4872] for setting up secondary LSPs. -The- The remote association approach,approach that simply consists of exchanging virtual TE-links idsIDs and parameters directly between TE- linkTE-link end points. This does not require state maintenance on transit LSRs, but reducereduces admission control capabilities. Such an association between Virtual TE-link end-points may rely on extensions to the RSVP-TE ASON Call procedure ([ASON-CALL]).([RSVP-CALL]). Note that the support of Virtual TE-linkTE-links does not require any GMPLS routing extension. 126.96.36.199.188.8.131.52. Traffic Disruption Minimization During FA Release Before deleting a given FA-LSP, all nested LSPs have to be rerouted and removed from the FA-LSP to avoid traffic disruption. The mechanisms required here are similar to those required for graceful deletion of a TE-Link. A Graceful TE-link deletion mechanism allows for the deletion of a TE-link without disrupting traffic of TE-LSPs that wherewere using the TE-link. GMPLS protocols do not provide for explicit indication to trigger such operation.Hence, GMPLS routing and/or signaling extensions are required to support graceful deletion of TE-links. This may rely, for instance, on new signaling Error code to notifyutilize the procedures described in [GR-SHUT]: A transit LSR notifies a head-end LSRsLSR that a TE-link along the path of a LSP is going to disappear,be torn down, and also withdraws the bandwidth on the TE-link so that it is not used for new routing attributes (if limited to a single IGP area), such as defined in [GR-SHUT]. 184.108.40.206.LSPs. 220.127.116.11. Stability The stability of upper-layer LSP stabilitymay be impaired if the VNT undergoes frequent changes. In this context robustness of the VNT is defined as the capability to smooth the impact of these changes and avoid their subsequent propagation. Guaranteeing VNT stability is out of the scope of GMPLS protocols and relies entirely on the capability of the TE and VNT management algorithms to minimize routing perturbations. This requires that the TE algorithmalgorithms takes into account the old VNT when computing a new VNT, and triestry to minimize the perturbation. 4.1.2.A full mesh of upper-layer LSPs MAY be created between every pair of border nodes between the upper and lower layers. The merit of a full mesh of upper-layer LSPs is that it provides stability to the upper layer routing. That is, forwarding table used in the upper layer is not impacted if the VNT undergoes changes. Further, there is always full reachability and immediate access to bandwidth to support LSPs in the upper layer. But it also has significant drawbacks, since it requires the maintenance of n^2 RSVP-TE sessions, which may be quite CPU and memory consuming (scalability impact). Also this may lead to significant bandwidth wastage. Note that the use of virtual TE-links solves the bandwidth wastage issue, and may reduce the control plane overload. 3.1.2. Support for FA-LSP Attributes Inheritance When a FA TE-linkTE Link is advertised, its parameters are inherited from FA-LSP parameters,the parameters of the FA-LSP, and specific inheritance rules are applied. This relies on local procedures and policies and is out of the scope of GMPLS protocols. Note that this requires that both head-end and tail-end of the FA-LSP are driven by same policies. 4.1.3. Support for Triggered Signaling. When a LSP crosses the boundary from an upper to a lower layer, it may be nested in or stitched to a lower-layer LSP. If such an LSP does not exist the LSP may be established dynamically. Such a mechanism is referred to as "Triggered signaling". Triggered signaling requires the following building blocks: - The identification of layer boundaries. - A path computation engine capable of computing a path containing multiple layers. - A mechanism for nested signaling. The identification of layer boundaries is supported by GMPLS routing protocols. The identification of layer boundaries is performed using the interface switching capability descriptor associated to the TE- link (see [RFC4206] and [RFC4202]). The capability to compute a path containing multiple layers is a local implementation issue and is out of the scope of GMPLS protocols. A mechanism for nested signaling is defined in [RFC4206]. Hence, GMPLS protocols already meet this requirement. 4.1.4. FA Connectivity Verification Once fully provisioned, FA liveliness3.1.3. FA-LSP Connectivity Verification Once fully provisioned, FA-LSP liveliness may be achieved by verifying its data plane connectivity. FAFA-LSP connectivity verification relies on technology specific mechanisms (e.g.(e.g., for SDH, G.707, G.783,SDH using G.707 and G.783; for MPLS, BFD,MPLS using BFD; etc.) as for any other LSP. Hence this requirement is out of the scope of GMPLS protocols. Note that the time to establish the FA-LSP must be minimized. 4.2. Multi-Region3.2. Specific Aspects 4.2.1.for Multi-Region Networks 3.2.1. Support for Multi-Region Signaling Applying the triggered signaling procedure discussed above, inThere are actually several cases where a MRN environment may lead to the setup of one-hop FA-LSPstransit node could choose between each node. Therefore, considering that the path computation is ablemultiple SCs to take into account richness of informationbe used for a lower region FA-LSP: - ERO expansion with regard to the Switching Capability (SC) available on given nodes belongingloose hops: The transit node has to expand the path, it is consistent to provide enough signaling informationand may have to indicateselect among a set of lower region SCs. - Multi-SC TE link: When the SCERO of a FA LSP, included in the ERO of an upper region LSP, comprises a multi-SC TE-link, the region border node has to select among these SCs. Existing GMPLS signalling procedures does not allow solving this ambiguous choice of SC that may be used and on over which link. Limitedalong a given path. Hence an extension to existingGMPLS signaling procedures is required for this purpose as it only mandates indication of the SCssignalling has to be included or excluded before initiatingdefined to indicate the LSP provisioning procedure. This enhancement would solveSC(s) that can be used and the ambiguous choice of SCSC(s) that are potentiallycannot be used along a given path, particularly in case of ERO expansion, or when an ERO sub-object identifies a multi-SC TE-link. This would givethe possibility to optimize resource usage on a multi-region basis. 4.2.2.path. 3.2.2. Advertisement of Internal Adaptation Capabilities In the MRN context, nodes supporting more than one switching capability on at least one interface are called Hybrid nodes.nodes ([MLN- REQ]). Hybrid nodes contain at least two distinct switching elements that are interconnected by internal links to provide adaptation between the supported switching capabilities. These internal links have finite capacities and must be taken into account when computing the path of a multi-region TE-LSP. The advertisement of the internal adaptation capability is required as it provides critical information when performing multi-region path computation. Figure 1a below shows an example of hybrid node. The hybrid node has two switching elements (matrices), which support here TDM and PSC switching respectively. The node terminates two PSC and TDM ports (port1 and port2 respectively). It also has internal link connecting the two switching elements. The two switching elements are internally interconnected in such a way that it is possible to terminate some of the resources of the TDM port 2 and provide through them adaptation for PSC traffic, received/sent over the internal PSC interface (#b). Two ways are possible to set up PSC LSPs (port 1 or port 2). Available resources advertisement e.g. Unreserved and Min/Max LSP Bandwidth should cover both ways. Network element ............................. : -------- : PSC : | PSC | : Port1-------------<->--|#aPort1-------------<->---|#a | : : +--<->---|#b | : : | -------- : TDM : | ---------- : +PSC : +--<->--|#c TDM | : Port2 ------------<->--|#d | : : ---------- : :............................ Figure 1a. Hybrid node. Port 1 and Port 2 can be grouped together thanks to internal DWDM, to result in a single interface: Link 1. This is illustrated in figure 1b below. Network element ............................. : -------- : : | PSC | : : | | : : --|#a | : : | | #b | : : | -------- : : | | : : | ---------- : : /| | | #c | : : | |-- | | : Link1 ========| | | TDM | : : | |----|#d | : : \| ---------- : :............................ Figure 1b. Hybrid node. Let's assume that all interfaces are STM16 (with VC4-16c capable as Max LSP bandwidth). After, setting up several PSC LSPs via port #a and setting up and terminating several TDM LSPs via port #d and port #b, there is only 155 Mb capacities still available on port #b. However a 622 Mb capacity remains on port #a and VC4-5c capacity on port #d. When computing the path for a new VC4-4c TDM LSP, one must know, that this node cannot terminate this LSP, as there is only 155Mb still available for TDM-PSC adaptation. Hence the internal TDM-PSC adaptation capability must be advertised. With current GMPLS routing [RFC4202] this advertisement is possible if link bundling is not used and if two TE-links are advertised for link1: We would have the following TE-link advertisements: TE-link 1 (port 1): - ISCD sub-TLV: PSC with Max LSP bandwidth = 622Mb, unreserved622Mb - Unreserved bandwidth = 622Mb. TE-Link 2 (port 2): - ISCD #1 sub-TLV: TDM with Max LSP bandwidth = VC4-4c, unreserved bandwidth = vc4-5c.- ISCD #2 sub-TLV: PSC with Max LSP bandwidth = 155 Mb, unreserved- Unreserved bandwidth = 155(equivalent): 777 Mb. The ISCD 2 in TE-link 2 represents actually the internal TDM-PSC adaptation capability. However if for obvious scalability reasons link bundling is done then the adaptation capability information is lost with current GMPLS routing, as we have the following TE-link advertisement: TE-link 1 (port 1 + port 2): - ISCD #1 sub-TLV: TDM with Max LSP bandwidth = VC4-4c, unreserved bandwidth = vc4-5c.- ISCD #2 sub-TLV: PSC with Max LSP bandwidth = 622 Mb, unreserved- Unreserved bandwidth = 777(equivalent): 1399 Mb. With such TE-link advertisement an element computing the path of a VC4-4c LSP cannot know that this LSP cannot be terminated on the node. Thus current GMPLS routing can support the advertisement of the internal adaptation capability but this precludes performing link bundling and thus faces significant scalability limitations. Hence, GMPLS routing must be extended to meet this requirement. This could rely on the advertisement of the internal adaptation capability as a new TE link attribute (that would complement the Interface Switching Capability Descriptor TE-link attribute). 5.Note: Multiple ISCDs MAY be associated to a single switching capability. This can be performed to provide e.g. for TDM interfaces the Min/Max LSP Bandwidth associated to each (set of) layer for that switching capability. As an example, an interface associated to TDM switching capability and supporting VC-12 and VC-4 switching, can be associated one ISCD sub-TLV or two ISCD sub-TLVs. In the first case, the Min LSP Bandwidth is set to VC-12 and the Max LSP Bandwidth to VC-4. In the second case, the Min LSP Bandwidth is set to VC-12 and the Max LSP Bandwidth to VC-12, in the first ISCD sub-TLV; and the Min LSP Bandwidth is set to VC-4 and the Max LSP Bandwidth to VC-4, in the second ISCD sub-TLV. Hence, in the first case, as long as the Min LSP Bandwidth is set to VC-12 (and not VC-4) and in the second case, as long as the first ISCD sub-TLV is advertised there is sufficient capacity across that interface to setup a VC-12 LSP." 4. Evaluation Conclusion Most of the required MLN/MRN functions will rely on mechanisms and procedures that are out of the scope of the GMPLS protocols, and thus do not require any GMPLS protocol extensions. They will rely on local procedures and policies, and on specific TE mechanisms and algorithms. As regards Virtual Network Topology (VNT) computation and reconfiguration, specific TE mechanisms that could for instance rely on PCE based mechanisms and protocols,need to be defined, but these mechanisms are out of the scope of GMPLS protocols. Four areas for extensions of GMPLS protocols and procedures have been identified: - GMPLS signallingsignaling extension for the setup/deletion of the virtual TE-links (as well as exact trigger for its actual provisioning);TE-links; - GMPLS routing and signallingsignaling extension for graceful TE-link deletion; - GMPLS signallingsignaling extension for constrained multi-region signalling (SC inclusion/exclusion); - GMPLS routing extension for the advertisement of the internal adaptation capability of hybrid nodes. 6.5. Security Considerations This document specifically addresses GMPLS control plane functionality for MLN/MRN in the context of a single administrative control plane partition and hence does not introduce additional security threats beyond those described in [RFC3945]. 7.6. Acknowledgments We would like to thank Julien Meuric andMeuric, Igor Bryskin and Adrian Farrel for their useful comments. 8.7. References 18.104.22.168. Normative [RFC3979] Bradner, S., "Intellectual Property Rights in IETF Technology", BCP 79, RFC 3979, March 2005. [RFC3945] Mannie, E., et. al. "Generalized Multi-Protocol Label Switching Architecture", RFC 3945, October 2004 [RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching", draft-ietf-ccamp-gmpls-routing, RFC4202, October 2005. [RFC3471] Berger, L., et. al. "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. 22.214.171.124. Informative [ASON-CALL][RSVP-CALL] Papadimitriou, D., Farrel, A., et. al., "Generalized MPLS (GMPLS) RSVP-TE Signaling Extensions in support of Calls", draft- ietf-ccamp-gmpls-rsvp-te-call,draft-ietf-ccamp-gmpls-rsvp-te-call, work in progress. [MLN-REQ] Shiomoto, K., Papadimitriou, D., Le Roux, J.L., Vigoureux, M., Brungard, D., "Requirements for GMPLS-basedGMPLS- based multi-region and multi-layer networks", draft-ietf-ccamp-gmpls-mrn-reqs,draft- ietf-ccamp-gmpls-mrn-reqs, work in progess. [RFC4206] K. Kompella and Y. Rekhter, "LSP hierarchy with generalized MPLS TE", draft-ietf-mpls-lsp-hierarchy, RFC4206, October 2005. [GR-SHUT] Ali, Z., Zamfir, A., "Graceful Shutdown in MPLS Traffic Engineering Network", draft-ietf-ccamp-mpls-graceful-shutdown,draft-ietf-ccamp-mpls-graceful- shutdown, work in progress. [GMPLS-RECOVERY][RFC4872] Lang, Rekhter, Papadimitriou, "RSVP-TE Extensions in support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS)-based Recovery", draft-ietf-ccamp-gmpls-recovery-e2e- signaling, work in progress.RFC4872, July 2007. [VNTM] Oki, Le Roux, Farrel, "Definition of Virtual Network Topology Manager (VNTM) for PCE-based Inter-Layer MPLS and GMPLS Traffic Engineering", draft-oki-pce-vntm-def, work in progress. [IW-MIG-FMWK] Shiomoto,[IW-MIG-FMWK]Shiomoto, K et al., "Framework for IP/MPLS-GMPLS interworking in support of IP/MPLS to GMPLS migration", draft-ietf- ccamp-mpls-gmpls-interwork-fmwk,draft-ietf-ccamp-mpls-gmpls-interwork-fmwk, work in progress. 9. Authors' Addresses:[RFC3473] Berger, L., et al. "GMPLS Singlaling RSVP-TE extensions", RFC3473, January 2003. [RFC4655] Farrel, A., Vasseur, J.-P., Ash,J., "A PCE based Architecture", RFC4655, August 2006. [RFC4802] Nadeau, T., Farrel, A., "GMPLS TE MIB", RFC4802, February 2007. 8. Editors' Addresses Jean-Louis Le Roux (Editor)France Telecom 2, avenue Pierre-Marzin 22307 Lannion Cedex, France Email: email@example.com@orange-ftgroup.com Dimitri Papadimitriou Alcatel-Lucent Francis Wellensplein 1, B-2018 Antwerpen, Belgium Email: firstname.lastname@example.org 9. Contributors' Addresses Deborah Brungard AT&T Rm. D1-3C22 - 200 S. Laurel Ave. Middletown, NJ, 07748 USA E-mail: email@example.com Eiji Oki NTT 3-9-11 Midori-Cho Musashino, Tokyo 180-8585, Japan Email: firstname.lastname@example.org Dimitri Papadimitriou Alcatel Francis Wellensplein 1, B-2018 Antwerpen, Belgium Email: email@example.comKohei Shiomoto NTT 3-9-11 Midori-Cho Musashino, Tokyo 180-8585, Japan Email: firstname.lastname@example.org MartinM. Vigoureux AlcatelAlcatel-Lucent France Route de Nozay, 91461 Marcoussis Cedex, FranceVillejust 91620 Nozay FRANCE Email: email@example.com@alcatel-lucent.fr 10. 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