Network Working Group Kohei Shiomoto (NTT) Internet Draft Dimitri Papadimitriou (Alcatel) Jean-Louis Le Roux (France Telecom) Martin Vigoureux (Alcatel) Deborah Brungard (AT&T) Expires: December 2005 July 2005 Requirements for GMPLS-based multi-region and multi-layer networks (MRN/MLN) draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. 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. Copyright Notice Copyright (C) The Internet Society (2005). All Rights Reserved. Abstract Most of the initial efforts on Generalized MPLS (GMPLS) have been related to environments hosting devices with a single switching capability, that is, one data plane switching layer. The complexity raised by the control of such data planes is similar to that seen in classical IP/MPLS networks. By extending MPLS to support multiple switching technologies, GMPLS provides a comprehensive framework for the control of a multi-layered network of either a single switching technology or multiple switching technologies. In GMPLS, a switching technology domain defines a region, and a network of multiple switching types is referenced in this document as a multi-region network (MRN). When referring in general to a layered network, Expires December 2005 [Page 1] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 which may consist of either a single or multiple regions, this document uses the term, Multi-layer Network (MLN). This draft defines a framework for GMPLS based multi-region/multi-layer networks and lists a set of functional requirements. Table of Contents 1. Introduction...................................................2 2. Conventions used in this document..............................4 3. Positioning....................................................4 3.1. LSP Region and layer.........................................4 4. Key mechanisms in GMPLS-based multi-region/multi-layer networks..........................................................6 4.1. Interface Switching Capability...............................8 4.2. Multiple Interface Switching Capabilities....................8 4.2.1. MRN/MLN with Simplex nodes.................................9 4.2.2. MRN/MLN with hybrid nodes..................................9 4.2.3. Vertical and Horizontal interaction and integration.......10 4.3. Integrated Traffic Engineering (TE) and Resource Control....12 4.4. Triggered signaling.........................................12 4.5. TE LSP......................................................12 4.6. Virtual network topology (VNT)..............................13 5. Requirements..................................................13 5.1. Scalability.................................................13 5.2. TE-LSP resource utilization.................................14 5.3. TE-LSP Attribute inheritance................................16 5.4. Verify the TE-LSP before it enters service..................16 5.5. Disruption minimization.....................................16 5.6. Path computation re-optimization stability..................16 5.7. Computing paths with and without nested signaling...........17 5.8. Handling single-switching and multi-switching type capable nodes............................................................17 5.9. Advertisement of the available adaptation resource..........18 6. Security Considerations.......................................18 7. References....................................................18 7.1. Normative Reference.........................................18 7.2. Informative References......................................19 8. Author's Addresses............................................19 9. Intellectual Property Considerations..........................20 10. Full Copyright Statement.....................................20 1. Introduction Generalized MPLS (GMPLS) extends MPLS to handle multiple switching technologies: packet switching, layer-two switching, TDM switching, wavelength switching, and fiber switching (see [GMPLS-ARCH]). The Interface Switching Capability (ISC) concept is introduced for these switching technologies and is designated as follows: PSC (packet switch capable), L2SC (Layer-2 switch capable), TDM (Time Division Multiplex capable), LSC (lambda switch capable), and FSC (fiber switch capable). Service providers may operate networks where multiple different switching technologies exist. The representation, in a GMPLS Expires December 2005 [Page 2] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 control plane, of a switching technology domain is referred to as a region [HIER]. A switching type describes the ability of a node to forward data of a particular data plane technology, and uniquely identifies a network region. A layer describes a data plane switching granularity level (e.g. VC4, VC-12). A data plane layer is associated with a region in the control plane (e.g. VC4 LSP associated to TDM, Packet LSP associated to PSC). More than one data plane layer can be associated to the same region (e.g. both VC4 and VC12 are associated to TDM). Thus, a control plane region identified by its switching type value (e.g. TDM) can itself be sub-divided into smaller granularity based on the bandwidth that defines the "data plane switching layers" e.g. from VC-11 to VC-4-256c. The Interface Switching Capability Descriptor (ISCD) [GMPLS-RTG] identifying the interface switching type, the encoding type and the switching bandwidth granularity, supports this additional granularity. The ISCD uniquely identifies a set of one or more network layers e.g. TDM ISC covers from VC-11 to VC-4-256c. A network comprising transport nodes with multiple data plane layers of either the same ISC or different ISCs, controlled by a single GMPLS control plane instance, is called a Multi-Layer Network (MLN). To differentiate a network supporting LSPs of different switching technologies (ISCs) from a single region network, a network supporting more than one switching technology is called a Multi-Region Network (MRN). MRNs can be categorized according to the distribution of the switching type values amongst the LSRs: - Network elements are single switching capable LSRs and different types of LSRs form the network. All TE links terminating on such nodes have the same switching type value. A typical example is a network composed of PSC and TDM LSRs with only PSC TE-link ends and with only TDM TE-link ends, respectively. - Network elements are multi-switching capable LSRs i.e. nodes hosting at least more than one switching capability. TE links terminating on such nodes may have a set of one or more switching type value. A typical example is a network composed of LSRs that are capable of switching with PSC+TDM TE-links. Multi-switching capable LSRs are further classified as "simplex" and "hybrid" nodes (see Section 4.2). - Any combination of the above two elements. A network composed of both single and multi-switching capable LSRs. Since GMPLS provides a comprehensive framework for the control of different switching capabilities, a single GMPLS instance may be used to control the MRNs/MLNs enabling rapid service provisioning and efficient traffic engineering across all switching capabilities. In such networks, TE Links are consolidated into a single Traffic Engineering Database (TED). Since this TED contains the information relative to all the Expires December 2005 [Page 3] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 different regions/layers existing in the network, a path across multiple regions/layers can be computed using this TED. Thus optimization of network resources can be achieved across multiple regions/layers. Consider, for example, a MRN consisting of IP/MPLS routers and TDM cross-connects. Assume that a packet LSP is routed between source and destination IP/MPLS routers, and that the LSP can be routed across the PSC-region (i.e., utilizing only resources of the IP/MPLS level topology). If the performance objective for the LSP is not satisfied, new TE links may be created between the IP/MPLS routers across the TDM-region (for example, VC-12 links) and the LSP can be routed over those links. Further, even if the LSP can be successfully established across the PSC-region, TDM hierarchical LSPs across the TDM region between the IP/MPLS routers may be established and used if doing so enables meeting an operators objectives on network resources available (e.g., link bandwidth, and adaptation port between regions) across the multiple regions. The same considerations hold when VC4 LSPs are provisioned to provide extra flexibility for the VC12 and/or VC11 layers in a MLN. This document describes the requirements to support multi- region/multi-layer networks. There is no intention to specify solution specific elements in this document. The applicability of existing GMPLS protocols and any protocol extensions to the MRN/MLN will be addressed in separate documents. 2. 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 [RFC2119]. 3. Positioning A multi-region network (MRN) is always a multi-layer network (MLN) since the network devices on region boundaries bring together different ISCs. A MLN, however, is not necessarily a MRN since multiple layers could be fully contained within a single region. For example, VC12, VC4, VC4-4c are different layers of the TDM region. 3.1. Data plane layers A data plane layer is a collection of network resources capable of terminating and/or switching data traffic of a particular format. These resources can be used for establishing LSPs or connectionless traffic delivery. For example, VC-11 and VC-4-64c represent two different layers. A network resource is atomic within the layer in which it is defined except PSC layers. For example, it is possible to Expires December 2005 [Page 4] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 allocate an integer number of VC12 resources to create a VC12 layer LSP, but fractions of VC12 resources cannot be allocated within the VC12 layer. 3.2. LSP Regions From the control plane viewpoint, an LSP region is defined as a set of one or several data plane layers that share the same type of switching technology, that is, the same switching type. Examples of regions are: PSC, L2SC, TDM, LSC, and FSC regions. Hence, an LSP region is a technology domain (identified by the ISC type) for which data plane resources (i.e. data links) are represented into the control plane as an aggregate of TE information associated with a set of links (i.e. TE links). For example VC-11 and VC-4-64c capable TE links are part of the same TDM Region. Note also 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 specific signaling objects. Multiple layers can exist in a single region network. Moreover, the control plane mechanisms introduced and defined for LSP regions, for example the Forwarding Adjacency (FA), and the Virtual FA Topology described as part of this document can equally be described from the perspective of a multi-layer data plane. 3.3. Services A service provider's network may be divided into different service layers. The customer's network is considered from the provider's perspective as the highest service layer. It interfaces to the highest service layer of the service provider's network. Connectivity across the highest service layer of the service provider's network may be provided with support from successively lower service layers. Service layers are realized via a hierarchy of network layers located generally in several regions and commonly arranged according to the switching capabilities of network devices. Some customers purchase Layer 1 (i.e. transport) services from the service provider, some Layer 2 (e.g. ATM), while others purchase Layer 3 (IP/MPLS) services. The service provider realizes the services by a stack of network layers located within one or more network regions. The network layers are commonly arranged according to the switching capabilities of the devices in the networks. Thus, a customer network may be provided on top of the GMPLS-based multi-region/multi-layer network. For example, a Layer One service (realized via the network layers of TDM, and/or LSC, and/or FSC regions) may support a Layer Two network (realized via ATM VP/VC) which may itself support a Layer Three network (IP/MPLS region). The supported data plane relationship is a data-plane client-server Expires December 2005 [Page 5] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 relationship where the lower layer provides a service for the higher layer using the data links realized in the lower layer. Services provided by a GMPLS-based multi-region/multi-layer network are referred to as "Multi-region/Multi-layer network services". For example legacy IP and IP/MPLS networks can be supported on top of multi-region/multi-layer networks. Details concerning the requirements for such services and the required functionality to deliver such services will be addressed in a future release of this document. It has, however, to be emphasized that delivery of such services is a strong motivator for the deployment of multi-region/multi-layer networks. 3.4. Vertical and Horizontal interaction and integration Vertical interaction is defined as the collaborative mechanisms within a network element that is capable of supporting more than one switching capability and of realizing the client/server relationships between them. Integration of these interactions as part of the control plane is referred to as vertical integration. The latter refers thus to the collaborative mechanisms within a single control plane instance driving multiple switching capabilities. Such a concept is useful in order to construct a framework that facilitates efficient network resource usage and rapid service provisioning in carrier's networks that are based on multiple switching technologies. Horizontal interaction is defined as the protocol exchange between network controllers that manage transport nodes within a given region (i.e. nodes with the same switching capability). For instance, the control plane interaction between two LSC network elements is an example of horizontal interaction. GMPLS protocol operations handle horizontal interactions within the same routing area. The case where the interaction takes place across a domain boundary, such as between two routing areas within the same network layer, is currently being evaluated as part of the inter-domain work [Inter-domain], and is referred to as horizontal integration. Thus horizontal integration refers to the collaborative mechanisms between network partitions and/or administrative divisions such as routing areas or autonomous systems. This distinction gets blurred when administrative domains match layer boundaries. For example, the collaborative mechanisms in place between two lambda switching capable areas relate to horizontal integration. On the other hand, the collaborative mechanisms in place in a network that supports IP/MPLS over TDM switching could be described as vertical and horizontal integration in the case where each network belongs to a separate area. 4. Key mechanisms in GMPLS-based multi-region/multi-layer networks An example of Multi-Region Networks (MRN) consisting of PSC and LSC is illustrated in Figure 1. The concept of region is by nature hierarchical. PSC and LSC are defined from the upper to Expires December 2005 [Page 6] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 the lower regions in Figure 1. Network elements with different switching technologies in the MRN are controlled by a unified GMPLS control plane. +-----+ | PSC | ----------| |--------- | | LSC | | | +-----+ | | | | +-----+ +-----+ +-----+ | PSC | | | | | | |-------| LSC |------| PSC | | LSC | | | | | +-----+ +-----+ +-----+ | | | | +-----+ | | | PSC | | ----------| |--------- | LSC | +-----+ Figure 1: Example of multi-region network An example of Multi-Layer Networks (MLN) consisting of two network layers L2 and L1 belonging to the same LSP region (e.g. TDM) is illustrated in Figure 2. Note that the two layers may belong to the same or different regions. In the latter case the network is also a multi-region network. The concept of data plane layer is by nature hierarchical. L2 and L1 are defined as higher and lower layers respectively in Figure 1. Network elements with different switching capabilities in the MLN are controlled by a unified (that is, a single) GMPLS control plane. +-----+ | L2 | ----------| |--------- | | L1 | | | +-----+ | | | | +-----+ +-----+ +-----+ | L2 | | | | | | |-------| L1 |------| L2 | | L1 | | | | | +-----+ +-----+ +-----+ | | | | +-----+ | | | L2 | | ----------| |--------- | L1 | +-----+ Figure 2: Example of multi-layer network Expires December 2005 [Page 7] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 4.1. Interface Switching Capability The Interface Switching Capability (ISC) is introduced in GMPLS to support various kinds of switching technology in a unified way [GMPLS-ROUTING]. An ISC is identified via a switching type. A switching type (also referred to as the switching capability types) describes the ability of a node to forward data of a particular data plane technology, and uniquely identifies a network region. The following ISC types (and, hence, regions) are defined: PSC, L2SC, TDM, LSC, and FSC. Each end of a data link (more precisely, each interface connecting a data link to a node) in a GMPLS network is associated with an ISC. For example, packet switch capable (PSC) is a property of an interface, which can distinguish IP/MPLS packets (for example, a router's interface) while lambda switch capable (LSC) is a property of an interface which models the switching of individual wavelengths multiplexed within a fiber link (for example, an OXC's interface). The ISC value is advertised as a part of the Interface Switching Capability Descriptor (ISCD) attribute (sub-TLV) of a TE link end associated with a particular link interface. Apart from the ISC, the ISCD contains information, such as the encoding type, the bandwidth granularity, and the unreserved bandwidth on each of eight priorities at which LSPs can be established. 4.2. Multiple Interface Switching Capabilities In a MLN, network elements may be single-switching or multi- switching type capable nodes. Single-switching type capable nodes advertise the same ISC value as part of their ISCD sub- TLV(s) to describe the termination capabilities of their TE Link(s). This case is described in [GMPLS-ROUTING]. Multi-switching capable LSRs are classified as "simplex" and "hybrid" nodes. Simplex and Hybrid nodes are categorized according to the way they advertise these multiple ISCs: - A simplex node can terminate links with different switching capabilities each of them connected to the node by a single link interface. So, it advertises several TE Links each with a single ISC value as part of its ISCD sub-TLVs. For example, an LSR with PSC and TDM links each of which is connected to the LSR via single interface. - A hybrid node can terminate links with different switching capabilities terminating on the same interface. So, it advertises at least one TE Link containing more than one ISCDs with different ISC values. For example, a node comprising of PSC and TDM links, which are interconnected via internal links. The external interfaces connected to the node have both PSC and TDM capability. Expires December 2005 [Page 8] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 Additionally TE link advertisements issued by a simplex or a hybrid node may need to advertise the internal node's link adaptation capabilities. That is, the node's capability to perform layer border node functions. The necessity of such advertisements will be described later in separate document. Networks with single switching capable nodes 4.2.1. Networks with single-switching capable nodes In this case, the network consists of a set of single-switching capable nodes, with at least two distinct switching capabilities in the network. For instance, nodes in Figure 3 are all single switching capable. There are two switching capabilities in the network: PCS and LSC. +-----+ | PSC | ----------| |--------- | | | | | +-----+ | | | | +-----+ +-----+ +-----+ | PSC | | | | | | |-------| LSC |------| PSC | | |-------| |------| | +-----+ +-----+ +-----+ | | | | +-----+ | | | PSC | | ----------| |--------- | | +-----+ Figure 3: Network wit single-switching capable nodes 4.2.2. Networks with multi-switching capable simplex nodes In this case, the network consists of at least one simplex node and includes a set of single switching type capable nodes (that is, all TE links terminating on such nodes have the same ISC). For example, the node TL2 in Figure 4 is a simplex node, which has data links with TDM switching type interfaces and data links with lambda switching type interfaces. At the layer boundary, the ISCs of the opposite ends of the links are different. When an LSP crosses the boundary (for example, an LSP from P2 to P4) from the upper layer to the lower layer, it is nested in a lower-layer hierarchical LSP (for example, an LSP from TL2 to T4). Expires December 2005 [Page 9] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 ......................................................... : ........................................... : : : ............................. : : : : : ............... : : : : PSC : TDM : LSC : FSC : : : : : +--+ : +--+ : +--+ : +--+ +--+ : +--+ : +--+ : +--+ : : |P1|---|T1|---|L1|---|F1|---|F3|---|L3|---|T3|---|P3| : : +--+ : +--+ : +--+ : +--+ +--+ : +--+ : +--+ : +--+ : : | : | : | : | | : | : | : | : : | : | : | : | | : | : | : | : : +--+ : +---------+ : +--+ +--+ : +--+ : +--+ : +--+ : : |P2|---| TL2 |---|F2|---|F4|---|L4|---|T4|---|P4| : : +--+ : +---------+ : +--+ +--+ : +--+ : +--+ : +--+ : : : : .............. : : : : : ............................. : : : ........................................... : ......................................................... Figure 4: Simplex node network. 4.2.3. Networks with multi-switching capable hybrid nodes In this case, the network contains at least one hybrid node, zero or more simplex nodes, and a set of single switching capable nodes. Figure 5a shows an example hybrid node. The hybrid node has two switching elements (matrices), which support, for instance, TDM and PSC switching respectively. The node terminates two TDM links (Link1 and Link2), which are connected to the TDM switching element by interfaces that model TDM switching. The two switching elements are internally interconnected in such a way that it is possible to terminate some of the resources of, say, Link1 and provide through them adaptation for PSC traffic received/sent over the PSC links. This situation is modeled in GMPLS by connecting the local end of Link1 to the TDM switching element via an additional interface realizing the termination/adaptation function. Network element ............................. : -------- : : | PSC | : : +--<->---| | : : | -------- : TDM : | ---------- : +PSC : +--<->--|#a TDM | : Link1 ------------<->--|#b | : Link2 ------------<->--|#c | : : ---------- : :............................ Figure 5a. Hybrid node. Expires December 2005 [Page 10] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 Figure 5b illustrates how existing GMPLS Routing is not sufficient and needs to be extended to advertise and consider termination/adaptation capabilities for hybrid nodes. Network element ............................. : -------- : : | PSC | : : | | : : --|#b1 | : : | | #d | : : | -------- : : | | : : | ---------- : : /| | | #c | : : | |-- | | : Link1 ========| | | TDM | : : | |----|#b2 | : : \| ---------- : :............................ Figure 5b. Hybrid node. Let's assume that all interfaces are STM64 (with VC4-16c capable as Max LSP bandwidth). So, initially, TE Link 1 is advertised with two ISCD sub-TLVs: - ISCD #1 sub-TLV: TDM with Max LSP bandwidth = STM16 (i.e. VC4- 16c capable as Max LSP bandwidth) and Unreserved bandwidth (of the whole incoming link) = STM64 - ISCD #2 sub-TLV: PSC with Max LSP bandwidth = 2.5 Gb (i.e. and Unreserved bandwidth (of the whole incoming link) = 10 Gb After, setting up several PSC LSPs via port #b1 qnd terminating several TDM LSPs via port #b2 (and #d), there is only 155 Mb capacity still available on port #d. However a 622 Mb capacity remains on port b1 and VC4-5x capacity in port b2. TE Link 1 is now advertised with the following ISCD sub-TLVs: - ISCD #1 sub-TLV: TDM with Max LSP bandwidth = VC4-4c, the Unreserved bandwidth reflects the VC4-5c capacity still available for the whole link - ISCD #2 sub-TLV: PSC with Max LSP bandwidth = 622 Mb, the Unreserved bandwidth reflects the capacity still available for the whole link i.e. 777 Mb. When computing the path for a new VC4-4c TDM LSP, one cannot know, based on existing GMPLS routing advertisements (i.e. two ISCD sub-TLVs), that this node cannot be used to setup this LSP terminated on port #d, as there is only 155M still available for TDM-PSC adaptation. Thus, in that case additional routing information is required to advertise the available TDM-PSC internal adaptation resources (i.e. 155 Mb here). Expires December 2005 [Page 11] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 4.3. Integrated Traffic Engineering (TE) and Resource Control In GMPLS-based multi-region/multi-layer networks, TE Links are consolidated into a single Traffic Engineering Database (TED). Since this TED contains the information relative to all the layers of all regions in the network, a path across multiple layers (possibly crossing multiple regions) can be computed using the information in this TED. Thus optimization of network resources across the multiple layers of the same region and multiple regions can be achieved. These concepts allow for the operation of one network layer over the topology (that is, TE links) provided by other network layer(s) (for example, the use of a lower layer LSC LSP carrying PSC LSPs). In turn, a greater degree of control and inter- working can be achieved, including (but not limited too): - dynamic establishment of Forwarding Adjacency LSPs (see Section 4.3.3) - provisioning of end-to-end LSPs with dynamic triggering of FA LSPs Note that in a multi-layer/multi-region network that includes multi-switching type capable nodes, an explicit route used to establish an end-to-end LSP can specify nodes that belong to different layers or regions. In this case, a mechanism to control the dynamic creation of FA LSPs may be required. There is a full spectrum of options to control how FA LSPs are dynamically established. It can be subject to the control of a policy, which may be set by a management component, and which may require that the management plane is consulted at the time that the FA LSP is established. Alternatively, the FA LSP can be established at the request of the control plane without any management control. 4.3.1. Triggered signaling When an LSP crosses the boundary from an upper to a lower layer, it may be nested into a lower layer FA LSP that crosses the lower layer. If such an LSP does not already exist, the LSP may be established dynamically. Such a mechanism is referred to as "triggered signaling". 4.3.2. FA-LSP Once an LSP is created across a layer, it can be used as a data link in an upper layer. Furthermore, it can be advertised as a TE-link, allowing other nodes to consider the LSP as a TE link for their path computation [HIER]. An LSP created dynamically by one instance of the control plane and advertised as a TE link into the same instance of the control plane is called a FA-LSP. An FA has the special quality of not requiring a routing adjacency (peering) Expires December 2005 [Page 12] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 between its ends yet still guaranteeing control plane connectivity between the FA-LSP ends. FA is a useful and powerful tool for improving the scalability of GMPLS Traffic Engineering (TE) capable networks. The aggregation of LSPs enables the creation of a vertical (nested) LSP Hierarchy. A set of FA-LSPs across or within a lower layer can be used during path selection by a higher layer LSP. Likewise, the higher layer LSPs may be carried over dynamic data links realized via LSPs (just as they are carried over any "regular" static data links). This process requires the nesting of LSPs through a hierarchical process [HIER]. The TED contains a set of LSP advertisements from different layers that are identified by the ISCD contained within the TE link advertisement associated with the LSP [GMPLS-ROUTING]. Note that ISCD contains the switching type (i.e. interface switching capability), the data encoding type, and the bandwidth granularity. 4.3.3. Virtual network topology (VNT) A set of lower-layer LSPs provides information for efficient path handling in upper-layer(s) of the MLN, or, in other words, provides a virtual network topology to the upper-layers. For instance, a set of LSPs, each of which is supported by an LSC LSP, provides a virtual network topology to the layers of a PSC region, assuming that the PSC region is connected to the LSC region. The virtual network topology is configured by setting up or tearing down the LSC LSPs. By using GMPLS signaling and routing protocols, the virtual network topology can be easily adapted to traffic demands. By reconfiguring the virtual network topology according to the traffic demand between source and destination node pairs, network performance factors, such as maximum link utilization and residual capacity of the network, can be optimized [MAMLTE]. Reconfiguration is performed by computing the new VNT from the traffic demand matrix and optionally from the current VNT. Exact details are outside the scope of this document. However, this method may be tailored according to the Service Provider's policy regarding network performance and quality of service (delay, loss/disruption, utilization, residual capacity, reliability). 5. Requirements 5.1. Scalability The MRN/MLN relies on a unified traffic engineering and routing model. The TED in each LSR is populated with TE-links from all layers of all regions. This may lead to a huge amount of information that has to be flooded and stored within the network. Furthermore, path computation times, which may be of great Expires December 2005 [Page 13] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 importance during restoration, will depend on the size of the TED. Thus MRN/MLN routing mechanisms MUST be designed to scale well with an increase of any of the following: - Number of nodes - Number of TE-links (including FA-LSPs) - Number of LSPs - Number of regions and layers - Number of ISCDs per TE-link. 5.2. LSP resource utilization It MUST be possible to utilize network resources efficiently. Particularly, resource usage in each layer SHOULD be optimized as a whole (i.e. across all layers), in a coordinated manner. The number of lower-layer LSPs carrying upper-layer LSPs SHOULD be minimized. Redundant lower-layer LSPs SHOULD be avoided (except for protection purpose). 5.2.1. FA-LSP release and setup Statistical multiplexing can only be employed in PSC and L2SC regions. A PSC or L2SC LSP may or may not consume the maximum reservable bandwidth of the FA LSP that carries it. On the other hand, a TDM, or LSC LSP always consumes a fixed amount of bandwidth as long as it exists (and is fully instantiated) because statistical multiplexing is not available. If there is low traffic demand, some FA LSPs, which do not carry any LSP may be released so that resources are released. Note that if a small fraction of the available bandwidth is still under use, the nested LSPs can also be re-routed optionally using the make-before-break technique. Alternatively, the FA LSPs may be retained for future usage. Release or retention of underutilized FA LSPs is a policy decision. As part of the re-optimization process, the solution MUST allow rerouting of FA LSPs while keeping interface identifiers of corresponding TE links unchanged. Additional FA LSPs MAY also be created based on policy, which might consider residual resources and the change of traffic demand across the region. By creating the new FA LSPs, the network performance such as maximum residual capacity may be improved. As the number of FA LSPs grows, the residual resource may decrease. In this case, re-optimization of FA LSPs MAY be invoked according the policy. Any solution MUST include measures to protect against network destabilization caused by the rapid set up and tear down of LSPs as traffic demand varies near a threshold. Expires December 2005 [Page 14] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 5.2.2. Virtual TE-Link It may be considered disadvantageous to fully instantiate (i.e. pre-provision) the set of lower layer LSPs since this may reserve bandwidth that could be used for other LSPs in the absence of the upper-layer traffic. However, in order to provision upper-layer LSPs across the lower-layer, the LSPs MAY still be advertised into the upper- layer as though they had been fully established. Such TE links that represent the possibility of an underlying LSP are termed "virtual TE-link". Note that this is not a mandatory (MUST) requirement since even if there are no LSPs advertised to the higher layer, it is possible to route an upper layer LSP into a lower layer based on the lower layer's TE-links and making assumptions that proper hierarchical LSPs in the lower layer will be dynamically created as needed. If an upper-layer LSP makes use of a virtual TE-Link is set up, the underlying LSP MUST be immediately signaled in the lower layer if it has not been established. If virtual TE-Links are used in place of pre-established LSPs, the TE links across the upper-layer can remain stable using pre- computed paths while wastage of bandwidth within the lower-layer and unnecessary reservation of adaptation ports at the border nodes can be avoided. The concept of VNT can be extended to allow the virtual TE-links to form part of the VNT. The combination of the fully provisioned TE-links and the virtual TE-links defines the VNT across the lower layer. The solution SHOULD provide operations to facilitate the build- up of such virtual TE-links, taking into account the (forecast) traffic demand and available resource in the lower-layer. Virtual TE-links MAY be modified dynamically (by adding or removing virtual TE links) according to the change of the (forecast) traffic demand and the available resource in the lower-layer. Any solution MUST include measures to protect against network destabilization caused by the rapid changes in the virtual network topology as traffic demand varies near a threshold. The VNT can be changed by setting up and/or tearing down virtual TE links as well as by modifying real links (i.e. the fully provisioned LSPs). The maximum number of virtual TE links that can be configured SHOULD be well-engineered. Expires December 2005 [Page 15] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 How to design the VNT and how to manage it are out of scope of this document and will be treated in a companion document on solution. 5.3. LSP Attribute inheritance TE-Link parameters SHOULD be inherited from the parameters of the LSP that provides the TE link, and so from the TE links in the lower layer that are traversed by the LSP. These include: - Interface Switching Capability - TE metric - Maximum LSP bandwidth per priority level - Unreserved bandwidth for all priority levels - Maximum Reservable bandwidth - Protection attribute - Minimum LSP bandwidth (depending on the Switching Capability) Inheritance rules MUST be applied based on specific policies. Particular attention should be given to the inheritance of TE metric (which may be other than a strict sum of the metrics of the component TE links at the lower layer) and protection attributes. 5.4. Verification of the LSP When the LSP is created, it SHOULD be verified that it has been established before it can be used by an upper layer LSP. Note, this is not within the GMPLS capability scope for non-PSC interfaces. 5.5. Disruption minimization When reconfiguring the VNT according to a change in traffic demand, the upper-layer LSP might be disrupted. Such disruption MUST be minimized. When residual resource decreases to a certain level, some LSPs MAY be released according to local or network policies. There is a trade-off between minimizing the amount of resource reserved in the lower layer LSPs and disrupting higher layer traffic (i.e. moving the traffic to other TE-LSPs so that some LSPs can be released). Such traffic disruption MAY be allowed but MUST be under the control of policy that can be configured by the operator. Any repositioning of traffic MUST be as non-disruptive as possible (for example, using make-before-break). 5.6. Stability The path computation is dependent on the network topology and associated link state. The path computation stability of an upper layer may be impaired if the VNT changes frequently and/or if the status and TE parameters (TE metric for instance) of links in the virtual network topology changes frequently. Expires December 2005 [Page 16] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 In this context, robustness of the VNT is defined as the capability to smooth changes that may occur and avoid their propagation into higher layers. Changes of the VNT may be caused by the creation and/or deletion of several LSPs. Creation and deletion of LSPs MAY be triggered by adjacent layers or through operational actions to meet changes in traffic demand. Routing robustness SHOULD be traded with adaptability with respect to the change of incoming traffic requests. A full mesh of LSPs MAY be created between every pair of border nodes of the PSC region. The merit of a full mesh of PSC TE-LSPs is that it provides stability to the PSC-level routing. That is, the forwarding table of an PSC-LSR is not impacted by re-routing changes within the lower-layer (e.g., TDM layer). Further, there is always full PSC reachability and immediate access to bandwidth to support PSC LSPs. 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 wasting if LSP with a certain amount of reserved bandwidth is used. Note that the use of virtual TE-links solves the bandwidth wasting issue, and may reduce the control plane overload. 5.7. Computing paths with and without nested signaling Path computation MAY take into account LSP region and layer boundaries when computing a path for an LSP. For example, path computation MAY restrict the path taken by an LSP to only the links whose interface switching capability is PSC-1. Interface switching capability is used as a constraint in computing the path. A TDM-LSP is routed over the topology composed of TE links of the same TDM layer. In calculating the path for the LSP, the TE database MAY be filtered to include only links where both end include requested LSP switching type. In this way hierarchical routing is done by using a TE database filtered with respect to switching capability (that is, with respect to particular layer). If triggered signaling is allowed, the path computation mechanism MAY produce a route containing multiple layers/ regions. 5.8. Handling single-switching and multi-switching type capable nodes The MRN/MLN can consist of single-switching type capable and multi-switching type capable nodes. The path computation mechanism in the MLN SHOULD be able to compute paths consisting of any combination of such nodes. Expires December 2005 [Page 17] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 Both single switching capable and multi-switching (simplex or hybrid) capable nodes could play the role of layer boundary. MRN/MLN Path computation SHOULD handle TE topologies built of any combination of single switching, simplex and hybrid nodes 5.9. Advertisement of the available adaptation resource A hybrid node SHOULD maintain resources and advertise the resource information on its internal links, the links required for vertical (layer) integration. Likewise, path computation elements SHOULD be prepared to use the availability of termination/adaptation resources as a constraint in MRN/MLN path computations to reduce the higher layer LSP setup blocking probability because of the lack of necessary termination/ adaptation resources in the lower layer(s). The advertisement of the adaptation capability to terminate LSPs of lower-region and forward traffic in the upper-region is REQUIRED, as it provides critical information when performing multi-region path computation. 6. Security Considerations The current version of this document does not introduce any new security considerations as it only lists a set of requirements. In the future versions, new security requirements may be added. 7. References 7.1. Normative Reference [RFC3979] Bradner, S., "Intellectual Property Rights in IETF Technology", BCP 79, RFC 3979, March 2005. [GMPLS-ROUTING] K.Kompella and Y.Rekhter, "Routing Extensions in Support of Generalized Multi-Protocol Label Switching," draft-ietf-ccamp-gmpls-routing-09.txt, October 2003 (work in progress). [Inter-domain] A.Farrel, J-P. Vasseur, and A.Ayyangar, "A framework for inter-domain MPLS traffic engineering," draft- ietf-ccamp-inter-domain-framework, work in progress. [HIER] K.Kompella and Y.Rekhter, "LSP hierarchy with generalized MPLS TE," draft-ietf-mpls-lsp-hierarchy-08.txt, work in progress, Sept. 2002. [STITCH] Ayyangar, A. and Vasseur, JP., "Label Switched Path Stitching with Generalized MPLS Traffic Engineering", draft- ietf-ccamp-lsp-stitching, work in progress. [LMP] J. Lang, "Link management protocol (LMP)," draft- ietf- ccamp-lmp-10.txt (work in progress), October 2003. Expires December 2005 [Page 18] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 [RFC3945] E.Mannie (Ed.), "Generalized Multi-Protocol Label Switching (GMPLS) Architecture", RFC 3945, October 2004. 7.2. Informative References [MPLSGMPLS] D.Brungard, J.L.Le Roux, E.Oki, D. Papadimitriou, D.Shimazaki, K.Shiomoto, "Migrating from IP/MPLS to GMPLS networks," draft-oki-ccamp-gmpls-ip-interworking, work in progress. [MAMLTE] K. Shiomoto et al., "Multi-area multi-layer traffic engineering using hierarchical LSPs in GMPLS networks", draft- shiomoto-multiarea-te, work in progress. 8. Author's Addresses Kohei Shiomoto NTT Network Service Systems Laboratories 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Email: shiomoto.kohei@lab.ntt.co.jp Dimitri Papadimitriou Alcatel Francis Wellensplein 1, B-2018 Antwerpen, Belgium Phone : +32 3 240 8491 Email: dimitri.papadimitriou@alcatel.be Jean-Louis Le Roux France Telecom R&D, Av Pierre Marzin, 22300 Lannion, France Email: jeanlouis.leroux@francetelecom.com Martin Vigoureux Alcatel Route de Nozay, 91461 Marcoussis cedex, France Phone: +33 (0)1 69 63 18 52 Email: martin.vigoureux@alcatel.fr Deborah Brungard AT&T Rm. D1-3C22 - 200 S. Laurel Ave., Middletown, NJ 07748, USA Phone: +1 732 420 1573 Email: dbrungard@att.com Contributors Eiji Oki (NTT Network Service Systems Laboratories) 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Phone: +81 422 59 3441 Email: oki.eiji@lab.ntt.co.jp Expires December 2005 [Page 19] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 Ichiro Inoue (NTT Network Service Systems Laboratories) 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Phone: +81 422 59 3441 Email: ichiro.inoue@lab.ntt.co.jp Emmanuel Dotaro (Alcatel) Route de Nozay, 91461 Marcoussis cedex, France Phone : +33 1 6963 4723 Email: emmanuel.dotaro@alcatel.fr 9. Intellectual Property Considerations The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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 RFC 3668. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. The IETF has been notified by Tellabs Operations, Inc. of intellectual property rights claimed in regard to some or all of the specification contained in this document. For more information, see http://www.ietf.org/ietf/IPR/tellabs-ipr-draft- shiomoto-ccamp-gmpls-mrn-reqs.txt 10. Full Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE Expires December 2005 [Page 20] draft-shiomoto-ccamp-gmpls-mrn-reqs-02.txt July 2005 REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Expires December 2005 [Page 21]