CCAMP Working Group D. Ceccarelli Internet-Draft Ericsson Intended status: Informational O. Gonzalez de Dios Expires: September 6, 2014 Telefonica I+D F. Zhang X. Zhang Huawei Technologies Z. Ali Cisco Systems, Inc. R. Rao Infinera Corporation S. Belotti Alcatel-Lucent March 5, 2014 Use cases for operating networks in the overlay model context draft-ceccadedios-ccamp-overlay-use-cases-05 Abstract This document defines a set of use cases for operating networks in the overlay model context through the Generalized Multiprotocol Label Switching (GMPLS) overlay interfaces. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on September 6, 2014. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Ceccarelli, et al. Expires September 6, 2014 [Page 1] Internet-Draft Overlay model use cases March 2014 Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Client domain to server domain connectivity . . . . . . . . . 6 3.1. Single homing . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Dual homing . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Services between different pairs of nodes . . . . . . . . 8 4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1. UC 1 - Provisioning . . . . . . . . . . . . . . . . . . . 9 4.2. UC 2 - Provisioning with optimization . . . . . . . . . . 9 4.3. UC 3 - Provisioning with constraints . . . . . . . . . . . 10 4.4. UC 4 - Diversity . . . . . . . . . . . . . . . . . . . . . 11 4.5. UC 4A - Service Affinity . . . . . . . . . . . . . . . . . 13 4.6. UC 5 - Concurrent provisioning . . . . . . . . . . . . . . 13 4.7. UC 6 - Reoptimization . . . . . . . . . . . . . . . . . . 14 4.8. UC 7 - Query . . . . . . . . . . . . . . . . . . . . . . . 14 4.9. UC 8 - Availability check . . . . . . . . . . . . . . . . 15 4.10. UC 9 - P2MP services . . . . . . . . . . . . . . . . . . . 15 4.11. UC 10 - Privacy . . . . . . . . . . . . . . . . . . . . . 15 4.12. UC 12 - Stacking of overlay interfaces . . . . . . . . . . 15 4.13. UC 13 - Server layer resiliency parameters . . . . . . . . 16 5. Security Considerations . . . . . . . . . . . . . . . . . . . 17 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 17 Appendix A. Appendix I - Colored overlay . . . . . . . . . . . . 18 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 8.1. Normative References . . . . . . . . . . . . . . . . . . . 20 8.2. Informative References . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 Ceccarelli, et al. Expires September 6, 2014 [Page 2] Internet-Draft Overlay model use cases March 2014 1. Introduction The GMPLS overlay model [RFC 4208] specifies a control plane client- server relationship between networks where client and server domains are managed as separate domains because of trustiness, control plane scalability and operational issues. By means of procedures from the GMPLS protocol suite it is possible to build a topology in the client (overlay) domain from Traffic Engineering paths in the server domain. In this context, the UNI (User to Network Interface) is the service demarcation point between domains. It is a boundary where policies, administrative and confidentiality issues apply that limit the exchange of information. This GMPLS overlay model supports a wide variety of network scenarios. The packet over optical scenario is probably the most popular example where the overlay model applies. The goal of this document is to define a set of solution independent use cases applicable to the overlay model. In particular it focuses on the network scenarios where the overlay model applies and analyzes the most interesting aspects of provisioning, recovery and path computation. 2. Terminology The following terms are used within the document: - Edge node [RFC4208]: node of the client domain belonging to the overlay network, i.e. nodes with at least one interface connected to the server domain. - Core node [RFC4208]: node of the server domain. - Access link: link between core node and edge node. It is the link where the UNI is usually implemented. - Remote node: node in the client domain which has no direct access to the server domain but can reach it through an edge node in its same administrative domain. - Local trigger: LSP setup request issued to an edge node. It triggers the setup of a client domain LSP through the server domain via a UNI interface. - Remote trigger: LSP setup request issued to a remote node. It triggers the setup of a client domain LSP which, upon reaching an edge node, will use connectivity in the server domain. Ceccarelli, et al. Expires September 6, 2014 [Page 3] Internet-Draft Overlay model use cases March 2014 All the use cases listed in the sections below can be applied to any combination of, unless otherwise specified: * Local or remote trigger * Administrative boundary or administrative plus technological boundary * Layer transition on edge node or on core node (applicable to administrative plus technological boundary case) With local trigger we mean the case in which a trigger for the provisioning of a service over the overlay interface is issued to one of the edge nodes belonging to the overlay network, i.e. directly connected to the UNI. 1.Trigger | 2. Setup V --------------------> +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ +--+ / | \ | \ | \ +--+/ |R4| | / \ | \| |R8| +--+ /-\ / \/-\ /-\ +--+ 3.Advertisement ( D )-----( E )---( F ) 3.Advertisement \-/ \-/ \-/ *** = overlay interfaces Figure 1: Local trigger As it is possible to see in the figure above, a trigger is issued on R3 (edge node) for starting the setup request procedure over the overlay interface (R3-A). Once the LSP in the server domain is setup and an adjacency in the packet domain between R3 and R5 is created, it can be advertised in the rest of the client domain and used by the signaling protocol (e.g. LDP) for setting up end-to-end (e.g. from R1 to R7) client domain LSPs. On the other hand, the remote signaling consists on the utilization of a connection oriented signaling protocol in the overlay domain that allows issuing the end to end service setup trigger directly on the end nodes of the client domain. The signaling message, upon Ceccarelli, et al. Expires September 6, 2014 [Page 4] Internet-Draft Overlay model use cases March 2014 reaching the edge node (R3), will trigger the setup of the service in the server domain via the overlay interface. 1.Trigger | 2. Signaling 3. Trigger V -------------> |------------>| |------>----------------->------->| |<-----<-----------------<--------| <----------------|---------------------------------|-------------| +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ +--+ / | \ | \ | \ +--+/ |R4| | / \ | \| |R8| +--+ /-\ / \/-\ /-\ +--+ ( D )-----( E )---( F ) \-/ \-/ \-/ Figure 2: Remote Signaling The utilization of the remote trigger allows for a strict control of the resources that will be used for the setup of the end to end service. In order to have a correct setup of the end to end service the trigger issued to R1 must include the overlay nodes to be used for the setup of the service in the server domain (R3 and R5). The network operator is supposed to know that the edge nodes to be used are R3 and R5. The second bullet above speaks about administrative boundaries and administrative plus technological boundaries. Since the overlay is an administrative boundary between an overlay network and a core network it may happen that overlay and core network can be configured based on the same switching capabilities (e.g., IP over IP) or with different switching capabilities (e.g. ODU over OCh). In the former case the boundary is referred to as administrative domain, while in the latter, it is referred to as both administrative and technological boundary. In the case of boundary which is both administrative and technological a further distinction is needed and regards the node where the technological transition occurs, i.e., on the edge or on the core node. Ceccarelli, et al. Expires September 6, 2014 [Page 5] Internet-Draft Overlay model use cases March 2014 One of the most common cases of administrative and technological boundary is the IP over WDM, where we speak about grey and colored overlay interfaces. In other words, in the case of grey interface the transponder and the domain transition are on the core node, while in the case of colored interface (i.e. OTN multi-vendor IsDI based upon G.698.2) they are on the edge node. The physical impairments to be considered are different in the two cases (for further details please see Appendix A) but the behavior of the interface does not change and all use cases depicted below can be applied both to the grey and colored interfaces. Editor note: Actually path computation is assumed to be performed typically at the server domain. The client domain can request the server domain for computing a path or select among a set of paths computed by the server domain and exported to the client domain as virtual/abstract topology. 3. Client domain to server domain connectivity A further distinction criterion, which is applicable to most of the use cases below, is the degree of connectivity between the client domain and the server domain. Three scenarios are identified: * Single homing * Dual homing * Services between different pairs of nodes 3.1. Single homing In the case of single homing we consider an end to end tunnel with a single LSP in the client domain and one or more LSPs in the server domain but a single overlay interface connecting them. The scenario is shown in figure below, where an end to end circuit between R1 and R7 is built over a tunnel between R3 and R5 composed by a single LSP restorable between A and C or more (possibly restorable) LSPs between A and C. Ceccarelli, et al. Expires September 6, 2014 [Page 6] Internet-Draft Overlay model use cases March 2014 +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ +--+ / | \ | \ | \ +--+/ |R4| | / \ | \| |R8| +--+ /-\ / \/-\ /-\ +--+ ( D )-----( E )---( F ) \-/ \-/ \-/ *** = overlay interfaces Figure 3: Single homing Typical examples of single restorable LSP between A and C is the case of IP over WDM with single transponder on A and single transponder of C with restoration capability in the WDM domain. A common case of multiple LSPs between A and C, on the other side, it the splitting of the electrical signal between a couple of transponders on A creating a 1+1 protection terminated on a couple of transponders of C. 3.2. Dual homing The dual homing is used to indicate a case in which two (or more) access links between the edge node and one or more core nodes exist. In this case we have an end to end tunnel with one or more LSPs in the server domain with two or more overlay interface connecting them. The scenario is shown in figure below, where an end to end circuit between R1 and R7 is built over a tunnel between R3 and R5 composed by two LSPs between different pairs of ingress/egress nodes (A-C and D-F). Ceccarelli, et al. Expires September 6, 2014 [Page 7] Internet-Draft Overlay model use cases March 2014 +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|*X**( A )--X--( B )-X-( C )**X**|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ * | \ / | \ | * * | \ / | \ | * Y | \ / | \ | Y * | \ | \ | * * | / \ | \| * *X*=LSP X * /-\ / \/-\ /-\* *Y*=LSP Y ( D )--Y--( E )-Y-( F ) \-/ \-/ \-/ Figure 4: Dual homing This network setup typically allows for fast client domain protection mechanisms, e.g., Fast ReRoute (FRR). 3.3. Services between different pairs of nodes This scenario is based on an end to end tunnel with two (or more) LSPs in the client domain each of which relies on one (or more) LSPs in the server domain. It is based on multiple independent single homing scenarios and is typically used to provide end to end diversity between two or more services. In figure below it is possible to see an end to end circuit between R1 and R8 composed by two services (A and B) which are built over two independent tunnels between R3 and R6 and between R5 and R9 respectively. +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )*****( B )***( C )*****|R6|---|R7|---|R8| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ | \ / | \ | / \ | \ / | \ | / \ | \ / | \ | / \ | \ | \ | / \ | / \ | \| / +--+ +--+ /-\ / \/-\ /-\ +--+ +---+ |R4|---|R5|####( D )#####( E )###( F )#####|R9|---|R10| +--+ +--+ \-/ \-/ \-/ +--+ +---+ ***=Service A ###=Service B Figure 5: Services between different pairs of nodes Ceccarelli, et al. Expires September 6, 2014 [Page 8] Internet-Draft Overlay model use cases March 2014 Typical usage of this network scenario consists on the combination of fast client domain protection mechaninsms (e.g.,1+1 protection) and server domain restoration mechanisms. 4. Use Cases 4.1. UC 1 - Provisioning Requirement: It must be possible to setup an unprotected end to end service between two client domain nodes with no constraint in the server domain. This use case simply consists on providing an operator with the capability of setting up a service in the client domain either by means or local trigger or remote signaling. The operator does not put any constraint over the path computation in the server domain (e.g. unprotected, no TE metric bounds). 4.2. UC 2 - Provisioning with optimization Requirement: It must be possible to setup a client service expressing server layer parameter(s) to be optimized when computing server domain path. This use case applies both to the local trigger and the remote signaling scenarios. In both cases the path computation function in the server domain (being it centralized or distributed) is demanded to provide a path between R3 and R5 which minimizes a given parameter (e.g. delay, jitter, TE metric). Ceccarelli, et al. Expires September 6, 2014 [Page 9] Internet-Draft Overlay model use cases March 2014 1.Trigger(param min) | 2. Setup(param min) 3.Path computation(param min) V ------> +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ +--+ / | \ | \ | \ +--+/ |R4| | / \ | \| |R8| +--+ /-\ / \/-\ /-\ +--+ ( D )-----( E )---( F ) \-/ \-/ \-/ *** = overlay interfaces Figure 6: Provisioning with optimization In the figure above the case of local trigger with specified parameter to be minimized is depicted, but same considerations apply to the remoe signaling (trigger on R1). In that case the parameter to be minimized needs to be conveyed from R1 to R3 so that the setup request over the overlay interface can be issued taking into account the OF. 4.3. UC 3 - Provisioning with constraints Requirement: It must be possible to setup a service imposing TE- metrics upper bounds for a set of parameters during the path computation. This use cases is extremely similar to the provisioning with Optimization one. This time, instead of/in addition to giving the possibility of specifying which parameter needs to be optimized during the path computation, the network operator is also able to indicate and upper bound for a set of parameters which is not being minimized in the path computation. Ceccarelli, et al. Expires September 6, 2014 [Page 10] Internet-Draft Overlay model use cases March 2014 1.Trigger(constraint) | 2.Setup(const) 3.Path computation(const) V ------> +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )-----( B )---( C )*****|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ / | \ / | \ | \ / \ +--+ / | \ | \ | \ +--+/ |R4| | / \ | \| |R8| +--+ /-\ / \/-\ /-\ +--+ ( D )-----( E )---( F ) \-/ \-/ \-/ *** = overlay interfaces Figure 7: Provisioning with constraints It is possible for example to ask for a path between R3 and R5 which, in addition to minimizing a given OF, does not introduce a delay higher than 10ms or where the jitter is not more than 3ms. As per the optimization use case, when remote signaling is used (trigger on R1) a mean to convey the path computation constraints till the edge node (R3) is needed. 4.4. UC 4 - Diversity Requirement: It must be possible to setup a service in the server domain in diversity with respect to server domain resources or not sharing the same fate with other server domain services. The network operator must also be able to decide whether such diversity degree must be automatically kept by the network upon failures and optimization procedures. This scenario is extremely common in those cases where different services in the server domain are used to provision protected services in the client domain. The services in the server domain can be computed/provisioned sequentially or in parallel but in both cases the requirement is to have them totally disjoint, so that a single failure in the server domain does not impact two or more services in the client domain which are supposed to be in a protection relationship between each other (e.g. 1+1 protection). Ceccarelli, et al. Expires September 6, 2014 [Page 11] Internet-Draft Overlay model use cases March 2014 +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|*X**( A )--X--( B )-X-( C )**X**|R5|---|R6|---|R7| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ * | \ / | \ | * * | \ / | \ | * Y | \ / | \ | Y * | \ | \ | * * | / \ | \| * *X*=Service X * /-\ / \/-\ /-\* *Y*=Service Y ( D )--Y--( E )-Y-( F ) \-/ \-/ \-/ Figure 8: Diversity In a scenario like the one depicted above, it is possible to use Service X and Service Y for the setup of a protected service in the client domain as a fault in the server domain would not impact both of them. In the case of parallel request, R3 asks the path computation in the server domain to provide two totally disjoint paths. On the other side, when sequential requests are issued, an identifier for Service X (or a set of identifiers indicating its resources) is needed so that the request for the setup of Service Y can be issued with the constraint of avoiding the resources related to such identifier. Please note that while Figure 8 depicts that the service X and the service Y have different ingress core nodes (node A and node D) but both service X and the service Y may share same ingress core node. Another case of provisioning with diversity is the one where the operator in the client domains wants the server domain to exclude some resources from the path computation. In such a case, it must be possible to indicate them as path computation constraint in the service setup request. Requesting an LSP with SRLG exclusion is an example of such service request. In addition to the provisioning of services with given diversity (and inclusion/exclusion) constraints, it must be possible to ask the server domain to at least keep such constraints also upon restoration or optimization procedures. It would be desirable to ask the server domain to relax constraints to be kept. The relaxation can be needed depending on resources availability, e.g., restoration of service X with partial diversity with service Y when total diversity is not possible). Ceccarelli, et al. Expires September 6, 2014 [Page 12] Internet-Draft Overlay model use cases March 2014 4.5. UC 4A - Service Affinity There are scenarios that require two or more Label Switched Paths (LSPs) to follow same route in the network. E.g., many deployments require member LSPs of a bundle/ aggregated link (or Forwarding Adjacency (FA)) follow the same route. Possible reasons for two or more LSPs to follow the same end-to-end or partial route include, but are not limited to: o Fate sharing: an application may require that two or more LSPs fail together. In the example of bundle link this would mean that if one component goes down, the entire bundle goes down. o Homogeneous Attributes: it is often required that two or more LSPs have the same TE metrics like latency, latency variation, etc. In the example of a bundle/ aggregated link this would meet the requirement that all component links (FAs) of a bundle should have same latency and latency variation. As noted in [OSPF-TE- METRIC] and [ISIS-TE-METRIC], in certain networks, such as financial information networks, network performance (e.g. latency and latency variation) is becoming critical and hence having bundles with component links (FAs) with homogeneous latency and latency variation is important. 4.6. UC 5 - Concurrent provisioning Requirement: The client network must be able to setup plurality of services which are diverse and not between same pair of egde nodes. Here is another case particularly interesting from a protection point of view. In the case above the same edge node was asking for different services in the server domain, but in order to have end to end diversity (i.e. from R1 to R8 in figure below), there is the need to be able to provide disjoint services between different pairs of edge nodes. Ceccarelli, et al. Expires September 6, 2014 [Page 13] Internet-Draft Overlay model use cases March 2014 +--+ +--+ +--+ /-\ /-\ /-\ +--+ +--+ +--+ |R1|---|R2|---|R3|****( A )*****( B )***( C )*****|R6|---|R7|---|R8| +--+ +--+ +--+ \-/ \-/\ \-/ +--+ +--+ +--+ \ | \ / | \ | / \ | \ / | \ | / \ | \ / | \ | / \ | \ | \ | / \ | / \ | \| / +--+ +--+ /-\ / \/-\ /-\ +--+ +---+ |R4|---|R5|####( D )#####( E )###( F )#####|R9|---|R10| +--+ +--+ \-/ \-/ \-/ +--+ +---+ ***=Service A ###=Service B Figure 9: Concurrent provisioning In this example Service A is provided between R3 and R6 and Service B between R5 and R9. Some sort of coordination is needed between R3 and R5 (directly between them or via R1) so that the requests to the server domain can be conveniently issued. 4.7. UC 6 - Reoptimization Requirement: It must be possible to setup a plurality of services so that the overall cost of the network is minimized and not the cost of a single service. TBD 4.8. UC 7 - Query Requirement: It must be possible to request information from the provider regarding the actual parameters characterizing an existing service (if supported by the SLA). The capability of retrieving from the server domain some parameters qualifying a service can be estremely useful in different cases. One of them is the case o sequential provisioning with diversity requirements. In the case the operator wants to set-up a service in diversity from an existing one, hence it must be possible for the server domain to export some parameters univocally identifying the resources (e.g. SRLGs). Another case where capability of retrieving from the server domain some parameters of service is useful is for flooding these parameters for the forwarding or routing adjacencies in the client network. Examples of recording of such parameters are SRLGs, latency, latency variation and cost. Ceccarelli, et al. Expires September 6, 2014 [Page 14] Internet-Draft Overlay model use cases March 2014 4.9. UC 8 - Availability check Requirement: It must be possible to check if in the server domain there are enough resources to setup a service with given parameters or to check attributes of a better path for an existing service to enable client to make reoptimization decision. Client node may like to check feasibility and attributes of a better path for an existing service. SRLG, Latency, latency variation, Cost, etc. values are examples of attributes that client node may like to inquire about (e.g., before making a reoptimization decision). 4.10. UC 9 - P2MP services Requirement: If allowed by the technology, It must be possible to setup a P2MP service with given parameters. TBD 4.11. UC 10 - Privacy Requirement: It must be possible to provision different groups of users with independent addressing spaces. This is a particularly useful functionality for those cases where the resources of the service provider are leased and shared among several other service providers or customers. 4.12. UC 12 - Stacking of overlay interfaces Requirement: It must be possible to manage a network with an arbitrarily high number of administrative boundaries (i.e.,>2). Operators might want to split their overlay networks in a number of administrative domains for several reasons, among which simplifying network operations and improving scalability. In order to do so it must be possible to create a stack of overlay interfaces between the different domains as shown in figure below: Ceccarelli, et al. Expires September 6, 2014 [Page 15] Internet-Draft Overlay model use cases March 2014 +--+ +--+ +--+ +--+ |A1|--|A2|* *|A4|--|A5| +--+ +--+ * /-\ /-\ /-\ /-\ * +--+ +--+ \ +--+ / *( B1)--( B2) ( B3)---( B4)* \ +--+ / \|A3|/ \-/ \-/ \-/ \-/ \|A6|/ +--+ * * +--+ * ==== ==== ==== * *|C1|---|C2|---|C3|* ==== ==== ==== *** = overlay interfaces Figure 10: Stacking of interfaces Nodes "Ax" belong to a domain which is client to the domain composed by nodes "Bx". The domain composed by nodes Bx is hence server domain to the "Ax" nodes domain but client to the "Cx" nodes domain. A pretty common deployment of this scenario consists of IP over OTN over WDM layers, where the OTN digital layer is used for the grooming of IP traffic over high bit rate lambdas. In figure 8, Node Bx can be assumed to be digital layer, which is interfacing with packet layer nodes (Ax) across overlay interface. Digital layer nodes Bx are interfacing with DWDM layer nodes Cx. If OTN (Bx) and DWDM (Cx) node belong to same IGP, then this becomes multi-layer path computation and signaling case, and it is out of scope of this document. However, as already shown in the intro of this memo, the three different domains of the example could have the same switching capability (e.g., IP) and be kept separate just for administrative reasons. 4.13. UC 13 - Server layer resiliency parameters Requirement: It must be possible to request an LSP in the server domain with resilience parameters. The minimum set of such parameters includes 1+1 protection and restoration. Moreover, it must be possible for the operator to change the resilience level after the path is established in the network (e.g. dynamic SLA negotiation). This functionality is interesting in a scenario like the one in Figure 9 with two concurrent paths. Let us assume service A and B are requested without any resilience requirements. If there is a failure in service A, the operator can request for protection in service B once this situation is detected. Ceccarelli, et al. Expires September 6, 2014 [Page 16] Internet-Draft Overlay model use cases March 2014 These parameters can be used both in the case of single homing (UC1) and concurrent paths (UC6). The aim of this section is to highlight two sub-cases for every resilience case: (1) during the provisioning the client domain can request to the server domain for resilience parameters. (2) Once a failure occurs, the client domain has to be notified via the overlay interface thus carrying information about the situation in the server domain, so the client domain can take its own decisions. For the different sub-use cases, the provisioning use case already highlights which is the workflow and the requirements for each scenario. This section does not include an example for each of them. 5. Security Considerations TBD 6. IANA Considerations TBD 7. Contributors Diego Caviglia, Ericsson Via E.Melen, 77 - Genova - Italy Email: diego.caviglia@ericsson.com Jeff Tantsura, Ericsson 300 Holger Way, San Jose, CA 95134 - USA Email: jeff.tantsura@ericsson.com Khuzema Pithewan, Infinera Corporation Ceccarelli, et al. Expires September 6, 2014 [Page 17] Internet-Draft Overlay model use cases March 2014 140 Caspian CT., Sunnyvale - CA - USA Email: kpithewan@infinera.com Cyril Margaria, Wandl Email: cyril.margaria@googlemail.com John Drake, Juniper Email: jdrake@juniper.net Sergio Belotti, Alcatel-Lucent Email: sergio.belotti@alcatel-lucent.com Victor Lopez, Telefonica I+D Email: vlopez@tid.es Appendix A. Appendix I - Colored overlay This use case applies to networks where the server domain is a WDM network. In those cases it is possible to either have a grey interface between client and server domains (i.e. transponder on the border core node) or a colored interface between them (i.e. transponder on the edge node). All the previous use cases assume the case of grey interface, but there are particular network scenarios in which it is possible to move the transponders from the core to the edge nodes and hence save on hardware cost. The issue with this solution is that the path computation in the server domain, being either centralized or distributed, has only visibility of what is inside the server domain and hence has not all the info needed to perform the validation of a path. The edge node must provide the pach computation functions in the server domain with a set of info needed for a correct path computation and path Ceccarelli, et al. Expires September 6, 2014 [Page 18] Internet-Draft Overlay model use cases March 2014 validation from transponder to transponder (i.e. between edge nodes) all along the server domain. The type of information needed for this scenario can be classified into three categories and must be in the context of G.698.2: - Feasibility: Parameters like the output power of the transponder are needed in order to state e.g. the amount of km that can be reached without regeneration. - Compatibility: The egress transponder must be compatible with the ingress one. Parameters that influence the level of compatibility can be for example the type of FEC (Forward Error Correction) used or the modulation format (which also impacts the feasibility together with the bit rate). - Availability: Transponders can be tunable within a range of lambdas or even locked to a single lambda. This impacts the path computation as not every path in the network might have such lambda(s) supported or available at the time the path computation is performed. Feasibility and compatibility are all governed by the application codes. In figure below it is possible to see that the PCE is aware of all the info between A and C (i.e. within the server domain scope) but what is missing is info related to the transponders on R1 and on R2 and of the access links. (i.e. R1-A and C-R2). Ceccarelli, et al. Expires September 6, 2014 [Page 19] Internet-Draft Overlay model use cases March 2014 -Feasibility -Compatibility |=====| -Availability | PCE | /---------->|=====| / / +--+ / /-\ /-\ /-\ +--+ |R1|*******( A )-----( B )---( C )********|R2| +--+ \-/ \-/\ \-/ +--+ | \ / | \ | | \ / | \ | | \ / | \ | | \ | \ | | / \ | \| /-\ / \/-\ /-\ ( D )-----( E )---( F ) \-/ \-/ \-/ *** = colored overlay interfaces Figure 11: PCE feeding for colored UNI There is not yet a standard set of parameters that is needed for path computation in WDM networks but an example of some of them is provided in the following list: o Modulation format o FEC (type or gain) o Minimum transponder output power o Bitrate o Dispersion tolerance o OSNR (minimum required) 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Ceccarelli, et al. Expires September 6, 2014 [Page 20] Internet-Draft Overlay model use cases March 2014 8.2. Informative References Authors' Addresses Daniele Ceccarelli Ericsson Via E. Melen 77 Genova - Erzelli Italy Email: daniele.ceccarelli@ericsson.com Oscar Gonzalez de Dios Telefonica I+D Don Ramon de la Cruz 82-84 Madrid 28045 Spain Email: ogondio@tid.es Fatai Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base Shenzhen 518129 P.R.China Bantian, Longgang District Phone: +86-755-28972912 Email: zhangfatai@huawei.com Xian Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base Shenzhen 518129 P.R.China Bantian, Longgang District Phone: +86-755-28972913 Email: zhang.xian@huawei.com Zafar Ali Cisco Systems, Inc. Email: zali@cisco.com Ceccarelli, et al. Expires September 6, 2014 [Page 21] Internet-Draft Overlay model use cases March 2014 Rajan Rao Infinera Corporation 140, Caspian CT. Sunnyvale, CA-94089 USA Email: rrao@infinera.com Sergio Belotti Alcatel-Lucent Via Trento, 30 Vimercate Italy Email: sergio.belotti@alcatel-lucent.com Ceccarelli, et al. Expires September 6, 2014 [Page 22]