Interdomain Routing Working Group X. Chen Internet-Draft Z. Li Intended status: Informational Huawei Technologies Expires: April 23, 2014 October 20, 2013 Use Cases for an Interface to LDP Protocol draft-chen-i2rs-mpls-ldp-usecases-00 Abstract The Label Distribution Protocol (LDP) [RFC5036] is a protocol defined for distributing labels in MPLS domain. Traditionally LDP protocol may be managed via CLI, SNMP or NETCONF. Interface to the Routing System's (I2RS) Programmatic interfaces, as defined in [I-D.ward-i2rs-framework], provides an alternate way to control the configuration and diagnose the operation of the LDP protocol. This document describes requirement and use cases for which I2RS can be used for LDP protocol. Requirements Language 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]. 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 April 23, 2014. Chen & Li Expires April 23, 2014 [Page 1] Internet-Draft Use Cases for an Interface to LDP Protocol October 2013 Copyright Notice Copyright (c) 2013 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. LDP Configuration . . . . . . . . . . . . . . . . . . . . . . 3 2.1. LDP Protocol Configuration . . . . . . . . . . . . . . . 3 2.2. LDP Policy Configuration . . . . . . . . . . . . . . . . 4 3. LDP Events . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Notification of LDP Session or LSP Events . . . . . . . . 4 3.2. LDP Protocol Statistics . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 5.1. Normative References . . . . . . . . . . . . . . . . . . 5 5.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The Label Distribution Protocol (LDP) is a protocol defined for distributing labels in MPLS domain. Traditionally LDP protocol may be managed via CLI, SNMP or NETCONF. The I2RS, as defined in [I-D.ward-i2rs-framework], may be used for the configuration, manipulation, polling or analyzing protocol data. The I2RS is not intended to replace any existing configuration mechanisms. Instead, I2RS is intended to augment those existing mechanisms by defining a standardized set of programmatic interfaces to enable easier configuration, interrogation and analysis of the protocol. This document describes requirement and use cases for which I2RS can be used for LDP protocol. The use cases described in this document encompass: LDP protocol configuration, LDP policy configuration, LDP protocol events. Chen & Li Expires April 23, 2014 [Page 2] Internet-Draft Use Cases for an Interface to LDP Protocol October 2013 2. LDP Configuration LDP can be used to create transport LSPs to carry MPLS-based service and establish the pseudowires for MPLS PWE3 service [RFC4447] or MPLS VPLS service [RFC4762]. LDP is deployed widely in the network because of its simple protocol configuration and flexible policy. For illustration purposes one service type related to pseudowires is described in following document: PWE3 service. By I2RS interface the network application can configure LDP sessions to deploy PWE3 service and can configure LDP policy to control the setup of LDP LSPs. The application can select proper programmatic interface. 2.1. LDP Protocol Configuration The basic configuration of LDP includes establishing and maintaining LDP sessions, setting parameters of LDP sessions like type of application over the established LDP session [I-D.ietf-mpls-ldp-ip-pw-capability] etc. An LDP session is set up between the pseudowire endpoints to provide MPLS-based PWE3 services. The PW label bindings are distributed over the LDP session. The pseudowire endpoints is normally configured as the LSR ID which is the first four octets of LDP Identifier. LSR can use the different local LSR ID to build sessions with different peers in order to isolate VPN services. LDP sessions used by PWE3 services are established normally by LDP extended discovery that the LSR periodically sending LDP Targeted Hellos to the specific address. I2RS would allow an application to push configuration using a set of programmatic APIs from a central location where a global PWE3 provisioning information could be stored. This helps avoid manual configuration of PWE3 and LDP on multiple pseudowire endpoints. Use of I2RS programmatic API can push the configuration of the local LDP LSR ID and peer address to set up the targeted session to the pseudowire endpoints. Sometimes end-user wants to disable IPoMPLS application on a L2VPN/PW Tarted LDP session [I-D.ietf-mpls-ldp-ip-pw-capability]. Use of I2RS programmatic API can set type of application over the established LDP session. In this way LDP speaker can only advertise to its peer the application data which is interested by the user. Chen & Li Expires April 23, 2014 [Page 3] Internet-Draft Use Cases for an Interface to LDP Protocol October 2013 2.2. LDP Policy Configuration LDP supports some policy configuration used to control the allocation of labels, to filter the advertisement and acceptance of label bindings, to trigger LDP DoD request for some prefixes and so on. In seamless MPLS scenario [I-D.ietf-mpls-seamless-mpls] access devices can only hold limited amount of state because of their compute and memory constraints. If LDP DU advertisement mode is used between AN and AGN, the outbound policy can be configured on AGN to advertise selective prefixes to specified AN. With I2RS a network operator can push LDP outbound policy configuration using a programmatic API from an I2RS controller to specific AGN according to the network condition. If LDP DoD advertisement mode is used between AN and AGN, and there is only default route in AN, the feature which is LDP Extension for Inter-Area LSPs [RFC5283] must be adopted and the LDP DoD request policy [I-D.ietf-mpls-ldp-dod] should be configured to trigger the establishment of LSP for /32 FEC which is PWE3 destination /32 FEC in PWE3 service or BGP next-hop /32 FEC BGP/MPLS IPVPN service [RFC4364]. With I2RS a network operator can push LDP DoD request policy configuration using a programmatic API from an I2RS controller to specific AN according to the service requirement. 3. LDP Events I2RS could provide a publish-subscribe capability to applications to: o subscribe state of LDP sessions or LSPs and related events; and, o subscribe number of LDP sessions or LSPs or other protocol-related events of interest. 3.1. Notification of LDP Session or LSP Events Some applications adopt LSPs established by LDP protocol to carry service and the end-user would care about the state of such LSPs and hope to know about changes of their state immediately. PWE3 service adopt targeted LDP sessions to establish pseudowires and the end-user would care about the state of such LDP sessions and hope to receive the immediate notification of changes in their state. Chen & Li Expires April 23, 2014 [Page 4] Internet-Draft Use Cases for an Interface to LDP Protocol October 2013 The applications can use the I2RS interface to subscribe the state of LDP sessions or LDP LSPs. When the requisite events about sessions coming up or going down are observed by an LSR, it would notify I2RS controllers. So applications would immediately receive the published events and take the appropriate action, for example, diagnosing why the service is invalid or analyzing whether an alternate path should be switched to and how the link failure or node failure is recovered. 3.2. LDP Protocol Statistics There are several statistics related to LDP protocol like the number of LDP sessions, the count of LDP LSPs. These statistics can help network operators know about the status of the resources LDP protocol makes use of. Some access device has limited label entry resource and need restricting the maximum number of LDP LSPs. The network administrator wants to know whether the current number of LDP LSPs is close to the maximum number and if close the administrator can take necessary action. The application can set the maximum number of LDP LSPs by I2RS programmatic API before LDP is enabled. The application can set the warning threshold too. When the number of LDP LSPs reaches the threshold the warning message is triggered and notified to the application in the I2RS controller. The operator can take some action according to the warning message. 4. Security Considerations The LDP use cases described in this document assumes use of I2RS's programmatic interfaces described in the I2RS framework mentioned in [I-D.ward-i2rs-framework]. This document does not change the underlying security issues inherent in the existing [I-D.ward-i2rs- framework]. 5. References 5.1. Normative References [I-D.ward-i2rs-framework] Atlas, A., Nadeau, T., and D. Ward, "Interface to the Routing System Framework", draft-ward-i2rs-framework-00 (work in progress), February 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Chen & Li Expires April 23, 2014 [Page 5] Internet-Draft Use Cases for an Interface to LDP Protocol October 2013 [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP Specification", RFC 5036, October 2007. 5.2. Informative References [I-D.ietf-mpls-ldp-dod] Beckhaus, T., Decraene, B., Tiruveedhula, K., Konstantynowicz, M., and L. Martini, "LDP Downstream-on- Demand in Seamless MPLS", draft-ietf-mpls-ldp-dod-09 (work in progress), July 2013. [I-D.ietf-mpls-ldp-ip-pw-capability] Raza, K. and S. Boutros, "Disabling IPoMPLS and P2P PW LDP Application's State Advertisement", draft-ietf-mpls-ldp- ip-pw-capability-06 (work in progress), June 2013. [I-D.ietf-mpls-seamless-mpls] Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz, M., and D. Steinberg, "Seamless MPLS Architecture", draft- ietf-mpls-seamless-mpls-04 (work in progress), July 2013. [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006. [RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006. [RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January 2007. [RFC5283] Decraene, B., Le Roux, JL., and I. Minei, "LDP Extension for Inter-Area Label Switched Paths (LSPs)", RFC 5283, July 2008. Authors' Addresses Xia Chen Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: smile.chen@huawei.com Chen & Li Expires April 23, 2014 [Page 6] Internet-Draft Use Cases for an Interface to LDP Protocol October 2013 Zhenbin Li Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: lizhenbin@huawei.com Chen & Li Expires April 23, 2014 [Page 7]