Network Working Group L. Zhang Internet-Draft Z. Li Intended status: Informational Huawei Technologies Expires: April 24, 2014 D. Liu China Mobile October 21, 2013 Use Cases of I2RS in Mobile Backhaul Network draft-zhang-i2rs-mbb-usecases-00 Abstract In mobile backhaul network, traditional configuration and diagnoses mechanisms base on device-level management tools and manual processing are ill-suited to meet the requirements of today's scalable, flexible, and complex network. Thanks to the new innovation of Interface to the Routing System's (I2RS) programmatic interfaces, as defined in [I-D.ward-i2rs-framework], an alternative way has been rolled out to control the configuration and diagnose the operation results. This document discusses the use case of I2RS in mobile backhaul network. 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 24, 2014. Copyright Notice Zhang, et al. Expires April 24, 2014 [Page 1] Internet-Draft Use Cases of I2RS in MBB October 2013 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. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Application Configuration . . . . . . . . . . . . . . . . . . 4 3.1. Application Configuration . . . . . . . . . . . . . . . . 4 3.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 5 4. Route Policy Enforcement . . . . . . . . . . . . . . . . . . 5 4.1. Route Policy Description . . . . . . . . . . . . . . . . 5 4.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 6 5. Service Tunnel Implementation . . . . . . . . . . . . . . . . 6 5.1. Service Tunnel Description . . . . . . . . . . . . . . . 6 5.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 7 6. Protection Mechanism . . . . . . . . . . . . . . . . . . . . 7 6.1. Protection Mechanism Description . . . . . . . . . . . . 7 6.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 8 7. Network Monitoring . . . . . . . . . . . . . . . . . . . . . 8 7.1. Network Monitoring Description . . . . . . . . . . . . . 8 7.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 9.2. Informative Reference . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction In mobile backhaul network, traditional configuration and diagnoses mechanisms base on device-level management tools and manual processing are ill-suited to meet the requirements of today's scalable, flexible, and complex network. The mobile backhaul network now need to serve various radio access modes and applications across 2G/3G / LTE/5G, build various network architectures based on the amount of network devices or the integration of different Areas or Autonomous System Numbers (ASNs), and support various network Zhang, et al. Expires April 24, 2014 [Page 2] Internet-Draft Use Cases of I2RS in MBB October 2013 protocols can be adopted to meet different network requirements, which make the mobile backhaul network configuration more and more arduous. Interface to the Routing System's (I2RS) Programmatic interfaces, as defined in [I-D.ward-i2rs-framework], provides an alternative way to control the configuration and diagnose the operation results. The use cases described in this document cover the critical elements of mobile backhaul network, such as: application configuration, route policy enforcement, service tunnel implementation, protection mechanism and network monitoring. The goal is to inform the community's understanding of the mobile backhaul requirements for I2RS in a viewpoint of entire network solution. 2. Definitions I2RS: Interface to the Routing System IGP: Interior Gateway Protocol BGP: Border Gateway Protocol MPLS: Multi-Protocol Label Switching LDP: Equal Cost Multi-path RSVP-TE: Resource Reservation Protocol Traffic Engineering PWE3: Pseudo Wire Emulation Edge-to-Edge VPN: Virtual Private Network L2VPN: L2 Virtual Private Network L3VPN: L3 Virtual Private Network SS-PW: Singe Segment PW MS-PW: Multi-Segment PW HVPN: Hierarchical VPN EPC: Pseudo Wire Emulation Edge-to-Edge LTE: Long Term Evolution FRR: Fast Reroute Zhang, et al. Expires April 24, 2014 [Page 3] Internet-Draft Use Cases of I2RS in MBB October 2013 ECMP: Equal Cost Multi-path 3. Application Configuration 3.1. Application Configuration The mobile backhaul network has evolved into an IP-based network, which faces three main challenges in network construction, including: 1. various radio access modes: Due to protect existing investment and end user resource, TDM/ ATM-based access mode belongs to 2G and 3G will coexist with Ethernet-based access mode belongs to 3G, LTE and 5G for a long period in future. The radio architecture evolution will bring out new radio interfaces, such as X2 interface in LTE which will not work in hub-spoke communication mode any more while needs much more shorter time delay. A mobile backhaul network must be built to have the ability to adapt to all of the mobile access modes, providing PWE3 service for TDM /ATM- based access mode and Native IP/Ethernet, PWE3/VPLS or L3VPN service for IP-based access mode. 2. various radio applications: A variety of radio applications (such as OM, signaling, data, video, etc. ) which have different quality of services (QoS), should be delivered in specific service channels in mobile backhaul network, that means there will be more than one PW or L3VPN instances binding with specific interfaces and service tunnels. 3. various network architectures: The mobile backhaul network maybe consist of hundreds of nodes in a small county or thousands of nodes in a populous region. It will be an integration of different ASNs rather than a single AS, when the EPC is deployed in the Core network when LTE. The network devices on different points of the network (e.g. access\aggregation\core) have different routing and protocol processing capabilities, resulting in an integration of different IGP routing areas rather than a single large IGP routing area. Refer to various network architectures, different service modes should be provided, such as SS- PW or MS-PW, E2E L3VPN or HVPN, Seamless MPLS, and the integration of them. Zhang, et al. Expires April 24, 2014 [Page 4] Internet-Draft Use Cases of I2RS in MBB October 2013 3.2. Requirements for I2RS The challenges in mobile backhaul network construction show the flexibility and complexity requirements of network configuration and modification, such as where the T-LDP should be configured, where the BGP peer should be established, where the VPN instance should be deployed, and where the BGP LSP should be set up. Faced with flat or reduced budget, the network operators are trying to squeeze the most from their network using device-level management tools and manual processing. In contrast to management of entire network devices, I2RS' programmable interface would allow network operators to distribute such configuration from a central location where a global mobile backhaul network solution provisioning information could be stored. Use of I2RS controllers to announce network configuration information would simplify and automate configuration of mobile backhaul network that readily adapt to changing network scales and radio applications. 4. Route Policy Enforcement 4.1. Route Policy Description The route policy in mobile backhaul network mainly refers to BGP policy when L3VPN is used to serve the radio applications. The complexity of today's network architecture and radio interfaces make it very difficult to apply a network-wide route policy, for: o avoiding route advertisement across entire network When a mobile backhaul network contains more than 500 nodes, complementing a multi-segments service like HVPN is recommended to reduce the routing and protocol processing quantity of network devices. BGP policy should be configured with prefix filters to advertise only the default or aggregate route to the access nodes which have poor capability, while to advertise the whole network routes to the core nodes which must have capability of fairly large routes. o supporting best route selection for VPN FRR or ECMP The mobile backhaul network is recommended to be built with a multi-homed network architecture for node failure protection, where VPN FRR or ECMP should be configured. The best route selection relay on the BGP Policy using Local Preference, MED or other path attributes defined in [RFC4760]. When BGP RR is adopted to simplify the BGP peer architecture from full-mesh mode, the policy would be more complex, in some cases may be per-peer or per-route more worse. Zhang, et al. Expires April 24, 2014 [Page 5] Internet-Draft Use Cases of I2RS in MBB October 2013 o allowing On-demand route advertisement The advent of X2 interface in LTE, which needs specific route information between any two access nodes, make the network route advertisement more dynamically and unpredictably. The BGP policy should be adjusted dynamically to meet this route advertisement need across the entire network. 4.2. Requirements for I2RS Route policy enforcement in mobile backhaul network need to be much more dynamical and flexible, and when to implement a network-wide route policy, network operators should configure thousands of devices with different policy details individually according to the role of the devices, such as ASRs in one AS, ASBRs between different ASs and other service-touch nodes. It will take hours, in some cases days to configure the route policy across the entire network. I2RS controllers could use common APIs to collect network information required to create different BGP policies dynamically, then push such policy onto the corresponding network device, and make it tack effect automatically. 5. Service Tunnel Implementation 5.1. Service Tunnel Description In mobile backhaul network, more than one kind of Service Tunnel can be used according to network ability or other consideration in different scenarios. The Tunnel deployment use case in mobile backhaul includes: o MPLS LDP LSP MPLS LDP LSP is set up through LDP protocol. Both Label Advertisement Mode of Downstream Unsolicited (DU) and Downstream on Demand (DOD) defined in [RFC3036] can be used individually or integrated across access network and aggregate/ core network. If needed, the longed length match define in [RFC5283] for LDP LSP should be supported. MPLS LDP LSP has great scalability with flexible policy to control the label advertisement of route, especially in DU mode, to decrease the needless LSPs, that is help to reduce the LSP capability requirement of network devices. o MPLS-TE LSP MPLS-TE LSP is set up through RSVP-TE protocol, which has multiple path control attributes (such as explicit-path, path Zhang, et al. Expires April 24, 2014 [Page 6] Internet-Draft Use Cases of I2RS in MBB October 2013 affinity property , path bandwidth assurance , path hop limitation, e.g.) and multiple protection modes (such as hot- standby, Fast Re-Route, protection group, e.g.). MPLS-TE LSP should be designed using the attributes and protection modes according to the requirements of the service delivery individually of integrated across access network and aggregate/ core network. o MPLS-TP LSP MPLS-TP includes unidirectional LSP, bidirectional co-routed LSP, and bidirectional associated LSP, which can be calculated and set up manually or using dynamic network protocols such as GMPLS. In mobile backhaul network, the LSP selection depends on the service need, and the creation of MPLS-TP LSP is always asked to be decoupled with the protocol control plane running on the separate network devices. In this case, the static MPLS-TP LSP should be designed and configured on the centralized control plane ideally. 5.2. Requirements for I2RS Since mobile backhaul network is divided into access network and aggregation/core network, where service tunnel implementation is not constant and unique, perhaps need to deploy different kind of LSPs separately (such as LDP LSP or MPLS-TE LSP in both access network and aggregate/core network) or simultaneously (such as MPLS-TP static LSP in access network while LDP LSP or MPLS-TE LSP in aggregate/core network). in this case, network operators should clearly know the ability of all of the network devices and the service requirements to make the most appropriate tunnel implementation. I2RS provide a centralized control of network devices, which should automate the collection and analysis of the device ability to calculate optimal LSP path and distribute the configuration to exact devices. 6. Protection Mechanism 6.1. Protection Mechanism Description The SLA for radio services is strict, which need interworking among multiple protection mechanisms. Two critical aspects should be taken into account for inter-working, hierarchical protection architectures and multiple OAM protocol interactions. 1. tunnel protection: The protection mechanism of different tunnel protocols, mentioned above, is different from each other. To enhance the Zhang, et al. Expires April 24, 2014 [Page 7] Internet-Draft Use Cases of I2RS in MBB October 2013 reliability, LDP LSP should configure LDP FRR, which is calculated depends on the protect route algorithm, which can be Loop-Free Algorithm (LFA), Remote-LFA, or Maximally Redundant Trees (MRT) used together with LDP MT described in [I-D.ietf-mpls-ldp-multi-topology]. MPLS-TE LSP should apply TE Fast Reroute or TE hot-standby. When MPLS-TP LSP is used, the LSP protection group should be configured with 1:1 or 1+1 mode for MPLS-TP line protection, as well as wrapping or steering modes fault processing for MPLS-TP ring protection. 2. service protection: Service protection is commended to be configured for node failure handover in mobile backhaul network, where PW redundancy defined in [RFC6718] or BGP VPN FRR or ECMP realization should be deployed exactly. 6.2. Requirements for I2RS The hierarchical protection architecture in mobile backhaul network offer high network reliability but more flexibility to meet the various needs of the tunnels and services. I2RS interface in this use case is needed to automate the configuration and make tunnel protection and service protection interwork with each other ideally. 7. Network Monitoring 7.1. Network Monitoring Description The mobile backhaul network operators are asked to give an accurate positioning when a link or node failure occurred, and get the real reason for service quality descent. This need to apply different network monitor tools for different service mode, like Network Quality Analysis (NQA), MPLS-TP OAM, and IP Flow Performance Monitor (IPFPM). In addition, to acquire the exact traffic path is really significant when use IPFPM for point-to-point detection. Multiple monitor tools require network operators to distinguish granular traffic flow to apply the appropriate one. At the same time, traditional device-level management tools is difficult to get the traffic path, which may need enhance the existing protocols or design a new specific protocol to do this work, both will increase the burden of mobile backhaul network. 7.2. Requirements for I2RS I2RS should solve the two problems mentioned above naturally by using centralized controllers, which control and manage the entire network Zhang, et al. Expires April 24, 2014 [Page 8] Internet-Draft Use Cases of I2RS in MBB October 2013 devices and store the whole routing and service information directly. Meanwhile, the defect and traffic congestion or dropping can be detected real-time with I2RS, which make the network keep optimal state dynamically all the time. 8. Security Considerations The mobile backhaul network 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]. 9. References 9.1. 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. 9.2. Informative Reference [I-D.ietf-mpls-ldp-multi-topology] Zhao, Q., Fang, L., Zhou, C., Li, L., and K. Raza, "LDP Extensions for Multi Topology Routing", draft-ietf-mpls- ldp-multi-topology-09 (work in progress), October 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. [I-D.li-mpls-seamless-mpls-mbb] Li, Z., Li, L., Morillo, M., and T. Yang, "Seamless MPLS for Mobile Backhaul", draft-li-mpls-seamless-mpls-mbb-00 (work in progress), July 2013. [RFC3036] Andersson, L., Doolan, P., Feldman, N., Fredette, A., and B. Thomas, "LDP Specification", RFC 3036, January 2001. [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007. Zhang, et al. Expires April 24, 2014 [Page 9] Internet-Draft Use Cases of I2RS in MBB October 2013 [RFC5283] Decraene, B., Le Roux, JL., and I. Minei, "LDP Extension for Inter-Area Label Switched Paths (LSPs)", RFC 5283, July 2008. [RFC6718] Muley, P., Aissaoui, M., and M. Bocci, "Pseudowire Redundancy", RFC 6718, August 2012. Authors' Addresses Li Zhang Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: monica.zhangli@huawei.comZ Zhenbin Li Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: lizhenbin@huawei.com Dapeng Liu China Mobile Unit2, 28 Xuanwumenxi Ave,Xuanwu District Beijing 100053 China Email: liudapeng@chinamobile.com Zhang, et al. Expires April 24, 2014 [Page 10]