Network Working Group L. Zhang Internet-Draft Z. Li Intended status: Informational Huawei Technologies Expires: January 5, 2015 D. Liu China Mobile S. Hares Hickory Hill Consulting L. Contreras Telefonica I+D July 4, 2014 Use Cases of I2RS in Mobile Backhaul Network draft-zhang-i2rs-mbh-usecases-00 Abstract In a mobile backhaul network, traditional configuration and diagnoses mechanisms based 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.ietf-i2rs-architecture], an alternative way is available to control the configuration and diagnose the operational results. This document discusses the use case for 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." Zhang, et al. Expires January 5, 2015 [Page 1] Internet-Draft Use Cases of I2RS in MBH July 2014 This Internet-Draft will expire on January 5, 2015. 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 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. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Topology Change Adaptation . . . . . . . . . . . . . . . . . 4 3.1. Frequently Access Network Topology Changes . . . . . . . 4 3.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 5 4. Application Configuration . . . . . . . . . . . . . . . . . . 5 4.1. Application Configuration . . . . . . . . . . . . . . . . 5 4.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 6 5. Route Policy Enforcement . . . . . . . . . . . . . . . . . . 7 5.1. Route Policy Description . . . . . . . . . . . . . . . . 7 5.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 8 6. Service Tunnel Implementation . . . . . . . . . . . . . . . . 9 6.1. Service Tunnel Description . . . . . . . . . . . . . . . 9 6.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 10 7. Protection Mechanism . . . . . . . . . . . . . . . . . . . . 10 7.1. Protection Mechanism Description . . . . . . . . . . . . 10 7.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 11 8. Network Monitoring . . . . . . . . . . . . . . . . . . . . . 11 8.1. Network Monitoring Description . . . . . . . . . . . . . 11 8.2. Requirements for I2RS . . . . . . . . . . . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 10.1. Normative References . . . . . . . . . . . . . . . . . . 12 10.2. Informative Reference . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Zhang, et al. Expires January 5, 2015 [Page 2] Internet-Draft Use Cases of I2RS in MBH July 2014 1. Introduction In mobile backhaul network, traditional configuration and diagnoses mechanisms based 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 needs to serve various radio access modes and applications across 2G/3G/LTE/5G, build various network architectures based on the number of network devices or the integration of different Areas or Autonomous System Numbers (ASNs), and support various network protocols that can be adopted to meet different network requirements. These needs make the mobile backhaul network configuration more and more arduous. Interface to the Routing System's (I2RS) Programmatic interfaces, as defined in [I-D.ietf-i2rs-architecture], provides an alternative way to control the configuration and diagnose the operational results. The use cases described in this document cover the critical elements of mobile backhaul networks, such as: application configuration, route policy enforcement, service tunnel implementation, protection mechanisms and network monitoring. The goal is to increase the community's understanding of the mobile backhaul requirements for I2RS in a the context of an entire network solution. This draft notes unique I2RS Requirements in the draft with the abbreviation "MBB-REQnn" where nn is the number of the requirements. 2. Definitions I2RS: Interface to the Routing System IGP: Interior Gateway Protocol BGP: Border Gateway Protocol MPLS: Multi-Protocol Label Switching LDP: Label Distribution Protocol 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 Zhang, et al. Expires January 5, 2015 [Page 3] Internet-Draft Use Cases of I2RS in MBH July 2014 SS-PW: Singe Segment PW MS-PW: Multi-Segment PW HVPN: Hierarchical VPN EPC: Evolved Packet Core LTE: Long Term Evolution FRR: Fast Reroute ECMP: Equal Cost Multi-path 3. Topology Change Adaptation 3.1. Frequently Access Network Topology Changes As wireless becomes the primary or even sole access method for more and more people, the mobile backhaul network must carry higher volumes of traffic. Growing traffic has necessitated more and more cells in the radio access networks (RANs) that provide mobile subscribers with an onramp to wireless networks. Mobile operators are turning to small-cell technology to increase capacity through frequency reuse, especially in densely populated areas. Finally, network capabilities must be highly scalable and agile, which lead to more frequently topology change, such as: o Change linear access network to ring access network Whether the access network is linear or ring is based on the optical links resource. The linear access network is less reliable than ring. So when the optical links are ready, it may be necessary to change linear access network to ring access network. o Add nodes for an access network Every access network is deployed to cover a given region. Along with the growth of wireless users, one access network may add new nodes to accommodate more users. o Split one ring access network into multiple linear or ring access networks The mobile traffic an access ring can bear is limited by the device capability such as the route/LSP specification and the bandwidth. When access users and traffic load are overloaded Zhang, et al. Expires January 5, 2015 [Page 4] Internet-Draft Use Cases of I2RS in MBH July 2014 in a ring access network, it may be necessary to split this ring into multiple linear or ring access networks according to the optical link resource. o Add more access networks This is the direct approach to cope with the growth of users and traffic, especially when the small-cell technology is introduced. 3.2. Requirements for I2RS The devices in the access network have limited capability for route and LSP specification, so the access network has to be divided into different IGP domains to reduce the number of routes and LSPs. This division into multiple IGPS has the benefit of isolating the impact of failure among different convergence domains and decreasing the time it takes to configure the IGP. Frequent changes of the access network topology require fast provision of IGP domain deployment, including both the whole IGP domain provision and the IGP configuration on the individual node. I2RS' programmatic interface would enable the IGP domain provisioning to operate automatically and simultaneously to topology changes while using global information of mobile backhaul network stored in a central location. MBH-REQ-01: The I2RS client-agent communication can distribute position-critical changes to IGP nodes using this global knowledge to quicken changes to support traffic during failures or traffic overloads. To enable this feature, the I2RS Clients-Agent communication needs to pass information on which IGP process or Level or Area the given node and links belong to. 4. Application Configuration 4.1. Application Configuration The mobile backhaul network has evolved into an IP-based network, which faces three main challenges in network construction: 1. various radio access modes: To protect existing investment and end user resource, TDM/ATM- based access modes belonging to 2G and 3G will coexist with Ethernet-based access mode belonging to 3G, LTE, and 5G for an Zhang, et al. Expires January 5, 2015 [Page 5] Internet-Draft Use Cases of I2RS in MBH July 2014 extended time into the future. The radio architecture evolution will bring out new radio interfaces, such as the X2 interface in LTE which will not work in hub-spoke communication mode and needs much more shorter latency. A mobile backhaul network must be built to have the ability to adapt to all 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 networks, meaning 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 may 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[I-D.li-mpls-seamless-mpls-mbb], when EPC is deployed in the Core network with 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. Within 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. 4. various traffic patterns User applications run on mobile phones now encompass the full range of user programs. Traffic from mobile phones may have different requirements for bandwidth and application responses (real-time, near real-time, non-real-time). This user traffic combines with the mobile phone control traffic that keeps tracks network usage and QoS. 4.2. Requirements for I2RS The challenges in mobile backhaul network construction show the flexibility and complexity requirements of network configuration and modification, such as: Zhang, et al. Expires January 5, 2015 [Page 6] Internet-Draft Use Cases of I2RS in MBH July 2014 o where the T-LDP should be configured, o where a BGP peer should be established, o where the VPN instance should be deployed, and o where the BGP-based LSP should be set up. Faced with flat or reduced budgets, 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' programmatic interface would allow network operators to distribute such configurations from a central location where global mobile backhaul network solution provisioning information could be stored. MBH-REQ-02: I2RS must allow operators to use of I2RS clients to distribute time-critical changes in configuration to I2RS agents associated with each routing node. This feature will simplify and automate configuration and monitoring of a mobile backhaul network to allow it to readily adapt to changing network sizes (and scales) and radio applications. MBB-REQ-03: I2RS Clients-Agent communication needs to pass information on: o T-LDP configurations and status; o BGP peer configurations, peer topologies and status; o BGP-based LSP topologies and status; o Reset VPN topologies, and per node configurations; While a beginning exists in the I2RS RIB Information Model [[I-D.ietf-i2rs-rib-info-model]] which includes in the route interfaces with MPLS LSP or VPN technology, additional features need to be added to support mobile backhaul networks. 5. Route Policy Enforcement 5.1. Route Policy Description The route policy in mobile backhaul networks mainly refers to BGP policy when L3VPN is used to serve the radio applications. The complexity of the existing network architecture and radio interfaces make it very difficult to apply a network-wide route policy, for: Zhang, et al. Expires January 5, 2015 [Page 7] Internet-Draft Use Cases of I2RS in MBH July 2014 o avoiding route advertisement across entire network When a mobile backhaul network contains more than 500 nodes, utilizing a multi-segments service like HVPN is recommended to reduce the routing and protocol processing overhead 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 limited capability, while advertising to the whole network routes to the core nodes which must have capability to store large number of 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 relies on BGP Policy using Local Preference, MED or other path attributes defined in [RFC4760]. When a BGP RR is adopted to simplify the BGP peer architecture from full-mesh mode, the policy would become more complex, in some cases may make be per-peer or per-route worse. o allowing On-demand route advertisement The advent of X2 interfaces in LTE, which need specific route information between any two access nodes, makes the network route advertisement more dynamic and unpredictable. The BGP policy should be adjusted dynamically to meet this route advertisement need across the entire network. 5.2. Requirements for I2RS MBB-REQ04: Route policy enforcement in mobile backhaul networks needs to be more dynamic and flexible than the current methods take hours (or even days) to configure route policy across a network. The I2RS interface must provide a programmatic way to configure (both policy and device) and monitor thousands of devices individually whose configuration is based on the devices role (such as ASRSs in one AS, ASBRs between ASs and other service-touch nodes). MBB-REQ-05: I2RS clients should be able to contact I2RS agents on nodes to query role-based information from the network status. After collecting the status, the I2RS client can develop the BGP policies based on role information and push the BGP policies to the I2RS agents that would load the alternate policies into the network device. The I2RS Agents loading the alternate policies could then send status back to the I2RS Client. Zhang, et al. Expires January 5, 2015 [Page 8] Internet-Draft Use Cases of I2RS in MBH July 2014 6. Service Tunnel Implementation 6.1. 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 networks and aggregate/core networks. If needed, the longest length match defined in [RFC5283] for LDP LSP should be supported. MPLS LDP LSP has excellent scalability with flexible policy to control the label advertisement of route, especially in DU mode, to decrease needless LSPs 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 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 as integrated across access network and aggregate/cores 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 networks, the LSP selection depends on the service need, and the creation of MPLS-TP LSP is always assumed to be decoupled with the protocol control plane running on separate network devices. Ideally, the static MPLS-TP LSP should be designed and configured on the centralized control plane. Zhang, et al. Expires January 5, 2015 [Page 9] Internet-Draft Use Cases of I2RS in MBH July 2014 6.2. Requirements for I2RS The mobile backhaul network is divided into an access network and an aggregation/core network where service tunnel implementation is not constant and unique. Therefore, it may be necessary to deploy different kind of LSPs separately (such as LDP LSP or MPLS-TE LSP in both access network and aggregate/core networks) or simultaneously (such as MPLS-TP static LSP in access network while LDP LSP or MPLS- TE LSP in aggregate/core network). Network operators need to know the ability of all of the network devices and the service requirements to make the most appropriate tunnel implementation. MBH-REQ06: I2RS clients can provide centralized control of many network devices via the I2RS Client-Agent communication. The I2RS programmatic interface can automate the collection and analysis of each device's capability so that the centralized I2RS client could calculate the optimal LSP path and distribute the configuration to individual devices. Automation of the collection of device capability should be available as query, notification, or a published stream. MBH-REQ07: While the I2RS RIB Information Model [[I-D.ietf-i2rs-rib-info-model]] provides for routes with tunnels or MPLS LSP, the features defined in this model are not sufficient to configure both types of LSPs needed for the VPN technology in mobile backhaul networks. Additional I2RS Informational models need to be created to support these features. 7. Protection Mechanism 7.1. Protection Mechanism Description The SLA for radio services is strict, which requires 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 mechanisms of different tunnel protocols, mentioned above, are different from each other. To enhance the reliability, LDP LSP should configure LDP FRR, which is calculated depending on the protect route algorithm, and be Loop-Free Algorithm (LFA), Remote-LFA, or Maximally Redundant Trees (MRT) used together with LDP MT as 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 Zhang, et al. Expires January 5, 2015 [Page 10] Internet-Draft Use Cases of I2RS in MBH July 2014 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 recommended 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. 7.2. Requirements for I2RS MBH-REQ08: The hierarchical protection architecture in mobile backhaul network offer high network reliability and more flexibility to meet the various needs of the tunnels and services. The I2RS interface in this use case is needed to automate the configuration and monitoring so that tunnel protection and service protection interwork in a flexible and reliable manner. 8. Network Monitoring 8.1. Network Monitoring Description The mobile backhaul network operators requires to determine the accurate cause as fast as possible when a link or node failure occurs and get the real reason for service quality degradation. For this, different network monitor tools are introduced for different service mode ( MPLS-TP OAM for section or LSP, Y.1731 for PW , IP Flow Performance Monitor (IPFPM) for IP service, etc.). The network operators should decide what a combination of multi-layer network monitor tools should be deployed, and what the exact detection parameters for these tools should be provisioned. Meanwhile, the network devices should report the detection result to the controller, which is used to analyze the network status. 8.2. Requirements for I2RS MBB-REQ09: The I2RS architecture (client-agent) should allow the two features for network monitoring naturally in its basic modes: o allow a combination of multi-layer network monitor tools with exact detection parameters to be configured on the network device o Facilitate the reporting the detection result as notification or publication stream It is important the result of these features allow the outages and traffic congestion or discards to be detected real-time with I2RS Zhang, et al. Expires January 5, 2015 [Page 11] Internet-Draft Use Cases of I2RS in MBH July 2014 Client(s) in each node, and the detection result will be reported to the I2RS agents to get the exact status of the network. 9. Security Considerations The mobile backhaul network use cases described in this document assumes use of I2RS' programmatic interfaces described in the I2RS framework mentioned in[I-D.ietf-i2rs-architecture]. This document does not change the underlying security issues inherent in the existing [I-D.ietf-i2rs-architecture]. 10. References 10.1. Normative References [I-D.ietf-i2rs-architecture] Atlas, A., Halpern, J., Hares, S., Ward, D., and T. Nadeau, "An Architecture for the Interface to the Routing System", draft-ietf-i2rs-architecture-04 (work in progress), June 2014. [I-D.ietf-i2rs-rib-info-model] Bahadur, N., Folkes, R., Kini, S., and J. Medved, "Routing Information Base Info Model", draft-ietf-i2rs-rib-info- model-03 (work in progress), May 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 10.2. Informative Reference [I-D.ietf-mpls-ldp-multi-topology] Zhao, Q., Raza, K., Zhou, C., Fang, L., Li, L., and D. King, "LDP Extensions for Multi Topology", draft-ietf- mpls-ldp-multi-topology-12 (work in progress), April 2014. [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-01 (work in progress), February 2014. [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 January 5, 2015 [Page 12] Internet-Draft Use Cases of I2RS in MBH July 2014 [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.com 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 Susan Hares Hickory Hill Consulting 7453 Hickory Hill Saline, MI 48176 USA Email: shares@ndzh.com Zhang, et al. Expires January 5, 2015 [Page 13] Internet-Draft Use Cases of I2RS in MBH July 2014 Luis M. Contreras Telefonica I+D Ronda de la Comunicacion, Sur-3 building, 3rd floor Madrid 28050 Spain Email: luismiguel.contrerasmurillo@telefonica.com URI: http://people.tid.es/LuisM.Contreras/ Zhang, et al. Expires January 5, 2015 [Page 14]