Network Working Group                                      A. Atlas, Ed.
Internet-Draft                                          Juniper Networks
Intended status: Informational                            T. Nadeau, Ed.
Expires: August 15, November 11, 2016                                       Brocade
                                                                 D. Ward
                                                           Cisco Systems
                                                       February 12,
                                                            May 10, 2016

           Interface to the Routing System Problem Statement


   Traditionally, routing systems have implemented routing and signaling
   (e.g.  MPLS) to control traffic forwarding in a network.  Route
   computation has been controlled by relatively static policies that
   define link cost, route cost, or import and export routing policies.
   With the advent of highly dynamic data center networking, on-demand
   WAN services, dynamic policy-driven traffic steering and service
   chaining, the need for real-time security threat responsiveness via
   traffic control, and a paradigm of separating policy-based decision-
   making from the router itself, the need has requirements have emerged to more
   dynamically manage and program routing systems in order to control systems.  These requirements
   should allow controlling routing information and traffic paths and to extract
   extracting network topology information, traffic statistics, and
   other network analytics from routing systems.

   This document proposes meeting this need via an Interface to the
   Routing System (I2RS).

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   This Internet-Draft will expire on August 15, November 11, 2016.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  I2RS Model and Problem Area for the IETF  . . . . . . . . . .   3
   3.  Standard Data-Models of Routing State for Installation  . . .   6
   4.  Learning Router Information . . . . . . . . . . . . . . . . .   6
   5.  Aspects to be Considered for an I2RS Protocol . . . . . . . .   7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  Existing Management Interfaces . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Traditionally, routing systems have implemented routing and signaling
   (e.g.  MPLS) to control traffic forwarding in a network.  Route
   computation has been controlled by relatively static policies that
   define link cost, route cost, or import and export routing policies.
   With the advent of highly dynamic data center networking, on-demand
   WAN services, dynamic policy-driven traffic steering and service
   chaining, the need for real-time security threat responsiveness via
   traffic control, and a paradigm of separating policy-based decision-
   making from the router itself, the need has emerged to more
   dynamically manage and program routing systems in order to control
   routing information and traffic paths and to extract network topology
   information, traffic statistics, and other network analytics from
   routing systems.

   As modern networks continue to grow in scale and complexity and
   desired policy has become more complex and dynamic, there is a need
   to support rapid control and analytics.  The scale of modern networks
   and data-centers and the associated operational expense drives the
   need to automate even the simplest operations.  The ability to
   quickly interact via more complex operations to support dynamic
   policy is even more critical.

   In order to enable network applications to have access to and control
   over information in the different vendors' routing systems, a
   publicly documented interface is required.  The interface needs to
   support real-time, asynchronous interactions using efficient data
   models and encodings that are based on and extend those previously
   defined.  Furthermore, the interface must be tailored to provide a
   solid base on which a variety of use cases can be supported.

   To support the requirements of orchestration software and automated
   network applications to dynamically modify the network, there is a
   need to learn topology, network analytics, and existing state from
   the network as well as to create or modify routing information and
   network paths.  A feedback loop is needed so that changes made can be
   verifiable and so that these applications can learn and react to
   network changes.

   Proprietary solutions to partially support the requirements outlined
   above have been developed to handle specific situations and needs.
   Standardizing an interface to the routing system will make it easier
   to integrate use of it into a network.  Because there are proprietary
   partial solutions already, the standardization of a common interface
   should be feasible.

   It should be noted that during the course of this document, the term
   "applications" is used.  This is meant to refer to an executable
   program of some sort that has access to a network, such as an IP or
   MPLS network, via a routing system.

2.  I2RS Model and Problem Area for the IETF

   Managing a network of systems running a variety of routing protocols
   and/or providing one or more additional services (e.g., forwarding,
   classification and policing, firewalling) involves interactions
   between multiple components within these systems.  Some of these
   systems or system components may be virtualized, colocated co-located within
   the same physical system or distributed.  In all cases, it is
   desirable to enable network applications to manage and control the
   services provided by many, if not all, of these components, subject
   to authenticated and authorized access and policies.

   A data-model driven interface to the routing system is needed.  This
   will allow expansion of what information can be read and controlled
   and allow for future flexibility.  At least one accompanying protocol
   with clearly defined operations is needed; the suitable protocol(s)
   can be identified and expanded to support the requirements of an
   Interface to the Routing System (I2RS).  These solutions must be
   designed to facilitate rapid, isolated, secure, and dynamic changes
   to a device's routing system.  These would facilitate wide-scale
   deployment of interoperable applications and routing systems.

   The I2RS model and problem area for IETF work is illustrated in
   Figure 1.  This document uses terminology defined in
   [I-D.ietf-i2rs-architecture].  The I2RS Agent is associated with a
   routing element, which may or may not be co-located with a data-
   plane.  The I2RS Client could be integrated in a network application
   or controlled and used by one or more separate network applications.
   For instance, an I2RS Client could be provided by a network
   controller or a network orchestration system that provides a non-I2RS
   interface to network applications and an I2RS interface to I2RS
   Agents on the systems being managed.  The scope of the data-models
   used by I2RS extends across the entire routing system and the
   selected protocol(s) for I2RS.

   As depicted in Figure 1, the I2RS Client and I2RS Agent in a routing
   system are objects with in the I2RS scope.  The selected protocol(s)
   for I2RS extend between the I2RS client and I2RS Agent.  All other
   objects and interfaces in Figure 1 are outside the I2RS scope for

        +***************+   +***************+   +***************+
        *  Application  *   *  Application  *   *  Application  *
        +***************+   +***************+   +***************+
        |  I2RS Client  |           ^                  ^
        +---------------+           *                  *
                 ^                  *   ****************
                 |                  *   *
                 |                  v   v
                 |           +---------------+         +-------------+
                 |           |  I2RS Client  |<------->| Other I2RS  |
                 |           +---------------+         | Agents      |
                 |                   ^                 +-------------+
                 |________________   |
                                  |  |  <== I2RS Protocol
                                  |  |
       .                          v  v                                 .
       . +*************+     +---------------+      +****************+ .

       . *  Policy     *     |               |      *   Routing  &   * .
       . * Database    *<***>|  I2RS Agent   |<****>*   Signaling    * .
       . +*************+     |               |      *   Protocols    * .
       .                     +---------------+      +****************+ .
       .                        ^   ^     ^                  ^         .
       . +*************+        *   *     *                  *         .
       . *  Topology   *        *   *     *                  *         .
       . *  Database   *<*******+   *     *                  v         .
       . +*************+            *     *         +****************+ .
       .                            *     +********>*  RIB Manager   * .
       .                            *               +****************+ .
       .                            *                        ^         .
       .                            v                        *         .
       .                 +*******************+               *         .
       .                 * Subscription &    *               *         .
       .                 * Configuration     *               v         .
       .                 * Templates for     *      +****************+ .
       .                 * Measurements,     *      *  FIB Manager   * .
       .                 * Events, QoS, etc. *      *  & Data Plane  * .
       .                 +*******************+      +****************+ .

     <-->  interfaces inside the scope of I2RS Protocol
     +--+  objects inside the scope of I2RS-defined behavior

     <**>  interfaces NOT within the scope of I2RS Protocol
     +**+  objects NOT within the scope of I2RS-defined behavior

     <==   used to point to the interface where the I2RS Protocol
           would be used

     ....  boundary of a router supporting I2RS

                   Figure 1: I2RS model and Problem Area

   The I2RS Working Group must select the suitable protocol(s) used to carry messages between the I2RS Clients and I2RS Agent.  The protocol
   Agents should provide the key features specified in Section 5.


   I2RS Working Group must identify or define will use a set of meaningful data-models for information in the
   routing system and in a topology database.  The  Each data-model should
   describe the meaning and relationships of the modeled items.  The
   data-models should be separable across different features of the
   managed components, versioned, and extendable.  As shown in Figure 1,
   I2RS needs to interact with several logical components of the routing
   element: policy database, topology database, subscription and
   configuration for dynamic measurements/events, routing signaling
   protocols, and its RIB manager.  This interaction is both for writing
   (e.g. to policy databases or RIB manager) as well as for reading
   (e.g. dynamic measurement or topology database).  An application
   should be able to combine data from individual routing elements to
   provide network-wide data-model(s).

   The data models should translate into a concise transfer syntax, sent
   via the I2RS protocol, that is straightforward for applications to
   use (e.g., a Web Services design paradigm).  The information transfer
   should use existing transport protocols to provide the reliability,
   security, and timeliness appropriate for the particular data.

3.  Standard Data-Models of Routing State for Installation

   As described in Section 1, there is a need to be able to precisely
   control routing and signaling state based upon policy or external
   measures.  One set of data-models that I2RS should focus on is for
   interacting with the RIB layer (e.g.  RIB, LIB, multicast RIB,
   policy-based routing) to provide flexibility and routing
   abstractions.  As an example, the desired routing and signaling state
   might range from simple static routes to policy-based routing to
   static multicast replication and routing state.  This means that, to
   usefully model next-hops, the data model employed needs to handle
   next-hop indirection and recursion (e.g. a prefix X is routed like
   prefix Y) as well as different types of tunneling and encapsulation.

   Efforts to provide this level of control have focused on
   standardizing data models that describe the forwarding plane (e.g.
   ForCES [RFC3746]).  I2RS recognizes that the routing system and a
   router's OS provide useful mechanisms that applications could
   usefully harness to accomplish application-level goals.  Using
   routing indirection, recursion and common routing abstractions (e.g.
   tunnels, LSPs, etc.) provides significant flexibility and
   functionality over collapsing the state to individual routes in the
   FIB that need to be individually modified when a change occurs.

   In addition to interfaces to control the RIB layer, there is a need
   to dynamically configure policies and parameter values for the
   various routing and signaling protocols based upon application-level
   policy decisions.

4.  Learning Router Information

   A router has information that applications may require so that they
   can understand the network, verify that programmed state is
   installed, measure the behavior of various flows, and understand the
   existing configuration and state of the router.  I2RS should provide
   a framework so that applications can register for asynchronous
   notifications and can make specific requests for information.

   Although there are efforts to extend the topological information
   available, even the best of these (e.g., BGP-LS
   [I-D.ietf-idr-ls-distribution]) still only provide the current active
   state as seen at the IGP and BGP layers.  Detailed topological state
   that provides more information than the current functional status
   (e.g. active paths and links) is needed by applications.  Examples of
   missing information include paths or link that are potentially
   available (e.g.  administratively down) or unknown (e.g. to peers or
   customers) to the routing topology.

   For applications to have a feedback loop that includes awareness of
   the relevant traffic, an application must be able to request the
   measurement and timely, scalable reporting of data.  While a
   mechanism such as IPFIX [RFC5470] may be the facilitator for
   delivering the data, providing the ability for an application to
   dynamically request that measurements be taken and data delivered is

   There are a wide range of events that applications could use for
   either verification of router state before other network state is
   changed (e.g. that a route has been installed), to act upon changes
   to relevant routes by others, or upon router events (e.g. link up/
   down).  While a few of these (e.g. link up/down) may be available via
   MIB notifications today, the full range is not (e.g. route-installed,
   route-changed, primary LSP changed, etc.)

5.  Aspects to be Considered for an I2RS Protocol

   This section describes required aspects of a protocol that could
   support I2RS.  Whether such a protocol is built upon extending
   existing mechanisms or requires a new mechanism requires further

   The key aspects needed in an interface to the routing system are:

   Multiple Simultaneous Asynchronous Operations:   A single application
      should be able to send multiple independent atomic operations via
      I2RS without being required to wait for each to complete before
      sending the next.

   Very Fine Granularity of Data Locking for Writing:   When an I2RS
      operation is processed, it is required that the data locked for
      writing is very granular (e.g. a particular prefix and route)
      rather than extremely coarse, as is done for writing
      configuration.  This should improve the number of concurrent I2RS
      operations that are feasible and reduce blocking delays.

   Multi-Headed Control:   Multiple applications may communicate to the
      same I2RS Agent in a minimally coordinated fashion.  It is
      necessary that the I2RS Agent can handle multiple requests in a
      well-known policy-based fashion.  Data written can be owned by
      different I2RS Clients at different times; data may even be
      overwritten by a different I2RS Client.  The details of how this
      should be handled are described in [I-D.ietf-i2rs-architecture].

   Duplex:   Communications can be established by either the I2RS Client
      (i.e., that resides within the application or is used by it to
      communicate with the I2RS Agent), or the I2RS Agent.  Similarly,
      events, acknowledgements, failures, operations, etc. can be sent
      at any time by both the router and the application.  The I2RS is
      not a pure pull-model where only the application queries to pull

   High-Throughput:   At a minimum, within the I2RS scope, the I2RS Agent and associated router
      should be able to handle a considerable number of operations per
      second (for example 10,000 per second to handle many individual
      subscriber routes changing simultaneously).

   Low-Latency:   Within a sub-second time-scale, it should be possible
      to complete simple operations (e.g. reading or writing a single
      prefix route).

   Multi-Channel:   It should be possible for information to be
      communicated via the interface from different components in the
      router without requiring going through a single channel.  For
      example, for scaling, some exported data or events may be better
      sent directly from the forwarding plane, while other interactions
      may come from the control-plane.  One channel, with authorization
      and authentication, may be considered primary; only an authorized
      client can then request that information be delivered on a
      different channel.  Writes from a client are only expected on
      channels that provide authorization and authentication.

   Scalable, Filterable Information Access:  To extract information in a
      scalable fashion that is more easily used by applications, the
      ability to specify filtering constructs in an operation requesting
      data or requesting an asynchronous notification is very valuable.

   Secure Control and Access:   Any ability to manipulate routing state
      must be subject to authentication and authorization.  Sensitive
      routing information may also may need to be provided via secure access
      back to the I2RS Client.  Such communications must be integrity
      protected.  Some  Most communications will also require confidentiality.

   Extensible and Interoperability:   Both the I2RS protocol and models
      must be extensible and interoperate between different versions of
      protocols and models.

6.  Acknowledgements

   The authors would like to thank Ken Gray, Ed Crabbe, Nic Leymann,
   Carlos Pignataro, Kwang-koog Lee, Linda Dunbar, Sue Hares, Russ
   Housley, Eric Grey, Qin Wu, Stephen Kent, Nabil Bitar, Deborah
   Brungard, and Sarah Banks for their suggestions and review.

7.  IANA Considerations

   This document includes no request to IANA.

8.  Security Considerations

   Security is a key aspect of any protocol that allows state
   installation and extracting of detailed router state.  The need for
   secure control and access is mentioned in Section 5.  More
   architectural security considerations are discussed in
   [I-D.ietf-i2rs-architecture].  Briefly, the I2RS Agent is assumed to
   have a separate authentication and authorization channel by which it
   can validate both the identity and the permissions associated with an
   I2RS Client.  Mutual authentication between the I2RS Agent and I2RS
   Client is required.  Different levels of integrity, confidentiality,
   and replay protection are relevant for different aspects of I2RS.

9.  References

9.1.  Normative References

              Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
              Nadeau, "An Architecture for the Interface to the Routing
              System", draft-ietf-i2rs-architecture-12 draft-ietf-i2rs-architecture-15 (work in
              progress), December 2015. April 2016.

9.2.  Informative References

              Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
              Ray, "North-Bound Distribution of Link-State and TE
              Information using BGP", draft-ietf-idr-ls-distribution-13
              (work in progress), October 2015.

   [RFC3746]  Yang, L., Dantu, R., Anderson, T., and R. Gopal,
              "Forwarding and Control Element Separation (ForCES)
              Framework", RFC 3746, DOI 10.17487/RFC3746, April 2004,

   [RFC4292]  Haberman, B., "IP Forwarding Table MIB", RFC 4292,
              DOI 10.17487/RFC4292, April 2006,

   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
              "Architecture for IP Flow Information Export", RFC 5470,
              DOI 10.17487/RFC5470, March 2009,

Appendix A.  Existing Management Interfaces

   This section discusses as a single entity the combination of the
   abstract data models, their representation in a data language, and
   the transfer protocol commonly used with them.  While other
   combinations of these existing standard technologies are possible,
   the ways described are those that have significant deployment.

   There are three basic ways that routers are managed.  The most
   popular is the command line interface (CLI), which allows both
   configuration and learning of device state.  This is a proprietary
   interface resembling a UNIX shell that allows for very customized
   control and observation of a device, and, specifically of interest in
   this case, its routing system.  Some form of this interface exists on
   almost every device (virtual or otherwise).  Processing of
   information returned to the CLI (called "screen scraping") is a
   burdensome activity because the data is normally formatted for use by
   a human operator, and because the layout of the data can vary from
   device to device, and between different software versions.  Despite
   its ubiquity, this interface has never been standardized and is
   unlikely to ever be standardized.  CLI standardization is not
   considered as a candidate solution for the problems motivating I2RS.

   The second most popular interface for interrogation of a device's
   state, statistics, and configuration is the Simple Network Management
   Protocol (SNMP) and a set of relevant standards-based and proprietary
   Management Information Base (MIB) modules.  SNMP has a strong history
   of being used by network managers to gather statistical and state
   information about devices, including their routing systems.  However,
   SNMP is very rarely used to configure a device or any of its systems
   for reasons that vary depending upon the network operator.  Some
   example reasons include complexity, the lack of desired configuration
   semantics (e.g., configuration "roll-back", "sandboxing" or
   configuration versioning), and the difficulty of using the semantics
   (or lack thereof) as defined in the MIB modules to configure device
   features.  Therefore, SNMP is not considered as a candidate solution
   for the problems motivating I2RS.

   Finally, the IETF's Network Configuration (or NETCONF) protocol has
   made many strides at overcoming most of the limitations around
   configuration that were just described.  However, as a new technology
   and with the initial lack of standard data models, the adoption of
   NETCONF has been slow.  I2RS will identify and define as needed
   information and data models to support I2RS applications.  Additional
   extensions to handle multi-headed control may need to be added to
   NETCONF and/or appropriate data models.

Authors' Addresses

   Alia Atlas (editor)
   Juniper Networks


   Thomas D. Nadeau (editor)


   Dave Ward
   Cisco Systems