Network Working Group                                      A. Atlas, Ed.
Internet-Draft                                            T. Nadeau, Ed.
Intended status: Informational                          Juniper Networks
Expires: February 15, 2014                                       D. Ward
                                                           Cisco Systems
                                                         August 14, 2013

           Interface to the Routing System Problem Statement


   As modern networks grow in scale and complexity, the need for rapid
   and dynamic control increases.  With scale, the need to automate even
   the simplest operations is important, but even more critical is the
   ability to quickly interact with more complex operations such as
   policy-based controls.

   In order to enable network applications to have access to and control
   over information in the Internet's routing system, we need a publicly
   documented interface specification.  The interface needs to support
   real-time, asynchronous interactions using data models and encodings
   that are efficient and potentially different from those available
   today.  Furthermore, the interface must be tailored to support a
   variety of use cases.

   This document expands upon these statements of requirements to
   provide a detailed problem statement for an Interface to the Routing
   System (I2RS).

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
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   This Internet-Draft will expire on February 15, 2014.

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Copyright Notice

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   ( in effect on the date of
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   described in the Simplified BSD License.

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  . . .   5
   4.  Learning Router Information . . . . . . . . . . . . . . . . .   5
   5.  Desired Aspects of a Protocol for I2RS  . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   8
   Appendix A.  Existing Management Interfaces . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   As modern networks grow in scale and complexity, the need for rapid,
   flexible and dynamic control increases.  With scale, the need to
   automate even the simplest operation is important, but even more
   critical is the ability for network operators to quickly interact
   with these operations using mechanisms such as policy-based controls.

   With complexity comes the need for more sophisticated automated
   network applications and orchestration software that can process
   large quantities of data, run complex algorithms, and adjust the
   routing state as required in order to support the network
   applications, their computations and their policies.  Changes made to
   the routing state of a network by external applications must be
   verifiable by those applications to ensure that the correct state has
   been installed in the correct places.

   In the past, mechanisms to support the requirements outlined above
   have been developed piecemeal as proprietary solutions to specific

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   situations and needs.  Many routing elements have an external
   interface to interact with routing - but since these vary between
   vendors, it is difficult to integrate use of those interfaces into a
   network.  The existence of such proprietary interfaces demonstrates
   both that the need for such an interface is understood and that
   technology solutions are understood.  What is needed are
   technological solutions with clearly defined operations that an
   application can initiate, and data-models to support such actions.
   These would facilitate wide-scale deployment of interoperable
   applications and routing systems.  These solutions must be designed
   to facilitate rapid, isolated, secure, and dynamic changes to a
   device's routing system.  In order to address these needs, the
   creation of an Interface to the Routing System (I2RS) is needed.

   It should be noted that during the course of this document, we will
   discuss and use the term "applications".  This is meant to refer to
   an executable program of some sort that has access to a network, such
   as an IP network.

2.  I2RS Model and Problem Area for The IETF

   Managing a network of production devices running a variety of routing
   protocols involves interactions with an between multiple components
   within a device.  Some of these components are virtual while some are
   physical; it may be desirable for many, or even all of these
   components to be made available to be managed and manipulated by
   applications, given that appropriate access, authentication, and
   policy hurdles have been crossed.  The management of only some of
   these components require standardization, as others have already been
   standardized.  The I2RS model is intended to incorporate existing
   mechanisms where appropriate, and to build extensions and new
   protocols where needed.  The I2RS model and problem area for IETF
   work is illustrated in Figure 1.  The I2RS Agent is associated with a
   routing element, which may or may not be co-located with a data-
   plane.  The I2RS Client is used and controlled by one or more network
   applications; they may be co-located or the I2RS Client might be part
   of a separate application, such as an orchestrator or controller.

        +***************+   +***************+   +***************+
        *  Application  *   *  Application  *   *  Application  *
        +***************+   +***************+   +***************+
        |  I2RS Client  |           ^                  ^
        +---------------+           *                  *
                 ^                  *   ****************
                 |                  *   *
                 |                  v   v
                 |           +---------------+         +-------------+

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                 |           |  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
     +--+  objects inside the scope of I2RS

     <**>  interfaces NOT within the scope of I2RS
     +**+  objects NOT within the scope of I2RS

     ....  boundary of a router participating in the I2RS

                   Figure 1: I2RS model and Problem Area

   A critical aspect of I2RS is defining a suitable protocol or
   protocols to carry messages between the I2RS Clients and the I2RS
   Agent, and defining the data-models for use with those I2RS
   protocol(s).  The data models should translate into a clear transfer
   syntax that is straightforward for applications to use (e.g., a Web

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   Services design paradigm), and should provide the key features
   specified in Section 5.  The information should use existing
   transport protocols to provide the reliability, security, and
   timeliness appropriate for the particular data.

   The second critical aspect are semantic-aware data-models for
   information in the routing system and in a topology database.  The
   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.  An
   application should be able to combine data from individual routing
   elements to provide network-wide data-model(s).

3.  Standard Data-Models of Routing State for Installation

   There is a need to be able to precisely control routing and signaling
   state based upon policy or external measures.  This can 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.  The
   relevant MIB modules (for example [RFC4292]) lack the necessary
   generality and flexibility.  In addition, by having I2RS focus
   initially on interfaces to the RIB layer (e.g. RIB, LIB, multicast
   RIB, policy-based routing), the ability to use routing indirection
   allows flexibility and functionality that can't be as easily obtained
   at the forwarding layer.

   Efforts to provide this level of control have focused on
   standardizing data models that describe the forwarding plane (e.g.
   ForCES [RFC3746]).  I2RS posits that the routing system and a
   router's OS provide useful mechanisms that applications could
   usefully harness to accomplish application-level goals.

   In addition to interfaces to the RIB layer, there is a need to
   configure the various routing and signaling protocols with differing
   dynamic state based upon application-level policy decisions.  The
   range desired is not available via MIBs at the present time.

4.  Learning Router Information

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

   Although there are efforts to extend the topological information
   available, even the best of these (e.g., BGP-LS
   [I-D.gredler-idr-ls-distribution]) still provide only the current
   active state as seen at the IGP layer and above.  Detailed
   topological state that provides more information than the current
   functional status is needed by applications; only the active paths or
   links are known versus those 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, the need for an application to be able 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 - nor is there the
   standardized ability to set up the router to trigger different
   actions upon an event's occurrence so that a rapid reaction can be

5.  Desired Aspects of a Protocol for I2RS

   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 operations via I2RS without being
      required to wait for each to complete before sending the next.

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   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.

   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, the I2RS Agent and associated router
      should be able to handle a considerable number of operations per
      second above what basic Netconf or a propretiary CLI can.

   Responsive:   It should be possible to complete simple operations
      within a sub-second time-scale.

   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.  Thus a single TCP session would
      not be a good match.

   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:   Any ability to manipulate routing state must be
      subject to authentication and authorization.  Such communications
      must also have its integrity protected.

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

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6.  Acknowledgements

   The authors would like to thank Ken Gray, Ed Crabbe, Nic Leymann,
   Carlos Pignataro, and Kwang-koog Lee for their suggestions and

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.  More
   investigation remains to fully define the security requirements, such
   as authorization and authentication levels.

9.  Informative References

              Gredler, H., Medved, J., Previdi, S., and A. Farrel,
              "North-Bound Distribution of Link-State and TE Information
              using BGP", draft-gredler-idr-ls-distribution-02 (work in
              progress), July 2012.

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

   [RFC4292]  Haberman, B., "IP Forwarding Table MIB", RFC 4292, April

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

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   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.  I2RS does not involve CLI

   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, the lack of
   standard data models have hampered the adoption of NetConf.
   Naturally, I2RS may help define needed information and data models.
   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
   10 Technology Park Drive
   Westford, MA  01886


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   Thomas D. Nadeau (editor)
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089


   Dave Ward
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134


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