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i2rs                                                            R. White
Internet-Draft                                                      IETF
Intended status: Informational                                  S. Hares
Expires: February 28, 2014                                         ADARA
                                                               A. Retana
                                                     Cisco Systems, Inc.
                                                         August 27, 2013


 Protocol Independent Use Cases for an Interface to the Routing System
                      draft-white-i2rs-use-case-01

Abstract

   Programmatic interfaces to provide control over individual forwarding
   devices in a network promise to reduce operational costs while
   improving scaling, control, and visibility into the operation of
   large scale networks.  To this end, several programmatic interfaces
   have been proposed.  OpenFlow, for instance, provides a mechanism to
   replace the dynamic control plane processes on individual forwarding
   devices throughout a network with off box processes that interact
   with the forwarding tables on each device.  Another example is
   NETCONF, which provides a fast and flexible mechanism to interact
   with device configuration and policy.

   There is, however, no proposal which provides an interface to all
   aspects of the routing system as a system.  Such a system would not
   interact with the forwarding system on individual devices, but rather
   with the control plane processes already used to discover the best
   path to any given destination through the network, as well as
   interact with the routing information base (RIB), which feeds the
   forwarding table the information needed to actually switch traffic at
   a local level.

   This document describes a set of use cases such a system could
   fulfill.  It is designed to provide underlying support for the
   framework, policy, and other drafts describing the 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
   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/.



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   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
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   This Internet-Draft will expire on February 28, 2014.

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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Distributed Reaction to Network Based Attacks . . . . . . . .   3
   3.  Remote Service Routing  . . . . . . . . . . . . . . . . . . .   4
   4.  Within Data Center Routing  . . . . . . . . . . . . . . . . .   6
   5.  Temporary Overlays between Data Centers . . . . . . . . . . .   7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Interface to the Routing System Framework
   [I-D.ward-i2rs-framework] describes a mechanism where the distributed
   control plane can be augmented by an outside control plane through an
   open, accessible interface, including the Routing Information Base
   (RIB), in individual devices.  This represents a "halfway point"
   between completely replacing the traditional distributed control
   plane and directly configuring devices to distribute policy or
   modifications to routing through off-board processes.  This draft
   proposes a set of use cases that explain where the work described in
   [I2RS - should this be a reference to the framework as above, or to
   the architecture, or the WG charter or ??] will be useful.  The goal
   is to inform not only the community's understanding of where I2RS



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   fits in the larger scheme of SDN proposals, but also to inform the
   requirements, framework, and specification of I2RS to provide the
   best fit for the purposes which make the most sense for this type of
   programmatic interface.

   Towards this end the authors have searched for a number of different
   use cases representing not only complex modifications of the control
   plane, including interaction with applications and network
   conditions, but also simpler use cases.  The array of use cases
   presented here should provide the reader with a solid understanding
   of the power of an SDN solution that will augment, rather than
   replace, traditional distributed control planes.

   Each use case is presented in its own section.

2.  Distributed Reaction to Network Based Attacks

   Quickly modifying the control plane to reroute traffic for one
   destination while leaving a standard configuration in place (filters,
   metrics, and other policy mechanisms) is a challenge --but this is
   precisely the challenge of a network engineer attempting to deal with
   a network incursion.  The ability to redirect specific flows of
   information or specific classes of traffic into, through, and back
   out of traffic analyzers on the fly is crucial in these situations.
   The following network diagram provides an illustration of the
   problem.

    Valid Source---\  /--R2--------------------\
                    R1                          R3---Valid Destination
    Attack Source--/  \--Monitoring Device-----/


   Modifying the cost of the link between R1 and R2 to draw the attack
   traffic through the monitoring device in the distributed control
   plane will, of necessity, also draw the valid traffic through the
   monitoring device.  Drawing valid traffic through a monitoring device
   introduces delay, jitter, and other quality of service issues, as
   well as posing a problem for the monitoring device itself in terms of
   traffic load and management.

   An I2RS controller could stand between the detection of the attack
   and the control plane to facilitate the rapid modification of control
   and forwarding planes to either block the traffic or redirect it to
   analysis devices connected to the network.

   Summary of IRS Capabilities and Interactions:





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   o  The ability to monitor the available routes installed in the RIB
      of each forwarding device, including near real time notification
      of route installation and removal.  This information must include
      the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), the metric
      of the installed route, and an identifier indicating the
      installing process.

   o  The ability to install source and destination based routes in the
      local RIB of each forwarding device.  This must include the
      ability to supply the destination prefix (NLRI), the source prefix
      (NLRI), a table identifier (if the forwarding device has multiple
      forwarding instances), a route preference, a route metric, a next
      hop, an outbound interface, and a route process identifier.

   o  The ability to install a route to a null destination, effectively
      filtering traffic to this destination.

   o  The ability to interact with various policies configured on the
      forwarding devices, in order to inform the policies implemented by
      the dynamic routing processes.  This interaction should be through
      existing configuration mechanisms, such as NETCONF, and should be
      recorded in the configuration of the local device so operators are
      aware of the full policy implemented in the network from the
      running configuration.

   o  The ability to interact with traffic flow and other network
      traffic level measurement protocols and systems, in order to
      determine path performance, top talkers, and other information
      required to make an informed path decision based on locally
      configured policy.

3.  Remote Service Routing

   In hub and spoke overlay networks, there is always an issue with
   balancing between the information held in the spoke routing table,
   optimal routing through the network underlying the overlay, and
   mobility.  Most solutions in this space use some form of centralized
   route server that acts as a directory of all reachable destinations
   and next hops, a protocol by which spoke devices and this route
   server communicate, and caches at the remote sites.










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   An I2RS solution would use the same elements, but with a different
   control plane.  Remote sites would register (or advertise through
   some standard routing protocol, such as BGP), the reachable
   destinations at each site, along with the address of the router (or
   other device) used to reach that destination.  These would, as
   always, be stored in a route server (or several redundant route
   servers) at a central location.

   When a remote site sends a set of packets to the central location
   that are eventually destined to some other remote site, the central
   location can forward this traffic, but at the same time simply
   directly insert the correct routing information into the remote
   site's routing table.  If the location of the destination changes,
   the route server can directly modify the routing information at the
   remote site as needed.

   An interesting aspect of this solution is that no new and specialized
   protocols are needed between the remote sites and the centralized
   route server(s).  Normal routing protocols can be used to notify the
   centralized route server(s) of modifications in reachability
   information, and the route server(s) can respond as needed, based on
   local algorithms optimized for a particular application or network.
   For instance, short lived flows might be allowed to simply pass
   through the hub site with no reaction, while longer lived flows might
   warrant a specific route to be installed in the remote router.
   Algorithms can also be developed that would optimize traffic flow
   through the overlay, and also to remove routing entries from remote
   devices when they are no longer needed based on far greater
   intelligence than simple non-use for some period of time.

   Summary of IRS Capabilities and Interactions:

   o  The ability to read the local RIB of each forwarding device,
      including the destination prefix (NLRI), a table identifier (if
      the forwarding device has multiple forwarding instances), the
      metric of each installed route, a route preference, and an
      identifier indicating the installing process.

   o  The ability to monitor the available routes installed in the RIB
      of each forwarding device, including near real time notification
      of route installation and removal.  This information must include
      the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), the metric
      of the installed route, and an identifier indicating the
      installing process.

   o  The ability to install destination based routes in the local RIB
      of each forwarding device.  This must include the ability to



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      supply the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), a route
      preference, a route metric, a next hop, an outbound interface, and
      a route process identifier.

4.  Within Data Center Routing

   Data Centers have evolved into massive topologies with thousands of
   server racks and millions of hosts.  Data Centers use BGP with ECMP,
   ISIS (with multiple LAGs), or other protocols to tie the data center
   together.  Data centers are currently designed around a three or four
   tier structure with: server, top-of-rack switches, aggregation
   switches, and router interfacing the data center to the Internet.
   [I-D.lapukhov-bgp-routing-large-dc] examines many of these elements
   of data center design.

   One element of these Data Center routing infrastructures is the
   ability to quickly read topology information and execute
   configuration from a centralized location.  Key to this environment
   is the tight feedback loop between learning about topology changes or
   loading changes, and instantiating new routing policy.  Without I2RS,
   may Data Centers are using extra physical topologies or logical
   topologies to work around the features.

   An I2RS solution would use the same elements, but with a different
   control plane.  The I2RS enabled control plane could provide the Data
   Center 4 tier infrastructure the quick access to topology and data
   flow information needed for traffic flow optimization.  Changes to
   the Data Center infrastructure done via I2RS could have a tight
   feedback loop.

   Again, this solution would reduce the need for new and specialized
   protocols while giving the Data Center the control it desire.  The
   I2RS routing interface could be extended to virtual routers.

   Summary of IRS Capabilities and Interactions:

   o  The ability to read the local RIB of each forwarding device,
      including the destination prefix (NLRI), a table identifier (if
      the forwarding device has multiple forwarding instances), the
      metric of each installed route, a route preference, and an
      identifier indicating the installing process.

   o  The ability to monitor the available routes installed in the RIB
      of each forwarding device, including near real time notification
      of route installation and removal.  This information must include
      the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), the metric



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      of the installed route, and an identifier indicating the
      installing process.

   o  The ability to install destination based routes in the local RIB
      of each forwarding device.  This must include the ability to
      supply the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), a route
      preference, a route metric, a next hop, an outbound interface, and
      a route process identifier.

   o  The ability to read the tables of other local protocol processes
      running on the device.  This reading action should be supported
      through an import/export interface which can present the
      information in a consistent manner across all protocol
      implementations, rather than using a protocol specific model for
      each type of available process.

   o  The ability to inject information directly into the local tables
      of other protocol processes running on the forwarding device.
      This injection should be supported through an import/export
      interface which can inject routing information in a consistent
      manner across all protocol implementations, rather than using a
      protocol specific model for each type of available process.

   o  The ability to interact with various policies configured on the
      forwarding devices, in order to inform the policies implemented by
      the dynamic routing processes.  This interaction should be through
      existing configuration mechanisms, such as NETCONF, and should be
      recorded in the configuration of the local device so operators are
      aware of the full policy implemented in the network from the
      running configuration.

   o  The ability to interact with traffic flow and other network
      traffic level measurement protocols and systems, in order to
      determine path performance, top talkers, and other information
      required to make an informed path decision based on locally
      configured policy.

5.  Temporary Overlays between Data Centers

   Data Centers within one organization may operate as one single entity
   even though they may be geographically distributed.  Applications are
   load balanced within Data Centers and between data centers to take
   advantage of cost economics in power, storage, and server
   availability for compute resources.  Applications are also transfer
   to alternate data centers in case of failures within a data center.
   To reduce time during failure, Data Centers often replicate user
   storage between two or more data centers.  During the transfer of



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   stored information prior to a Data Center to Data Center move, the
   Data Center controllers need to dynamically acquire a large amount of
   inter-data center bandwidth through an overlay network, often during
   off hours.

   I2RS could provide the connection between the overlay network
   configuration, local policies, and the control plane to dynamically
   bring a large bandwidth inter-data center overlay or channel into
   use, and then to remove it from use when the data transfer is
   completed.

   Similarly, during a fail-over, a control process within data centers
   interacts with a group host process and the network to seamless move
   the processing to another data center.  During the fail-over case,
   additional process state may need to be moved as well to restart the
   system.  The difference between these data-to-data center moves is
   immediate and urgent need to move systems.  If an application (such
   as medical or banking services) pays to have this type of fail-over,
   it is likely the service will pay for preemption on network
   bandwidth.  I2RS can allow the Data Center network and the Network
   connecting the data center to preempt other best-effort traffic to
   send this priority data flow.  After the high priority data flow has
   finished, networks can return to their previous condition.

   Summary of IRS Capabilities and Interactions:

   o  The ability to read the local RIB of each forwarding device,
      including the destination prefix (NLRI), a table identifier (if
      the forwarding device has multiple forwarding instances), the
      metric of each installed route, a route preference, and an
      identifier indicating the installing process.

   o  The ability to monitor the available routes installed in the RIB
      of each forwarding device, including near real time notification
      of route installation and removal.  This information must include
      the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), the metric
      of the installed route, and an identifier indicating the
      installing process.

   o  The ability to install destination based routes in the local RIB
      of each forwarding device.  This must include the ability to
      supply the destination prefix (NLRI), a table identifier (if the
      forwarding device has multiple forwarding instances), a route
      preference, a route metric, a next hop, an outbound interface, and
      a route process identifier.





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   o  The ability to interact with various policies configured on the
      forwarding devices, in order to inform the policies implemented by
      the dynamic routing processes.  This interaction should be through
      existing configuration mechanisms, such as NETCONF, and should be
      recorded in the configuration of the local device so operators are
      aware of the full policy implemented in the network from the
      running configuration.

   o  The ability to interact with policies and configurations on the
      forwarding devices using time based processing, either through
      timed auto-rollback or some other mechanism.  This interaction
      should be through existing configuration mechanisms, such as
      NETCONF, and should be recorded in the configuration of the local
      device so operators are aware of the full policy implemented in
      the network from the running configuration.

   o  The ability to interact with traffic flow and other network
      traffic level measurement protocols and systems, in order to
      determine path performance, top talkers, and other information
      required to make an informed path decision based on locally
      configured policy.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

6.2.  Informative References

   [I-D.lapukhov-bgp-routing-large-dc]
              Lapukhov, P., Premji, A., and J. Mitchell, "Use of BGP for
              routing in large-scale data centers", draft-lapukhov-bgp-
              routing-large-dc-06 (work in progress), August 2013.

   [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.

Authors' Addresses

   Russ White
   IETF

   Email: russw@riw.us




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   Susan Hares
   ADARA

   Email: shares@ndzh.com


   Alvaro Retana
   Cisco Systems, Inc.
   7025 Kit Creek Road
   Research Triangle Park, NC  27617
   USA

   Email: aretana@cisco.com






































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