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Network Working Group                                         K.P. Patel
Internet-Draft                                               R. Fernando
Intended status: Informational                             Cisco Systems
Expires: September 12, 2013                                   H. Gredler
                                                        Juniper Networks
                                                               S. Amante
                                            Level 3 Communications, Inc.
                                                          March 11, 2013


               Use Cases for an Interface to BGP Protocol
                draft-keyupate-i2rs-bgp-usecases-00.txt

Abstract

   A network routing protocol like BGP is typically configured and
   results of its operation are analyzed through some form of Command
   Line Interface (CLI) or NETCONF.  These interactions to control BGP
   and diagnose its operation encompass: configuration of protocol
   parameters, display of protocol data, setting of certain protocol
   state and debugging of the protocol.

   Interface to the Routing System's (I2RS) Programmatic interfaces, as
   defined in [I-D.ward-i2rs-framework], provides an alternate way to
   control the configuration and diagnose the operation of the BGP
   protocol.  I2RS may be used for the configuration, manipulation,
   polling or analyzing protocol data.  This document describes set of
   use cases for which I2RS can be used for BGP protocol.  It is
   intended to provide a base for the solution draft describing a set of
   interfaces to the BGP protocol.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 12, 2013.




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Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  BGP Configuration . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  BGP Protocol Configuration  . . . . . . . . . . . . . . .   4
     2.2.  BGP Policy Configuration  . . . . . . . . . . . . . . . .   5
   3.  BGP Protocol Operation  . . . . . . . . . . . . . . . . . . .   7
     3.1.  BGP Error Handling for Internal BGP Sessions  . . . . . .   7
   4.  BGP Route Manipulation  . . . . . . . . . . . . . . . . . . .   8
     4.1.  Customized Best Path Selection Criteria . . . . . . . . .   8
     4.2.  Flowspec Routes . . . . . . . . . . . . . . . . . . . . .   8
     4.3.  Route Filter Routes for Legacy Routers  . . . . . . . . .   9
     4.4.  Optimized Exit Control  . . . . . . . . . . . . . . . . .   9
   5.  BGP Events  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Notification of Routing Events  . . . . . . . . . . . . .  10
     5.2.  Tracing Dropped BGP Routes  . . . . . . . . . . . . . . .  11
     5.3.  BGP Protocol Statistics . . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13



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     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   Typically, a network routing protocol like BGP is configured and
   results of its operation are analyzed through some form of Command
   Line Interface (CLI) or NETCONF.  These interactions to control BGP
   and diagnose its operation encompass: configuration of protocol
   parameters, display of protocol data, setting of certain protocol
   state and debugging of the protocol.

   The I2RS Framework document [I-D.ward-i2rs-framework] describes a
   mechanism to control network protocols like BGP using a set of
   programmatic interfaces.  These programmatic interfaces allow one to
   control the BGP protocol by analyzing its operational state and
   routing protocol data, plus manipulating BGP's configuration to
   achieve various goals.  The I2RS is not intended to replace any
   existing configuration mechanisms, (i.e.: Command Line Interface or
   NETCONF).  Instead, I2RS is intended to augment those existing
   mechanisms by defining a standardized set of programmatic interfaces
   to enable easier configuration, interrogation and analysis of the BGP
   protocol.

   This document describes set of use cases for which I2RS's
   programmatic interfaces can be used to control and analyze the
   operation of BGP.  The use cases described in this document cover the
   following aspects of BGP: protocol parameter configuration,
   configuration of routing policies, protocol route manipulation and
   tracking of protocol events.  The goal is to inform the community's
   understanding of where the I2RS BGP extensions fit within the overall
   I2RS architecture.  It is intended to provide a basis for the
   solutions draft describing the set of Interfaces to the BGP protocol.

1.1.  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].

2.  BGP Configuration

   The configuration of BGP is arduous to establish and maintain,
   particularly on networks whose services have a requirement for
   complex routing policies.  This need is magnified by the need to
   routinely perform changes to large numbers of BGP routers to, for
   example: add or remove customer's BGP sessions, announce or withdraw



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   (customer) IP prefixes in BGP, modify BGP policies to effect changes
   in Traffic Engineering, audit BGP routers to ensure they have
   consistent and appropriate BGP policies, etc.

   There are three categories of BGP configuration:

   1.  Local BGP routing protocol configuration: local Autonomous System
       Number (ASN), BGP path selection properties of the router,
       injection of (aggregate) routes into BGP, etc.

   2.  Local BGP policies: policies designed to filter and then
       manipulate BGP attributes associated with BGP routes learned
       through BGP sessions.  These policies typically live in the
       global configuration of a BGP router, but are applied on a per-
       BGP neighbor basis (or, group of BGP neighbors); and,

   3.  BGP neighbor sessions: remote ASN, remote IP address, address
       families, BGP policies to applied to routes, max-prefix limits,
       etc.

   The sum total of BGP configuration on a BGP router is typically the
   largest quantify of configuration on Service Provider's BGP routers,
   by a fairly large margin.  When that is combined with the large set
   of routine configuration changes, mentioned above, it should be
   fairly clear that systematic reading, configuration and control of
   BGP routers through a mechanism like I2RS would greatly benefit all
   operators of BGP routers.

   While it may not be possible to provide programmatic APIs for
   esoteric vendor-specific policy configuration, it is possible to
   provide such API's for BGP protocol specific configuration and the
   more commonly used BGP routing policies.

2.1.  BGP Protocol Configuration

   Ability to enable and disable new address families within a BGP
   protocol for a network of BGP speaking routers is a challenge.  The
   challenge is mainly in keeping track of BGP speaker's feature
   capabilities and then configuration of new address families on a
   multiple BGP speakers within a given network.  With the necessary
   information, I2RS controllers allow a network operator to push
   configuration information for enabling and disabling of new address
   families on a partial or entire set of BGP speakers within a given
   network.  This would assist in building BGP overlay networks as
   needed.

   For VPN address families, the main challenge lies in the complex VPN
   configuration required to setup the control plane for Customer VPNs.



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   The configuration involves creating a Virtual Routing and Forwarding
   instance (VRF), a Route Distinguisher (RD) that ensures each customer
   prefixes remains unique across VPNs, and Route Targets (RT) that help
   ensure that the Customer prefixes are segregated appropriately so
   that they do not cross the VPN boundaries.  I2RS would allow a
   network operator to push such configuration from a central location
   where a global VPN provisioning information could be stored.  This
   helps avoid manual configuration of a VPN on multiple routers.
   Instead the configuration is controlled and pushed though a central
   I2RS controller using a programmatic set of APIs on targeted set of
   BGP speakers.

   Use of I2RS controllers to announce protocol configuration
   information would simplify and automate configuration of BGP protocol
   in IBGP deployments where the protocol based policies are seldom
   used.  To facilitate such a centralized configuration model, BGP
   speakers could be extended to use programmatic APIs to announce their
   feature capabilities as part of protocol initialization to the
   centralized I2RS controllers.  This would assist I2RS controllers to
   auto-discover BGP protocol capabilities of various BGP speakers in a
   given network.  I2RS controllers in turn would use the information
   towards enabling/disabling of BGP specific features on BGP speakers.

2.2.  BGP Policy Configuration

   Filtering of BGP routes is strongly recommended to control the
   announcements of BGP prefixes across the internet.  Most providers
   make extensive use of BGP prefix filtering policies at the edge of
   their networks.  The reasons for filtering BGP prefixes are:

   o  Avoid Unwanted Route Announcements.  Filter prefixes that MUST not
      be routed [RFC5735], [RFC5156].  Filter prefixes that are not
      allocated by Internet Routing Registries.

   o  Facilitate Route Summarization.  Filter prefixes beyond certain
      agreed prefix mask length between providers.  Route Summarization
      helps control BGP RIB and FIB table size.

   o  Defensive Security.  Filter prefixes from Stub customer ASes that
      are not owned by the customers.  Filter customer prefixes
      announced by other providers.  This helps avoid prefix hijacking.

   A set of standards-based schemas to enable configuration of Local BGP
   policies and BGP neighbor sessions was realized through the Routing
   Policy Specification Language (RSPL) [RFC2622].  The RPSL defined a
   standards-based schemas, or 'objects' as it called them, that
   defined:




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   o  binding of IP prefixes to (one or more) Origin AS, (route
      objects);

   o  collections of routes (route-set objects);

   o  collections of Autonomous Systems (as-set objects); and,

   o  routing policy of an Autonomous System to/from its adjacent
      neighbor AS'es, (aut-num objects)

   Each ASN is responsible for creation, modification and deletion of
   its RPSL objects in an Internet Routing Registry (IRR).  IRR's are
   typically operated by Regional Internet Registries (RIR's) and a few
   dozen larger ISP's and independent organizations.  The IRR's provide
   a well-known location for all organizations attached to the Internet
   to retrieve or update RPSL objects.

   While still widely and actively used by Internet Service Providers,
   the prevailing belief is that the data contained in the IRR's is
   inaccurate, primarily due to a lack of deployed authorization method
   with respect to the creation of modification of RPSL objects.  It
   should be noted that this criticism is not directed at the previously
   defined RPSL schemas, but rather at the data contained in RPSL
   schemas by end-users of the IRR system.  Please refer to the IRR And
   Routing Policy Configuration Considerations
   [I-D.mcpherson-irr-routing-policy-considerations] document for a more
   thorough discussion of the history and present state of the IRR's.

   Currently, RPSL schemas are exchanged between non-routing systems
   (servers) used within the IRR system.  In addition, open-source and
   proprietary applications create or modify RPSL schemas, as necessary,
   to signal the announcement (or, withdrawal) of an IP prefix from an
   ASN or the creation (or, teardown) of a neighbor relationship between
   two adjacent ASN's.  Most importantly, these RPSL schemas are
   consumed by similar applications to automatically build routing
   policies, (i.e.: lists of IP prefixes, corresponding Origin ASN's and
   /or AS_PATH's), that then get translated to device-specific syntax
   (i.e.: CLI) before being pushed into individual BGP routers to effect
   routing policy on the network.  It is common for Internet Service
   Providers to perform updates to these routing policies across their
   entire network on a daily basis.

   With I2RS it would be desirable to change the last step in the above
   process so that BGP policies derived from RPSL schemas, and other
   information sources, are translated into standards-based schemas that
   are then pushed, or pulled, into individual BGP routers.  More
   generally, I2RS controllers could use API's to gather information
   required to build various types of BGP routing policies plus the



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   corresponding set of Autonomous System Border Routers (ASBR's) where
   such policies need to be applied in the network and, finally, making
   those changes to individual network elements so those BGP policies
   take effect in the network.  In doing so, a network operator now has
   a centralized way of building and making these policies take effect
   across the network in a coordinated manner.

3.  BGP Protocol Operation

   It is increasingly common for services facilitated via BGP to be
   subject to severe, widespread disruptions (outages), primarily due to
   the destructive teardown of BGP sessions as a result of receiving
   malformed BGP attributes.  The document Operational Requirements for
   Enhanced Error Handling Behaviour in BGP-4
   [I-D.ietf-grow-ops-reqs-for-bgp-error-handling] outlines requirements
   to try to minimize the scope of the impact attributed to such errors.
   Unfortunately, more fine-grained BGP error handling solutions, which
   would result in little to no impact on the operation of BGP protocol,
   remain elusive.

3.1.  BGP Error Handling for Internal BGP Sessions

   It is possible that I2RS could enable enhanced error handling
   techniques for Internal BGP sessions.  At a minimum, I2RS-capable BGP
   routers could signal an event such as "Malformed Attribute Received"
   toward an I2RS controller(s).  I2RS controller(s) may already have a
   real-time view of BGP routes, and corresponding BGP attributes, or
   may dynamically interrogate BGP routers in the network to identify
   the present propagation scope of the BGP route(s) that are affected.
   Finally, the I2RS controller(s) could then signal back to BGP routers
   to apply a filter that would block propagation of the BGP attribute
   or BGP route, as necessary, in order to temporarily aid in
   consistency of BGP routing information across the entire network
   until a permanent fix can be developed and deployed within BGP
   routers.

   I2RS would enable the global visibility and global control over the
   operational state of BGP, within a given Autonomous System, that is
   necessary to facilitate the learning of, rapid response to and more
   fine-grained isolation/scoping of BGP protocol events that currently
   cause a destructive tear-down of BGP sessions that lead to widespread
   disruptions of services.









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4.  BGP Route Manipulation

   Multiprotocol BGP [RFC4760] provides support to carry routing
   information for different BGP address families.  Route manipulation
   is heavily done across these different address families for different
   reasons.  BGP IPv4 and IPv6 address families use BGP Communities
   [RFC1997] and other IBGP and EBGP attributes to manipulate BGP routes
   for Traffic Engineering purpose.  BGP VPN adddress families use
   Extended Communities [RFC4360] to filter unwanted BGP routes.  BGP
   Flowspec address family [RFC5575] is used to install Flow based
   filters to filter unwanted data traffic.  The following sub-sections
   describe the use of I2RS towards BGP Route Manipulation for different
   BGP address families.

4.1.  Customized Best Path Selection Criteria

   The BGP customized Bestpath facilitates custom bestpath computations
   within a BGP speaking network.  It is usually used within an IBGP
   network.  Customized bestpaths use special extended communities known
   as cost communities.  Cost communities carry enough information;
   Point of Insertion (POI) and the cost value to signal where in BGP
   bestpath the customize checks need to be done.  Both, the traffic
   engineering as well as backdoor (SHAM) links use customized bestpath
   computation.

   With I2RS, it would be possible for an I2RS controller to push routes
   with custom cost communities on the BGP routers for Traffic
   Engineering purpose.  I2RS controller now can act as a central entity
   keeping track of all Traffic engineering data that get applied to BGP
   routes within an IBGP network.

4.2.  Flowspec Routes

   The BGP flowspec address family is used to disseminate the traffic
   flow specification to the BGP Autonomous System Border Routers
   (ASBRs) and Provider Edge (PE) routers.  Both, the BGP ASBRs and the
   PEs would translate the received BGP traffic flow specification into
   an Access Control List (ACL) and install it in router's forwarding
   path.  Using such ACLs routers can now classify, shape, rate limit,
   filter, or redirect traffic flows.

   With I2RS, it would be possible for an I2RS controller to push
   traffic flow specifications to the BGP ASBRs and the PE routers.
   I2RS controller can act as a central entity tracking all the traffic
   flow specifications that are installed within an IBGP network.  I2RS
   controller could also prioritize and control the announcement of
   traffic flow specifications according to various ASRBs and PE
   router's capacity.  BGP ASBRs and PE routers MAY forward traffic flow



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   specifications received from EBGP speakers to I2RS Controllers.  This
   would allow I2RS controllers to centrally manage and track any
   externally received traffic flow specifications.

4.3.  Route Filter Routes for Legacy Routers

   The BGP Route Filter address family is used to disseminate the Route
   Target filter information between VPN BGP speakers.  This information
   is then used to build a route distribution graph that helps in
   limiting the propagation of VPN NLRI within a VPN network.  However,
   it requires that all the BGP VPN routers are upgraded to support this
   functionality.  Otherwise, the graph information is incomplete when a
   VPN network consists of legacy routers that participates in VPN but
   does not implement the BGP route filter address family.

   With I2RS, it would be possible for an I2RS controller to push router
   filter information to BGP RR routers on behalf of all legacy routers
   that participates in VPN but does not support or implement the BGP
   route filter address family.  I2RS controller can act as a central
   entity tracking all the configured Route Filters for legacy routers
   and push them on appropriate RRs who in turn would push it to ASBRs
   and PE routers.  In this way, I2RS controllers help build an optimal
   route distribution graph that would assist in filtering of VPN NLRIs
   in a VPN network.

4.4.  Optimized Exit Control

   Optimized Exit Control is used to provide route optimization and load
   distribution for multiple network connections between networks.
   Network operators can monitor IP traffic flows and then could define
   policies and rules based on traffic class performance, link bandwidth
   monetary costs, link load distribution, traffic types, link failures,
   etc.

   With I2RS, it would be possible for an I2RS controller to manipulate
   BGP routes and its parameters that influence BGP bestpath decisions.
   I2RS controller could act as a central entity that would monitor and
   manipulate BGP routes based on central network based policies.  Such
   routes would then be injected by a I2RS controller into the network
   so as to get the load distribution for multiple network connections.

5.  BGP Events









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   Given the extremely large number of BGP Routes in networks, it is
   critical to have scalable mechanisms that can be used to monitor for
   events affecting routing state and, consequently, reachability.  In
   addition, similar tools are needed in order to monitor BGP protocol
   statistics, which help operators and developers better understand
   scalability of software and hardware that BGP utilizes.

   I2RS could provide a publish-subscribe capability to applications to:

   o  request monitoring of BGP routes and related events; and,

   o  subscribe to the I2RS controller to receive events related to BGP
      routes or other protocol-related events of interest.

5.1.  Notification of Routing Events

   There are certain IP prefixes, for example those that are arbitrarily
   classified by a given network operator as "high visibility" by its
   end-users, for which immediate notification of changes in their state
   are extremely useful to know about.  Upon notification of such
   events, a Network Operations Center (NOC) could respond to customer
   inquiries in a more timely fashion; alternatively, the NOC may decide
   to perform Traffic Engineering to restore service, etc.

   Currently, the only way to learn of such events is for a BGP
   monitoring system to establish a BGP session with a multitude of BGP
   routers in an AS.  Then, the BGP monitoring system needs to look
   through all BGP UPDATE's in order to identify those events that are
   of interest to it.  Note, this doesn't account for the fact that
   there are several applications that might be simultaneously
   interested in learning of events to a given IP prefix nor the fact
   that some applications may want to dynamically insert or remove "IP
   prefixes of interest", depending on the needs of their constituent
   applications.

   With I2RS, it is conceivable that applications could tell an I2RS
   controller, through a North-Bound API, their "IP prefixes" (or,
   AS_PATH's, BGP communities, etc.)  that are of interest.  For
   example, a NOC application may be interested in changes to high
   visibility content or service-provider Web sites; alternatively, a
   security application may be interested in events associated with a
   different set of IP prefixes.  The I2RS controller would then
   consolidate the list of IP prefixes, and associated characteristics,
   to be monitored and program BGP routers in an AS to observe this
   subset of routes for changes.  Some examples of changes in routing
   state might include:

   o  an IP prefix being announced or withdrawn



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   o  an IP prefix being suppressed, due to route flap dampening

   o  an alternative best-path being chosen for a given IP prefix

   When the requisite events for a BGP Route are observed by a BGP
   router, it would notify I2RS controllers.

   The I2RS controllers would have a publish/subscribe mechanism whereby
   various sets of applications may subscribe to events of interest.
   The I2RS controller would then publish these events so applications
   would immediately receive them and take the appropriate domain-
   specific action necessary.

5.2.  Tracing Dropped BGP Routes

   It is extremely useful to operators to be able to rapidly identify
   instances where a BGP route is not being propagated within an
   Autonomous System.  At a minimum, this could result in sub-optimal
   performance when attempting to reach such destinations.

   There are two instances when this scenario will occur.  First, when a
   Service Provider is using "Soft Reconfiguration Inbound", it allows
   their ASBR routers to receive a copy of a BGP route, but show that
   route was not permitted into the Adj-RIB-In most likely as a result
   of the inbound BGP policy not permitting that IP prefix.  Thus, this
   BGP route is not even eligible for BGP Path Selection.  The second
   instance is where the BGP route is permitted by the inbound BGP
   policy into the Adj-RIB-In, but due to BGP Path Selection (i.e.:
   lower LOCAL_PREF, longer AS_PATH length, etc.)  was not chosen as the
   best path and, subsequently, this particular BGP route is not
   forwarded on to other internal BGP speakers in the AS.  In both
   instances, the BGP route is only visible within the ASBR on which
   that BGP route was first learned.  Needless to say, in large Service
   Provider networks with a numerous interconnects to a single customer
   it can be very time-consuming to discover where such a BGP route is
   learned before ultimately determining why the route was blocked or
   not preferred.

   With I2RS, it would be possible for an I2RS controller to rapidly
   gather information from across a large set of BGP routers in the
   network to determine at what ASBR's the BGP route is being learned.
   Next, the I2RS controller could interrogate those routers BGP
   policies to determine the root cause of why the route was either not
   learned or not preferred in BGP.  Finally, if necessary, the I2RS
   controller(s) could amend BGP policies and push them out to BGP
   routers to permit the BGP route or make it a preferred route
   according to the BGP path selection algorithm.




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5.3.  BGP Protocol Statistics

   There are a variety of statistics related to the operation of BGP
   that are invaluable to network operators.  These statistics generally
   help operators, and developers, understand the present state and
   future scalability of BGP.

   One statistic that is invaluable to operators is the current number
   of BGP routes learned through an eBGP session.  Operators then apply
   a command against each eBGP session to limit the maximum number of
   BGP routes that may be learned through that eBGP session before a
   warning message is triggered and/or the eBGP session is torn down
   completely.  This configuration capability is often referred to as a
   "max-prefix limit".  This command must be routinely audited and, if
   necessary, adjusted in order to not trigger a false warning or
   teardown due to the natural organic growth in BGP routes learned from
   a given BGP neighbor.

   I2RS controllers could provide an invaluable capability to help audit
   and re-program the "max-prefix limit" on a periodic basis, which is
   generally once per day.  Specifically, the first task would be for an
   I2RS controller to validate that there is a "max-prefix limit"
   applied to every eBGP session.  (If there is not, that should either
   trigger a red alarm to the NOC to manually fix this condition or for
   the I2RS controller to automatically apply a "max-prefix limit" that
   would alleviate this hazardous condition).  Assuming there is a "max-
   prefix limit" already in place, the I2RS controller would
   simultaneously retrieve, from each BGP router, the current number of
   BGP routes learned through a BGP session and value used for the "max-
   prefix limit" on that same BGP session.  These two values could then
   be handed off to an application that determines if adjustments in the
   "max-prefix limit" value are required for each BGP session.  The
   application would then notify the I2RS controller of the subset of
   eBGP sessions and their associated change in "max-prefix limit"
   value, whereby the I2RS controller would then adjust the BGP protocol
   configuration on each requisite BGP router in the network.  Finally,
   it should be noted that the above is just one method whereby "max-
   prefix limit" values are adjusted.  It's similarly possible that the
   BGP routers may, through the I2RS, pull the "max-prefix limit" values
   for each eBGP neighbor they have onboard on a periodic basis and
   validate their accuracy.

   The above is just one use case related to BGP protocol statistics.
   There are wealth of other BGP protocol statistics or state
   informatioin that would be invaluable to have programmatic visibility
   into that operators do not have today.





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6.  Security Considerations

   The BGP use cases described in this document assumes use of I2RS's
   programmatic interfaces described in the I2RS framework mentioned in
   [I-D.ward-i2rs-framework].  This document does not change the
   underlying security issues inherent in the existing
   [I-D.ward-i2rs-framework].

7.  Acknowledgements

   TBD.

8.  References

8.1.  Normative References

   [I-D.ward-i2rs-framework]
              Atlas, A., Nadeau, T., and D. Ward, "Interface to the
              Routing System Framework", draft-ward-i2rs-framework-00
              (work in progress), February 2013.

   [RFC1997]  Chandrasekeran, R., Traina, P., and T. Li, "BGP
              Communities Attribute", RFC 1997, August 1996.

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

   [RFC2629]  Rose, M.T., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

   [RFC3392]  Chandra, R. and J. Scudder, "Capabilities Advertisement
              with BGP-4", RFC 3392, November 2002.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July
              2003.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760, January
              2007.





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8.2.  Informative References

   [I-D.ietf-grow-ops-reqs-for-bgp-error-handling]
              Shakir, R., "Operational Requirements for Enhanced Error
              Handling Behaviour in BGP-4", draft-ietf-grow-ops-reqs-
              for-bgp-error-handling-06 (work in progress), December
              2012.

   [I-D.mcpherson-irr-routing-policy-considerations]
              McPherson, D., Amante, S., Osterweil, E., and L. Blunk,
              "IRR & Routing Policy Configuration Considerations",
              draft-mcpherson-irr-routing-policy-considerations-01 (work
              in progress), September 2012.

   [RFC2622]  Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D.,
              Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra,
              "Routing Policy Specification Language (RPSL)", RFC 2622,
              June 1999.

   [RFC2858]  Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
              "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.

   [RFC5156]  Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156,
              April 2008.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, August 2009.

   [RFC5735]  Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses",
              BCP 153, RFC 5735, January 2010.

Authors' Addresses

   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: keyupate@cisco.com










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   Rex Fernando
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: rex@cisco.com


   Hannes Gredler
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA  94089
   USA

   Email: hannes@juniper.net


   Shane Amante
   Level 3 Communications, Inc.
   1025 Eldorado Blvd
   Broomfield, CO  80021
   USA

   Email: shane@level3.net

























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