GROW Working Group                                          D. McPherson
Internet-Draft                                            Verisign, Inc.
Intended status: Informational                                 S. Amante
Expires: February 28, 2015                        Level 3 Communications
                                                            E. Osterweil
                                                          Verisign, Inc.
                                                                L. Blunk
                                                     Merit Network, Inc.
                                                             D. Mitchell
                                                           Twitter, Inc.
                                                         August 27, 2014

           IRR & Routing Policy Configuration Considerations


   The purpose of this document is to catalog past issues influencing
   the efficacy of Internet Routing Registries (IRR) for inter-domain
   routing policy specification and application in the global routing
   system over the past two decades.  Additionally, it provides a
   discussion regarding which of these issues are still problematic in
   practice, and which are simply artifacts that are no longer
   applicable but continue to stifle inter-provider policy-based
   filtering adoption and IRR utility to this day.

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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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 28, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4

   2.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  4

   3.  Historical Artifacts Influencing IRR Efficacy  . . . . . . . .  4

   4.  Accuracy and Integrity of Data Contained within the IRR  . . .  5
     4.1.  Lack of Resource Certification . . . . . . . . . . . . . .  5
     4.2.  Incentives to Maintain Data within the IRR . . . . . . . .  6
     4.3.  Inability for Third Parties to Remove (Stale)
           Information from the IRRs  . . . . . . . . . . . . . . . .  7
     4.4.  Lack of Authoritative IRR for Resources  . . . . . . . . .  8
     4.5.  Conclusions with respect to Data in the IRR  . . . . . . .  9

   5.  Operation of the IRR Infrastructure  . . . . . . . . . . . . .  9
     5.1.  Replication of Resources Among IRRs  . . . . . . . . . . .  9
     5.2.  Updating Routing Policies from Updated IRR Resources . . . 10

   6.  Historical BGP Protocol Limitations  . . . . . . . . . . . . . 12

   7.  Historical Limitations of Routers  . . . . . . . . . . . . . . 13
     7.1.  Incremental Updates to Policy on Routers . . . . . . . . . 13
     7.2.  Storage Requirements for Policy on Routers . . . . . . . . 14
     7.3.  Updating Configuration on Routers  . . . . . . . . . . . . 14

   8.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16

   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16

   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16

   12. Informative References . . . . . . . . . . . . . . . . . . . . 16

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   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18

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1.  Introduction

   The purpose of this document is to catalog past issues influencing
   the efficacy of Internet Routing Registries (IRR) for inter-domain
   routing policy specification and application in the global routing
   system over the past two decades.  Additionally, it provides a
   discussion regarding which of these issues still pose problems in
   practice, and which are no longer obstacles, but whose perceived
   drawbacks continue to stifle inter-provider policy-based filtering
   support and IRR utility to this day.

2.  Background

   IRRs can be used to express a multitude of Internet number bindings
   and policy objectives, to include bindings between an origin AS and a
   given prefix, AS and community import and export policies for a given
   AS, as well as AS macros (as-sets in RPSL-speak) that convey the set
   of ASes for which a given AS intends to include in some common group.

   As quoted from Section 7 of [RFC1787], Routing in a Multi-Provider

      While ensuring Internet-wide coordination may be more and more
      difficult, as the Internet continues to grow, stability and
      consistency of the Internet-wide routing could significantly
      benefit if the information about routing requirements of various
      organizations could be shared across organizational boundaries.
      Such information could be used in a wide variety of situations
      ranging from troubleshooting to detecting and eliminating
      conflicting routing requirements.  The scale of the Internet
      implies that the information should be distributed.  Work is
      currently underway to establish depositories of this information
      (Routing Registries), as well as to develop tools that analyze, as
      well as utilize this information.

3.  Historical Artifacts Influencing IRR Efficacy

   The term IRR is often used, incorrectly, as a broad catch-all term to
   categorize issues related to the accuracy of data in the IRR, the
   Routing Policy Specification Language (RPSL) and the operational
   deployment of policy (derived from RPSL contained within the IRR) to
   routers.  It is important to classify these issues into distinct
   categories so that the reader can understand which categories of
   issues are historical artifacts that are no longer applicable and
   which categories of issues still exist and might be addressed by the

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   The following sections will separate out challenges related to the
   IRR into the following categories.  First, accuracy and integrity of
   data contained within the IRR.  Second, the Resource Policy
   Specification Language (RPSL) used to represent various types of data
   in the IRR.  Third, operation of the IRR infrastructure, i.e.:
   synchronization of resources from one IRR to other IRRs.  Finally,
   the methods related to extraction of policy from the IRR and the
   input plus activation of that policy within routers.

4.  Accuracy and Integrity of Data Contained within the IRR

   The following section will examine issues related to accuracy and
   integrity of data contained within the IRR.

4.1.  Lack of Resource Certification

   Internet number resources include IPv4 addresses, IPv6 addresses,
   Autonomous System Numbers (ASNs), and more.  While these resources
   are generally allocated by hierarchical authorities, a general
   mechanism for formally verifying (such as through cryptographic
   mechanisms) when parties have been allocated resource remains an open
   challenge.  We generally define such a system a Resource
   Certification System, and we note that some candidate examples of how
   such a general system might be implemented and deployed exist
   [TASRS], [RC_HotNetsX], [RFC6480].

   One of the largest weaknesses often cited with the IRR system is that
   the data contained within the IRRs is out of date or lacks integrity.
   This is largely attributable to the fact that existing IRR mechanisms
   do not provide ways for a relying party to (cryptographically) verify
   the validity of an IRR object.  That is, there has never existed a
   resource certification infrastructure that enables a resource holder
   to authorize a particular autonomous system to originate network
   layer reachability advertisements for a given IPv4 or IPv6 prefix.
   It should be noted that this is not a weakness of the underlying
   Routing Policy Specification Language (RPSL) [RFC2622], but rather,
   was largely the result of no clear demand by the operator community
   for Internet Number Resource Registries to provide sufficient
   resource certification infrastructure that would enable a resource
   holder to develop a cryptographic binding between, for example, a
   given AS number and an IP prefix.

   Another noteworthy (but slightly different) deficiency in the IRR
   system is the absence of a tangible tie between the resource and the
   resource holder.  That is, generally there is no assurance of the
   validity of objects at their creation time (except for a subset of,
   for example, the RIPE IRR where RPSS [RFC2725] attests for RIPE

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   address holders and RIPE ASN holders).  If a resource holder's
   authorization cannot be certified, then consumers cannot verify
   attestations made.  In effect, without resource certification,
   consumers are basically only certifying the assertions that the
   creator / maintainer of the resource object has made (not if that
   assertion is valid).

   The RIPE community addressed this last issue by putting in a
   foundation policy [RIPE2007-01], which requires a contractual link
   between the RIPE NCC and the end user in direct assignment + ASN
   assignment cases, which weren't previously covered by LIR contracts
   for address allocations.  There were a couple of intentions with this

   1.  There was an encumbrance placed in the policy for the LIR to
       charge the end-user for provider independent resources.  This
       action created a collection mechanism for PI address resources
       (IPv4 / IPv6 space, ASNs).

   2.  It guaranteed that all RIPE NCC allocated/assigned space would be
       subject to a contractual link, and that this contractual chain
       might end up actually meaning something when it came to the issue
       of who made what claim about what number resource.

   3.  It tied into the RIPE NCC's object grandfathering policy which
       ties the registration details of the end-user to the object
       registered in the IRR database.

   While this policy specifically addressed PI/portable space holders,
   other regions address this issue, too.  Further, it is indeed a
   prerequisite for resource certification, though it does not directly
   address the IRR deficiencies.

   One of the central observations of this policy was that without a
   chain-of-ownership functionality in IRR databases, the discussion of
   certifying their contents becomes moot.

4.2.  Incentives to Maintain Data within the IRR

   A second problem with data contained in the IRRs is that the
   incentives for resource holders to maintain both accurate and up-to-
   date information in one, or more, IRRs; including deletion of out-of-
   date or stale data from the IRRs can diminish rapidly when changing
   their peering policies (such as switching transit providers).
   Specifically, there is a very strong incentive for an ISP's customers
   to register new routing information in the IRR, because some ISPs
   enforce a strict policy that they will only build or update a
   customer's prefix-lists applied to the customer's inbound eBGP

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   sessions based off information found within the IRRs.  Unfortunately,
   there is little incentive for an ISP's customers to remove out-of-
   date information from an IRR, most likely attributed to the fact that
   some ISPs do not use, or enforce use of, data contained within the
   IRRs to automatically build incoming policy applied to customer's
   eBGP sessions.  For example, if a customer is terminating service
   from one ISP that requires use of IRR data to build incoming policy
   and, at the same time, enabling service with another ISP that does
   not require use of IRR data, then that customer will likely let the
   data in the IRR become stale or inaccurate.

   Further, policy filters are almost exclusively generated based on the
   origin AS information contained within IRR route objects and used by
   providers to filter downstream transit customers.  Since providers
   only look for route objects containing the origin AS of their
   downstream customer(s), stale route objects with historical and,
   possibly, incorrect origin AS information are ignored.  Assuming that
   the downstream customer(s) do not continue to announce those routes
   with historical, or incorrect, origin AS information in BGP to the
   upstream provider, there is no significant incentive to remove them
   as they do not impact offline policy filter generation nor routing on
   the Internet.  On the other hand, the main incentive that causes the
   Service Provider to work with downstream customer(s) is when the
   resultant filter list becomes too large that it is difficult for it
   to be stored on-board PE routers; however, this is more practically
   an operational issue with very old, legacy PE routers, not more
   modern PE router hardware with more robust Control Plane Engines.

4.3.  Inability for Third Parties to Remove (Stale) Information from the

   A third challenge with data contained in IRRs is that it is not
   possible for IRR operators, and ISPs who use them, to proactively
   remove (perceived) out-of-date or "stale" resources in an IRR, on
   behalf of resource holders who may not be diligent in maintaining
   this information themselves.  The reason is that, according to the
   Resource Policy Specification Language (RPSL) [RFC2622], only the
   resource holder ('mntner') specified in a 'mnt-by' value field of an
   RPSL resource is authorized to add, modify or delete their own
   resources within the IRR.  To address this issue, the 'auth-override'
   mechanism [RFC2725] was later developed that would have enabled a
   third party to update and/or remove "stale" resources from the IRR.
   While it is unclear if this was ever implemented or deployed, it does
   provide language semantics needed to overcome this obstacle.

   Nevertheless, with such a mechanism in place, there is still a risk
   that the original RPSL resource holder would not receive
   notifications (via the 'notify' attribute in various RPSL resources)

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   about the pending or actual removal of a resource from the IRR in
   time to halt that action if those resources were still being used.
   In this case, if the removal of a resource was not suspended, it
   could potentially result in an unintentional denial of service for
   the RPSL resource holder when, for example, ISPs automatically
   generated and deployed a new policy based on the newly removed
   resources from the IRR, thus dropping any reachability announcement
   for the removed resource in eBGP.

4.4.  Lack of Authoritative IRR for Resources

   According to [RFC2622], within an RPSL resource "the source attribute
   specifies the registry where the object is registered."  Note that
   this source attribute only exists within the RPSL resource itself.
   Unfortunately, given a specific resource, (e.g.: a specific IPv4 or
   IPv6 prefix), most of the time it is impossible to tell a priori the
   authoritative IRR where to query and retrieve an authoritative copy
   of that resource.

   This makes it difficult for consumers of data from the IRR to
   automatically know the authoritative IRR of a resource holder, which
   will contain their most up-to-date set of resources.  This is
   typically not a problem for an ISP that has a direct (customer)
   relationship with the resource holder, because the ISP will ask the
   resource holder which (authoritative) IRR to pull their resources
   from on, for example, a "Customer BGP Order Form".  However, third
   parties that do not have a direct relationship with the resource
   holder, have a difficult time attempting to infer the authoritative
   IRR, preferred by the resource holder, that likely contains the most
   up-to-date set of resources.  As a result, it would be helpful for
   third parties if there was a robust referral mechanism so that a
   query to one IRR would be automatically redirected toward the
   authoritative IRR for the most up-to-date and authoritative copy of
   that particular resource.  This problem is worked around by
   individual IRR operators storing a local copy of other IRR's
   resources, through periodic mirroring, which allows the individual
   IRR to respond to a client's query with all registered instances of a
   particular IRR resource that exist in both the local IRR and all
   other IRRs.  Of course, the problem with this approach is that an
   individual IRR operator is under no obligation to mirror all other
   IRRs and, in practice, some IRRs do not mirror the resources from all
   other IRRs.  This could lead to the false impression that a
   particular resource is not registered or maintained at a particular
   IRR.  Furthermore, the authentication process of accepting updates by
   any given IRR may, or may not, be robust enough to overcome
   impersonation attacks.  As a result, there is no rigorous assurance
   that a mirrored RPSL statement was actually made by the authorized
   resource holder.

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4.5.  Conclusions with respect to Data in the IRR

   All of the aforementioned issues related to integrity and accuracy of
   data within the IRR stem from a distinct lack of resource
   certification for resources contained within the IRR.  Only now is an
   experimental test bed that reports to provide this function (under
   the auspices of the Resource PKI [RFC6480]) being formally discussed,
   which could also aid in certification of resources within the IRR.
   It should be noted that the RPKI is only currently able to support
   signing of Route Origin Authorization (ROA) resources that are the
   equivalent of 'route' resources in the IRR.  It is unclear if, in the
   future, the RPKI will be extended to support additional resources
   that already exist in the IRR, e.g.: aut-num, as-net, route-set, etc.
   Finally, a seemingly equivalent resource certification specification
   for all resources in the IRR has already been developed [RFC2725],
   however it is unclear how widely it was ever implemented or deployed.

5.  Operation of the IRR Infrastructure

5.1.  Replication of Resources Among IRRs

   Currently, several IRRs [IRR_LIST] use a Near-Real-Time Mirroring
   (NRTM) protocol to replicate each others contents.  However, this
   protocol has a several weaknesses.  Namely, there is no way to
   validate that the copy of mirror is correct and synchronization
   issues have often resulted.  Furthermore, the NRTM protocol does not
   employ any security mechanisms.  The NRTM protocol relies on a pull
   mechanism and is generally configured with a poll interval of 5 to 10
   minutes.  There is currently no mechanism to notify an IRR when an
   update has occurred in a mirrored IRR so that an immediate update can
   be made.

   Some providers employ a process of mirroring an instance of an IRR
   that involves downloading a flat text file copy of the IRR that is
   made available via FTP.  These FTP files are exported at regular
   intervals of typically anywhere between 2 and 24 hours by the IRRs.
   When a provider fetches those text files, it will process them to
   identify any updates and reflect changes within its own internally
   maintained database.  The use of an internally maintained database is
   out-of-scope of this document, but is generally used to assist with
   more straightforward access to or modification of data by the IRR
   operator.  Providers typically employ a 24 hour cycle to pull updated
   resources from IRRs.  Thus, depending on when resource holders
   submitted their changes to an IRR, it may take up to 24 hours for
   those changes to be reflected in their policy configurations.  In
   practice, it appears that the RPKI will also employ a 24 hour cycle
   whereby changes in resources are pushed out to other RPKI caches

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   IRRs originated from Section 7 of [RFC1787], specifically: "The scale
   of the Internet implies that the [routing requirements] information
   should be distributed."  Regardless, the practical effect of an
   organization maintaining its own local cache of IRR resources is an
   increase in resource resiliency (due to multiple copies of the same
   resource being geographically distributed), a reduction in query time
   for resources and, likely, a reduction in inter-domain bandwidth
   consumption and associated costs.  This is particularly beneficial
   when, for example, an ISP is evaluating resources in an IRR just to
   determine if there are any modifications to those resources that will
   ultimately be reflected in a new routing policy that will get
   propagated to (Edge) routers in the ISP's network.  Cache locality
   results in reduced inter-domain bandwidth utilization for each round

   On the other hand, it is unclear from where the current provider
   replication interval of 24 hours originated or even whether it still
   provides enough freshness in the face of available resources,
   particularly in today's environment where a typical IRR system
   consists of a (multi-core) multi-GHz CPU connected to a network via a
   physical connection of 100 Mbps or, more likely, higher bandwidth.
   In addition, it can be observed that the most common circuit size
   used by ISPs is now 10 Gbps, thus eliminating bandwidth as a
   significant factor in the transfer of data between IRRs.
   Furthermore, it should be noted that Merit's Internet Routing
   Registry Daemon (IRRd) [MERIT-IRRD], uses 10 minutes as its default
   for "irr_mirror_interval".

   Lastly, it should be noted that [RFC2769], Routing Policy System
   Replication, attempted to offer a more methodical solution for
   distributed replication of resources between IRRs.  It is unclear why
   this RFC failed to gain traction, but it is suspected that this was
   due to that specification's reliance on [RFC2725], Routing Policy
   System Security, that addressed "the need to assure integrity of the
   data by providing an authentication and authorization model."

5.2.  Updating Routing Policies from Updated IRR Resources

   Ultimately, the length of time it takes to replicate resources among
   IRRs is, generally, the dominant factor in reflecting changes to
   resources in policy that is eventually applied within the Control
   Plane of routers.  The length of time to update network elements will
   vary considerably depending on the size of the ISP and the number of
   IRR resources that were updated during any given interval.  However,
   there are a variety of common techniques, that are outside the scope
   of this document, that allow for this automated process to be

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   optimized to considerably reduce the length of time it takes to
   update policies in the ISP's network.

   An ISP will begin the process of updating the policy in their
   network, by first fetching IRR resources associated with, for
   example, a customer ASN attached to their network.  Next, the ISP
   constructs a new policy associated to that customer and then
   evaluates if that new policy is different from existing policy
   associated with that same customer.  If there are no changes between
   the new and existing policy associated with that customer, then the
   ISP does not make any changes to the policy in their routers specific
   to that customer.  On the other hand, if the new policy does reflect
   changes from the existing policy for that customer, then the ISP
   begins a process of uploading the new policy to the routers attached
   to that customer.

   The process of constructing a new policy involves use of a set of
   programs, e.g.: IRRtoolset, that performs recursive expansion of an
   RPSL aut-num resource, that comprises an arbitrary combination of
   other RPSL aut-num, as-set, route and route-set resources, according
   to procedures defined by RPSL.  The end result of this process is,
   traditionally, a router vendor dependent configuration snippet that
   defines the routing policy for that customer.  This routing policy
   may consist of the set of IPv4 or IPv6 prefixes, associated prefix
   lengths and AS_PATH's that are supposed to be accepted from a
   customer's eBGP session.  However, if indicated in the appropriate
   RPSL resource, the policy may also set certain BGP Attributes, such
   as MED, AS_PATH prepend value, LOCAL_PREF, etc., at either the
   incoming eBGP session from the customer or on static routes that are
   originated by the resource holder.

   An ISP's customers may not adequately plan for pre-planned
   maintenance or, more likely, need to rapidly begin announcing a new
   IP prefix as a result of, for example, an emergency turn-up of the
   ISP customer's new downstream customer.  Unfortunately, the routine,
   automated process employed by the ISP means that they may not begin
   updating their routing policy on their network for up to 24 hours,
   because the ISP or the IRRs the ISP uses might only mirror changes to
   IRR resources once every 24 hours.  The time interval for the
   routine/automated process is not responsive to the needs of directly
   paying customer(s) who need rapid changes in their policy in rare
   situations.  In these situations, when a customer has an urgent need
   for updates to take affect immediately, they will call up the Network
   Operations Center (NOC) of their ISP and request that the ISP
   immediately fetch new IRR objects and push those changes out to their
   network.  This is often accomplished in as little as five minutes
   from the time a customer contacts their ISP's NOC to the time a new
   filtering policy is pushed out to the PE routers that are attached to

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   that customer's Attachment Circuits (AC's).  It is conceivable that
   some ISPs automate this using out-of-band mechanisms as well,
   although the authors are unaware of any existing mechanisms that
   support this.

   Ultimately, the aforementioned latency with respect to "emergency
   changes" in IRR resources that need to be reflected in near-real-time
   in the network is compounded if the IRR resources were being used by
   third party ISPs to perform filtering on their peering circuits,
   where typically no such policies are employed today for this very
   reason.  It is likely that the length of time at which IRRs mirror
   changes will have to be dramatically reduced with a corresponding
   reduction in time at the ISPs that, in turn, need to evaluate whether
   changes in a set of IRR resources need to get reflected in updated
   router policies that will get pushed out to ASBR's, connected to
   peering circuits, on their network.

6.  Historical BGP Protocol Limitations

   As mentioned previously, after a resource holder made changes to
   their resources in an IRR, those changes would automatically be
   distributed to other IRRs, ISPs would then learn of those changes,
   generate a new BGP policies, and then apply those to the appropriate
   subset of routers in their ASes.  However, in the past, one
   additional step is necessary in order to have any of those new BGP
   policies take effect in the Control Plane and to allow/deny the
   updated resource from a customer to their ISP and from their
   immediately upstream ISP to the ISP's peers.  It was necessary (often
   manually) to actually induce BGP on each router to apply the new
   policy within the Control Plane, thus learning of a newly announced/
   changed IP prefix (or, dropping a deleted IP prefix).  Unfortunately,
   most of these methods were not only highly operationally impactful,
   but also affected traffic forwarding to IP destinations that were
   unrelated to the most recent changes to the BGP policy.

   Historically, a customer would have to (re-)announce the new IP
   prefix toward their ISP, but only after the ISP had placed the new
   BGP policies into affect.  Alternatively, the ISP would have to reset
   the entire PE-CE eBGP session either by: a) bouncing the entire
   interface toward the customer, (e.g.: shutdown/no shutdown); or, b)
   clearing the eBGP session toward the customer, (e.g.: clear ip bgp
   neighbor >IP address of CE router<).  The latter two cases were, of
   course, the most highly impactful and thus could generally only be
   performed off-hours during a maintenance window.

   Once the new IP prefix has been successfully announced by the
   customer and permitted by the newly updated policy at the ISP's PE's

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   (attached to that customer), it would be propagated to that ISP's
   ASBR's, attached to peers, at the perimeter of the ISP network.
   Unfortunately, if those peers had either not yet learned of the
   changes to resources in the IRR or pushed out new BGP policies (and,
   reset their BGP sessions immediately afterward) incorporating those
   changes, then the newly announced route would also get dropped at the
   ingress ASBR's of the peers.

   Ultimately, either of the two scenarios above further lengthen the
   effective time it would take for changes in IRR resources to take
   affect within BGP in the network.  Fortunately, BGP has been enhanced
   over the last several years in order that changes within BGP policy
   will take affect without requiring a service impacting reset of BGP
   sessions.  Specifically, BGP soft-reconfiguration [REF?] and, later,
   Route Refresh Capability for BGP-4 [RFC2918] were developed so that
   ISPs, or their customers, could induce BGP to apply a new policy
   while leaving both the existing eBGP session active as well as
   (unaffected) routes active in both the Loc-RIB and, more importantly,
   FIB of the router.  Thus, using either of these mechanisms, an ISP or
   its peers currently will deploy a newly generated BGP policy, based
   on changes to resources within the IRR, and immediately trigger a
   non-service impacting notification to the BGP process to have those
   changes take affect in their Control Plane, either allowing a new IP
   prefix to be announced or an old IP prefix to be dropped.  This
   dramatically reduces the length of time after changes are propagated
   throughout the IRRs to when those changes are actually operational
   within BGP policy in an ISP's network.

7.  Historical Limitations of Routers

7.1.  Incremental Updates to Policy on Routers

   Routers in the mid 1990's rarely supported incrementally updatable
   prefix filters for BGP, and therefore, if new information was
   received from a policy or internal configuration database that would
   impact a policy applied to a given eBGP peer, the entire prefix list
   or access list would need to be deleted and rewritten, compiled, and
   installed.  This was very tedious and commonly led to leaked routes
   during the time when the policy was being rewritten, compiled, and
   applied on a router.  Furthermore, application of a new policy would
   not automatically result in new ingress or egress reachability
   advertisements, from that new policy, because routers at the time
   would require a reset of the eBGP sessions for routing information to
   be evaluated by the new policy.  Of course, resetting of an eBGP
   session had implications on traffic forwarding during the time the
   eBGP session was reestablished and new routing information was

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   Routers now support the ability to perform incremental, and in situ,
   updates to filter lists consisting of IP prefixes and/or AS_PATH's
   that are used within an ingress or egress BGP policy.  In addition,
   routers also can apply those incremental updates to policy, with no
   traffic disruption, using BGP soft-reconfiguration or BGP Route
   Refresh, as discussed in the previous section.

7.2.  Storage Requirements for Policy on Routers

   Historically, routers had very limited storage capacity and would
   have difficulty in storing an extremely large BGP policy on-board.
   This was typically the result of router hardware vendors using an
   extremely limited amount of NVRAM for storage of router

   Another challenge with historical router hardware was that writing to
   NVRAM was extremely slow.  Thus, when the router configuration had
   changed as a result of, for example, updating a BGP policy to
   accommodate changes in IRR resources, this would result in extremely
   long times to write out these configuration changes and, sometimes,
   due to bugs would result in loss of protocol keep-alives, thus
   causing an impact to routing or forwarding of packets through the

   The above limitations have largely been resolved with more modern
   equipment from the last few years shipping with increasing amounts of
   non-volatile storage such as: PCMCIA or USB Flash Cards, Hard Disk
   Drives or Solid State Disk Drives.

   However, as capacities and technologies have evolved on modern
   routing hardware, so have the some of the scaling requirements of the
   data.  In some large networks, configuration growth has begun to
   "pose challenges" [IEPG89_NTT].  While the enhancements of hardware
   have overcome some historical limitations, evidence suggests that
   further optimizations in configuration processing may be needed in
   some cases.  Some of the more recent operational issues include
   scheduler slips and protracted commit times.  This suggests that even
   though many historical hurdles have been overcome, there are still
   motivations to optimize and modernize IRR technologies.

7.3.  Updating Configuration on Routers

   Historically, there has not been a standardized network configuration
   modeling language or an associated method to update router
   configurations.  When an ISP detected a change in resources within
   the IRR, it would fashion a router vendor dependent BGP policy and
   upload that to the router usually via the following method.

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   First, an updated BGP policy configuration 'snippet' is generated via
   processes running on an offline server.  Next, the operator uses
   either telnet or SSH to login to the CLI of a target router and issue
   router vendor dependent CLI commands that will trigger the target
   router to fetch the new configuration snippet via TFTP, FTP or Secure
   Copy (SCP) stored on the offline server.  The target router will then
   perform syntax checking on that configuration snippet and, if that
   passes, merge that configuration snippet into the running
   configuration of the router's Control Software.  At this point, the
   new BGP policy configuration 'snippet' is active within the Control
   Plane of the router.  One last step remains, which is the operator
   will issue a CLI command to induce the router to perform a "soft
   reset", via BGP soft-reconfiguration or BGP Route Refresh, of the
   associated BGP session in order to trigger the router to apply the
   new policy to routes learned from that BGP session without disrupting
   traffic forwarding.

   More recently, operators have the ability to use NETCONF/SSH (or,
   TLS) from an offline server to push a BGP configuration 'snippet'
   from an offline server toward a target router that has that
   capability.  However, this activity is still dependent on generating,
   via the offline server, a router vendor dependent XML configuration
   snippet that would get uploaded via SSH or TLS to the target router.

   In the future, the ability to upload new Route Origin Authorization
   (ROA) information may be provided from the RPKI to routers via the
   RPKI-RTR [RFC6810] protocol.  However, this will not allow operators
   the ability to upload other configuration information such as BGP
   policy information, such as AS_PATH's, BGP communities, etc. that
   might be associated with that ROA information, like they can from IRR
   generated BGP policies.

8.  Summary

   As discussed above, many of the problems that have historically
   stifled IRR deployment have, themselves, become historical.  However,
   there are still real operational considerations that limit IRR usage
   from realizing its full effectiveness.  The potential for IRRs to
   express inter-domain routing policy, and to allow relying parties to
   learn policy, has always positioned it as a strong candidate to aid
   the security postures of operators.  However, while routing density
   and complexity have grown, so have some of the challenges facing IRRs
   (even today).  Because of this state increase, the potential to model
   all policies for all ASes in all routers may still remain illusive.
   In addition, without an operationally deployed resource certification
   framework that can tie policies to resource holders, there is a
   fundamental limitation that still exists.

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9.  Security Considerations

   One of the central concerns with IRRs is the ability of an IRR
   operator to remotely influence the routing operations of an external
   consumer.  Specifically, if the processing of IRR contents can become
   burdensome, or if the policy statements can be crafted to introduce
   routing problems or anomalies, then operators may want to be
   circumspect about ingesting contents from external parties.  However,
   in regards to routing anomalies, as mentioned in Section 4.1 a
   resource certification framework should be used to address the
   authorization issues of IRR statements to make attestations and

   Additionally, the external and systemic dependencies introduced by
   IRRs and other such systems employed to inform routing policy, and
   how tightly or loosely coupled those systems are to the global
   routing system and operational networks, introduces additional
   vectors that operators and system architects should consider when
   evaluating attack surface and service dependencies associated with
   those elements.  These attributes and concerns are certainly not
   unique to IRRs, and operators should evaluate the implications of
   external systems and varying degrees of coupling and operational
   buffers that might be installed in their environments.

10.  IANA Considerations

   There are no IANA considerations.

11.  Acknowledgements

   The editors would like to acknowledge and thank Chris Morrow, Jeff
   Haas, and Wes George for their help and constructive feedback.

12.  Informative References

              "NTT BGP Configuration Size and Scope", IEPG 89 http://

              Merit Network, Inc., "List of Routing Registries", List of
              Routing Registries

              Merit, "IRRd - Internet Routing Registry Daemon",

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              Osterweil, E., Amante, S., McPherson, D., and D. Massey,
              "The Great IPv4 Land Grab: Resource Certification for the
              IPv4 Grey Market",

   [RFC1787]  Rekhter, Y., "Routing in a Multi-provider Internet",
              RFC 1787, April 1995.

   [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.

   [RFC2725]  Villamizar, C., Alaettinoglu, C., Meyer, D., and S.
              Murphy, "Routing Policy System Security", RFC 2725,
              December 1999.

   [RFC2769]  Villamizar, C., Alaettinoglu, C., Govindan, R., and D.
              Meyer, "Routing Policy System Replication", RFC 2769,
              February 2000.

   [RFC2918]  Chen, E., "Route Refresh Capability for BGP-4", RFC 2918,
              September 2000.

   [RFC6480]  Lepinski, M. and S. Kent, "An Infrastructure to Support
              Secure Internet Routing", RFC 6480, February 2012.

   [RFC6810]  Bush, R. and R. Austein, "The Resource Public Key
              Infrastructure (RPKI) to Router Protocol", RFC 6810,
              January 2013.

              RIPE NCC, "DRAFT: Autonomous System (AS) Number Assignment
              Policies and Procedures", Foundation

              Osterweil, E., Manderson, T., White, R., and D. McPherson,
              "Sizing Estimates for a Fully Deployed RPKI", Verisign
              Labs Technical Report 1120005 version 2 http://

   [TASRS]    Osterweil, E., Amante, S., and D. McPherson, "TASRS:
              Towards a Secure Routing System Through Internet Number

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              Resource Certification", Verisign Labs Technical Report
              1130009 /tr-

Authors' Addresses

   Danny McPherson
   Verisign, Inc.


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


   Eric Osterweil
   Verisign, Inc.


   Larry J. Blunk
   Merit Network, Inc.


   Dave Mitchell
   Twitter, Inc.


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