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Obsoleted by: 2622 PROPOSED STANDARD

Network Working Group                                     C. Alaettinoglu
Request for Comments: 2280             USC/Information Sciences Institute
Category: Standards Track                                        T. Bates
                                                            Cisco Systems
                                                                E. Gerich
                                                          At Home Network
                                                            D. Karrenberg
                                                                     RIPE
                                                                 D. Meyer
                                                     University of Oregon
                                                              M. Terpstra
                                                             Bay Networks
                                                            C. Villamizar
                                                                      ANS
                                                             January 1998

              Routing Policy Specification Language (RPSL)

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   Table of Contents

   1 Introduction                                                     2
   2 RPSL Names, Reserved Words, and Representation                   3
   3 Contact Information                                              6
     3.1 mntner Class  . . . . . . . . . . . . . . . . . . . . . . .  6
     3.2 person Class  . . . . . . . . . . . . . . . . . . . . . . .  8
     3.3 role Class  . . . . . . . . . . . . . . . . . . . . . . . .  9
   4 route Class                                                     10
   5 Set Classes                                                     12
     5.1 route-set Class . . . . . . . . . . . . . . . . . . . . . . 12
     5.2 as-set Class  . . . . . . . . . . . . . . . . . . . . . . . 14
     5.3 Predefined Set Objects  . . . . . . . . . . . . . . . . . . 15
     5.4 Hierarchical Set Names  . . . . . . . . . . . . . . . . . . 15
   6 aut-num Class                                                   16
     6.1 import Attribute:  Import Policy Specification  . . . . . . 16
       6.1.1 Peering Specification . . . . . . . . . . . . . . . . . 17
       6.1.2 Action Specification  . . . . . . . . . . . . . . . . . 19



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       6.1.3 Filter Specification  . . . . . . . . . . . . . . . . . 20
       6.1.4 Example Policy Expressions  . . . . . . . . . . . . . . 24
     6.2 export Attribute:  Export Policy Specification  . . . . . . 24
      6.3 Other Routing  Protocols, Multi-Protocol Routing
       Protocols, and Injecting Routes Between Protocols   . . . . . 25
     6.4 Ambiguity Resolution  . . . . . . . . . . . . . . . . . . . 26
     6.5 default Attribute:  Default Policy Specification  . . . . . 28
     6.6 Structured Policy Specification . . . . . . . . . . . . . . 29
   7 dictionary Class                                                33
     7.1 Initial RPSL Dictionary and Example Policy Actions
      and Filters  . . . . . . . . . . . . . . . . . . . . . . . . . 36
   8 Advanced route Class                                            41
     8.1 Specifying Aggregate Routes . . . . . . . . . . . . . . . . 41
       8.1.1 Interaction with policies in aut-num class  . . . . . . 45
       8.1.2 Ambiguity resolution with overlapping aggregates  . . . 46
     8.2 Specifying Static Routes  . . . . . . . . . . . . . . . . . 47
   9 inet-rtr Class                                                  48
   10 Security Considerations                                        49
   11 Acknowledgements                                               50
   A Routing Registry Sites                                          51
   B Authors' Addresses                                              52
   C Full Copyright Statement                                        53

1 Introduction

   This memo is the reference document for the Routing Policy
   Specification Language (RPSL). RPSL allows a network operator to be
   able to specify routing policies at various levels in the Internet
   hierarchy; for example at the Autonomous System (AS) level.  At the
   same time, policies can be specified with sufficient detail in RPSL
   so that low level router configurations can be generated from them.
   RPSL is extensible; new routing protocols and new protocol features
   can be introduced at any time.

   RPSL is a replacement for the current Internet policy specification
   language known as RIPE-181 [4] or RFC-1786 [5].  RIPE-81 [6] was the
   first language deployed in the Internet for specifying routing
   policies.  It was later replaced by RIPE-181 [4].  Through
   operational use of RIPE-181 it has become apparent that certain
   policies cannot be specified and a need for an enhanced and more
   generalized language is needed.  RPSL addresses RIPE-181's
   limitations.









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RFC 2280                          RPSL                      January 1998


   RPSL was designed so that a view of the global routing policy can be
   contained in a single cooperatively maintained distributed database
   to improve the integrity of Internet's routing.  RPSL is not designed
   to be a router configuration language.  RPSL is designed so that
   router configurations can be generated from the description of the
   policy for one autonomous system (aut-num class) combined with the
   description of a router (inet-rtr class), mainly providing router ID,
   autonomous system number of the router, interfaces and peers of the
   router, and combined with a global database mappings from AS sets to
   ASes (as-set class), and from origin ASes and route sets to route
   prefixes (route and route-set classes).  The accurate population of
   the RPSL database can help contribute toward such goals as router
   configurations that protect against accidental (or malicious)
   distribution of inaccurate routing information, verification of
   Internet's routing, and aggregation boundaries beyond a single AS.

   RPSL is object oriented; that is, objects contain pieces of policy
   and administrative information.  These objects are registered in the
   Internet Routing Registry (IRR) by the authorized organizations.  The
   registration process is beyond the scope of this document.  Please
   refer to [1, 15, 2] for more details on the IRR.

   In the following sections, we present the classes that are used to
   define various policy and administrative objects.  The "mntner" class
   defines entities authorized to add, delete and modify a set of
   objects.  The "person" and "role" classes describes technical and
   administrative contact personnel.  Autonomous systems (ASes) are
   specified using the "aut-num" class.  Routes are specified using the
   "route" class.  Sets of ASes and routes can be defined using the
   "as-set" and "route-set" classes.  The "dictionary" class provides
   the extensibility to the language.  The "inet-rtr" class is used to
   specify routers.  Many of these classes were originally defined in
   earlier documents [4, 11, 14, 10, 3] and have all been enhanced.

   This document is self-contained.  However, the reader is encouraged
   to read RIPE-181 [5] and the associated documents [11, 14, 10, 3] as
   they provide significant background as to the motivation and
   underlying principles behind RIPE-181 and consequently, RPSL. For a
   tutorial on RPSL, the reader should read the RPSL applications
   document [2].

2 RPSL Names, Reserved Words, and Representation

   Each class has a set of attributes which store a piece of information
   about the objects of the class.  Attributes can be mandatory or
   optional: A mandatory attribute has to be defined for all objects of





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   the class; optional attributes can be skipped.  Attributes can also
   be single or multiple valued.  Each object is uniquely identified by
   a set of attributes, referred to as the class "key".

   The value of an attribute has a type.  The following types are most
   widely used.  Note that RPSL is case insensitive and only the
   characters from the ASCII character set can be used.

   <object-name>Many objects in RPSL have a name.  An <object-name>
       is made up of letters, digits, the character underscore "_", and
       the character hyphen "-"; the first character of a name must be a
       letter, and the last character of a name must be a letter or a
       digit.  The following words are reserved by RPSL, and they can
       not be used as names:

             any as-any rs-any peeras
             and or not
             atomic from to at action accept announce except refine
             networks into inbound outbound

       Names starting with certain prefixes are reserved for certain
       object types.  Names starting with "as-" are reserved for as set
       names.  Names starting with "rs-" are reserved for route set
       names.

   <as-number>An AS number x is represented as the string "ASx".  That
       is, the AS 226 is represented as AS226.

   <ipv4-address>An IPv4 address is represented as a sequence of four
       integers in the range from 0 to 255 separated by the character
       dot ".".  For example, 128.9.128.5 represents a valid IPv4
       address.  In the rest of this document, we may refer to IPv4
       addresses as IP addresses.

   <address-prefix>An address prefix is represented as an IPv4
       address followed by the character slash "/" followed by an
       integer in the range from 0 to 32.  The following are valid
       address prefixes: 128.9.128.5/32, 128.9.0.0/16, 0.0.0.0/0; and
       the following address prefixes are invalid: 0/0, 128.9/16 since 0
       or 128.9 are not strings containing four integers.

   <address-prefix-range>An address prefix range is an address
       prefix followed by one of the following range operators:








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       ^- is the exclusive more specifics operator; it stands
           for the more specifics of the address prefix excluding the
           address prefix itself.  For example, 128.9.0.0/16^- contains
           all the more specifics of 128.9.0.0/16 excluding
           128.9.0.0/16.

       ^+ is the inclusive more specifics operator; it stands
           for the more specifics of the address prefix including the
           address prefix itself.  For example, 5.0.0.0/8^+ contains all
           the more specifics of 5.0.0.0/8 including 5.0.0.0/8.

       ^n where n is an integer, stands for all the length n specifics
           of the address prefix.  For example, 30.0.0.0/8^16 contains
           all the more specifics of 30.0.0.0/8 which are of length 16
           such as 30.9.0.0/16.

       ^n-m where n and m are integers, stands for all the length n to
           length m specifics of the address prefix.  For example,
           30.0.0.0/8^24-32 contains all the more specifics of
           30.0.0.0/8 which are of length 24 to 32 such as 30.9.9.96/28.

       Range operators can also be applied to address prefix sets.  In
       this case, they distribute over the members of the set.  For
       example, for a route-set (defined later) rs-foo, rs-foo^+
       contains all the inclusive more specifics of all the prefixes in
       rs-foo.

   <date>A date is represented as an eight digit integer of the
       form YYYYMMDD where YYYY represents the year, MM represents the
       month of the year (01 through 12), and DD represents the day of
       the month (01 through 31).  For example, June 24, 1996 is
       represented as 19960624.

   <email-address>is as described in RFC-822[8].

   <dns-name>is as described in RFC-1034[16].

   <nic-handle>is a uniquely assigned identifier[13] used by routing,
       address allocation, and other registries to unambiguously refer
       to contact information.  person and role classes map NIC handles
       to actual person names, and contact information.

   <free-form>is a sequence of ASCII characters.

   <X-name>is a name of an object of type X. That is <mntner-name>
       is a name of a mntner object.





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   <registry-name>is a name of an IRR registry.  The routing
       registries are listed in Appendix A.

   A value of an attribute may also be a list of one of these types.  A
   list is represented by separating the list members by commas ",".
   For example, "AS1, AS2, AS3, AS4" is a list of AS numbers.  Note that
   being list valued and being multiple valued are orthogonal.  A
   multiple valued attribute has more than one value, each of which may
   or may not be a list.  On the other hand a single valued attribute
   may have a list value.

   An RPSL object is textually represented as a list of attribute-value
   pairs.  Each attribute-value pair is written on a separate line.  The
   attribute name starts at column 0, followed by character ":" and
   followed by the value of the attribute.  The object's representation
   ends when a blank line is encountered.  An attribute's value can be
   split over multiple lines, by starting the continuation lines with a
   white-space (" " or tab) character.  The order of attribute-value
   pairs is significant.

   An object's description may contain comments.  A comment can be
   anywhere in an object's definition, it starts at the first "#"
   character on a line and ends at the first end-of-line character.
   White space characters can be used to improve readability.

3 Contact Information

   The mntner, person and role classes, admin-c, tech-c, mnt-by,
   changed, and source attributes of all classes describe contact
   information.  The mntner class also specifies what entities can
   create, delete and update other objects.  These classes do not
   specify routing policies and each registry may have different or
   additional requirements on them.  Here we present the common
   denominator for completeness which is the RIPE database
   implementation[15].  Please consult your routing registry for the
   latest specification of these classes and attributes.

3.1 mntner Class

   The mntner class defines entities that can create, delete and update
   RPSL objects.  A provider, before he/she can create RPSL objects,
   first needs to create a mntner object.  The attributes of the mntner
   class are shown in Figure 1.  The mntner class was first described in
   [11].

   The mntner attribute is mandatory and is the class key attribute.
   Its value is an RPSL name.  The auth attribute specifies the scheme
   that will be used



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Attribute Value                    Type
mntner    <object-name>            mandatory, single-valued, class key
descr     <free-form>              mandatory, single-valued
auth      see description in text  mandatory, multi-valued
upd-to    <email-address>          mandatory, multi-valued
mnt-nfy   <email-address>          optional, multi-valued
tech-c    <nic-handle>             mandatory, multi-valued
admin-c   <nic-handle>             mandatory, multi-valued
remarks   <free-form>              optional, multi-valued
notify    <email-address>          optional, multi-valued
mnt-by    list of <mntner-name>    mandatory, multi-valued
changed   <email-address> <date>   mandatory, multi-valued
source    <registry-name>          mandatory, single-valued

   to identify and authenticate update requests from this maintainer.
   It has the following syntax:

      auth: <scheme-id> <auth-info>

      E.g.
             auth: NONE
             auth: CRYPT-PW dhjsdfhruewf
             auth: MAIL-FROM .*@ripe\.net

   The <scheme-id>'s currently defined are: NONE, MAIL-FROM, PGP and
   CRYPT-PW.  The <auth-info> is additional information required by a
   particular scheme: in the case of MAIL-FROM, it is a regular
   expression matching valid email addresses; in the case of CRYPT-PW,
   it is a password in UNIX crypt format; and in the case of PGP, it is
   a PGP public key.  If multiple auth attributes are specified, an
   update request satisfying any one of them is authenticated to be from
   the maintainer.

   The upd-to attribute is an email address.  On an unauthorized update
   attempt of an object maintained by this maintainer, an email message
   will be sent to this address.  The mnt-nfy attribute is an email
   address.  A notification message will be forwarded to this email
   address whenever an object maintained by this maintainer is added,
   changed or deleted.

   The descr attribute is a short, free-form textual description of the
   object.  The tech-c attribute is a technical contact NIC handle.
   This is someone to be contacted for technical problems such as
   misconfiguration.  The admin-c attribute is an administrative contact
   NIC handle.  The remarks attribute is a free text explanation or
   clarification.  The notify attribute is an email address to which
   notifications of changes to this object should be sent.  The mnt-by
   attribute is a list of mntner object names.  The authorization for



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RFC 2280                          RPSL                      January 1998


   changes to this object is governed by any of the maintainer objects
   referenced.  The changed attribute documents who last changed this
   object, and when this change was made.  Its syntax has the following
   form:

      changed: <email-address> <YYYYMMDD>

      E.g.
      changed: johndoe@terabit-labs.nn 19900401

   The <email-address> identifies the person who made the last change.
   <YYYYMMDD> is the date of the change.  The source attribute specifies
   the registry where the object is registered.  Figure 2 shows an
   example mntner object.  In the example, UNIX crypt format password
   authentication is used.

      mntner:      RIPE-NCC-MNT
      descr:       RIPE-NCC Maintainer
      admin-c:     DK58
      tech-c:      OPS4-RIPE
      upd-to:      ops@ripe.net
      mnt-nfy:     ops-fyi@ripe.net
      auth:        CRYPT-PW lz1A7/JnfkTtI
      mnt-by:      RIPE-NCC-MNT
      changed:     ripe-dbm@ripe.net 19970820
      source:      RIPE

                       Figure 2:  An example mntner object.

   The descr, tech-c, admin-c, remarks, notify, mnt-by, changed and
   source attributes are attributes of all RPSL classes.  Their syntax,
   semantics, and mandatory, optional, multi-valued, or single-valued
   status are the same for for all RPSL classes.  We do not further
   discuss them in other sections.

3.2 person Class

   A person class is used to describe information about people.  Even
   though it does not describe routing policy, we still describe it here
   briefly since many policy objects make reference to person objects.
   The person class was first described in [14].

   The attributes of the person class are shown in Figure 3.  The person
   attribute is the full name of the person.  The phone and the fax-no
   attributes have the following syntax:






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RFC 2280                          RPSL                      January 1998


Attribute  Value                    Type
person     <free-form>              mandatory, single-valued
nic-hdl    <nic-handle>             mandatory, single-valued, class key
address    <free-form>              mandatory, multi-valued
phone      see description in text  mandatory, multi-valued
fax-no     same as phone            optional, multi-valued
e-mail     <email-address>          mandatory, multi-valued


                     Figure 3:  person Class Attributes

         phone: +<country-code> <city> <subscriber> [ext. <extension>]

      E.g.:
         phone: +31 20 12334676
         phone: +44 123 987654 ext. 4711


   Figure 4 shows an example person object.


      person:      Daniel Karrenberg
      address:     RIPE Network Coordination Centre (NCC)
      address:     Singel 258
      address:     NL-1016 AB  Amsterdam
      address:     Netherlands
      phone:       +31 20 535 4444
      fax-no:      +31 20 535 4445
      e-mail:      Daniel.Karrenberg@ripe.net
      nic-hdl:     DK58
      changed:     Daniel.Karrenberg@ripe.net 19970616
      source:      RIPE


                       Figure 4:  An example person object.

3.3 role Class

   The role class is similar to the person object.  However, instead of
   describing a human being, it describes a role performed by one or
   more human beings.  Examples include help desks, network monitoring
   centers, system administrators, etc.  Role object is particularly
   useful since often a person performing a role may change, however the
   role itself remains.

   The attributes of the role class are shown in Figure 5.  The nic-hdl
   attributes of the person and role classes share the same name space.
   The



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RFC 2280                          RPSL                      January 1998


 Attribute  Value                    Type
 role       <free-form>              mandatory, single-valued
 nic-hdl    <nic-handle>             mandatory, single-valued, class key
 trouble    <free-form>              optional, multi-valued
 address    <free-form>              mandatory, multi-valued
 phone      see description in text  mandatory, multi-valued
 fax-no     same as phone            optional, multi-valued
 e-mail     <email-address>          mandatory, multi-valued


                      Figure 5:  role Class Attributes

   NIC handle of a role object cannot be used in an admin-c field.  The
   trouble attribute of role object may contain additional contact
   information to be used when a problem arises in any object that
   references this role object.  Figure 6 shows an example role object.

      role:        RIPE NCC Operations
      address:     Singel 258
      address:     1016 AB Amsterdam
      address:     The Netherlands
      phone:       +31 20 535 4444
      fax-no:      +31 20 545 4445
      e-mail:      ops@ripe.net
      admin-c:     CO19-RIPE
      tech-c:      RW488-RIPE
      tech-c:      JLSD1-RIPE
      nic-hdl:     OPS4-RIPE
      notify:      ops@ripe.net
      changed:     roderik@ripe.net 19970926
      source:      RIPE


                        Figure 6:  An example role object.

4 route Class

   Each interAS route (also referred to as an interdomain route)
   originated by an AS is specified using a route object.  The
   attributes of the route class are shown in Figure 7.  The route
   attribute is the address prefix of the route and the origin attribute
   is the AS number of the AS that originates the route into the interAS
   routing system.  The route and origin attribute pair is the class
   key.

   Figure 8 shows examples of four route objects (we do not include
   contact.




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Attribute     Value                      Type
route         <address-prefix>           mandatory, single-valued,
                                         class key
origin        <as-number>                mandatory, single-valued,
                                         class key
withdrawn     <date>                     optional, single-valued
member-of     list of <route-set-names>  optional, single-valued
              see Section 5
inject        see Section 8              optional, multi-valued
components    see Section 8              optional, single-valued
aggr-bndry    see Section 8              optional, single-valued
aggr-mtd      see Section 8              optional, single-valued
export-comps  see Section 8              optional, single-valued
holes         see Section 8              optional, single-valued


                     Figure 7:  route Class Attributes

   attributes such as admin-c, tech-c for brevity).  Note that the last
   two route objects have the same address prefix, namely 128.8.0.0/16.
   However, they are different route objects since they are originated
   by different ASes (i.e. they have different keys).

      route: 128.9.0.0/16
      origin: AS226

      route: 128.99.0.0/16
      origin: AS226

      route: 128.8.0.0/16
      origin: AS1

      route: 128.8.0.0/16
      origin: AS2
      withdrawn: 19960624


                         Figure 8:  Route Objects

   The withdrawn attribute, if present, signifies that the originator AS
   no longer originates this address prefix in the Internet.  Its value
   is a date indicating the date of withdrawal.  In Figure 8, the last
   route object is withdrawn (i.e. no longer originated by AS2) on June
   24, 1996.







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RFC 2280                          RPSL                      January 1998


5 Set Classes

   To specify policies, it is often useful to define sets of objects.
   For this purpose we define two classes: route-set and as-set.  These
   classes define a named set.  The members of these sets can be
   specified by either explicitly listing them in the set object's
   definition, or implicitly by having route and aut-num objects refer
   to the set names, or a combination of both methods.

5.1 route-set Class

   The attributes of the route-set class are shown in Figure 9.  The
   route-set attribute defines the name of the set.  It is an RPSL name
   that starts with "rs-".  The members attribute lists the members of
   the set.  The members attribute is a list of address prefixes or
   other route-set names.  Note that, the route-set class is a set of
   route prefixes, not of RPSL route objects.

   Attribute    Value                          Type
   route-set    <object-name>                  mandatory, single-valued,
                                               class key
   members      list of <address-prefixes> or  optional, single-valued
                <route-set-names>
   mbrs-by-ref  list of <mntner-names>         optional, single-valued


                   Figure 9:  route-set Class Attributes

   Figure 10 presents some example route-set objects.  The set rs-foo
   contains two address prefixes, namely 128.9.0.0/16 and 128.9.0.0/16.
   The set rs-bar contains the members of the set rs-foo and the address
   prefix 128.7.0.0/16.  The set rs-empty contains no members.

      route-set: rs-foo
      members: 128.9.0.0/16, 128.9.0.0/24

      route-set: rs-bar
      members: 128.7.0.0/16, rs-foo

      route-set: rs-empty


                       Figure 10:  route-set Objects

   An address prefix or a route-set name in a members attribute can be
   optionally followed by a range operator.  For example, the following
   set




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      route-set: rs-bar
      members: 5.0.0.0/8^+, 30.0.0.0/8^24-32, rs-foo^+

   contains all the more specifics of 5.0.0.0/8 including 5.0.0.0/8, all
   the more specifics of 30.0.0.0/8 which are of length 24 to 32 such as
   30.9.9.96/28, and all the more specifics of address prefixes in route
   set rs-foo.

   The mbrs-by-ref attribute is a list of maintainer names or the
   keyword ANY.  If this attribute is used, the route set also includes
   address prefixes whose route objects are registered by one of these
   maintainers and whose member-of attribute refers to the name of this
   route set.  If the value of a mbrs-by-ref attribute is ANY, any route
   object referring to the route set name is a member.  If the mbrs-by-
   ref attribute is missing, only the address prefixes listed in the
   members attribute are members of the set.

      route-set: rs-foo
      mbrs-by-ref: MNTR-ME, MNTR-YOU

      route-set: rs-bar
      members: 128.7.0.0/16
      mbrs-by-ref: MNTR-YOU

      route: 128.9.0.0/16
      origin: AS1
      member-of: rs-foo
      mnt-by: MNTR-ME

      route: 128.8.0.0/16
      origin: AS2
      member-of: rs-foo, rs-bar
      mnt-by: MNTR-YOU


                      Figure 11:  route-set objects.

   Figure 11 presents example route-set objects that use the mbrs-by-ref
   attribute.  The set rs-foo contains two address prefixes, namely
   128.8.0.0/16 and 128.9.0.0/16 since the route objects for
   128.8.0.0/16 and 128.9.0.0/16 refer to the set name rs-foo in their
   member-of attribute.  The set rs-bar contains the address prefixes
   128.7.0.0/16 and 128.8.0.0/16.  The route 128.7.0.0/16 is explicitly
   listed in the members attribute of rs-bar, and the route object for
   128.8.0.0/16 refer to the set name rs-bar in its member-of attribute.

   Note that, if an address prefix is listed in a members attribute of a
   route set, it is a member of that route set.  The route object



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   corresponding to this address prefix does not need to contain a
   member-of attribute referring to this set name.  The member-of
   attribute of the route class is an additional mechanism for
   specifying the members indirectly.

5.2 as-set Class

   The attributes of the as-set class are shown in Figure 12.  The as-
   set attribute defines the name of the set.  It is an RPSL name that
   starts with "as-".  The members attribute lists the members of the
   set.  The members attribute is a list of AS numbers, or other as-set
   names.

      Attribute    Value                    Type
      as-set       <object-name>            mandatory, single-valued,
                                            class key
      members      list of <as-numbers> or  optional, single-valued
                   <as-set-names>
      mbrs-by-ref  list of <mntner-names>   optional, single-valued


                    Figure 12:  as-set Class Attributes

   Figure 13 presents two as-set objects.  The set as-foo contains two
   ASes, namely AS1 and AS2.  The set as-bar contains the members of the
   set as-foo and AS3, that is it contains AS1, AS2, AS3.

    as-set: as-foo                      as-set: as-bar
    members: AS1, AS2                   members: AS3, as-foo


                    Figure 13:  as-set objects.


   The mbrs-by-ref attribute is a list of maintainer names or the
   keyword ANY.  If this attribute is used, the AS set also includes
   ASes whose aut-num objects are registered by one of these maintainers
   and whose member-of attribute refers to the name of this AS set.  If
   the value of a mbrs-by-ref attribute is ANY, any AS object referring
   to the AS set is a member of the set.  If the mbrs-by-ref attribute
   is missing, only the ASes listed in the members attribute are members
   of the set.

   Figure 14 presents an example as-set object that uses the mbrs-by-ref
   attribute.  The set as-foo contains AS1, AS2 and AS3.  AS4 is not a
   member of the set as-foo even though the aut-num object references
   as-foo.  This is because MNTR-OTHER is not listed in the as-foo's
   mbrs-by-ref attribute.



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    as-set: as-foo
    members: AS1, AS2
    mbrs-by-ref: MNTR-ME

    aut-num: AS3                          aut-num: AS4
    member-of: as-foo                     member-of: as-foo
    mnt-by: MNTR-ME                       mnt-by: MNTR-OTHER


                        Figure 14:  as-set objects.

5.3 Predefined Set Objects


   In a context that expects a route set (e.g.  members attribute of the
   route-set class), an AS number ASx defines the set of routes that are
   originated by ASx; and an as-set AS-X defines the set of routes that
   are originated by the ASes in AS-X. A route p is said to be
   originated by ASx if there is a route object for p with ASx as the
   value of the origin attribute.  For example, in Figure 15, the route
   set rs-special contains 128.9.0.0/16, routes of AS1 and AS2, and
   routes of the ASes in AS set AS-FOO.

      route-set: rs-special
      members: 128.9.0.0/16, AS1, AS2, AS-FOO


         Figure 15:  Use of AS numbers and AS sets in route sets.

   The set rs-any contains all routes registered in IRR.  The set as-any
   contains all ASes registered in IRR.

5.4 Hierarchical Set Names

   Set names can be hierarchical.  A hierarchical set name is a sequence
   of set names and AS numbers separated by colons ":".  For example,
   the following names are valid: AS1:AS-CUSTOMERS, AS1:RS-EXCEPTIONS,
   AS1:RS-EXPORT:AS2, RS-EXCEPTIONS:RS-BOGUS. All components of an
   hierarchical set name which are not AS numbers should start with
   "as-" or "rs-" for as sets and route sets respectively.

   A set object with name X1:...:Xn-1:Xn can only be created by the
   maintainer of the object with name X1:...:Xn-1.  That is, only the
   maintainer of AS1 can create a set with name AS1:AS-FOO; and only the
   maintainer of AS1:AS-FOO can create a set with name AS1:AS-FOO:AS-
   BAR.





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   The purpose of an hierarchical set name is to partition the set name
   space so that the controllers of the set name X1 controls the whole
   set name space under X1, i.e.  X1:...:Xn-1.  This is important since
   anyone can create a set named AS-MCI-CUSTOMERS but only the people
   created AS3561 can create AS3561:AS-CUSTOMERS. In the former, it is
   not clear if the set AS-MCI-CUSTOMERS has any relationship with MCI.
   In the latter, we can guarantee that AS3561:AS-CUSTOMERS and AS3561
   are created by the same entity.

6 aut-num Class

   ASes are specified using the aut-num class.  The attributes of the
   aut-num class are shown in Figure 16.  The value of the aut-num
   attribute is the AS number of the AS described by this object.  The
   as-name attribute is a symbolic name (in RPSL name syntax) of the AS.
   The import, export and default routing policies of the AS are
   specified using import, export and default attributes respectively.

   Attribute  Value                  Type
   aut-num    <as-number>            mandatory, single-valued, class key
   as-name    <object-name>          mandatory, single-valued
   member-of  list of <as-set-names> optional, single-valued
   import     see Section 6.1        optional, multi valued
   export     see Section 6.2        optional, multi valued
   default    see Section 6.5        optional, multi valued

                    Figure 16:  aut-num Class Attributes

6.1 import Attribute:  Import Policy Specification

   Figure 17 shows a typical interconnection of ASes that we will be
   using in our examples throughout this section.  In this example
   topology, there are three ASes, AS1, AS2, and AS3; two exchange
   points, EX1 and EX2; and six routers.  Routers connected to the same
   exchange point peer with each other, i.e. open a connection for
   exchanging routing information.  Each router would export a subset of
   the routes it has to its peer routers.  Peer routers would import a
   subset of these routes.  A router while importing routes would set
   some route attributes.  For example, AS1 can assign higher preference
   values to the routes it imports from AS2 so that it prefers AS2 over
   AS3.  While exporting routes, a router may also set some route
   attributes in order to affect route selection by its peers.  For
   example, AS2 may set the MULTI-EXIT-DISCRIMINATOR BGP attribute so
   that AS1 prefers to use the router 9.9.9.2.  Most interAS policies
   are specified by specifying what route subsets can be imported or
   exported, and how the various BGP route attributes are set and used.





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     ----------------------                   ----------------------
     |            7.7.7.1 |-------|   |-------| 7.7.7.2            |
     |                    |     ========      |                    |
     |   AS1              |      EX1  |-------| 7.7.7.3     AS2    |
     |                    |                   |                    |
     |            9.9.9.1 |------       ------| 9.9.9.2            |
     ----------------------     |       |     ----------------------
                               ===========
                                   |    EX2
     ----------------------        |
     |            9.9.9.3 |---------
     |                    |
     |   AS3              |
     ----------------------

   Figure 17: Example topology consisting of three ASes, AS1, AS2, and
   AS3; two exchange points, EX1 and EX2; and six routers.

   In RPSL, an import policy is divided into import policy expressions.
   Each import policy expression is specified using an import attribute.
   The import attribute has the following syntax (we will extend this
   syntax later in Sections 6.3 and 6.6):

       import: from <peering-1> [action <action-1>]
               . . .
               from <peering-N> [action <action-N>]
               accept <filter>

   The action specification is optional.  The semantics of an import
   attribute is as follows: the set of routes that are matched by
   <filter> are imported from all the peers in <peerings>; while
   importing routes at <peering-M>, <action-M> is executed.


     E.g.
       aut-num: AS1
       import: from AS2 action pref = 1; accept { 128.9.0.0/16 }

   This example states that the route 128.9.0.0/16 is accepted from AS2
   with preference 1.  In the next few subsections, we will describe how
   peerings, actions and filters are specified.

6.1.1 Peering Specification

   Our example above used an AS number to specify peerings.  The
   peerings can be specified at different granularities.  The syntax of
   a peering specification has two forms.  The first one is as follows:




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               <peer-as> [<peer-router>] [at <local-router>]

   where <local-router> and <peer-router> are IP addresses of routers,
   <peer-as> is an AS number.  <peer-as> must be the AS number of
   <peer-router>.  Both <local-router> and <peer-router> are optional.
   If both <local-router> and <peer-router> are specified, this peering
   specification identifies only the peering between these two routers.
   If only <local-router> is specified, this peering specification
   identifies all the peerings between <local-router> and any of its
   peer routers in <peer-as>.  If only <peer-router> is specified, this
   peering specification identifies all the peerings between any router
   in the local AS and <peer-router>.  If neither <local-router> nor
   <peer-router> is specified, this peering specification identifies all
   the peerings between any router in the local AS and any router in
   <peer-as>.

   We next give examples.  Consider the topology of Figure 17 where
   7.7.7.1, 7.7.7.2 and 7.7.7.3 peer with each other; 9.9.9.1, 9.9.9.2
   and 9.9.9.3 peer with each other.  In the following example 7.7.7.1
   imports 128.9.0.0/16 from 7.7.7.2.

    (1) aut-num: AS1
        import: from AS2 7.7.7.2 at 7.7.7.1 accept { 128.9.0.0/16 }

   In the following example 7.7.7.1 imports 128.9.0.0/16 from 7.7.7.2
   and 7.7.7.3.

    (2) aut-num: AS1
        import: from AS2 at 7.7.7.1 accept { 128.9.0.0/16 }

   In the following example 7.7.7.1 imports 128.9.0.0/16 from 7.7.7.2
   and 7.7.7.3, and 9.9.9.1 imports 128.9.0.0/16 from 9.9.9.2.

    (3) aut-num: AS1
        import: from AS2 accept { 128.9.0.0/16 }

   The second form of <peering> specification has the following syntax:

        <as-expression> [at <router-expression>]

   where <as-expression> is an expression over AS numbers and sets using
   operators AND, OR, and NOT, and <router-expression> is an expression
   over router IP addresses and DNS names using operators AND, OR, and
   NOT. The DNS name can only be used if there is an inet-rtr object for
   that name that binds the name to IP addresses.  This form identifies
   all the peerings between any local router in <router-expression> to





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   any of their peer routers in the ASes in <as-expression>.  If
   <router-expression> is not specified, it defaults to all routers of
   the local AS.

   In the following example 9.9.9.1 imports 128.9.0.0/16 from 9.9.9.2
   and 9.9.9.3.

    (4) as-set: AS-FOO
        members: AS2, AS3
        aut-num: AS1
        import: from AS-FOO at 9.9.9.1 accept { 128.9.0.0/16 }

   In the following example 9.9.9.1 imports 128.9.0.0/16 from 9.9.9.2
   and 9.9.9.3, and 7.7.7.1 imports 128.9.0.0/16 from 7.7.7.2 and
   7.7.7.3.

    (5) aut-num: AS1
        import: from AS-FOO accept { 128.9.0.0/16 }

   In the following example AS1 imports 128.9.0.0/16 from AS3 at router
   9.9.9.1

    (6) aut-num: AS1
        import: from AS-FOO and not AS2
                at not 7.7.7.1
                accept { 128.9.0.0/16 }

   This is because  "AS-FOO and not  AS2" equals AS3  and "not 7.7.7.1"
   equals 9.9.9.1.

6.1.2 Action Specification

   Policy actions in RPSL either set or modify route attributes, such as
   assigning a preference to a route, adding a BGP community to the BGP
   community path attribute, or setting the MULTI-EXIT-DISCRIMINATOR
   attribute.  Policy actions can also instruct routers to perform
   special operations, such as route flap damping.

   The routing policy attributes whose values can be modified in policy
   actions are specified in the RPSL dictionary.  Please refer to
   Section 7 for a list of these attributes.  Each action in RPSL is
   terminated by the character ';'.  It is possible to form composite
   policy actions by listing them one after the other.  In a composite
   policy action, the actions are executed left to right.  For example,







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aut-num: AS1
import: from AS2
        action pref = 10; med = 0; community.append(10250, {3561,10});
        accept { 128.9.0.0/16 }

   sets pref to 10, med to 0, and then appends 10250 and {3561,10} to
   the community path attribute.

6.1.3 Filter Specification

   A policy filter is a logical expression which when applied to a set
   of routes returns a subset of these routes.  We say that the policy
   filter matches the subset returned.  The policy filter can match
   routes using any path attribute, such as the destination address
   prefix (or NLRI), AS-path, or community attributes.

   The policy filters can be composite by using the operators AND, OR,
   and NOT.  The following policy filters can be used to select a subset
   of routes:

   ANY The filter-keyword ANY matches all routes.

   Address-Prefix Set This is an explicit list of address prefixes
   enclosed in braces '{' and '}'.  The policy filter matches the set of
   routes whose destination address-prefix is in the set.  For example:

        { 0.0.0.0/0 }
        { 128.9.0.0/16, 128.8.0.0/16, 128.7.128.0/17, 5.0.0.0/8 }
        { }

   An address prefix can be optionally followed by a range operator
   (i.e. '^-', '^+', '^n', or '^n-m').  For example, the set

     { 5.0.0.0/8^+, 128.9.0.0/16^-, 30.0.0.0/8^16, 30.0.0.0/8^24-32 }

   contains all the more specifics of 5.0.0.0/8 including 5.0.0.0/8, all
   the more specifics of 128.9.0.0/16 excluding 128.9.0.0/16, all the
   more specifics of 30.0.0.0/8 which are of length 16 such as
   30.9.0.0/16, and all the more specifics of 30.0.0.0/8 which are of
   length 24 to 32 such as 30.9.9.96/28.

   Route Set Name A route set name matches the set of routes that are
   members of the set.  A route set name may be a name of a route-set
   object, an AS number, or a name of an as-set object (AS numbers and
   as-set names implicitly define route sets; please see Section 5.3).
   For example:





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         aut-num: AS1
         import: from AS2 action pref = 1; accept AS2
         import: from AS2 action pref = 1; accept AS-FOO
         import: from AS2 action pref = 1; accept RS-FOO

   The keyword PeerAS can be used instead of the AS number of the peer
   AS.  PeerAS is particularly useful when the peering is specified
   using an AS expression.  For example:

         as-set: AS-FOO
         members: AS2, AS3

         aut-num: AS1
         import: from AS-FOO action pref = 1; accept PeerAS

   is same as:

         aut-num: AS1
         import: from AS2 action pref = 1; accept AS2
         import: from AS3 action pref = 1; accept AS3

   A route set name can also be followed by one of the operators '^-',
   '^+', '^n' or '^n-m'.  These operators are distributive over the
   route sets.  For example, { 5.0.0.0/8, 6.0.0.0/8 }^+ equals {
   5.0.0.0/8^+, 6.0.0.0/8^+ }, and AS1^- equals all the exclusive more
   specifics of routes originated by AS1.

   AS Path Regular Expressions An AS-path regular expression can be used
   as a policy filter by enclosing the expression in `<' and `>'.  An
   AS-path policy filter matches the set of routes which traverses a
   sequence of ASes matched by the AS-path regular expression.  A router
   can check this using the AS_PATH attribute in the Border Gateway
   Protocol [18], or the RD_PATH attribute in the Inter-Domain Routing
   Protocol[17].

   AS-path Regular Expressions are POSIX compliant regular expressions
   over the alphabet of AS numbers.  The regular expression constructs
   are as follows:

    ASN where ASN is an AS number.  ASN matches the AS-path
                that is of length 1 and contains the corresponding AS
                number (e.g.  AS-path regular expression AS1 matches the
                AS-path "1").

                The keyword PeerAS can be used instead of the AS number
                of the peer AS.





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    AS-set where AS-set is an AS set name.  AS-set matches the AS-paths
                that is matched by one of the ASes in the AS-set.

    .        matches the AS-paths matched by any AS number.

    [...]    is an AS number set.   It matches the AS-paths  matched by
                the AS numbers listed between the brackets.  The AS
                numbers in the set are separated by white space
                characters.  If a `-' is used between two AS numbers in
                this set, all AS numbers between the two AS numbers are
                included in the set.  If an as-set name is listed, all
                AS numbers in the as-set are included.

    [^...]   is a complemented AS number set.  It matches any AS-path
                which is not matched by the AS numbers in the set.

    ^        Matches the empty string at the beginning of an AS-path.

    $        Matches the empty string at the end of an AS-path.

   We next list the regular expression operators in the decreasing order
   of evaluation.  These operators are left associative, i.e. performed
   left to right.

   Unary postfix operators * + ?  {m} {m,n} {m,}
                For a regular expression A, A* matches zero or more
                occurrences of A; A+ matches one or more occurrences of
                A; A?  matches zero or one occurrence of A; A{m} matches
                m occurrence of A; A{m,n} matches m to n occurrence of
                A; A{m,} matches m or more occurrence of A. For example,
                [AS1 AS2]{2} matches AS1 AS1, AS1 AS2, AS2 AS1, and AS2
                AS2.

   Unary postfix operators ~* ~+ ~{m} ~{m,n} ~{m,}
                These operators have similar functionality as the
                corresponding operators listed above, but all
                occurrences of the regular expression has to match the
                same pattern.  For example, [AS1 AS2]~{2} matches AS1
                AS1 and AS2 AS2, but it does not match AS1 AS2 and AS2
                AS1.

   Binary catenation operator
                This is an implicit operator and exists between two
                regular expressions A and B when no other explicit
                operator is specified.  The resulting expression A B
                matches an AS-path if A matches some prefix of the AS-
                path and B matches the rest of the AS-path.




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   Binary alternative (or) operator |
                For a regular expressions A and B, A | B matches any
                AS-path that is matched by A or B.

   Parenthesis can be used to override the default order of evaluation.
   White spaces can be used to increase readability.

   The following are examples of AS-path filters:

      <AS3>
      <^AS1>
      <AS2$>
      <^AS1 AS2 AS3$>
      <^AS1 .* AS2$>.

   The first example matches any route whose AS-path contains AS3, the
   second matches routes whose AS-path starts with AS1, the third
   matches routes whose AS-path ends with AS2, the fourth matches routes
   whose AS-path is exactly "1 2 3", and the fifth matches routes whose
   AS-path starts with AS1 and ends in AS2 with any number of AS numbers
   in between.

   Composite Policy Filters The following operators (in decreasing order
   of evaluation) can be used to form composite policy filters:

   NOT Given a policy filter x, NOT x matches the set of routes that are
       not matched by x.  That is it is the negation of policy filter x.

   AND Given two policy filters x and y, x AND y matches the
       intersection of the routes that are matched by x and that are
       matched by y.

   OR Given two policy filters x and y, x OR y matches the union of
       the routes that are matched by x and that are matched by y.

   Note that an OR operator can be implicit, that is `x y' is equivalent
   to `x OR y'.

     E.g.

       NOT {128.9.0.0/16, 128.8.0.0/16}
       AS226 AS227 OR AS228
       AS226 AND NOT {128.9.0.0/16}
       AS226 AND {0.0.0.0/0^0-18}







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   The first example matches any route except 128.9.0.0/16 and
   128.8.0.0/16.  The second example matches the routes of AS226, AS227
   and AS228.  The third example matches the routes of AS226 except
   128.9.0.0/16.  The fourth example matches the routes of AS226 whose
   length are not longer than 18.

   Routing Policy Attributes Policy filters can also use the values of
   other attributes for comparison.  The attributes whose values can be
   used in policy filters are specified in the RPSL dictionary.  Please
   refer to Section 7 for details.  An example using the the BGP
   community attribute is shown below:

       aut-num: AS1
       export: to AS2 announce AS1 AND NOT community.contains(NO_EXPORT)

   Filters using the routing policy attributes defined in the dictionary
   are evaluated before evaluating the operators AND, OR and NOT.

6.1.4 Example Policy Expressions

    aut-num: AS1
    import: from AS2 action pref = 1;
            from AS3 action pref = 2;
            accept AS4

   The above example states that AS4's routes are accepted from AS2 with
   preference 1, and from AS3 with preference 2 (routes with lower
   integer preference values are preferred over routes with higher
   integer preference values).

    aut-num: AS1
    import: from AS2 7.7.7.2 at 7.7.7.1 action pref = 1;
            from AS2                    action pref = 2;
            accept AS4

   The above example states that AS4's routes are accepted from AS2 on
   peering 7.7.7.1-7.7.7.2 with preference 1, and on any other peering
   with AS2 with preference 2.

6.2 export Attribute: Export Policy Specification

   Similarly, an export policy expression is specified using an export
   attribute.  The export attribute has the following syntax:

       export: to <peering-1> [action <action-1>]
               . . .
               to <peering-N> [action <action-N>]
               announce <filter>



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   The action specification is optional.  The semantics of an export
   attribute is as follows: the set of routes that are matched by
   <filter> are exported to all the peers specified in <peerings>; while
   exporting routes at <peering-M>, <action-M> is executed.

     E.g.
       aut-num: AS1
       export: to AS2 action med = 5; community .= 70;
               announce AS4

   In this example, AS4's routes are announced to AS2 with the med
   attribute's value set to 5 and community 70 added to the community
   list.

   Example:

       aut-num: AS1
       export: to AS-FOO announce ANY

   In this example, AS1 announces all of its routes to the ASes in the
   set AS-FOO.

6.3 Other Routing Protocols, Multi-Protocol Routing Protocols, and
       Injecting Routes Between Protocols

   The more complete syntax of the import and export attributes are as
   follows:

       import: [protocol <protocol-1>] [into <protocol-2>]
               from <peering-1> [action <action-1>]
               . . .
               from <peering-N> [action <action-N>]
               accept <filter>
       export: [protocol <protocol-1>] [into <protocol-2>]
               to <peering-1> [action <action-1>]
               . . .
               to <peering-N> [action <action-N>]
               announce <filter>

   Where the optional protocol specifications can be used for specifying
   policies for other routing protocols, or for injecting routes of one
   protocol into another protocol, or for multi-protocol routing
   policies.  The valid protocol names are defined in the dictionary.
   The <protocol-1> is the name of the protocol whose routes are being
   exchanged.  The <protocol-2> is the name of the protocol which is
   receiving these routes.  Both <protocol-1> and <protocol-2> default
   to the Internet Exterior Gateway Protocol, currently BGP.




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   In the following example, all interAS routes are injected into RIP.

    aut-num: AS1
    import: from AS2 accept AS2
    export: protocol BGP4 into RIP
            to AS1 announce ANY

   In the following example, AS1 accepts AS2's routes including any more
   specifics of AS2's routes, but does not inject these extra more
   specific routes into OSPF.

    aut-num: AS1
    import: from AS2 accept AS2^+
    export: protocol BGP4 into OSPF
            to AS1 announce AS2

   In the following example, AS1 injects its static routes (routes which
   are members of the set AS1:RS-STATIC-ROUTES) to the interAS routing
   protocol and appends AS1 twice to their AS paths.

    aut-num: AS1
    import: protocol STATIC into BGP4
            from AS1 action aspath.prepend(AS1, AS1);
            accept AS1:RS-STATIC-ROUTES

   In the following example, AS1 imports different set of unicast routes
   for multicast reverse path forwarding from AS2:

    aut-num: AS1
    import: from AS2 accept AS2
    import: protocol IDMR
            from AS2 accept AS2:RS-RPF-ROUTES

6.4 Ambiguity Resolution

   It is possible that the same peering can be covered by more that one
   peering specification in a policy expression.  For example:

    aut-num: AS1
    import: from AS2 7.7.7.2 at 7.7.7.1 action pref = 2;
            from AS2 7.7.7.2 at 7.7.7.1 action pref = 1;
            accept AS4

   This is not an error, though definitely not desirable.  To break the
   ambiguity, the action corresponding to the first peering
   specification is used.  That is the routes are accepted with
   preference 2.  We call this rule as the specification-order rule.




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   Consider the example:

    aut-num: AS1
    import: from AS2                    action pref = 2;
            from AS2 7.7.7.2 at 7.7.7.1 action pref = 1; dpa = 5;
            accept AS4

   where both peering specifications cover the peering 7.7.7.1-7.7.7.2,
   though the second one covers it more specifically.  The specification
   order rule still applies, and only the action "pref = 2" is executed.
   In fact, the second peering-action pair has no use since the first
   peering-action pair always covers it.  If the intended policy was to
   accept these routes with preference 1 on this particular peering and
   with preference 2 in all other peerings, the user should have
   specified:

    aut-num: AS1
    import: from AS2 7.7.7.2 at 7.7.7.1 action pref = 1; dpa = 5;
            from AS2                    action pref = 2;
            accept AS4

   It is also possible that more than one policy expression can cover
   the same set of routes for the same peering.  For example:

    aut-num: AS1
    import: from AS2 action pref = 2; accept AS4
    import: from AS2 action pref = 1; accept AS4

   In this case, the specification-order rule is still used.  That is,
   AS4's routes are accepted from AS2 with preference 2.  If the filters
   were overlapping but not exactly the same:

    aut-num: AS1
    import: from AS2 action pref = 2; accept AS4
    import: from AS2 action pref = 1; accept AS4 OR AS5

   the AS4's routes are accepted from AS2 with preference 2 and however
   AS5's routes are also accepted, but with preference 1.

   We next give the general specification order rule for the benefit of
   the RPSL implementors.  Consider two policy expressions:

    aut-num: AS1
    import: from peerings-1 action action-1 accept filter-1
    import: from peerings-2 action action-2 accept filter-2

   The above policy expressions are equivalent to the following three
   expressions where there is no ambiguity:



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aut-num: AS1
import: from peerings-1 action action-1 accept filter-1
import: from peerings-3 action action-2 accept filter-2 AND NOT filter-1
import: from peerings-4 action action-2 accept filter-2

   where peerings-3 are those that are covered by both peerings-1 and
   peerings-2, and peerings-4 are those that are covered by peerings-2
   but not by peerings-1 ("filter-2 AND NOT filter-1" matches the routes
   that are matched by filter-2 but not by filter-1).

   Example:

    aut-num: AS1
    import: from AS2 7.7.7.2 at 7.7.7.1
            action pref = 2;
            accept {128.9.0.0/16}
    import: from AS2
            action pref = 1;
            accept {128.9.0.0/16, 75.0.0.0/8}

   Lets consider two peerings with AS2, 7.7.7.1-7.7.7.2 and 9.9.9.1-
   9.9.9.2.  Both policy expressions cover 7.7.7.1-7.7.7.2.  On this
   peering, the route 128.9.0.0/16 is accepted with preference 2, and
   the route 75.0.0.0/8 is accepted with preference 1.  The peering
   9.9.9.1-9.9.9.2 is only covered by the second policy expressions.
   Hence, both the route 128.9.0.0/16 and the route 75.0.0.0/8 are
   accepted with preference 1 on peering 9.9.9.1-9.9.9.2.

   Note that the same ambiguity resolution rules also apply to export
   and default policy expressions.

6.5 default Attribute:  Default Policy Specification

   Default routing policies are specified using the default attribute.
   The default attribute has the following syntax:

       default: to <peering> [action <action>] [networks <filter>]

   The <action> and <filter> specifications are optional.  The semantics
   are as follows: The <peering> specification indicates the AS (and the
   router if present) is being defaulted to; the <action> specification,
   if present, indicates various attributes of defaulting, for example a
   relative preference if multiple defaults are specified; and the
   <filter> specifications, if present, is a policy filter.  A router
   chooses a default router from the routes in its routing table that
   matches this <filter>.

   In the following example, AS1 defaults to AS2 for routing.



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    aut-num: AS1
    default: to AS2

   In the following example, router 7.7.7.1 in AS1 defaults to router
   7.7.7.2 in AS2.

    aut-num: AS1
    default: to AS2 7.7.7.2 at 7.7.7.1

   In the following example, AS1 defaults to AS2 and AS3, but prefers
   AS2 over AS3.

    aut-num: AS1
    default: to AS2 action pref = 1;
    default: to AS3 action pref = 2;

   In the following example, AS1 defaults to AS2 and uses 128.9.0.0/16
   as the default network.

    aut-num: AS1
    default: to AS2 networks { 128.9.0.0/16 }

6.6 Structured Policy Specification

   The import and export policies can be structured.  We only reccomend
   structured policies to advanced RPSL users.  Please feel free to skip
   this section.

   The syntax for a structured policy specification is the following:

      <import-factor> ::= from <peering-1> [action <action-1>]
                          . . .
                          from <peering-N> [action <action-N>]
                          accept <filter>;

      <import-term> ::=  <import-factor> |
                         LEFT-BRACE
                         <import-factor>
                         . . .
                         <import-factor>
                         RIGHT-BRACE

      <import-expression> ::= <import-term>                            |
                              <import-term> EXCEPT <import-expression> |
                              <import-term> REFINE <import-expression>

      import: [protocol <protocol1>] [into <protocol2>]
              <import-expression>



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   Please note the semicolon at the end of an <import-factor>.  If the
   policy specification is not structured (as in all the examples in
   other sections), this semicolon is optional.  The syntax and
   semantics for an <import-factor> is already defined in Section 6.1.

   An <import-term> is either a sequence of <import-factor>'s enclosed
   within matching braces (i.e. `{' and `}') or just a single <import-
   factor>.  The semantics of an <import-term> is the union of <import-
   factor>'s using the specification order rule.  An <import-expression>
   is either a single <import-term> or an <import-term> followed by one
   of the keywords "except" and "refine", followed by another <import-
   expression>.  Note that our definition allows nested expressions.
   Hence there can be exceptions to exceptions, refinements to
   refinements, or even refinements to exceptions, and so on.

   The semantics for the except operator is as follows: The result of an
   except operation is another <import-term>.  The resulting policy set
   contains the policies of the right hand side but their filters are
   modified to only include the routes also matched by the left hand
   side.  The policies of the left hand side are included afterwards and
   their filters are modified to exclude the routes matched by the right
   hand side.  Please note that the filters are modified during this
   process but the actions are copied verbatim.  When there are multiple
   levels of nesting, the operations (both except and refine) are
   performed right to left.

   Consider the following example:

    import: from AS1 action pref = 1; accept as-foo;
            except {
               from AS2 action pref = 2; accept AS226;
               except {
                  from AS3 action pref = 3; accept {128.9.0.0/16};
               }
            }

   where the route 128.9.0.0/16 is originated by AS226, and AS226 is a
   member of the as set as-foo.  In this example, the route 128.9.0.0/16
   is accepted from AS3, any other route (not 128.9.0.0/16) originated
   by AS226 is accepted from AS2, and any other ASes' routes in as-foo
   is accepted from AS1.

   We can come to the same conclusion using the algebra defined above.
   Consider the inner exception specification:







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      from AS2 action pref = 2; accept AS226;
      except {
         from AS3 action pref = 3; accept {128.9.0.0/16};
      }

   is equivalent to

     {
      from AS3 action pref = 3; accept AS226 AND {128.9.0.0/16};
      from AS2 action pref = 2; accept AS226 AND NOT {128.9.0.0/16};
     }

   Hence, the original expression is equivalent to:

    import: from AS1 action pref = 1; accept as-foo;
            except {
               from AS3 action pref = 3;
                   accept AS226 AND {128.9.0.0/16};
               from AS2 action pref = 2;
                   accept AS226 AND NOT {128.9.0.0/16};
            }

   which is equivalent to

    import: {
       from AS3 action pref = 3;
                accept as-foo AND AS226 AND {128.9.0.0/16};
       from AS2 action pref = 2;
                accept as-foo AND AS226 AND NOT {128.9.0.0/16};
       from AS1 action pref = 1;
                accept as-foo AND NOT
                  (AS226 AND NOT {128.9.0.0/16} OR
                   AS226 AND {128.9.0.0/16});
       }

   Since AS226 is in as-foo and 128.9.0.0/16 is in AS226, it simplifies to:

    import: {
              from AS3 action pref = 3; accept {128.9.0.0/16};
              from AS2 action pref = 2;
                   accept AS226 AND NOT {128.9.0.0/16};
              from AS1 action pref = 1; accept as-foo AND NOT AS226;
            }

   In the case of the refine operator, the resulting set is constructed
   by taking the cartasian product of the two sides as follows: for each
   policy l in the left hand side and for each policy r in the right
   hand side, the peerings of the resulting policy are the peerings



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   common to both r and l; the filter of the resulting policy is the
   intersection of l's filter and r's filter; and action of the
   resulting policy is l's action followed by r's action.  If there are
   no common peerings, or if the intersection of filters is empty, a
   resulting policy is not generated.

   Consider the following example:

    import: { from AS-ANY action pref = 1;
                   accept community.contains({3560,10});
              from AS-ANY action pref = 2;
                   accept community.contains({3560,20});
            } refine {
               from AS1 accept AS1;
               from AS2 accept AS2;
               from AS3 accept AS3;
            }

   Here, any route with community {3560,10} is assigned a preference of
   1 and any route with community {3560,20} is assigned a preference of
   2 regardless of whom they are imported from.  However, only AS1's
   routes are imported from AS1, and only AS2's routes are imported from
   AS2, and only AS3's routes are imported form AS3, and no routes are
   imported from any other AS. We can reach the same conclusion using
   the above algebra.  That is, our example is equivalent to:

    import: {
      from AS1 action pref = 1;
           accept community.contains({3560,10}) AND AS1;
      from AS1 action pref = 2;
           accept community.contains({3560,20}) AND AS1;
      from AS2 action pref = 1;
           accept community.contains({3560,10}) AND AS2;
      from AS2 action pref = 2;
           accept community.contains({3560,20}) AND AS2;
      from AS3 action pref = 1;
           accept community.contains({3560,10}) AND AS3;
      from AS3 action pref = 2;
           accept community.contains({3560,20}) AND AS3;
    }

   Note that the common peerings between "from AS1" and "from AS-ANY"
   are those peerings in "from AS1".  Even though we do not formally
   define "common peerings", it is straight forward to deduce the
   definition from the definitions of peerings (please see Section
   6.1.1).

   Consider the following example:



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    import: {
      from AS-ANY action med = 0; accept {0.0.0.0/0^0-18};
      } refine {
           from AS1 at 7.7.7.1 action pref = 1; accept AS1;
           from AS1            action pref = 2; accept AS1;
        }

   where only routes of length 0 to 18 are accepted and med's value is
   set to 0 to disable med's effect for all peerings; In addition, from
   AS1 only AS1's routes are imported, and AS1's routes imported at
   7.7.7.1 are preferred over other peerings.  This is equivalent to:

    import: {
      from AS1 at 7.7.7.1 action med=0; pref=1;
           accept {0.0.0.0/0^0-18} AND AS1;
      from AS1 action med=0; pref=2; accept {0.0.0.0/0^0-18} AND AS1;

   The above syntax and semantics also apply equally to structured
   export policies with "from" replaced with "to" and "accept" is
   replaced with "announce".

7 dictionary Class

   The dictionary class provides extensibility to RPSL.  Dictionary
   objects define routing policy attributes, types, and routing
   protocols.  Routing policy attributes, henceforth called rp-
   attributes, may correspond to actual protocol attributes, such as the
   BGP path attributes (e.g. community, dpa, and AS-path), or they may
   correspond to router features (e.g. BGP route flap damping).  As new
   protocols, new protocol attributes, or new router features are
   introduced, the dictionary object is updated to include appropriate
   rp-attribute and protocol definitions.

   An rp-attribute is an abstract class; that is a data representation
   is not available.  Instead, they are accessed through access methods.
   For example, the rp-attribute for the BGP AS-path attribute is called
   aspath; and it has an access method called prepend which stuffs extra
   AS numbers to the AS-path attributes.  Access methods can take
   arguments.  Arguments are strongly typed.  For example, the method
   prepend above takes AS numbers as argument.

   Once an rp-attribute is defined in the dictionary, it can be used to
   describe policy filters and actions.  Policy analysis tools are
   required to fetch the dictionary object and recognize newly defined
   rp-attributes, types, and protocols.  The analysis tools may
   approximate policy analyses on rp-attributes that they do not





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   understand: a filter method may always match, and an action method
   may always perform no-operation.  Analysis tools may even download
   code to perform appropriate operations using mechanisms outside the
   scope of RPSL.

   We next describe the syntax and semantics of the dictionary class.
   This description is not essential for understanding dictionary
   objects (but it is essential for creating one).  Please feel free to
   skip to the RPSL Initial Dictionary subsection (Section 7.1).

   The attributes of the dictionary class are shown in Figure 18.  The
   dictionary attribute is the name of the dictionary object, obeying
   the RPSL naming rules.  There can be many dictionary objects, however
   there is always one well-known dictionary object "RPSL". All tools
   use this dictionary by default.

   The rp-attribute attribute has the following syntax:

    Attribute     Value                   Type
    dictionary    <object-name>           mandatory, single-valued,
                                           class key
    rp-attribute  see description in text optional, multi valued
    typedef       see description in text optional, multi valued
    protocol      see description in text optional, multi valued


                     Figure 18:  dictionary Class Attributes


      rp-attribute: <name>
         <method-1>(<type-1-1>, ..., <type-1-N1> [, "..."])
         ...
         <method-M>(<type-M-1>, ..., <type-M-NM> [, "..."])

   where <name> is the name of the rp-attribute; and <method-i> is the
   name of an access method for the rp-attribute, taking Ni arguments
   where the j-th argument is of type <type-i-j>.  A method name is
   either an RPSL name or one of the operators defined in Figure 19.
   The operator methods with the exception of operator() and operator[]
   can take only one argument.











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      operator=           operator==
      operator<<=         operator<
      operator>>=         operator>
      operator+=          operator>=
      operator-=          operator<=
      operator*=          operator!=
      operator/=          operator()
      operator.=          operator[]


                       Figure 19:  Operators

   An rp-attribute can have many methods defined for it.  Some of the
   methods may even have the same name, in which case their arguments
   are of different types.  If the argument list is followed by "...",
   the method takes a variable number of arguments.  In this case, the
   actual arguments after the Nth argument are of type <type-N>.

   Arguments are strongly typed.  A type of an argument can be one of
   the predefined types or one of the dictionary defined types.  The
   predefined type names are listed in Figure 20.  The integer and the
   real types can be followed by a lower and an upper bound to specify
   the set of valid values of the argument.  The range specification is
   optional.  We use the ANSI C language conventions for representing
   integer, real and string values.  The enum type is followed by a list
   of RPSL names which are the valid values of the type.  The boolean
   type can take the values true or false.  as_number, ipv4_address,
   address_prefix and dns_name types are as in Section 2.  filter type
   is a policy filter as in Section 6.

      integer[lower, upper]              as_number
      real[lower, upper]                 ipv4_address
      enum[name, name, ...]              address_prefix
      string                             address_prefix_range
      boolean                            dns_name
      rpsl_word                          filter
      free_text                          as_set_name
      email                              route_set_name


                     Figure 20:  Predefined Types

   The typedef attribute specifies a dictionary defined type.  Its
   syntax is as follows:

      typedef: <name> union <type-1>, ... , <type-N>
             | <name> list [<min_elems>:<max_elems>] of <type>




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   where <name> is the name of the type being defined and <type-M> is
   another type name, either predefined or dictionary defined.  In the
   first form, the type defined is either of the types <type-1> through
   <type-N> (analogous to unions in C[12]).  In the second form, the
   type defined is a list type where the list elements are of <type> and
   the list contains at least <min_elems> and at most <max_elems>
   elements.  The size specification is optional.  In this case, there
   is no restriction in the number of list elements.  A value of a list
   type is represented as a sequence of elements separated by the
   character "," and enclosed by the characters "{" and "}".

   A protocol attribute of the dictionary class defines a protocol and a
   set of peering options for that protocol (which are used in inet-rtr
   class in Section 9).  Its syntax is as follows:

      protocol: <name>
         MANDATORY | OPTIONAL <option-1>(<type-1-1>, ...,
                                         <type-1-N1> [, "..."])
         ...
         MANDATORY | OPTIONAL <option-M>(<type-M-1>, ...,
                                         <type-M-NM> [, "..."])

   where <name> is the name of the protocol; MANDATORY and OPTIONAL are
   keywords; and <option-i> is a peering option for this protocol,
   taking Ni many arguments.  The syntax and semantics of the arguments
   are as in the rp-attribute.  If the keyword MANDATORY is used the
   option is mandatory and needs to be specified for each peering of
   this protocol.  If the keyword OPTIONAL is used the option can be
   skipped.

7.1 Initial RPSL Dictionary and Example Policy Actions and Filters

dictionary:   RPSL
rp-attribute: # preference, smaller values represent higher preferences
              pref
              operator=(integer[0, 65535])
rp-attribute: # BGP multi_exit_discriminator attribute
              med
              operator=(integer[0, 65535])
              # to set med to the IGP metric: med = igp_cost;
              operator=(enum[igp_cost])
rp-attribute: # BGP destination preference attribute (dpa)
              dpa
              operator=(integer[0, 65535])
rp-attribute: # BGP aspath attribute
              aspath
              # prepends AS numbers from last to first order
              prepend(as_number, ...)



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typedef:      # a community value in RPSL is either
              #  - a 4 byte integer
              #  - internet, no_export, no_advertise (see RFC-1997)
              #  - two 2-byte integers to be concatanated eg. {3561,70}
              community_elm union
              integer[1, 4294967200],
              enum[internet, no_export, no_advertise],
              list[2:2] of integer[0, 65535]
typedef:      # list of community values { 40, no_export, {3561,70}}
              community_list
              list of community_elm
rp-attribute: # BGP community attribute
              community
              # set to a list of communities
              operator=(community_list)
              # order independent equality comparison
              operator==(community_list)
              # append community values
              operator.=(community_elm)
              append(community_elm, ...)
              # delete community values
              delete(community_elm, ...)
              # a filter: true if one of community values is contained
              contains(community_elm, ...)
              # shortcut to contains: community(no_export, {3561,70})
              operator()(community_elm, ...)
rp-attribute: # next hop router in a static route
              next-hop
              operator=(ipv4_address)       # a router address
              operator=(enum[self])         # router's own address
rp-attribute: # cost of a static route
              cost
              operator=(integer[0, 65535])
protocol: BGP4
          # as number of the peer router
          MANDATORY asno(as_number)
          # enable flap damping
          OPTIONAL flap_damp()
          OPTIONAL flap_damp(integer[0,65535],# penalty per flap
                             integer[0,65535],
                                # penalty value for supression
                             integer[0,65535],# penalty value for reuse
                             integer[0,65535],# halflife in secs when up
                             integer[0,65535],
                                # halflife in secs when down
                             integer[0,65535])# maximum penalty





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protocol: OSPF
protocol: RIP
protocol: IGRP
protocol: IS-IS
protocol: STATIC
protocol: RIPng
protocol: DVMRP
protocol: PIM-DM
protocol: PIM-SM
protocol: CBT
protocol: MOSPF


                     Figure 21:  RPSL Dictionary

   Figure 21 shows the initial RPSL dictionary.  It has seven rp-
   attributes: pref to assign local preference to the routes accepted;
   med to assign a value to the MULTI_EXIT_DISCRIMINATOR BGP attribute;
   dpa to assign a value to the DPA BGP attribute; aspath to prepend a
   value to the AS_PATH BGP attribute; community to assign a value to or
   to check the value of the community BGP attribute; next-hop to assign
   next hop routers to static routes; and cost to assign a cost to
   static routes.  The dictionary defines two types: community_elm and
   community_list.  community_elm type is either a 4-byte unsigned
   integer, or one of the keywords no_export or no_advertise (defined in
   [7]), or a list of two 2-byte unsigned integers in which case the two
   integers are concatenated to form a 4-byte integer.  (The last form
   is often used in the Internet to partition the community number
   space.  A provider uses its AS number as the first two bytes, and
   assigns a semantics of its choice to the last two bytes.)

   The initial dictionary (Figure 21) defines only options for the
   Border Gateway Protocol: asno and flap_damp.  The mandatory asno
   option is the AS number of the peer router.  The optional flap_damp
   option instructs the router to damp route flaps[19] when importing
   routes from the peer router.

   It can be specified with or without parameters.  If parameters are
   missing, they default to:

      flap_damp(1000, 2000, 750, 900, 900, 20000)

   That is, a penalty of 1000 is assigned at each route flap, the route
   is suppressed when penalty reaches 2000.  The penalty is reduced in
   half after 15 minutes (900 seconds) of stability regardless of
   whether the route is up or down.  A supressed route is reused when
   the penalty falls below 750.  The maximum penalty a route can be




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   assigned is 20,000 (i.e. the maximum suppress time after a route
   becomes stable is about 75 minutes).  These parameters are consistent
   with the default flap damping parameters in several routers.

   Policy Actions and Filters Using RP-Attributes

   The syntax of a policy action or a filter using an rp-attribute x is
   as follows:

       x.method(arguments)
       x "op" argument

   where method is a method and "op" is an operator method of the rp-
   attribute x.  If an operator method is used in specifying a composite
   policy filter, it evaluates earlier than the composite policy filter
   operators (i.e. AND, OR, NOT, and implicit or operator).

   The pref rp-attribute can be assigned a positive integer as follows:

      pref = 10;

   The med rp-attribute can be assigned either a positive integer or the
   word "igp_cost" as follows:

      med = 0;
      med = igp_cost;

   The dpa rp-attribute can be assigned a positive integer as follows:

      dpa = 100;

   The BGP community attribute is list-valued, that is it is a list of
   4-byte integers each representing a "community".  The following
   examples demonstrate how to add communities to this rp-attribute:

      community .= 100;
      community .= NO_EXPORT;
      community .= {3561,10};

   In the last case, a 4-byte integer is constructed where the more
   significant two bytes equal 3561 and the less significant two bytes
   equal 10.  The following examples demonstrate how to delete
   communities from the community rp-attribute:

      community.delete(100, NO_EXPORT, {3561,10});

   Filters that use the community rp-attribute can be defined as
   demonstrated by the following examples:



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      community.contains(100, NO_EXPORT, {3561,10});
      community(100, NO_EXPORT, {3561,10});             # shortcut

   The community rp-attribute can be set to a list of communities as
   follows:

      community = {100, NO_EXPORT, {3561,10}, 200};
      community = {};

   In this first case, the community rp-attribute contains the
   communities 100, NO_EXPORT, {3561,10}, and 200.  In the latter case,
   the community rp-attribute is cleared.  The community rp-attribute
   can be compared against a list of communities as follows:

      community == {100, NO_EXPORT, {3561,10}, 200};   # exact match

   To influence the route selection, the BGP as_path rp-attribute can be
   made longer by prepending AS numbers to it as follows:

      aspath.prepend(AS1);
      aspath.prepend(AS1, AS1, AS1);

   The following examples are invalid:

      med = -50;                     # -50 is not in the range
      med = igp;                     # igp is not one of the enum values
      med.assign(10);                # method assign is not defined
      community.append({AS3561,20}); # the first argument should be 3561

   Figure 22 shows a more advanced example using the rp-attribute
   community.  In this example, AS3561 bases its route selection
   preference on the community attribute.  Other ASes may indirectly
   affect AS3561's route selection by including the appropriate
   communities in their route announcements.

    aut-num: AS1
    export: to AS2 action community.={3561,90};
            to AS3 action community.={3561,80};
            announce AS1

    as-set: AS3561:AS-PEERS
    members: AS2, AS3

    aut-num: AS3561
    import: from AS3561:AS-PEERS
            action pref = 10;
            accept community.contains({3561,90})




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    import: from AS3561:AS-PEERS
            action pref = 20;
            accept community.contains({3561,80})
    import: from AS3561:AS-PEERS
            action pref = 20;
            accept community.contains({3561,70})
    import: from AS3561:AS-PEERS
            action pref = 0;
            accept ANY


           Figure 22:  Policy example using the community rp-attribute.

8 Advanced route Class

8.1 Specifying Aggregate Routes

   The components, aggr-bndry, aggr-mtd, export-comps, inject, and holes
   attributes are used for specifying aggregate routes [9].  A route
   object specifies an aggregate route if any of these attributes, with
   the exception of inject, is specified.  The origin attribute for an
   aggregate route is the AS performing the aggregation, i.e. the
   aggregator AS. In this section, we used the term "aggregate" to refer
   to the route generated, the term "component" to refer to the routes
   used to generate the path attributes of the aggregate, and the term
   "more specifics" to refer to any route which is a more specific of
   the aggregate regardless of whether it was used to form the path
   attributes.

   The components attribute defines what component routes are used to
   form the aggregate.  Its syntax is as follows:

      components: [ATOMIC] [[protocol <protocol>] <filter>
                            [protocol <protocol> <filter> ...]]

   where <protocol> is a routing protocol name such as BGP, OSPF or RIP
   (valid names are defined in the dictionary) and <filter> is a policy
   expression.  The routes that match one of these filters and are
   learned from the corresponding protocol are used to form the
   aggregate.  If <protocol> is omitted, it defaults to any protocol.
   <filter> implicitly contains an "AND" term with the more specifics of
   the aggregate so that only the component routes are selected.  If the
   keyword ATOMIC is used, the aggregation is done atomically [9].  If a
   <filter> is not specified it defaults to more specifics.  If the
   components attribute is missing, all more specifics without the
   ATOMIC keyword is used.





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      route: 128.8.0.0/15
      origin: AS1
      components: <^AS2>

      route: 128.8.0.0/15
      origin: AS1
      components: protocol BGP  {128.8.0.0/16^+}
                  protocol OSPF {128.9.0.0/16^+}


                     Figure 23:  Two aggregate route objects.


   Figure 23 shows two route objects.  In the first example, more
   specifics of 128.8.0.0/15 with AS paths starting with AS2 are
   aggregated.  In the second example, some routes learned from BGP and
   some routes learned form OSPF are aggregated.

   The aggr-bndry attribute is an expression over AS numbers and sets
   using operators AND, OR, and NOT.  The result defines the set of ASes
   which form the aggregation boundary.  If the aggr-bndry attribute is
   missing, the origin AS is the sole aggregation boundary.  Outside the
   aggregation boundary, only the aggregate is exported and more
   specifics are suppressed.  However, within the boundary, the more
   specifics are also exchanged.

   The aggr-mtd attribute specifies how the aggregate is generated.  Its
   syntax is as follow:

     aggr-mtd: inbound
             | outbound [<as-expression>]

   where <as-expression> is an expression over AS numbers and sets using
   operators AND, OR, and NOT. If <as-expression> is missing, it
   defaults to AS-ANY. If outbound aggregation is specified, the more
   specifics of the aggregate will be present within the AS and the
   aggregate will be formed at all inter-AS boundaries with ASes in
   <as-expression> before export, except for ASes that are within the
   aggregating boundary (i.e.  aggr-bndry is enforced regardless of
   <as-expression>).  If inbound aggregation is specified, the aggregate
   is formed at all inter-AS boundaries prior to importing routes into
   the aggregator AS. Note that <as-expression> can not be specified
   with inbound aggregation.  If aggr-mtd attribute is missing, it
   defaults to "outbound AS-ANY".







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      route:      128.8.0.0/15            route:      128.8.0.0/15
      origin:     AS1                     origin:     AS2
      components: {128.8.0.0/15^-}        components: {128.8.0.0/15^-}
      aggr-bndry: AS1 OR AS2              aggr-bndry: AS1 OR AS2
      aggr-mtd:   outbound AS-ANY         aggr-mtd:   outbound AS-ANY


                Figure 24:  Outbound multi-AS aggregation example.

   Figure 24 shows an example of an outbound aggregation.  In this
   example, AS1 and AS2 are coordinating aggregation and announcing only
   the less specific 128.8.0.0/15 to outside world, but exchanging more
   specifics between each other.  This form of aggregation is useful
   when some of the components are within AS1 and some are within AS2.

   When a set of routes are aggregated, the intent is to export only the
   aggregate route and suppress exporting of the more specifics outside
   the aggregation boundary.  However, to satisfy certain policy and
   topology constraints (e.g. a multi-homed component), it is often
   required to export some of the components.  The export-comps
   attribute equals an RPSL filter that matches the more specifics that
   need to be exported outside the aggregation boundary.  If this
   attribute is missing, more specifics are not exported outside the
   aggregation boundary.  Note that, the export-comps filter contains an
   implicit "AND" term with the more specifics of the aggregate.

   Figure 25 shows an example of an outbound aggregation.  In this
   example, the more specific 128.8.8.0/24 is exported outside AS1 in
   addition to the aggregate.  This is useful, when 128.8.8.0/24 is
   multi-homed site to AS1 with some other AS.

      route:      128.8.0.0/15
      origin:     AS1
      components: {128.8.0.0/15^-}
      aggr-mtd:   outbound AS-ANY
      export-comps: {128.8.8.0/24}


             Figure 25:  Outbound aggregation with export exception.

   The inject attribute specifies which routers perform the aggregation
   and when they perform it.  Its syntax is as follow:

     inject: [at <router-expression>] ...
             [action <action>]
             [upon <condition>]





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   where <action> is an action specification (see Section 6.1.2),
   <condition> is a boolean expression described below, and<router-
   expression> is an expression over router IP addresses and DNS names
   using operators AND, OR, and NOT. The DNS name can only be used if
   there is an inet-rtr object for that name that binds the name to IP
   addresses.

   All routers in <router-expression> and in the aggregator AS perform
   the aggregation.  If a <router-expression> is not specified, all
   routers inside the aggregator AS perform the aggregation.  The
   <action> specification may set path attributes of the aggregate, such
   as assign a preferences to the aggregate.

   The upon clause is a boolean condition.  The aggregate is generated
   if and only if this condition is true.  <condition> is a boolean
   expression using the logical operators AND and OR (i.e. operator NOT
   is not allowed) over:

      HAVE-COMPONENTS { list of prefixes }
      EXCLUDE { list of prefixes }
      STATIC

   The list of prefixes in HAVE-COMPONENTS can only be more specifics of
   the aggregate.  It evaluates to true when all the prefixes listed are
   present in the routing table of the aggregating router.  The list can
   also include prefix ranges (i.e. using operators ^-, ^+, ^n, and ^n-
   m).  In this case, at least one prefix from each prefix range needs
   to be present in the routing table for the condition to be true.  The
   list of prefixes in EXCLUDE can be arbitrary.  It evaluates to true
   when none of the prefixes listed is present in the routing table.
   The list can also include prefix ranges, and no prefix in that range
   should be present in the routing table.  The keyword static always
   evaluates to true.  If no upon clause is specified the aggregate is
   generated if an only if there is a component in the routing table
   (i.e.  a more specific that matches the filter in the components
   attribute).

      route:      128.8.0.0/15
      origin:     AS1
      components: {128.8.0.0/15^-}
      aggr-mtd:   outbound AS-ANY
      inject:     at 1.1.1.1 action dpa = 100;
      inject:     at 1.1.1.2 action dpa = 110;

      route:      128.8.0.0/15
      origin:     AS1
      components: {128.8.0.0/15^-}
      aggr-mtd:   outbound AS-ANY



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      inject:     upon HAVE-COMPONENTS {128.8.0.0/16, 128.9.0.0/16}
      holes:      128.8.8.0/24


                         Figure 26:  Examples of inject.

   Figure 26 shows two examples.  In the first case, the aggregate is
   injected at two routers each one setting the dpa path attribute
   differently.  In the second case, the aggregate is generated only if
   both 128.8.0.0/16 and 128.9.0.0/16 are present in the routing table,
   as opposed to the first case where the presence of just one of them
   is sufficient for injection.

   The holes attribute lists the component address prefixes which are
   not reachable through the aggregate route (perhaps that part of the
   address space is unallocated).  The holes attribute is useful for
   diagnosis purposes.  In Figure 26, the second example has a hole,
   namely 128.8.8.0/24.  This may be due to a customer changing
   providers and taking this part of the address space with it.

8.1.1 Interaction with policies in aut-num class

   An aggregate formed is announced to other ASes only if the export
   policies of the AS allows exporting the aggregate.  When the
   aggregate is formed, the more specifics are suppressed from being
   exported except to the ASes in aggr-bndry and except the components
   in export-comps.  For such exceptions to happen, the export policies
   of the AS should explicitly allow exporting of these exceptions.

   If an aggregate is not formed (due to the upon clause), then the more
   specifics of the aggregate can be exported to other ASes, but only if
   the export policies of the AS allows it.  In other words, before a
   route (aggregate or more specific) is exported it is filtered twice,
   once based on the route objects, and once based on the export
   policies of the AS.

      route:        128.8.0.0/16
      origin:       AS1

      route:        128.9.0.0/16
      origin:       AS1

      route:        128.8.0.0/15
      origin:       AS1
      aggr-bndry:   AS1 or AS2 or AS3
      aggr-mtd:     outbound AS3 or AS4 or AS5
      components:   {128.8.0.0/16, 128.9.0.0/16}
      inject:       upon HAVE-COMPONENTS {128.9.0.0/16, 128.8.0.0/16}



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      aut-num: AS1
      export:  to AS2 announce AS1
      export:  to AS3 announce AS1 and not {128.9.0.0/16}
      export:  to AS4 announce AS1
      export:  to AS5 announce AS1
      export:  to AS6 announce AS1


             Figure 27:  Interaction with policies in aut-num class.

   In Figure 27 shows an interaction example.  By examining the route
   objects, the more specifics 128.8.0.0/16 and 128.9.0.0/16 should be
   exchanged between AS1, AS2 and AS3 (i.e.  the aggregation boundary).
   Outbound aggregation is done to AS4 and AS5 and not to AS3, since AS3
   is in the aggregation boundary.  The aut-num object allows exporting
   both components to AS2, but only the component 128.8.0.0/16 to AS3.
   The aggregate can only be formed if both components are available.
   In this case, only the aggregate is announced to AS4 and AS5.
   However, if one of the components is not available the aggregate will
   not be formed, and any available component or more specific will be
   exported to AS4 and AS5.  Regardless of aggregation is performed or
   not, only the more specifics will be exported to AS6 (it is not
   listed in the aggr-mtd attribute).

   When doing an inbound aggregation, configuration generators may
   eliminating the aggregation statements on routers where import policy
   of the AS prohibits importing of any more specifics.

8.1.2 Ambiguity resolution with overlapping aggregates

   When several aggregate routes are specified and they overlap, i.e.
   one is less specific of the other, they must be evaluated more
   specific to less specific order.  When an aggregation is performed,
   the aggregate and the components listed in the export-comps attribute
   are available for generating the next less specific aggregate.  The
   components that are not specified in the export-comps attribute are
   not available.  A route is exportable to an AS if it is the least
   specific aggregate exportable to that AS or it is listed in the
   export-comps attribute of an exportable route.  Note that this is a
   recursive definition.

      route:        128.8.0.0/15
      origin:       AS1
      aggr-bndry:   AS1 or AS2
      aggr-mtd:     outbound
      inject:       upon HAVE-COMPONENTS {128.8.0.0/16, 128.9.0.0/16}





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      route:        128.10.0.0/15
      origin:       AS1
      aggr-bndry:   AS1 or AS3
      aggr-mtd:     outbound
      inject:       upon HAVE-COMPONENTS {128.10.0.0/16, 128.11.0.0/16}
      export-comps: {128.11.0.0/16}

      route:        128.8.0.0/14
      origin:       AS1
      aggr-bndry:   AS1 or AS2 or AS3
      aggr-mtd:     outbound
      inject:       upon HAVE-COMPONENTS {128.8.0.0/15, 128.10.0.0/15}
      export-comps: {128.10.0.0/15}


                  Figure 28:  Overlapping aggregations.

   In Figure 28, AS1 together with AS2 aggregates 128.8.0.0/16 and
   128.9.0.0/16 into 128.8.0.0/15.  Together with AS3, AS1 aggregates
   128.10.0.0/16 and 128.11.0.0/16 into 128.10.0.0/15.  But altogether
   they aggregate these four routes into 128.8.0.0/14.  Assuming all
   four components are available, a router in AS1 for an outside AS, say
   AS4, will first generate 128.8.0.0/15 and 128.10.0.0/15.  This will
   make 128.8.0.0/15, 128.10.0.0/15 and its exception 128.11.0.0/16
   available for generating 128.8.0.0/14.  The router will then generate
   128.8.0.0/14 from these three routes.  Hence for AS4, 128.8.0.0/14
   and its exception 128.10.0.0/15 and its exception 128.11.0.0/16 will
   be exportable.

   For AS2, a router in AS1 will only generate 128.10.0.0/15.  Hence,
   128.10.0.0/15 and its exception 128.11.0.0/16 will be exportable.
   Note that 128.8.0.0/16 and 128.9.0.0/16 are also exportable since
   they did not participate in an aggregate exportable to AS2.

   Similarly, for AS3, a router in AS1 will only generate 128.8.0.0/15.
   In this case 128.8.0.0/15, 128.10.0.0/16, 128.11.0.0/16 are
   exportable.

8.2 Specifying Static Routes

   The inject attribute can be used to specify static routes by using
   "upon static" as the condition:

     inject: [at <router>] ...
             [action <action>]
             upon static





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   In this case, the <router> executes the <action> and injects the
   route to the interAS routing system statically.  <action> may set
   certain route attributes such as a next-hop router or a cost.

   In the following example, the router 7.7.7.1 injects the route
   128.7.0.0/16.  The next-hop routers (in this example, there are two
   next-hop routers) for this route are 7.7.7.2 and 7.7.7.3 and the
   route has a cost of 10 over 7.7.7.2 and 20 over 7.7.7.3.

      route:  128.7.0.0/16
      origin: AS1
      inject: at 7.7.7.1 action next-hop = 7.7.7.2; cost = 10; upon static
      inject: at 7.7.7.1 action next-hop = 7.7.7.3; cost = 20; upon static

9 inet-rtr Class

   Routers are specified using the inet-rtr class.  The attributes of
   the inet-rtr class are shown in Figure 29.  The inet-rtr attribute is
   a valid DNS name of the router described.  Each alias attribute, if
   present, is a canonical DNS name for the router.  The local-as
   attribute specifies the AS number of the AS which owns/operates this
   router.

     Attribute  Value                    Type
     inet-rtr   <dns-name>               mandatory, single-valued,
                                           class key
     alias      <dns-name>               optional, multi-valued
     local-as   <as-number>              mandatory, single-valued
     ifaddr     see description in text  mandatory, multi-valued
     peer       see description in text  optional, multi-valued


                      Figure 29:  inet-rtr Class Attributes

   The value of an ifaddr attribute has the following syntax:

      <ipv4-address> masklen <integer> [action <action>]

   The IP address and the mask length are mandatory for each interface.
   Optionally an action can be specified to set other parameters of this
   interface.

   Figure 30 presents an example inet-rtr object.  The name of the
   router is "amsterdam.ripe.net".  "amsterdam1.ripe.net" is a canonical
   name for the router.  The router is connected to 4 networks.  Its IP
   addresses and mask lengths in those networks are specified in the
   ifaddr attributes.




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    inet-rtr: Amsterdam.ripe.net
    alias:    amsterdam1.ripe.net
    local-as: AS3333
    ifaddr:   192.87.45.190 masklen 24
    ifaddr:   192.87.4.28   masklen 24
    ifaddr:   193.0.0.222   masklen 27
    ifaddr:   193.0.0.158   masklen 27
    peer:     BGP4 192.87.45.195 asno(AS3334), flap_damp()


                           Figure 30:  inet-rtr Objects

   Each peer attribute, if present, specifies a protocol peering with
   another router.  The value of a peer attribute has the following
   syntax:

      <protocol> <ipv4-address> <options>

   where <protocol> is a protocol name, <ipv4-address> is the IP address
   of the peer router, and <options> is a comma separated list of
   peering options for <protocol>.  Possible protocol names and
   attributes are defined in the dictionary (please see Section 7).  In
   the above example, the router has a BGP peering with the router
   192.87.45.195 in AS3334 and turns the flap damping on when importing
   routes from this router.

10 Security Considerations

   This document describes RPSL, a language for expressing routing
   policies.  The language defines a maintainer (mntner class) object
   which is the entity which controls or "maintains" the objects stored
   in a database expressed by RPSL. Requests from maintainers can be
   authenticated with various techniques as defined by the "auth"
   attribute of the maintainer object.

   The exact protocols used by IRR's to communicate RPSL objects is
   beyond the scope of this document, but it is envisioned that several
   techniques may be used, ranging from interactive query/update
   protocols to store and forward protocols similar to or based on
   electronic mail (or even voice telephone calls).  Regardless of which
   protocols are used in a given situation, it is expected that
   appropriate security techniques such as IPSEC, TLS or PGP/MIME will
   be utilized.








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11 Acknowledgements

   We would like to thank Jessica Yu, Randy Bush, Alan Barrett, David
   Kessens, Bill Manning, Sue Hares, Ramesh Govindan, Kannan Varadhan,
   Satish Kumar, Craig Labovitz, Rusty Eddy, David J. LeRoy, David
   Whipple, Jon Postel, Deborah Estrin, Elliot Schwartz, Joachim
   Schmitz, Mark Prior, Tony Przygienda, David Woodgate, and the
   participants of the IETF RPS Working Group for various comments and
   suggestions.

References

    [1] Internet Routing Registry. Procedures.
        http://www.ra.net/RADB.tools.docs/,
        http://www.ripe.net/db/doc.html.

    [2] Alaettinouglu, C., Meyer, D., and J.  Schmitz, "Application of
        Routing Policy Specification Language (RPSL) on the Internet",
        Work in Progress.

    [3] T.  Bates. Specifying an `Internet Router' in the Routing
        Registry.  Technical Report RIPE-122, RIPE, RIPE NCC, Amsterdam,
        Netherlands, October 1994.

    [4] T.  Bates, E.  Gerich, L. Joncheray, J-M. Jouanigot, D.
        Karrenberg, M.  Terpstra, and J.  Yu.  Representation of IP
        Routing Policies in a Routing Registry.  Technical Report ripe-
        181, RIPE, RIPE NCC, Amsterdam, Netherlands, October 1994.

    [5] Bates, T., Gerich, E., Joncheray, L., Jouanigot, J.M.,
        Karrenberg, D., Terpstra, M., and J.  Yu, "Representation of IP
        Routing Policies in a Routing Registry," RFC 1786, March 1995.

    [6] T. Bates, J-M. Jouanigot, D. Karrenberg, P. Lothberg, and
        M. Terpstra.  Representation of IP Routing Policies in the RIPE
        Database.  Technical Report ripe-81, RIPE, RIPE NCC, Amsterdam,
        Netherlands, February 1993.

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

    [8] Crocker, D., "Standard for the format of ARPA Internet text
        messages, STD 11, RFC 822, August 1982.

    [9] V.  Fuller, T.  Li, J. Yu, and K. Varadhan.  Classless Inter-
        Domain Routing (CIDR): an Address Assignment and Aggregation
        Strategy, 1993.




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    [10] D. Karrenberg and T. Bates.  Description of Inter-AS Networks
         in the RIPE Routing Registry.  Technical Report RIPE-104, RIPE,
         RIPE NCC, Amsterdam, Netherlands, December 1993.

    [11] D.  Karrenberg and M.  Terpstra.  Authorisation and
         Notification of Changes in the RIPE Database. Technical Report
         ripe-120, RIPE, RIPE NCC, Amsterdam, Netherlands, October 1994.

    [12] B.  W.  Kernighan and D.  M.  Ritchie.  The C Programming
         Language. Prentice-Hall, 1978.

    [13] Kessens, D., Woeber, W., and D. Conrad, "RIDE referencing",
         Work in Progress.

    [14] A.  Lord and M.  Terpstra.  RIPE Database Template for
         Networks and Persons. Technical Report ripe-119, RIPE, RIPE
         NCC, Amsterdam, Netherlands, October 1994.

    [15] A.  M. R.  Magee.  RIPE NCC Database Documentation.  Technical
         Report RIPE-157, RIPE, RIPE NCC, Amsterdam, Netherlands, May
         1997.

    [16] Mockapetris, P., "Domain names - concepts and facilities,"
         STD 13, RFC 1034, November 1987.

    [17] Y.  Rekhter.  Inter-Domain Routing Protocol (IDRP).  Journal
         of Internetworking Research and Experience, 4:61--80, 1993.

    [18] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4 (BGP-4),"
         RFC 1771, March 1995.

    [19] Villamizar, C., Chandra, R., and R. Govindan, "BGP Route
         Flap Damping", Work in Progress.

A Routing Registry Sites

   The set of routing registries as of November 1996 are RIPE, RADB,
   CANet, MCI and ANS. You may contact one of these registries to find
   out the current list of registries.












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RFC 2280                          RPSL                      January 1998


B Authors' Addresses

   Cengiz Alaettinoglu
   USC Information Sciences Institute
   4676 Admiralty Way, Suite 1001
   Marina del Rey, CA  90292
   EMail: cengiz@isi.edu


   Tony Bates
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134
   EMail: tbates@cisco.com


   Elise Gerich
   At Home Network
   385 Ravendale Drive
   Mountain View, CA 94043
   EMail: epg@home.net


   Daniel Karrenberg
   RIPE Network Coordination Centre (NCC)
   Kruislaan 409
   NL-1098 SJ Amsterdam
   Netherlands
   EMail: dfk@ripe.net


   David Meyer
   University of Oregon
   Eugene, OR 97403
   EMail: meyer@antc.uoregon.edu


   Marten Terpstra
   c/o Bay Networks, Inc.
   2 Federal St
   Billerica MA 01821
   EMail: marten@BayNetworks.com


   Curtis Villamizar
   ANS
   EMail: curtis@ans.net




Alaettinoglu, et. al.       Standards Track                    [Page 52]

RFC 2280                          RPSL                      January 1998


C  Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























Alaettinoglu, et. al.       Standards Track                    [Page 53]


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