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rfc:rfc2280

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

Alaettinoglu, et. al. Standards Track [Page 1] RFC 2280 RPSL January 1998

     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.

Alaettinoglu, et. al. Standards Track [Page 2] 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

Alaettinoglu, et. al. Standards Track [Page 3] RFC 2280 RPSL January 1998

 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:

Alaettinoglu, et. al. Standards Track [Page 4] RFC 2280 RPSL January 1998

     ^- 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.

Alaettinoglu, et. al. Standards Track [Page 5] RFC 2280 RPSL January 1998

 <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

Alaettinoglu, et. al. Standards Track [Page 6] RFC 2280 RPSL January 1998

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

Alaettinoglu, et. al. Standards Track [Page 7] 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:

Alaettinoglu, et. al. Standards Track [Page 8] 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

Alaettinoglu, et. al. Standards Track [Page 9] 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.

Alaettinoglu, et. al. Standards Track [Page 10] RFC 2280 RPSL January 1998

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.

Alaettinoglu, et. al. Standards Track [Page 11] 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

Alaettinoglu, et. al. Standards Track [Page 12] RFC 2280 RPSL January 1998

    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

Alaettinoglu, et. al. Standards Track [Page 13] RFC 2280 RPSL January 1998

 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.

Alaettinoglu, et. al. Standards Track [Page 14] RFC 2280 RPSL January 1998

  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.

Alaettinoglu, et. al. Standards Track [Page 15] RFC 2280 RPSL January 1998

 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.

Alaettinoglu, et. al. Standards Track [Page 16] RFC 2280 RPSL January 1998

  1. ——————— ———————-

| 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:

Alaettinoglu, et. al. Standards Track [Page 17] RFC 2280 RPSL January 1998

             <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

Alaettinoglu, et. al. Standards Track [Page 18] RFC 2280 RPSL January 1998

 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,

Alaettinoglu, et. al. Standards Track [Page 19] RFC 2280 RPSL January 1998

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:

Alaettinoglu, et. al. Standards Track [Page 20] RFC 2280 RPSL January 1998

       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.

Alaettinoglu, et. al. Standards Track [Page 21] RFC 2280 RPSL January 1998

  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.

Alaettinoglu, et. al. Standards Track [Page 22] RFC 2280 RPSL January 1998

 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}

Alaettinoglu, et. al. Standards Track [Page 23] RFC 2280 RPSL January 1998

 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>

Alaettinoglu, et. al. Standards Track [Page 24] RFC 2280 RPSL January 1998

 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.

Alaettinoglu, et. al. Standards Track [Page 25] RFC 2280 RPSL January 1998

 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.

Alaettinoglu, et. al. Standards Track [Page 26] RFC 2280 RPSL January 1998

 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:

Alaettinoglu, et. al. Standards Track [Page 27] RFC 2280 RPSL January 1998

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.

Alaettinoglu, et. al. Standards Track [Page 28] RFC 2280 RPSL January 1998

  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>

Alaettinoglu, et. al. Standards Track [Page 29] RFC 2280 RPSL January 1998

 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:

Alaettinoglu, et. al. Standards Track [Page 30] RFC 2280 RPSL January 1998

    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

Alaettinoglu, et. al. Standards Track [Page 31] RFC 2280 RPSL January 1998

 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:

Alaettinoglu, et. al. Standards Track [Page 32] RFC 2280 RPSL January 1998

  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

Alaettinoglu, et. al. Standards Track [Page 33] RFC 2280 RPSL January 1998

 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.

Alaettinoglu, et. al. Standards Track [Page 34] RFC 2280 RPSL January 1998

    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>

Alaettinoglu, et. al. Standards Track [Page 35] RFC 2280 RPSL January 1998

 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, ...)

Alaettinoglu, et. al. Standards Track [Page 36] RFC 2280 RPSL January 1998

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

Alaettinoglu, et. al. Standards Track [Page 37] RFC 2280 RPSL January 1998

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

Alaettinoglu, et. al. Standards Track [Page 38] RFC 2280 RPSL January 1998

 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:

Alaettinoglu, et. al. Standards Track [Page 39] RFC 2280 RPSL January 1998

    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})

Alaettinoglu, et. al. Standards Track [Page 40] RFC 2280 RPSL January 1998

  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.

Alaettinoglu, et. al. Standards Track [Page 41] RFC 2280 RPSL January 1998

    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".

Alaettinoglu, et. al. Standards Track [Page 42] RFC 2280 RPSL January 1998

    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>]

Alaettinoglu, et. al. Standards Track [Page 43] RFC 2280 RPSL January 1998

 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

Alaettinoglu, et. al. Standards Track [Page 44] RFC 2280 RPSL January 1998

    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}

Alaettinoglu, et. al. Standards Track [Page 45] RFC 2280 RPSL January 1998

    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}

Alaettinoglu, et. al. Standards Track [Page 46] RFC 2280 RPSL January 1998

    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

Alaettinoglu, et. al. Standards Track [Page 47] RFC 2280 RPSL January 1998

 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.

Alaettinoglu, et. al. Standards Track [Page 48] RFC 2280 RPSL January 1998

  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.

Alaettinoglu, et. al. Standards Track [Page 49] RFC 2280 RPSL January 1998

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.

Alaettinoglu, et. al. Standards Track [Page 50] RFC 2280 RPSL January 1998

  [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.

Alaettinoglu, et. al. Standards Track [Page 51] 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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