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. Many objects in RPSL have a name. An 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. An AS number x is represented as the string "ASx". That is, the AS 226 is represented as AS226. 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. 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. 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. 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. is as described in RFC-822[8]. is as described in RFC-1034[16]. 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. is a sequence of ASCII characters. is a name of an object of type X. That is is a name of a mntner object. Alaettinoglu, et. al. Standards Track [Page 5] RFC 2280 RPSL January 1998 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 mandatory, single-valued, class key descr mandatory, single-valued auth see description in text mandatory, multi-valued upd-to mandatory, multi-valued mnt-nfy optional, multi-valued tech-c mandatory, multi-valued admin-c mandatory, multi-valued remarks optional, multi-valued notify optional, multi-valued mnt-by list of mandatory, multi-valued changed mandatory, multi-valued source mandatory, single-valued to identify and authenticate update requests from this maintainer. It has the following syntax: auth: E.g. auth: NONE auth: CRYPT-PW dhjsdfhruewf auth: MAIL-FROM .*@ripe\.net The 's currently defined are: NONE, MAIL-FROM, PGP and CRYPT-PW. The 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: E.g. changed: johndoe@terabit-labs.nn 19900401 The identifies the person who made the last change. 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 mandatory, single-valued nic-hdl mandatory, single-valued, class key address mandatory, multi-valued phone see description in text mandatory, multi-valued fax-no same as phone optional, multi-valued e-mail mandatory, multi-valued Figure 3: person Class Attributes phone: + [ext. ] 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 mandatory, single-valued nic-hdl mandatory, single-valued, class key trouble optional, multi-valued address mandatory, multi-valued phone see description in text mandatory, multi-valued fax-no same as phone optional, multi-valued e-mail 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 mandatory, single-valued, class key origin mandatory, single-valued, class key withdrawn optional, single-valued member-of list of 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 mandatory, single-valued, class key members list of or optional, single-valued mbrs-by-ref list of 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 mandatory, single-valued, class key members list of or optional, single-valued mbrs-by-ref list of 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 mandatory, single-valued, class key as-name mandatory, single-valued member-of list of 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 ---------------------- ---------------------- | 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 [action ] . . . from [action ] accept The action specification is optional. The semantics of an import attribute is as follows: the set of routes that are matched by are imported from all the peers in ; while importing routes at , 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 [] [at ] where and are IP addresses of routers, is an AS number. must be the AS number of . Both and are optional. If both and are specified, this peering specification identifies only the peering between these two routers. If only is specified, this peering specification identifies all the peerings between and any of its peer routers in . If only is specified, this peering specification identifies all the peerings between any router in the local AS and . If neither nor is specified, this peering specification identifies all the peerings between any router in the local AS and any router in . 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 specification has the following syntax: [at ] where is an expression over AS numbers and sets using operators AND, OR, and NOT, and 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 to Alaettinoglu, et. al. Standards Track [Page 18] RFC 2280 RPSL January 1998 any of their peer routers in the ASes in . If 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 expres