Network Working Group L. Blunk
Request for Comments: 4012 Merit Network
Updates: 2725, 2622 J. Damas
Category: Standards Track Internet Systems Consortium
F. Parent
Hexago
A. Robachevsky
RIPE NCC
March 2005
Routing Policy Specification Language next generation (RPSLng)
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 (2005).
Abstract
This memo introduces a new set of simple extensions to the Routing
Policy Specification Language (RPSL), enabling the language to
document routing policies for the IPv6 and multicast address families
currently used in the Internet.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Specifying routing policy for different address families . . . 2
2.1. Ambiguity Resolution . . . . . . . . . . . . . . . . . . 3
2.2. The afi dictionary attribute . . . . . . . . . . . . . . 3
2.3. RPSL dictionary extensions . . . . . . . . . . . . . . . 4
2.4. IPv6 RPSL types . . . . . . . . . . . . . . . . . . . . 4
2.5. mp-import, mp-export, and mp-default . . . . . . . . . . 4
2.5.1. . . . . . . . . . . . . . . . . . . 6
2.5.2. . . . . . . . . . . . . . . . . . . 6
2.5.3. Policy examples . . . . . . . . . . . . . . . . 7
3. route6 Class . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Updates to existing Classes to support the extensions . . . . 8
4.1. as-set Class . . . . . . . . . . . . . . . . . . . . . . 8
4.2. route-set Class . . . . . . . . . . . . . . . . . . . . 9
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4.3. filter-set Class . . . . . . . . . . . . . . . . . . . . 9
4.4. peering-set Class . . . . . . . . . . . . . . . . . . . 9
4.5. inet-rtr Class . . . . . . . . . . . . . . . . . . . . . 10
4.6. rtr-set Class . . . . . . . . . . . . . . . . . . . . . 11
5. RFC 2725 Extensions . . . . . . . . . . . . . . . . . . . . . 11
5.1. Authorization model for route6 Objects . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 16
1. Introduction
RFC 2622 [1] defines the RPSL language for the IPv4 unicast routing
protocols and provides a series of guidelines for extending the RPSL
language itself. Additionally, security extensions to the RPSL
language are specified in RFC 2725 [2].
This document proposes to extend RPSL according to the following
goals and requirements:
o Provide RPSL extensibility in the dimension of address families,
specifically, to allow users to document routing policy for IPv6
and multicast.
o Extensions should be backward compatible with minimal impact on
existing tools and processes, following Section 10 of RFC 2622 [1]
for guidelines on extending RPSL.
o Maintain clarity and non-ambiguity: RPSL information is used by
humans in addition to software tools.
o Minimize duplication of information, particularly when routing
policies for different address families are the same.
The addition of IPv6 and multicast support to RPSL leads to four
distinct routing policies that need to be distinguished in this
specification, namely, (IPv4 {unicast|multicast}, IPv6
{unicast|multicast}).
2. Specifying Routing Policy for Different Address Families
Routing policy is currently specified in the aut-num class using
"import:", "export:", and "default:" attributes. Sometimes it is
important to distinguish policy for different address families, as
well as a unicast routing policy from a multicast one.
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Although the syntax of the existing import, export, and default
attributes could be extended, this would present backward
compatibility issues and could undermine clarity in the expressions.
Keeping this in mind, the "import:", "export:", and "default:"
attributes implicitly specify IPv4 unicast policy and will remain as
previously defined in RPSL, and new multi-protocol (prefixed with the
string "mp-") attributes will be introduced. These new "mp-"
attributes are described below.
2.1. Ambiguity Resolution
The same peering can be covered by more than one multi-protocol
policy attribute or by a combination of multi-protocol policy
attributes (when specifying IPv4 unicast policy) and the previously
defined IPv4 unicast policy attributes. In these cases,
implementations should follow the specification-order rule as defined
in Section 6.4 of RFC 2622 [1]. To break the ambiguity, the action
corresponding to the first peering specification is used.
2.2. The afi Dictionary Attribute
This section introduces a new dictionary attribute:
Address Family Identifier, , is an RPSL list of address families
for which a given routing policy expression should be evaluated.
is optional within the new multi-protocol attributes introduced
in the aut-num class. A pseudo identifier named "any" is defined to
allow for more compact policy expressions with converged routing
policy.
The possible values for are as follows:
ipv4.unicast
ipv4.multicast
ipv4 (equivalent to ipv4.unicast, ipv4.multicast)
ipv6.unicast
ipv6.multicast
ipv6 (equivalent to ipv6.unicast, ipv6.multicast)
any (equivalent to ipv4, ipv6)
any.unicast (equivalent to ipv4.unicast, ipv6.unicast)
any.multicast (equivalent to ipv4.multicast, ipv6.multicast)
Appearance of these values in an attribute must be preceded by the
keyword afi.
An is defined as a comma-separated list of one or more afi
values.
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2.3. RPSL Dictionary Extensions
In order to support IPv6 addresses specified with the next-hop rp-
attribute, a new predefined dictionary type entitled "ipv6_address"
is added to the RPSL dictionary. The definition of this type is
taken from Section 2.2 of RFC 3513 [3].
The next-hop rp-attribute is expanded in the dictionary as follows:
rp-attribute: # next hop router in a static route
next-hop
operator=(union ipv4_address, ipv6_address, enum[self])
A new value has been added for the dictionary
specification:
MPBGP
MPBGP is understood to be BGP4 with multi-protocol extensions (often
referred to as BGP4+). BGP4+ could not be used, as the '+' character
is not allowed by the RPSL specification in protocol names.
2.4. IPv6 RPSL Types
This document will reference three new IPv6 RPSL types, namely,
, , and . The and types are
defined in Sections 2.2 and 2.3 of RFC 3513 [3]. The type adds a range operator to the
type. The range operator is defined in Section 2 of RFC 2622 [1].
2.5. mp-import, mp-export, and mp-default
Three new policy attributes are introduced in the aut-num Class:
mp-import:
mp-export:
mp-default:
These attributes incorporate the afi (address-family) specification.
Note that the afi specification is optional. If no afi specification
is present, the policy expression is presumed to apply to all
protocol families, namely, ipv4.unicast, ipv4.multicast,
ipv6.unicast, and ipv6.multicast. This is the equivalent of the afi
specification "afi any". The mp-import and mp-export attributes have
both a basic policy specification and a more powerful structured
policy specification.
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The syntax for the mp-default attribute and the basic policy
specification of the mp-import and mp-export attributes is as
follows:
Attribute Value Type
mp-import [protocol ] [into ] optional,
[afi ] multi-valued
from [action ; ... ;]
. . .
from [action ; ... ;]
accept [;]
mp-export [protocol ] [into ] optional,
[afi ] multi-valued
to [action ; ... ;]
. . .
to [action ; ... ;]
announce [;]
mp-default [afi ] to optional,
[action ; ... ;] multi-valued
[networks ]
The mp-import and mp-export policies can be structured. As with RFC
2622 [1], structured policies are recommended only to advanced RPSL
users. The mp-import structured policy syntax is defined below.
Please note the semicolon at the end of an is
mandatory for structured policy expressions, while being optional on
non-structured policy expressions. The mp-export structured policy
syntax is expressed symmetrically to the mp-import attribute. The
structured syntax allows exceptions and refinements to policies by
use of the "except" and "refine" keywords. Further, the exceptions
and refinements may specify an optional "afi" list to restrict the
policy expression to particular address families.
Note that the definition allows subsequent or "cascading" refinements
and exceptions. RFC 2622 [1] incorrectly refers to these as "nested"
expressions. The syntax does not allow true nested expressions.
::=
from [action ; ... ;]
. . .
from [action ; ... ;]
accept ;
:: = import-factor |
{
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. . .
}
::= |
EXCEPT |
REFINE
::= [afi ]
mp-import: [protocol ] [into ]
2.5.1.
indicates the AS (and the router if present) and is
defined as follows:
::= []
[at ] |
where is an expression over AS numbers and AS sets
using operators AND, OR, and EXCEPT, and is an
expression over router ipv4-addresses or ipv6-addresses, inet-rtr
names, and rtr-set names using operators AND, OR, and EXCEPT. The
binary "EXCEPT" operator is the set subtraction operator and has the
same precedence as the operator AND (it is semantically equivalent to
"AND NOT" combination). That is, "(AS65001 OR AS65002) EXCEPT
AS65002" equals "AS65001".
2.5.2.
The policy filter expression is derived from the RPSL
policy filter expression defined in section 5.4 of RFC 2622
[1]. extends the expression to allow the
specification of IPv6 prefixes and prefix ranges. In particular, an
Address-Prefix Set expression in an expression may
include both IPv4 and IPv6 prefixes or prefix ranges. is
otherwise identical to the RPSL expression. Address-Prefix
Sets are enclosed in braces, '{' and '}'. The policy filter matches
the set of routes whose destination address-prefix is in the set.
For example:
{ 192.0.2.0/24, 2001:0DB8::/32 }
{ 2001:0DB8:0100::/48^+, 2001:0DB8:0200::/48^64 }
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2.5.3. Policy Examples
The address family may be specified in subsequent refine or except
policy expressions and is valid only within the policy expression
that contains it.
Therefore, in the example
aut-num: AS65534
mp-import: afi any.unicast from AS65001 accept as-foo;
except afi any.unicast {
from AS65002 accept AS65226;
} except afi ipv6.unicast {
from AS65003 accept {2001:0DB8::/32};
}
the last "except" is evaluated only for the IPv6 unicast address
family, while other import-expressions are evaluated for both the
IPv6 and IPv4 unicast address families.
The evaluation of a policy expression is done by evaluating each of
its components. Evaluation of peering-sets and filter-sets is
constrained by the address family. Such constraints may result in a
"NOT ANY" or invalid depending on implicit
or explicit definitions of the address family in the set. Conflicts
with explicit or implicit declarations are resolved at runtime during
the evaluation of a policy expression. An RPSL evaluation
implementation may wish to issue a warning in the case of a "NOT ANY"
. The following mp-import policy contains an example of
an that should be evaluated as "NOT ANY":
aut-num: AS65002
mp-import: afi ipv6.unicast from AS65001 accept {192.0.2.0/24}
3. route6 Class
The route6 class is the IPv6 equivalent of the route class. As with
the route class, the class key for the route6 class is specified by
the route6 and origin attribute pair. Other than the route6
attribute, the route6 class shares the same attribute names with the
route class. Although the attribute names remain identical, the
inject, components, exports-comps, holes, and mnt-routes attributes
must specify IPv6 prefixes and addresses rather than IPv4 prefixes
and addresses. This requirement is reflected by the specification of
, , and
below. has been previously defined. is related to as defined above in Section 2.5.2,
with the exception that only types are
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permitted. Similarly, is related to
as defined above in Section 2.5.1 with the
exception that only types are permitted.
Attribute Value Type
route6 mandatory, class key,
single-valued
origin mandatory, class key,
single-valued
member-of list of optional, multi-valued
inject [at ] ... optional, multi-valued
[action ]
[upon ]
components [ATOMIC] [[] optional, single-valued
[protocol ...]]
aggr-bndry optional, single-valued
aggr-mtd inbound or outbound optional, single-valued
[]
export-comps optional, single-valued
holes list of optional, multi-valued
mnt-lower list of optional, multi-valued
mnt-routes list of optional, multi-valued
[{list of } or ANY]
Example:
route6: 2001:0DB8::/32
origin: AS65001
4. Updates to Existing Classes to Support the Extensions
4.1. as-set Class
The as-set class defines a set of Autonomous Systems (AS), specified
either directly by listing them in the members attribute or
indirectly by referring to another as-set or using the mbrs-by-ref
facility. More importantly, "In a context that expects a route set
(e.g., members attribute of the route-set class), [...] an as-set
AS-X defines the set of routes that are originated by the ASes in
AS-X", (section 5.3 of RFC 2622 [1]).
The as-set class is therefore used to collect a set of route
prefixes, which may be restricted to a specific address family.
The existing as-set class does not need any modifications. The
evaluation of the class must be filtered to obtain prefixes belonging
to a particular address family using the traditional filtering
mechanism in use in Internet Routing Registry (IRR) systems today.
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4.2. route-set Class
This class is used to specify a set of route prefixes.
A new attribute "mp-members:" is defined for this class. This
attribute allows the specification of IPv4 or IPv6
address-prefix-ranges.
Attribute Value Type
mp-members list of ( optional, multi-valued
or
or
or )
Example:
route-set: rs-foo
mp-members: rs-bar
mp-members: 2001:0DB8::/32 # v6 member
mp-members: 192.0.2.0/24 # v4 member
4.3. filter-set Class
The new "mp-filter:" attribute defines the set's policy filter. A
policy filter is a logical expression that when applied to a set of
routes returns a subset of these routes. The relevant parts of the
updated filter-set class are shown below:
Attribute Value Type
filter-set mandatory, single-valued, class key
filter optional, single-valued
mp-filter optional, single-valued
Where is defined above in Section 2.5.2. While the
"filter:" and "mp-filter:" attributes are of type "optional", a
filter-set must contain one of these two attributes. Implementations
should reject instances where both attributes are defined in an
object, as the interpretation of such a filter-set is undefined.
4.4. peering-set Class
The peering set class is updated with a "mp-peering:" attribute.
Attribute Value Type
peering-set mandatory, single-valued, class key
peering optional, multi-valued
mp-peering optional, multi-valued
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Example:
peering-set: prng-ebgp-peers
mp-peering: AS65002 2001:0DB8::1 at 2001:0DB8::2
With defined as above in Section 2.5.1. While the
"peering:" and "mp-peering:" attributes are of type "optional", a
peering-set must contain at least one of these two attributes.
4.5. inet-rtr Class
Two new attributes are introduced to the inet-rtr class --
"interface:", which allows the definition of generic interfaces,
including the information previously contained in the "ifaddr:"
attribute, as well as support for tunnel definitions; and "mp-
peer:", which includes and extends the functionality of the existing
"peer:" attribute. The syntax definition for the "interface:"
attribute follows:
Attribute Value Type
interface or optional, multi-valued
masklen
[action ]
[tunnel ,]
The syntax allows native IPv4 and IPv6 interface definitions, as well
as the definition of tunnels as virtual interfaces. Without the
optional tunnel definition, this attribute allows the same
functionality as the "ifaddr:" attribute but extends it to allow IPv6
addresses.
If the interface is a tunnel, the syntax is as follows:
indicates the IPv4 or IPv6 address of the
remote endpoint of the tunnel. The address family must match that of
the local endpoint. denotes the encapsulation used
in the tunnel and is one of {GRE,IPinIP} (note that the outer and
inner IP protocol versions can be deduced from the interface context
-- for example, IPv6-in-IPv4 encapsulation is just IPinIP). Routing
policies for these routers should be described in the appropriate
classes (e.g., aut-num).
The "mp-peer:" attribute is defined below. The difference between
this attribute and the "peer:" attribute is the inclusion of support
for IPv6 addresses.
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Attribute Value Type
mp-peer or optional,
or multi-valued
or
or
where is a protocol name, and is a
comma-separated list of peering options for , as provided
in the RPSL dictionary.
4.6. rtr-set Class
The rtr-set class is extended with a new attribute, "mp-members:".
This attribute extends the original "members:" attribute by allowing
the specification of IPv6 addresses. It is defined as follows:
Attribute Value Type
mp-members list of ( or optional, multi-valued
or
or
)
5. RFC 2725 Extensions
RFC 2725 [2] introduces an authorization model to address the
integrity of policy expressed in routing registries. Two new
attributes were defined to support this authorization model: the
"mnt-routes" and "mnt-lower" attributes.
In RPSLng, these attributes are extended to the route6 and inet6num
(described below) classes. Further, the syntax of the existing mnt-
routes attribute is modified to allow the optional specification of
IPv6 prefix range lists when present in inet6num, route6, and aut-num
class objects. This optional list of prefix ranges is a comma-
separated list enclosed in curly braces. In the aut-num class, the
IPv6 prefix ranges may be mixed with IPv4 prefix ranges. The keyword
"ANY" may also be used instead of prefix ranges. In the case of
inet6num and route6 objects, "ANY" refers to all more specifics of
the prefix in the class key field. For the aut-num class, "ANY"
literally means any prefix. The default when no additional set items
are specified is "ANY". An abbreviated definition of the aut-num
class with the updated syntax for the mnt-routes attribute is
presented below.
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Attribute Value Type
aut-num mandatory, class key,
single-valued
mnt-routes list of optional, multi-valued
[{list of ( or
)} or ANY]
The following is an example of mnt-routes usage. This example
authorizes MAINT-65001 to create route6 objects with an origin AS of
65002 for IPv6 address prefixes within the 2001:0DB8::/32^+ range,
and route objects with origin AS 65002 for IPv4 prefixes within the
192.0.2.0/24^+ range.
aut-num: AS65002
mnt-routes: MAINT-AS65001 {2001:0DB8::/32^+, 192.0.2.0/24^+}
Note, that the inclusion of IPv6 prefix ranges within a mnt-routes
attribute in an aut-num object may conflict with existing
implementations of RPSL that support only IPv4 prefix ranges.
However, given the perceived lack of implementation of this optional
prefix range list, it was considered more acceptable to extend the
existing definition of the mnt-routes attribute in the aut-num class
rather than to create a new attribute type.
Attribute Value Type
inet6num mandatory, single-valued,
class key
netname mandatory, single-valued
descr mandatory, multi-valued
country mandatory, multi-valued
admin-c mandatory, multi-valued
tech-c mandatory, multi-valued
remarks optional, multi-valued
notify optional, multi-valued
mnt-lower list of optional, multi-valued
mnt-routes list of optional, multi-valued
[{list of } or ANY]
mnt-by list of mandatory, multi-valued
changed mandatory, multi-valued
source mandatory, single-valued
The must be a valid two-letter ISO 3166 country code
identifier. is a symbolic name for the specified IPv6
address space. It does not have a restriction on RPSL reserved
prefixes. These definitions are taken from the RIPE Database
Reference Manual [4].
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5.1. Authorization Model for route6 Objects
Deletion and update of a route6 object is not different from other
objects, as defined in RFC 2725 [2]. Creation rules of a route6
object is replicated here from the corresponding rules for route
object in RFC 2725 [2] section 9.9.
When a route6 object is added, the submission must satisfy two
authentication criteria. It must match the authentication specified
in the aut-num object and that specified in either a route6 object
or, if no applicable route6 object is found, an inet6num object.
An addition is submitted with an AS number and IPv6 prefix as its
key. If the aut-num object does not exist on a route6 to add, then
the addition is rejected. If the aut-num exists, then the submission
is checked against the applicable maintainers. A search is then done
for the prefix, looking first for an exact match and then, failing
that, for the longest prefix match less specific than the prefix
specified. If this search succeeds, it will return one or more
route6 objects. The submission must match an applicable maintainer
in at least one of these route6 objects for the addition to succeed.
If the search for a route6 object fails, then a search is performed
for an inet6num object that exactly matches the prefix, or for the
most specific inet6num less specific than the route6 object
submission.
Once the aut-num and either a list of route6 objects or an inet6num
is found, the authorization is taken from these objects. The
applicable maintainer object is any referenced by the mnt-routes
attributes. If one or more mnt-routes attributes are present in an
object, the mnt-by or mnt-lower attributes are not considered. In
the absence of a mnt-routes attribute in a given object, the first
mnt-lower attributes are used (only if the given object is an
inet6num object and it is less specific than the route6 object to be
added). If no applicable mnt-lower attribute is found, then the
mnt-by attributes are used for that object. The authentication must
match one of the authorizations in each of the two objects.
6. Security Considerations
This document describes extensions to RFC 2622 [1] and RFC 2725 [2].
The extensions address the limitations of the aforementioned
documents with respect to IPv6 and multicast. The extensions do not
introduce any new security functionality or threats.
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Although the extensions introduce no additional security threats, it
should be noted that the original RFC 2622 [1] RPSL standard included
several weak and/or vulnerable authentication mechanisms: first, the
"MAIL-FROM" scheme, which can be easily defeated via source email
address spoofing; second, the "CRYPT-PW" scheme, which is subject to
dictionary attacks and password sniffing if RPSL objects are
submitted via unencrypted channels such as email; and, finally, the
"NONE" mechanism, which offers no protection for objects.
7. Acknowledgements
The authors wish to thank all the people who have contributed to this
document through numerous discussions, particularly Ekaterina
Petrusha, for highly valuable discussions and suggestions: Shane
Kerr, Engin Gunduz, Marc Blanchet, and David Kessens who participated
constructively in many discussions and Cengiz Alaettinoglu, who is
still the reference in all things RPSL.
8. References
8.1. Normative References
[1] Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D.,
Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra, "Routing
Policy Specification Language (RPSL)", RFC 2622, June 1999.
[2] Villamizar, C., Alaettinoglu, C., Meyer, D., and S. Murphy,
"Routing Policy System Security", RFC 2725, December 1999.
[3] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
Addressing Architecture", RFC 3513, April 2003.
8.2. Informative References
[4] Damas, J. and A. Robachevsky, "RIPE Database Reference Manual",
August 2002.
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Authors' Addresses
Larry Blunk
Merit Network
EMail: ljb@merit.edu
Joao Damas
Internet Systems Consortium
EMail: Joao_Damas@isc.org
Florent Parent
Hexago
EMail: Florent.Parent@hexago.com
Andrei Robachevsky
RIPE NCC
EMail: andrei@ripe.net
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Full Copyright Statement
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Blunk, et al. Standards Track [Page 16]
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