Network Working Group L. Blunk
Internet-Draft Merit Network
Expires: November 5, 2003 J. Damas
Internet Software Consortium
F. Parent
Viagenie
A. Robachevski
RIPE NCC
May 7, 2003
RPSLng
draft-blunk-rpslng-00.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This memo presents a new set of simple extensions to the RPSL
language enabling the language to document routing policies for the
IPv6 and multicast address families currently used in the Internet.
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1. Introduction
RFC 2622 [1] defines the RPSL language for the IPv4 unicast routing
protocols and a series of guidelines for extending the RPSL language
itself. Additionally, security extensions to the RPSL language are
specificed in RFC 2725 [2].
This document proposes to extend RPSL according to the following
goals and requirements:
provide RPSL extensibility in the dimension of address families.
Specifically, to allow users to document routing policy for ipv6
and multicast.
the extensions must be backwards compatible and minimise the risk
of breaking existing tools. For instance, introducing a new class
or attribute would less likely impact a tool or script than
changing the syntax of an existing attribute. Section 10 of RFC
2622 [1] provides guidelines for extending RPSL.
clarity and non-ambiguity: RPSL information is used by software
tools and by humans.
minimise duplication of information, particularly when routing
policies for different address families are the same.
Internet Routing Registry (IRR) system requirements -- It is
important to consider the ramifications of RPSL extensions on IRR
systems. The capabilities of IRR servers, as well as the
established operational practices of users who interact with these
servers, must be considered.
An important point to note is the fact that there are two address
families, corresponding to the two versions of the IP protocol
currently in use in the Internet, but there are at least four
distinct routing policies that need to be described (IPv4
{unicast|multicast}, IPv6 {unicast|multicast}).
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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.
Use of existing import, export, and default attributes is not a good
option since it breaks backward compatibility and could undermine
clarity in the expressions.
Keeping this in mind, the "import:", "export:", and "default:"
attributes implicitly specify ipv4 unicast policy and remain as
defined previously in RPSL, and new multi-protocol (prefixed with the
string "mp-") attributes are introduced. These will be described
below.
2.1 The afi dictionary attribute
In this section we introduce a new dictionary attribute:
Address family, <afi>, is an RPSL list of address families for which
the policy expression should be evaluated. <afi> is mandatory within
the new multi-protocol attributes introduced in this document.
The possible values for <afi> are:
ipv4
ipv4.unicast (equivalent to ipv4)
ipv4.multicast
ipv6
ipv6.unicast (equivalent to ipv6)
ipv6.multicast
Appearance of these values in an attribute's value must be preceded
by the keyword afi.
An <afi-list> is defined as a comma separated list of one or more afi
values.
2.2 ipv6_address predefined type and next-hop dictionary extension
In order to support IPv6 addresses specificied with the next-hop
rp-attribute, a new predefined dictionary type entitled ipv6_address
is added to the RPSL dictionary. In addition, the next-hop
rp-attribute is re-defined in the dictionary as follows:
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rp-attribute: # next hop router in a static route
next-hop
operator=(union ipv4_address, ipv6_address, enum[self])
2.3 mp-import, mp-export, and mp-default
Three new policy attributes are introduced:
mp-import:
mp-export:
mp-default:
These attributes incorporate the afi (address-family) specification.
The mp-import and mp-export attributes have both a basic policy
specification and a more powerful structured policy specification.
The syntax for the basic policy specification of the mp-import and
mp-export attributes is as follows:
mp-import: [protocol <protocol-1>] [into <protocol-2>]
afi <afi-list>
from <peering-1> [action <action-1>]
. . .
from <peering-N> [action <action-N>]
accept <filter>
mp-export: [protocol <protocol-1>] [into <protocol-2>]
afi <afi-list>
to <peering-1> [action <action-1>]
. . .
to <peering-N> [action <action-N>]
announce <filter>
The mp-import and mp-export policies can be structured. As with RFC
2622 [1], structured policies are recommended only to advanced RPSL
users. For the sake of brevity, only the mp-import structured policy
syntax is defined below. The mp-export structured policy syntax is
expressed in a symmetric way to the mp-import attribute.
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mp-import ::=
[protocol <protocol1>] [into <protocol2>] <importexpression>
<importexpression> ::=
afi <afi-list> <import-term> accept <filter> |
afi <afi-list> <import-term> accept <filter> except
<importexpression> |
afi <afi-list> <import-term> accept <filter> refine
<importexpression>
<import-term> ::= <import-factor> |
{
<import-factor>
...
<import-factor>
}
<import-factor> ::= from <peering> [action <action>];
The <peering> specification indicates the AS (and the router if
present)
<peering> ::= <as-expression> [<router-expression-1>]
[at <router-expression-2>] |
<peering-set-name>
with <router-expression-1> and <router-expression-2> being
expressions over router IPv4 or IPv6 addresses (specifying their
address family with the use of the appropriate "afi <afi>" term),
inet-rtr names, and rtr-set names using operators AND, OR, and
EXCEPT.
In the same manner, the <filter> expression is the extension of the
RPSL <filter> expression [section 5.4 of RFC 2622 [1]], requiring the
presence of an "afi <afi>" term before each address or address-prefix
set.
The address family may be specified at any level of nesting of
<importexpression>, and is valid only within the <importexpression>
that contains it.
Therefore in the example
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aut-num: AS65534
mp-import: afi ipv6.unicast,ipv4 from AS1 action pref = 1; accept as-foo
except { afi ipv6.unicast,ipv4
from AS2 action pref = 2; accept AS226
except { afi ipv6.unicast
from AS3 action pref = 3; accept {3FFE:FFFF::/35}
}
}
the last (rightmost) "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 an <importexpression> is done by evaluating all of
its components. Evaluation of peering-sets and filter-sets is
constrained by the address family. Such constraints may result in a
{NOT ANY} <filter> or invalid <peering> depending on implicit or
explicit definitions of the address family in the set. In the latter
case an error is returned. {NOT ANY} filter may issue a warning.
Conflicts with explicit or implicit declarations are resolved at
runtime, that is during evaluation of a policy expression. For
example, when evaluating the following import policy:
aut-num: AS2
mp-import: afi ipv6 from AS1 accept {193.0.0.0/22}
the filter should be evaluated as {NOT ANY}.
aut-num: AS2
mp-import: afi ipv6.unicast {
from AS-ANY action med = 0; accept {3FFE:FFFF::/35};
} refine { afi ipv6.unicast
from AS1 at 3FFE:FFFF::1 action pref = 1; accept AS-UPSTREAM;
from prng6-ebgp-peers action pref = 2; accept AS1;
}
In this example only ipv6 prefixes originated by AS1 will be
collected, and while evaluating AS-UPSTREAM, an as-set, only ipv6
prefixes of the member ASes will be considered.
The "mp-default:" attribute is defined as
mp-default: afi <afi-list> to <peering> [action <action>]
[networks <filter>]
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using the definitions above for <peering> and <filter>
2.4 Additional value for <protocol>
A new value has been added for the <protocol> 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.
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3. New classes and attributes to support the extensions
3.1 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-sets 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 RFC2622].
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 IRR systems today.
3.2 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 attributes and meanings
with the route class. The exception being the inject, holes,
components, and exports-comps attributes must specify ipv6 prefixes
and addresses rather than ipv4 prefixes and addresses.
Attribute Value Type
route6 <ipv6-address-prefix> mandatory, single-valued,
class key
... (rest an in the route class, with exception listed above)
Example:
route6: 2001:610:240::/48
origin: AS3333
3.3 route-set Class
This class is used in <filter> expressions to specify a set of route
prefixes.
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A new attribute "mp-members:" is defined for this class with the
following syntax:
Attribute Value Type
mp-members afi <afi-list> list of <address-prefix-range> or optional,
<route-set-name> or multi-valued
<route-set-name><range-operator>
Example:
route-set: rs-foo
mp-members: afi ipv6 rs-bar # common members with afi constraint
mp-members: afi ipv6 rs-foo2, 3FFE:FFFF::/35 # v6 only members...
mp-members: afi ipv4 rs-foo3, 128.9.0.0/16
3.4 filter-set Class
The new "mp-filter:" attribute defines the set's policy filter. A
policy filter is a logical expression which when applied to a set of
routes returns a subset of these routes.
<filter> is defined in section Section 2.3.
The relevant parts of the updated filter-set class are shown below:
Attribute Value Type
filter-set <object-name> mandatory, single-valued, class key
filter <filter> optional, single-valued
mp-filter afi <afi> <filter> optional, single-valued
...
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.
3.5 peering-set Class
The peering set class is updated with a "mp-peering:" attribute, with
<peering> defined as in section Section 2.3
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Attribute Value Type
peering-set <object-name> mandatory, single-valued, class key
peering <peering> optional, multi-valued
mp-peering afi <afi> <peering> optional, multi-valued
...
Example:
peering-set: prng-ebgp-peers
mp-peering: afi ipv6 AS2 3FFE:FFFF::1 at 3FFE:FFFF::2
3.6 inet-rtr Class
This class gets two new attributes: "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 exisiting "peer:" attribute.
Below is the syntax definition for the new "interface:" attribure.
Attribute Value Type
interface afi <afi-list> <address> masklen <mask> optional,
[action <action>] multi-valued
[tunnel <remote-endpoint-address>,<encapsulation>]
The new syntax allows native IPv4 and IPv6 interface definitions as
well as the definition of tunnels as virtual interfaces. Without the
optional part, this attribute allows the same functionality as the
"ifaddr:" attribute but extends it to allow IPv6 addresses.
In the case of the interface being a tunnel, the optional part
describes the tunnel configuration as follows:
<remote-endpoint-address> indicates the IP address of the remote
endpoint of the tunnel. The address family must match that of the
local endpoint. <encapsulation> denotes the encapsulation used in the
tunnel and is one of {GRE,IPv6inIPv4,IPinIP,DVMRP}. Routing policies
for these routers should be described in the appropriate classes (eg.
peering and autnum).
The new "mp-peer:" attribute is defined below. The sole difference
between this attribute and the "peer:" attribute is the addition of
an <afi> specification to allow the use of IPv6 addresses.
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Attribute Value Type
mp-peer <protocol> afi <afi> <address> <options> or optional,
<protocol> <inet-rtr-name> <options> or multi-valued
<protocol> <rtr-set-name> <options> or
<protocol> <peering-set-name> <options>
3.7 rtr-set Class
The rtr-set class is extended with a new attribute, "mp-members:",
defined as
Attribute Value Type
mp-members list of <inet-rtr-name> or optional, multi-valued
<rtr-set-name> or
afi <afi> list of <address-prefix>
This allows specification of ipv4 or ipv6 as values for afi when
listing the routers that are members of the set name, or by
specifying their IPv4 of IPv6 addresses directly.
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4. RFC 2725 extensions
RFC 2725 [2] introduces an authorization model to address the
integrity of policy expressed in routing registries. In particular,
two new attributes were defined to support this authorization model,
namely, 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 lists when present in inet6num, route6, and aut-num
class objects. This optional list of prefixes is a comma-separated
list enclosed in curly braces. In the aut-num class, the IPv6
prefixes may be mixed with IPv4 prefixes.
Note the inclusion of IPv6 prefixes within a mnt-routes attribute in
an aut-num object may conflict with existing implementations of RPSL
which support only IPv4 prefixes. However, given the perceived lack
of implementation of this optional prefix list, it was considered
acceptable to extend the existing definition of the mnt-routes
attribute in the aut-num class rather than creating a new attribute
type.
Attribute Value Type
inet6num <ipv6-address-prefix> mandatory, single-valued, class key
netname <netname> mandatory, single-valued
descr <free-form> mandatory, multi-valued
country <country-code> mandatory, multi-valued
admin-c <nic-handle> mandatory, multi-valued
tech-c <nic-handle> mandatory, multi-valued
remarks <free-form> optional, multi-valued
notify <email-address> optional, multi-valued
mnt-lower list of <mntner-name> optional, multi-valued
mnt-routes list of <mntner-name> 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
The <country-code> must be a valid two-letter ISO 3166 country code
identifier. <netname> 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 [3].
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5. Security Considerations
This document describes extensions to RPSL, a language for expressing
routing policies. The extensions introduce ways of making the
configurations currently available for describing IPv4 routing
policies to IPv6. They introduce no additional security mechanisms
or threats.
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6. Acknowledgments
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, Mark Blanchet and David
Kessens participated constructively in many discussions. Finally,
Cengiz Alaettinoglu who is still the reference in all things RPSL.
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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] Damas, J. and A. Robachevski, "RIPE Database Reference Manual",
August 2002.
Authors' Addresses
Larry Blunk
Merit Network
EMail: ljb@merit.edu
Joao Damas
Internet Software Consortium
EMail: joao@psg.com
Florent Parent
Viagenie
EMail: Florent.Parent@viagenie.qc.ca
Andrei Robachevski
RIPE NCC
EMail: andrei@ripe.net
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