Network Working Group J. Damas
Internet-Draft
Expires: June 18, 2003 F. Parent
Viagenie
A. Robachevski
RIPE NCC
December 18, 2002
RPSLng
draft-damas-rpslng-00.txt
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Copyright (C) The Internet Society (2002). 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 language
itself.
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 risk of
breaking existing tools. For instance, introducing a new class or
attribute will less probably break the tools than would changing
the format of an existing attribute. Section 10 of RFC2622
provides guidelines.
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
impossible to consider RPSL extensions as a pure language
modification. The capabilities and established operational
practices the users are familiar with when interacting with the
servers supporting IRR must also be taken into account.
An important point is to note 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:"and "export:" 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 and export attributes is not a good option
since itbreaks backward compatibility and could undermine clarity in
the expressions.
Keeping this in mind, the "import:" and "export:" attributes
implicitly specifyipv4 unicast policy and remain as defined
previously in RPSL and new multi-protocol (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 mp 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 mp-import and mp-export
Three new policy attributes are introduced:
mp-import:
mp-export:
mp-default:
These attributes incorporate the afi (address-family) specification.
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The definition of the "mp-import:" attribute is as follows:
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 RFC2622], 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
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<importexpression>, and is valid only within the <importexpression>
that contains it.
Therefore in the example
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.
Export policy is specified in the mp-export attribute. The mp-export
attribute is defined in a symmetric way to the mp-import attribute.
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The "mp-default:" attribute is defined as
mp-default: <peering> [action <action>] [networks <filter>]
using the definitions above for <peering> and <filter>
2.3 Additional values for <protocol>
Two new additional values are possible for <protocol> specification:
BGP4+
MBGP
both support the same options available for the BGP4 value.
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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
An ipv6 inter-AS route has specific properties, such as prefix
format, storage requirements that are different from the existing
route class.
Additionally, IRR systems use filters to select which type of
information is returned to the requester. These filters are designed
to operate by receiving a class type as operand. In the case of
route objects, the attribute which is the class's primary key is
where the route itself is defined.
It is therefore preferable to create a new route6 class than a
multi-protocol class.
Each inter-AS ipv6 route originated by an AS is thus specified as:
route6: [mandatory] [single] [primary/look-up key]
... (rest an in the route class)
route6: 2001:610:240::/48
origin: AS3333
...
3.3 route-set
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:
mp-members: afi <afi-list> list of <address-prefix-range> or
afi <afi-list> <route-set-name> or
afi <afi-list> <route-set-name><range-operator>
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
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.
mp-filter: afi <afi> <filter>
<filter> is defined in section Section 2.2.
The relevant parts of the new filter-set class are shown below:
filter-set: [mandatory] [ single] [class key]
mp-filter: [optional] [multiple]
filter: [optional] [multiple]
...
Note that according to this definition empty filters are possible and
should be handled correctly.
3.5 peering-set
An "mp-peering:" attribute is introduced in this class.
mp-peering: afi <afi> <peering> Section 2.2
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peering-set: [mandatory] [single] [class key]
peering: [optional] [multiple]
mp-peering: [optional] [multiple]
...
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 and new types such as
tunnels.
mp-peer which includes and extends the functionality of the exisiting
"peer:" attribute.
interface: afi <afi> <address> masklen <mask>
[ 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).
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mp-peer: <protocol> afi <afi> <address> <options> |
<protocol> <inet-rtr-name> <options> |
<protocol> <rtr-set-name> <options> |
<protocol> <peering-set-name> <options>
3.7 rtr-set Class
mp-members: list of <inet-rtr-name> |
<rtr-set-name> |
afi <afi> list of <address-prefix>
mp-members: [optional] [multiple]
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4. 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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5. Acknowldegments
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.
Authors' Addresses
Joao Damas
EMail: joao@psg.com
Florent Parent
Viagenie
EMail: Florent.Parent@viagenie.qc.ca
Andrei Robachevksi
RIPE NCC
EMail: andrei@ripe.net
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