Internet DRAFT - draft-ietf-bess-orf-covering-prefixes
draft-ietf-bess-orf-covering-prefixes
BESS Working Group H. Jeng
Internet-Draft AT&T
Intended status: Standards Track L. Jalil
Expires: September 7, 2015 Verizon
R. Bonica
Juniper Networks
K. Patel
Cisco Systems
L. Yong
Huawei Technologies
March 6, 2015
Covering Prefixes Outbound Route Filter for BGP-4
draft-ietf-bess-orf-covering-prefixes-06
Abstract
This document defines a new Outbound Route Filter (ORF) type, called
the "Covering Prefixes ORF (CP-ORF)". CP-ORF is applicable in
Virtual Hub-and-Spoke VPNs. It also is applicable in BGP/MPLS
Ethernet VPN (EVPN) networks.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 7, 2015.
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Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. CP-ORF Encoding . . . . . . . . . . . . . . . . . . . . . . . 3
3. Processing Rules . . . . . . . . . . . . . . . . . . . . . . 6
4. Applicability In Virtual Hub-and-Spoke VPNs . . . . . . . . . 9
4.1. Multicast Considerations . . . . . . . . . . . . . . . . 12
5. Applicability In BGP/MPLS Ethernet VPN (EVPN) . . . . . . . . 12
6. Clean-up . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 17
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
A BGP [RFC4271] speaker can send Outbound Route Filters (ORF)
[RFC5291] to a peer. The peer uses ORFs to filter routing updates
that it sends to the BGP speaker. Using ORF, a BGP speaker can
realize a "route pull" paradigm, in which the BGP speaker, on demand,
pulls certain routes from the peer.
This document defines a new ORF-type, called the "Covering Prefixes
ORF (CP-ORF)". A BGP speaker sends a CP-ORF to a peer in order to
pull routes that cover a specified host address. A prefix covers a
host address if it can be used to forward traffic towards that host
address. Section 3 provides a more complete description of covering
prefix selection criteria.
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CP-ORF is applicable in Virtual Hub-and-Spoke VPNs [RFC7024]
[RFC4364]. It also is applicable BGP/MPLS Ethernet VPN (EVPN)
[RFC7432] networks.
1.1. Terminology
This document uses the following terms:
o Address Family Identifier (AFI) - defined in [RFC4760]
o Subsequent Address Family Identifier (SAFI) - defined in [RFC4760]
o VPN IP Default Route - defined in [RFC7024].
o V-Hub - defined in [RFC7024].
o V-Spoke - defined in [RFC7024].
o BGP/MPLS Ethernet VPN (EVPN) - defined in [RFC7432]
o EVPN Instance (EVI) - defined in [RFC7432]
o Unknown MAC Route (UMR) - A regular EVPN MAC/IP Advertisement
route where the MAC Address Length is set to 48 and the MAC
address to 00:00:00:00:00:00
o Default MAC Gateway (DMG) - An EVPN PE that advertises a UMR
2. CP-ORF Encoding
RFC 5291 augments the BGP ROUTE-REFRESH message so that it can carry
ORF entries. When the ROUTE-REFRESH message carries ORF entries, it
includes the following fields:
o AFI [IANA.AFI]
o SAFI [IANA.SAFI]
o When-to-refresh (IMMEDIATE or DEFERRED)
o ORF Type
o Length (of ORF entries)
The ROUTE-REFRESH message also contains a list of ORF entries. Each
ORF entry contains the following fields:
o Action (ADD, REMOVE, or REMOVE-ALL)
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o Match (PERMIT or DENY)
The ORF entry may also contain Type-specific information. Type-
specific information is present only when the Action is equal to ADD
or REMOVE. It is not present when the Action is equal to REMOVE-ALL.
When the BGP ROUTE-REFRESH message carries CP-ORF entries, the
following conditions MUST be true:
o ORF Type MUST be equal to CP-ORF (65).
o The AFI MUST be equal to IPv4, IPv6 or L2VPN
o If the AFI is equal to IPv4 or IPv6, SAFI MUST be equal to MPLS-
labeled VPN address
o If the AFI is equal to L2VPN, the SAFI MUST be equal to BGP EVPN
o Match field MUST be equal to PERMIT
Figure 1 depicts the encoding of the CP-ORF type-specific
information.
+--------------------------------+
| Sequence (32 bits) |
+--------------------------------+
| Minlen (8 bits) |
+--------------------------------+
| Maxlen (8 bits) |
+--------------------------------+
| VPN Route Target (64 bits) |
+--------------------------------+
| Import Route Target (64 bits) |
+--------------------------------+
| Route Type (8 bits) |
+--------------------------------+
| Host Address |
| (0, 32, 48 or 128 bits) |
| ....
+--------------------------------+
Figure 1: CP-ORF Type-specific Encoding
The CP-ORF recipient uses the following fields to select routes
matching the CP-ORF:
o Sequence: Relative position of CP-ORF entry among other CP-ORF
entries
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o Minlen: Minimum length of selected route (measured in bits)
o Maxlen: Maximum length of selected route (measured in bits)
o VPN Route Target : VPN Route Target carried by selected route
o Route Type: Type of selected route
o Host Address: Address covered by selected route
See Section 3 for details.
The CP-ORF recipient marks routes that match CP-ORF with the Import
Route Target before advertising those routes to the CP-ORF
originator. See Section 3 for details.
If the ROUTE-REFRESH AFI is equal to IPv4:
o The value of Minlen MUST be less than or equal to 32
o The value of Maxlen MUST be less than or equal to 32
o The value of Minlen MUST be less than or equal to the value of
Maxlen
o The value of Route Type MUST be 0 (i.e., RESERVED)
o The Host Address MUST contain exactly 32 bits
If the ROUTE-REFRESH AFI is equal to IPv6:
o The value of Minlen MUST be less than or equal to 128
o The value of Maxlen MUST be less than or equal to 128
o The value of Minlen MUST be less than or equal to the value of
Maxlen
o The value of Route Type MUST be 0 (i.e., RESERVED)
o The Host Address MUST contain exactly 128 bits
If the ROUTE-REFRESH AFI is equal to L2VPN, the value of Route Type
MUST be one of the following values, taken from IANA EVPN Registry
[IANA.EVPN]:
o 1 - Ethernet Autodiscovery Route
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o 2 - MAC/IP Advertisement Route
o 3 - Inclusive Multicast Route
o 4 - Ethernet Segment Route
If the ROUTE-REFRESH AFI is equal to L2VPN and the value of Route
Type is equal to Ethernet Autodiscovery Route, Inclusive Multicast
Route, or Ethernet Segment Route:
o The value of Minlen MUST be equal to 0
o The value of Maxlen MUST be equal to 0
o The Host Address MUST be absent (i.e., contain 0 bits)
If the ROUTE-REFRESH AFI is equal to L2VPN and the value of Route
Type is equal to MAC/IP Advertisement Route:
o The value of Minlen MUST be less than or equal to 48
o The value of Maxlen MUST be less than or equal to 48
o The value of Minlen MUST be less than or equal to the value of
Maxlen
o The Host Address MUST contain exactly 48 bits.
3. Processing Rules
According to [RFC4271], every BGP speaker maintains a single Loc-RIB.
For each of its peers, the BGP speaker also maintains an Outbound
Filter and an Adj-RIB-Out. The Outbound Filter defines policy that
determines which Loc-RIB entries are processed into the corresponding
Adj-RIB-Out. Mechanisms such as RT-Contstrain [RFC4684] and ORF
[RFC5291] enable a router's peer to influence the Outbound Filter.
Therefore, the Outbound Filter for a given peer is constructed using
a combination of the locally configured policy and the information
received via RT-Constrain and ORF from the peer.
Using this model we can describe the operations of CP-ORF as follows:
When a BGP speaker receives a ROUTE-REFRESH message that contains a
CP-ORF, and that ROUTE-REFRESH message violates any of the encoding
rules specified in Section 2, the BGP speaker MUST ignore the entire
ROUTE-REFRESH message. It SHOULD also log the event. However, an
implementation MAY apply logging thresholds to avoid excessive
messaging or log file overflow.
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Otherwise, the BGP speaker processes each CP-ORF entry as indicated
by the Action field. If the Action is equal to ADD, the BGP speaker
adds the CP-ORF entry to the Outbound Filter associated with the peer
in the position specified by the Sequence field. If the Action is
equal to REMOVE, the BGP speaker removes the CP-ORF entry from the
Outbound Filter. If the Action is equal to REMOVE-ALL, the BGP
speaker removes all CP-ORF entries from the Outbound Filter.
Whenever the BGP speaker applies an Outbound Filter to a route
contained in its Loc-RIB, it evaluates the route in terms of the CP-
ORF entries first. It then evaluates the route in terms of the
remaining, non-CP-ORF entries. The rules for the former are
described below. The rules for the latter are outside the scope of
this document.
The following route types can match a CP-ORF:
o IPv4-VPN
o IPv6-VPN
o L2VPN
In order for an IPv4-VPN route or IPv6-VPN route to match a CP-ORF,
all of the following conditions MUST be true:
o the route carries an RT whose value is the same as the CP-ORF VPN
Route Target
o the route prefix length is greater than or equal to the CP-ORF
Minlen plus 64 (i.e., the length of a VPN Route Distinguisher)
o the route prefix length is less than or equal to the CP-ORF Maxlen
plus 64 (i.e., the length of a VPN Route Distinguisher)
o ignoring the Route Distinguisher, the leading bits of the route
prefix are identical to the leading bits of the CP-ORF Host
Address. CP-ORF Minlen defines the number of bits that must be
identical.
o Loc-RIB does not contain a more specific route that also satisfies
all of the above listed conditions.
The BGP speaker ignores Route Distinguishers when determining whether
a prefix matches a host address. For example, assume that a CP-ORF
carries the following information:
o Minlen equal to 1
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o Maxlen equal to 32
o Host Address equal to 192.0.2.1
Assume also that Loc-RIB contains routes for the following IPv4-VPN
prefixes, and that all of these routes carry an RT whose value is the
same as the CP-ORF VPN Route Target:
o 1:0.0.0.0/64.
o 2:192.0.2.0/88
o 3:192.0.2.0/89
Only the prefix 3:192.0.2.0/89 matches the CP-ORF. The prefix
1:0.0.0.0/64 does not match, because its length (64) is less than the
CP-ORF Minlen (1) plus the length of an L3VPN Route Distinguisher
(64). If Loc-RIB did not contain the prefix 3:192.0.2.0/89,
2:192.0.2.0/88 would match the CP-ORF. However, because Loc-RIB also
contains a more specific covering route (3:192.0.2.0/89),
2:192.0.2.0/88 does not match. Only 3:192.0.2.0/89 satisfies all of
the above listed match criteria. Note that the matching algorithm
ignored Route Distinguishers.
In order for an EVPN route to match a CP-ORF, all of the following
conditions MUST be true:
o the EVPN route type is equal to the CP-ORF Route Type
o the route carries an RT whose value is equal to the CP-ORF VPN
Route Target
In addition, if the CP-ORF Route Type is equal to MAC/IP
Advertisement Route, the following conditions also MUST be true:
o the EVPN Route MAC Address Length is greater than or equal to the
CP-ORF Minlen plus 64 (i.e., the length of a VPN Route
Distinguisher)
o the EVPN Route MAC Address Length is less than or equal to the CP-
ORF Maxlen plus 64 (i.e., the length of a VPN Route Distinguisher)
o ignoring the Route Distinguisher, the leading bits of the EVPN
Route MAC Address are identical to the leading bits of the CP-ORF
Host Address. CP-ORF Minlen defines the number of bits that must
be identical.
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If a route matches the selection criteria of a CP-ORF entry, and it
does not violate any subsequent rule specified by the Outbound Filter
(e.g., rules that reflect local policy, or rules that are due to RT-
Constrains), the BGP speaker places the route into the Adj-RIB-Out.
In Adj-RIB-Out, the BGP speaker adds the CP-ORF Import Route Target
to the list of Route Targets that the route already carries. The BGP
speaker also adds a Transitive Opaque Extended Community [RFC4360]
with subtype equal to CP-ORF (0x03). As a result of being placed in
Adj-RIB-Out, the route is advertised to the peer associated with the
Adj-RIB-Out.
Receiving CP-ORF entries with REMOVE or REMOVE-ALL Actions may cause
a route that has previously been installed in a particular Adj-RIB-
Out be excluded from that Adj-RIB-Out. In this case, as specified in
[RFC4271], "the previously advertised route in that Adj-RIB-Out MUST
be withdrawn from service by means of an UPDATE message".
RFC 5291 states that a BGP speaker should respond to a ROUTE REFRESH
message as follows:
"If the When-to-refresh indicates IMMEDIATE, then after processing
all the ORF entries carried in the message the speaker re-advertises
to the peer routes from the Adj-RIB-Out associated with the peer that
have the same AFI/SAFI as what is carried in the message, and taking
into account all the ORF entries for that AFI/SAFI received from the
peer. The speaker MUST re-advertise all the routes that have been
affected by the ORF entries carried in the message, but MAY also re-
advertise the routes that have not been affected by the ORF entries
carried in the message."
When the ROUTE-REFRESH message includes only CP-ORF entries, the BGP
speaker MUST re-advertise routes that have been affected by these CP-
ORF entries. It is RECOMMENDED not to re-advertise the routes that
have not been affected by the CP-ORF entries.
The behavior when the ROUTE-REFRESH message includes one or more CP-
ORF entries and one or more ORF entries of a different type remains
unchanged from that described in RFC 5291.
4. Applicability In Virtual Hub-and-Spoke VPNs
In a Virtual Hub-and-Spoke environment, VPN sites are attached to
Provider Edge (PE) routers. For a given VPN, a PE router acts in
exactly one of the following roles:
o As neither a V-hub nor a V-Spoke
o As a V-hub
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o As a V-spoke
To illustrate CP-ORF operation in conjunction with Virtual Hub-and-
Spoke assume the following:
o One of the sites in a particular VPN, RED-VPN, is connected to a
PE that acts as neither a V-hub nor a V-Spoke for RED-VPN. We
refer to this PE as PE1.
o Another site in RED-VPN is connected to another PE, and that PE
acts as a V-hub for RED-VPN. We refer to this PE as V-hub1.
o Yet another site in RED-VPN is connected to another PE, and that
PE acts as a V-spoke for RED-VPN. We refer to this PE as
V-spoke1.
All of these PEs advertise RED-VPN routes to a route reflector (RR).
They mark these routes with a route target, which we will call RT-
RED. In particular, PE1 advertises a RED-VPN route to a prefix that
we will call P. P covers a host address, that we will call H.
For the purpose of illustration also assume that the PEs and the RRs
use Route Target Constraint [RFC4684].
V-hub1 serves the RED-VPN. Therefore, V-hub1 advertises a VPN IP
default route for the RED-VPN to the RR, carrying the route target
RT-RED-FROM-HUB1.
V-spoke1 establishes a BGP session with the RR, negotiating the CP-
ORF capability, as well as the Multiprotocol Extensions Capability
[RFC4760]. Upon establishment of the BGP session, the RR does not
advertise any routes to V-spoke1. The RR will not advertise any
routes until it receives either a ROUTE-REFRESH message or a BGP
UPDATE message containing a Route Target Membership NLRI [RFC4684].
Immediately after the BGP session is established, V-spoke1 sends the
RR a BGP UPDATE message containing a Route Target Membership NLRI.
The Route Target Membership NLRI specifies RT-RED-FROM-HUB1 as its
route target. In response to the BGP-UPDATE message, the RR
advertises the VPN IP default route for the RED-VPN to V-spoke1.
This route carries the route target RT-RED-FROM-HUB1. V-spoke1
subjects this route to its import policy and accepts it because it
carries the route target RT-RED-FROM-HUB1.
Now, V-spoke1 begins normal operation, sending all of its RED-VPN
traffic through V-hub1. At some point, V-spoke1 determines that it
might benefit from a more direct route to H. (Criteria by which
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V-spoke1 determines that it needs a more direct route to H are beyond
the scope of this document.)
In order to discover a more direct route, V-spoke1 assigns a unique
numeric identifier to H. V-spoke1 then sends a ROUTE-REFRESH message
to the RR, containing the following information:
o AFI is equal to IPv4 or IPv6, as appropriate
o SAFI is equal to "MPLS-labeled VPN address"
o When-to-refresh is equal IMMEDIATE
o Action is equal to ADD
o Match is equal to PERMIT
o ORF Type is equal to CP-ORF
o CP-ORF Sequence is equal to the identifier associated with H
o CP-ORF Minlen is equal to 1
o CP-ORF Maxlen is equal to 32 or 128, as appropriate
o CP-ORF VPN Route Target is equal to RT-RED
o CP-ORF Import Route Target is equal to RT-RED-FROM-HUB1
o CP-ORF Route Type is equal to 0 (i.e., undefined)
o CP-ORF Host Address is equal H
Upon receipt of the ROUTE-REFRESH message, the RR MUST ensure that it
carries all routes belonging to the RED-VPN. In at least one special
case, where all of the RR clients are V-spokes and none of the RR
clients are V-hubs, the RR will lack some or all of the required RED-
VPN routes. So, the RR sends a BGP UPDATE message containing a Route
Target Membership NLRI for VPN-RED to all of its peers. This causes
the peers to advertise VPN-RED routes to the RR, if they have not
done so already.
Next, the RR adds the received CP-ORF to the Outbound Filter
associated with V-spoke1. Using the procedures in Section 3, the RR
determines whether any of the routes in its Loc-RIB satisfy the
selection criteria of the newly updated Outbound Filter. If any
routes satisfy the match criteria, they are added to the Adj-RIB-Out
associated with V-spoke1. In Adj-RIB-Out, the RR adds RT-RED-FROM-
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HUB1 to the list of Route Targets that the route already carries.
The RR also adds a Transitive Opaque Extended Community [RFC4360]
with subtype equal to CP-ORF. Finally, RR advertises the newly added
routes to V-spoke1. In this example, the RR advertises P to V-Spoke1
with a next-hop of PE1.
V-spoke1 subjects the advertised routes to its import policy and
accepts them because they carry the route target RT-RED-FROM-HUB1.
V-spoke1 may repeat this process whenever it discovers another flow
that might benefit from a more direct route to its destination.
4.1. Multicast Considerations
When applying Multicast VPN [RFC6513][RFC6514] procedures, routes
bearing a Transitive Opaque Extended Community [RFC4360] with subtype
equal to CP-ORF MUST NOT be used to determine Eligible Upstream
Multicast Hops (UMH).
5. Applicability In BGP/MPLS Ethernet VPN (EVPN)
In a EVPN environment, CE devices are attached to Provider Edge (PE)
routers. A CE can be a host, a router or a switch. For a given EVPN
Instance (EVI), a PE router acts in exactly one of the following
roles:
o As neither a Default MAC Gateway (DMG) nor a Spoke
o As a DMG
o As a Spoke
To illustrate CP-ORF operation in the EVPN environment assume the
following:
o A CE device in a particular EVI, RED-EVI, is connected to a PE
that acts as neither a DMG nor a Spoke for RED-EVI. We refer to
this PE as PE1.
o Another CE device in RED-EVI is connected to another PE, and that
PE acts as a DMG for RED-EVI. We refer to this PE as DMG1.
o Yet another CE device in RED-EVI is connected to another PE, and
that PE acts as a Spoke for RED-EVI. We refer to this PE as
Spoke1.
All of these PEs advertise RED-EVI routes to a RR. They mark these
routes with a route target, which we will call RT-RED. In
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particular, PE1 advertises a RED-EVI route to a MAC Address that we
will call M.
The RED-EVI VRFs on all of these PEs are provisioned to import EVPN
routes that carry RT-RED.
Since DMG1 acts as a DMG for RED-EVI, DMG1 advertises a Unknown MAC
Route (UMR) for the RED-EVI to the RR, carrying the route target RT-
RED. The UMR is characterized as follows:
o EVPN Route Type is equal to MAC/IP Advertisement Route
o MAC address length is equal to 0
o IP address length is equal to 0
Spoke1 establishes a BGP session with the RR, negotiating the CP-ORF
capability, as well as the Multiprotocol Extensions Capability
[RFC4760]. Upon establishment of the BGP session, the RR does not
advertise any routes to Spoke1. The RR will not advertise any routes
until it receives a ROUTE-REFRESH message.
Immediately after the BGP session is established, Spoke1 sends the RR
a ROUTE REFRESH message containing the following information:
o AFI is equal to L2VPN
o SAFI is equal to BGP EVPN
o When-to-refresh is equal IMMEDIATE
o Action is equal to ADD
o Match is equal to PERMIT
The ROUTE REFRESH message also contains four ORF entries. The first
ORF entry contains the following information:
o ORF Type is equal to CP-ORF
o CP-ORF Sequence is equal 1
o CP-ORF Minlen is equal to 0
o CP-ORF Maxlen is equal to 0
o CP-ORF VPN Route Target is equal to RT-RED
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o CP-ORF Import Route Target is equal to RT-RED
o CP-ORF Route Type is equal to 1 (Ethernet Autodiscovery Route)
The second ORF entry contains the following information:
o ORF Type is equal to CP-ORF
o CP-ORF Sequence is equal 2
o CP-ORF Minlen is equal to 0
o CP-ORF Maxlen is equal to 0
o CP-ORF VPN Route Target is equal to RT-RED
o CP-ORF Import Route Target is equal to RT-RED
o CP-ORF Route Type is equal to 2 (MAC/IP Advertisement Route)
The third ORF entry contains the following information:
o ORF Type is equal to CP-ORF
o CP-ORF Sequence is equal 3
o CP-ORF Minlen is equal to 0
o CP-ORF Maxlen is equal to 0
o CP-ORF VPN Route Target is equal to RT-RED
o CP-ORF Import Route Target is equal to RT-RED
o CP-ORF Route Type is equal to 3 (Inclusive Multicast Route)
The fourth ORF entry contains the following information:
o ORF Type is equal to CP-ORF
o CP-ORF Sequence is equal 4
o CP-ORF Minlen is equal to 0
o CP-ORF Maxlen is equal to 0
o CP-ORF VPN Route Target is equal to RT-RED
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o CP-ORF Import Route Target is equal to RT-RED
o CP-ORF Route Type is equal to 4 (Ethernet Segment Route)
In response to the ROUTE REFRESH message, the RR advertises the
following to V-spoke1:
o All Ethernet Autodiscovery Routes belonging to RED-EVI
o A UMR advertised by DMG1 and belonging to RED-EVI
o All Inclusive Multicast Routes belonging to RED-EVI
o All Ethernet Segment Routes belonging to RED-EVI
All of these routes carries the route target RT-RED. Spoke1 subjects
these routes to its import policy and accepts them because they carry
the route target RT-RED.
Now, Spoke1 begins normal operation, sending all of its RED-VPN
traffic through DMG1. At some point, Spoke1 determines that it might
benefit from a more direct route to M. (Criteria by which Spoke1
determines that it needs a more direct route to M are beyond the
scope of this document.)
In order to discover a more direct route, Spoke1 assigns a unique
numeric identifier to M. V-spoke1 then sends a ROUTE-REFRESH message
to the RR, containing the following information:
o AFI is equal to L2VPN
o SAFI is equal to BGP EVPN
o When-to-refresh is equal IMMEDIATE
o Action is equal to ADD
o Match is equal to PERMIT
o ORF Type is equal to CP-ORF
o CP-ORF Sequence is equal to the identifier associated with M
o CP-ORF Minlen is equal to 1
o CP-ORF Maxlen is equal to 48
o CP-ORF VPN Route Target is equal to RT-RED
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o CP-ORF Import Route Target is equal to RT-RED
o CP-ORF Route Type is equal to 2 (i.e., MAC/IP Advertisement Route)
o CP-ORF Host Address is equal M
Next, the RR adds the received CP-ORF to the Outbound Filter
associated with Spoke1. Using the procedures in Section 3, the RR
determines whether any of the routes in its Loc-RIB satisfy the
selection criteria of the newly updated Outbound Filter. If any
routes satisfy the match criteria, they are added to the Adj-RIB-Out
associated with Spoke1. The RR adds a Transitive Opaque Extended
Community [RFC4360] with subtype equal to CP-ORF. Note that as these
routes are added to the Adj-RIB-Out, the RR does not change the list
of Route Targets that the route already carries. Finally, RR
advertises the newly added routes to V-spoke1. In this example, the
RR advertises M to V-Spoke1 with a next-hop of PE1.
Spoke1 subjects the advertised routes to its import policy and
accepts them because they carry the route target RT-RED.
Spoke1 may repeat this process whenever it discovers another flow
that might benefit from a more direct route to its destination.
Note that in general an EVI may have more than one DMG, in which case
each spoke would receive a UMR from each of them. The spoke should
follow its local route selection procedures to select one of them as
the "best", and use the selected one.
6. Clean-up
Each CP-ORF consumes memory and compute resources on the device that
supports it. Therefore, in order to obtain optimal performance, BGP
speakers periodically evaluate all CP-ORFs that they have originated
and remove unneeded CP-ORFs. The criteria by which a BGP speaker
identifies unneeded CP-ORF entries is a matter of local policy, and
is beyond the scope of this document.
7. IANA Considerations
This memo uses code points from the first-come-first-served range of
the following registries:
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+-----------------------------------------------+---------------+
| Registry | Code Point |
+-----------------------------------------------+---------------+
| BGP Outbound Route Filtering (ORF) Types | CP-ORF (65) |
| Transitive Opaque Extended Community Sub-Type | CP-ORF (0x03) |
+-----------------------------------------------+---------------+
IANA is requested to update the above mentioned registry entries so
that they include a stable reference to this memo.
8. Security Considerations
Each CP-ORF consumes memory and compute resources on the device that
supports it. Therefore, a device supporting CP-ORF takes the
following steps to protect itself from oversubscription:
o When negotiating the ORF capability, advertise willingness to
receive the CP-ORF only to known, trusted iBGP peers. See
Section 5 of RFC 5291 for negotiation details.
o Enforce a per-peer limit on the number of CP-ORFs that can be
installed at any given time. Ignore all requests to add CP-ORFs
beyond that limit
Security considerations for BGP are presented in RFC4271 while
further security analysis of BGP is found in [RFC6952].
9. Contributors
The following individuals contributed to the development of this
document:
o Yakov Rekhter
o Xiaohu Xu
10. Acknowledgements
The authors wish to acknowledge Han Nguyen, James Uttaro and Alvaro
Retana for their comments and contributions.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, February 2006.
[RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
R., Patel, K., and J. Guichard, "Constrained Route
Distribution for Border Gateway Protocol/MultiProtocol
Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
Private Networks (VPNs)", RFC 4684, November 2006.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January
2007.
[RFC5291] Chen, E. and Y. Rekhter, "Outbound Route Filtering
Capability for BGP-4", RFC 5291, August 2008.
[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, February 2012.
[RFC7024] Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter,
Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS
VPNs", RFC 7024, October 2013.
[RFC7432] Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., Uttaro,
J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
VPN", RFC 7432, February 2015.
11.2. Informative References
[IANA.AFI]
IANA, "Address Family Numbers",
<http://www.iana.org/assignments/address-family-numbers/
address-family-numbers.xhtml>.
[IANA.EVPN]
IANA, "Ethernet VPN (EVPN)",
<http://www.iana.org/assignments/evpn/evpn.xhtml>.
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[IANA.SAFI]
IANA, "Subsequent Address Family Identifiers (SAFI)
Parameters", <http://www.iana.org/assignments/safi-
namespace/safi-namespace.xhtml#safi-namespace-2>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, May 2013.
Authors' Addresses
Huajin Jeng
AT&T
Email: hj2387@att.com
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
Ron Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, Virginia 20170
USA
Email: rbonica@juniper.net
Keyur Patel
Cisco Systems
170 W. Tasman Drive
San Jose, California 95134
USA
Email: keyupate@cisco.com
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Lucy Yong
Huawei Technologies
Austin, Texas
USA
Email: lucy.yong@huawei.com
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