VPN Prefix Outbound Route Filter (VPN Prefix ORF) for BGP-4
draft-wang-idr-vpn-prefix-orf-04
| Document | Type | Active Internet-Draft (candidate for idr WG) | |
|---|---|---|---|
| Authors | Wei Wang , Aijun Wang , Haibo Wang , Gyan Mishra , Shunwan Zhuang , Jie Dong | ||
| Last updated | 2022-10-09 | ||
| Replaces | draft-wang-idr-rd-orf | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | WG state | Call For Adoption By WG Issued | |
| Document shepherd | Susan Hares | ||
| Shepherd write-up | Show Last changed 2022-02-04 | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | shares@ndzh.com |
draft-wang-idr-vpn-prefix-orf-04
IDR Working Group W. Wang
Internet-Draft A. Wang
Intended status: Standards Track China Telecom
Expires: 13 April 2023 H. Wang
Huawei Technologies
G. Mishra
Verizon Inc.
S. Zhuang
J. Dong
Huawei Technologies
10 October 2022
VPN Prefix Outbound Route Filter (VPN Prefix ORF) for BGP-4
draft-wang-idr-vpn-prefix-orf-04
Abstract
This draft defines a new Outbound Route Filter (ORF) type, called the
VPN Prefix ORF. The described VPN Prefix ORF mechanism is applicable
when the VPN routes from different VRFs are exchanged via one shared
BGP session (e.g., routers in a single-domain connect via Route
Reflector).
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
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 13 April 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Operation process of VPN Prefix ORF mechanism on sender . . . 5
4.1. Intra-domain Scenarios and Solutions . . . . . . . . . . 5
4.1.1. Scenario-1 and Solution (Unique RD, One RT) . . . . . 6
4.1.2. Scenario-2 and Solution (Unique RD, Multiple RTs) . . 7
4.1.3. Scenario-3 and Solution (Universal RD) . . . . . . . 9
5. VPN Prefix ORF Encoding . . . . . . . . . . . . . . . . . . . 11
5.1. Source PE TLV . . . . . . . . . . . . . . . . . . . . . . 13
5.2. Route Target TLV . . . . . . . . . . . . . . . . . . . . 14
6. Operation process of VPN Prefix ORF mechanism on receiver . . 14
7. Withdraw of VPN Prefix ORF entries . . . . . . . . . . . . . 15
8. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 15
9. Implementation Considerations . . . . . . . . . . . . . . . . 17
10. Security Considerations . . . . . . . . . . . . . . . . . . . 17
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 18
13. Normative References . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
[I-D.wang-idr-vpn-routes-control-analysis] analysis the scenarios and
necessaries for VPN routes control in the shared BGP session. This
draft analyzes the existing solutions and their limitations for these
scenarios, proposes the new VPN Prefix ORF solution to meet the
requirements that described in section 8 of
[I-D.wang-idr-vpn-routes-control-analysis].
Now, there are several solutions can be used to alleviate these
problem:
* Route Target Constraint (RTC) as defined in [RFC4684]
* Address Prefix ORF as defined in [RFC5292]
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* CP-ORF mechanism as defined in [RFC7543]
* PE-CE edge peer Maximum Prefix
* Configure the Maximum Prefix for each VRF on edge nodes
However, there are limitations to existing solutions:
1) Route Target Constraint
RTC can only filter the VPN routes from the uninterested VRFs, if the
"offending routes" come from the interested VRF, RFC mechanism can't
filter them.
2) Address Prefix ORF
Using Address Prefix ORF to filter VPN routes need to pre-
configuration, but it is impossible to know which prefix may cause
overflow in advance.
3) CP-ORF Mechanism
[RFC7543] defines 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.
CP-ORF is applicable in Virtual Hub-and-Spoke[RFC7024] VPN and also
the BGP/MPLS Ethernet VPN (EVPN) [RFC7432]networks, but its main aim
is also to get the wanted VPN prefixes and can't be used to filter
the overwhelmed VPN prefixes dynamically.
4) PE-CE edge peer Maximum Prefix
The BGP Maximum-Prefix feature is used to control how many prefixes
can be received from a neighbor. By default, this feature allows a
router to bring down a peer when the number of received prefixes from
that peer exceeds the configured Maximum-Prefix limit. This feature
is commonly used for external BGP peers. If it is applied to
internal BGP peers, for example the VPN scenarios, all the VPN routes
from different VRFs will share the common fate, which is not
desirable for the fining control of the VPN Prefixes advertisement.
5) Configure the Maximum Prefix for each VRF on edge nodes
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When a VRF overflows, it stops the import of routes and log the extra
VPN routes into its RIB. However, PEs still need to parse the BGP
updates. These processes will cost CPU cycles and further burden the
overflowed PE.
This draft defines a new ORF-type, called the VPN Prefix ORF. This
mechanism is event-driven and does not need to be pre-configured.
When a VRF of a router overflows, the router will find out the VPN
prefix (RD, RT, source PE, etc.) of offending VPN routes in this VRF,
and send a VPN Prefix ORF to its BGP peer that carries the relevant
information. If a BGP speaker receives a VPN Prefix ORF entry from
its BGP peer, it will filter the VPN routes it tends to send
according to the entry.
The purpose of this mechanism is to control the outrage within the
minimum range and avoid churn effects when a VRF on a device in the
network overflows.
VPN Prefix ORF is applicable when the VPN routes from different VRFs
are exchanged via one shared BGP session.
2. Conventions used in this document
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 [RFC2119] .
3. Terminology
The following terms are defined in this draft:
* RD: Route Distinguisher, defined in [RFC4364]
* ORF: Outbound Route Filter, defined in [RFC5291]
* AFI: Address Family Identifier, defined in [RFC4760]
* SAFI: Subsequent Address Family Identifier, defined in [RFC4760]
* EVPN: BGP/MPLS Ethernet VPN, defined in [RFC7432]
* RR: Router Reflector, provides a simple solution to the problem of
IBGP full mesh connection in large-scale IBGP implementation.
* VRF: Virtual Routing Forwarding, a virtual routing table based on
VPN instance.
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4. Operation process of VPN Prefix ORF mechanism on sender
The operation of VPN Prefix ORF mechanism on each device is
independent, each of them makes a local judgement to determine
whether it needs to send VPN Prefix ORF to its upstream peer. The
operators need to make sure the algorithms in different devices
consistent.
a) No quota value is set on PE
On PE, each VRF has a prefix limit, when VPN routes exceed the prefix
limit and there is no other VRFs on the offended PE need these VPN
routes, PE should trigger VPN Prefix ORF mechanism and send
corresponding VPN Prefix ORF message (VRF Prefix Limit, RD, RT). The
RD value of this message is set to 0, and the RT value is set to the
value of RT-import of the PE.
b) Quota value is set on PE
On PE, each VRF has a prefix limit, and routes associated with each
<RD, source PE> tuple has a pre-configurated quota.
* when routes associated with <RD, source PE> tuple pass the quota
but the prefix limit of VRF is not exceeded, PE should send
warnings to the operator, and the VPN Prefix ORF mechanism should
not be triggered.
* when routes associated with <RD, source PE> tuple pass the quota
and the prefix limit is exceeded and there is no other VRFs on
offended PE need VPN routes with this <RD, source PE> tuple, they
should be dropped via VPN Prefix ORF mechanism.
When the VPN Prefix ORF mechanism is triggered, the device must send
an alarm information to network operators.
4.1. Intra-domain Scenarios and Solutions
For intra-AS VPN deployment, there are three scenarios:
* RD is allocated per VPN per PE, each VRF only import one RT (see
Section 4.1.1).
* RD is allocated per VPN per PE. Multiple RTs are associated with
such VPN routes, and are imported into different VRFs in other
devices(see Section 4.1.2).
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* RD is allocated per VPN, each VRF imports one/multiple RTs(see
Section 4.1.3).
The following sections will describe solutions to the above scenarios
in detail.
4.1.1. Scenario-1 and Solution (Unique RD, One RT)
In this scenario, RD is allocated per VPN per PE. The offending VPN
routes only carry one RT. We assume the network topology is shown in
Figure 1.
+------------------------------------------------------------------------+
| |
| |
| +-------+ +-------+ |
| | PE1 +----------------+ +-----------------+ PE4 | |
| +-------+ | | +-------+ |
| VPN1(RD11,RT1) | | VPN2(RD12,RT2) |
| VPN2(RD12,RT2) | | |
| +-+----+-+ |
| | RR | |
| +-+----+-+ |
| | | |
| | | |
| +-------+ | | +-------+ |
| | PE2 +----------------+ +-----------------+ PE3 | |
| +-------+ +-------+ |
| VPN1(RD21,RT1) VPN1(RD31,RT1) |
| VPN2(RD22,RT2,RT1) VPN2(RD32,RT2) |
| |
| AS 100 |
| |
+------------------------------------------------------------------------+
Figure 1 Network Topology of Scenario-1
When PE3 sends excessive VPN routes with RT1, while both PE1 and PE2
import VPN routes with RT1, the process of offending VPN routes will
influence performance of VRFs on PEs. PEs and RR should have some
mechanisms to identify and control the advertisement of offending VPN
routes.
a) PE1
If quota value is not set on PE1, and each VRF has a prefix limit on
PE1. When the prefix limit of VPN1 VRF is exceeded, due to there is
no other VRFs on PE1 need the VPN routes with RT1, PE1 will send VPN
Prefix ORF message to RR and send warning to operator. The message
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will carry the prefix limit of VPN1 VRF, the RD value is set to 0 and
the RT value is set to RT1. RR will withdraw the offending VPN
routes and control the number of VPN routes sending to PE1.
If quota value is set on PE1, each VRF has a prefix limit, and each
<RD, source PE> tuple imported into VRF has a quota. When routes
associated with <RD31, PE3> tuple pass the quota but the prefix limit
of VPN1 VRF is not exceeded, PE1 sends a warning message to the
operator, and the VPN Prefix ORF mechanism should not be triggered.
After the prefix limit of VPN1 VRF is exceeded, due to there is no
other VRFs on PE1 need the VPN routes with RT1, PE1 will generate a
BGP ROUTE-REFRESH message contains a VPN Prefix ORF entry, and send
to RR. RR will withdraw and stop to advertise such offending VPN
routes (RD31, the prefix limit of VPN1 VRF, source PE is PE3, RT is
RT1) to PE1.
b) PE2
If quota value is not set on PE2, when the prefix limit of VPN1 VRF
is exceeded, PE2 cannot trigger VPN Prefix ORF mechanism directly,
because VPN2 VRF needs the VPN routes with RT1. Only when both VPN1
VRF and VPN2 VRF are overflow, PE2 triggers the mechanism. The VPN
Prefix ORF message will carry the VRF Prefix Limit = min(prefix limit
of VPN1 VRF, prefix limit of VPN2 VRF), the RD value is set to 0 and
the RT value is set to RT1. RR will withdraw the offending VPN
routes and control the number of VPN routes sending to PE1.
If quota value is set on PE2, both VPN1 VRF and VPN2 VRF import VPN
routes with RT1. If PE2 triggers VPN Prefix ORF mechanism when VPN1
VRF overflows, VPN2 VRF cannot receive VPN routes with RT1 as well.
PE2 should not trigger the VPN Prefix ORF mechanism to RR (RD31,
min(prefix limit of VPN1 VRF, prefix limit of VPN2 VRF), source PE is
PE3) until all the VRFs that import RT1 on it overflow.
4.1.2. Scenario-2 and Solution (Unique RD, Multiple RTs)
In this scenario, RD is allocated per VPN per PE. Multiple RTs are
associated with the offending VPN routes, and be imported into
different VRFs in other devices. We assume the network topology is
shown in Figure 2.
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+------------------------------------------------------------------------+
| |
| |
| +-------+ +-------+ |
| | PE1 +----------------+ +-----------------+ PE4 | |
| +-------+ | | +-------+ |
| VPN1(RD11,RT1) | | VPN2(RD42,RT2) |
| VPN2(RD12,RT2) | | |
| +-+----+-+ |
| | RR | |
| +-+----+-+ |
| | | |
| | | |
| +-------+ | | +-------+ |
| | PE2 +----------------+ +-----------------+ PE3 | |
| +-------+ +-------+ |
| VPN1(RD21,RT1) VPN1(RD31,RT1,RT2) |
| VPN2(RD32,RT2) |
| |
| AS 100 |
| |
+------------------------------------------------------------------------+
Figure 2 Network Topology of Scenario-2
When PE3 sends excessive VPN routes with RT1 and RT2, while both PE1
and PE2 import VPN routes with RT1, and PE1 also imports VPN routes
with RT2.
a) PE1
If quota value is not set on PE1, when the prefix limit of VPN1 VRF
is exceeded, PE1 cannot trigger VPN Prefix ORF mechanism directly,
because VPN2 VRF needs the VPN routes with RT1. Only when both VPN1
VRF and VPN2 VRF are overflow, PE1 will send VPN Prefix ORF message
to RR and send warning to operator. The message will carry the VRF
Prefix Limit = min(prefix limit of VPN1 VRF, prefix limit of VPN2
VRF), the RD value is set to 0 and the RT value is set to RT1, RT2.
RR will withdraw the offending VPN routes and control the number of
VPN routes sending to PE1.
If quota value is set on PE1, when routes associated with <RD31, PE3>
tuple pass the quota but the prefix limit of VPN1 VRF is not
exceeded, PE1 sends a warning to the operator. When the prefix limit
of VPN1 VRF is exceeded, if the VPN2 VRF does not reach its limit at
the same time, PE1 should still not send out the trigger message,
because if it does so, the VPN2 VRF can't receive the VPN routes too
(RR will filter all the VPN prefixes that contain RT1). PE1 just
discard the offending VPN routes locally. PE1 should only generate a
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BGP ROUTE-REFRESH message contains a VPN Prefix ORF entry(RD31,
min(prefix limit of VPN1 VRF, prefix limit of VPN2 VRF), comes from
PE3) when both the VRFs that import such prefixes are overflow.
b) PE2
If quota value is not set on PE2, when the prefix limit of VPN1 VRF
is exceeded, due to there is no other VRFs on PE2 need the VPN routes
with RT1, PE2 will send VPN Prefix ORF message to RR and send warning
to operator. The message will carry the prefix limit of VPN1 VRF,
the RD value is set to 0 and the RT value is set to RT1. RR will
withdraw the offending VPN routes and control the number of VPN
routes sending to PE2.
If quota value is set on PE2, due to there is only one VRF imports
VPN routes with RT1. If it overflows, it will trigger VPN Prefix ORF
(RD31, the prefix limit of VPN1 VRF, comes from PE3) mechanisms. RR
will withdraw and stop to advertise such offending VPN routes to PE2.
4.1.3. Scenario-3 and Solution (Universal RD)
In this scenario, RD is allocated per VPN. One/Multiple RTs are
associated with the offending VPN routes, and be imported into
different VRFs in other devices. We assume the network topology is
shown in Figure 3.
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+------------------------------------------------------------------------+
| |
| |
| +-------+ +-------+ |
| | PE1 +----------------+ +-----------------+ PE4 | |
| +-------+ | | +-------+ |
| VPN1(RD1,RT1) | | VPN2(RD12,RT2) |
| VPN2(RD12,RT2) | | |
| +-+----+-+ |
| | RR | |
| +-+----+-+ |
| | | |
| | | |
| +-------+ | | +-------+ |
| | PE2 +----------------+ +-----------------+ PE3 | |
| +-------+ +-------+ |
| VPN1(RD1,RT1) VPN1(RD1,RT1,RT2) |
| VPN2(RD32,RT2) |
| |
| AS 100 |
| |
+------------------------------------------------------------------------+
Figure 3 Network Topology of Scenario-3
When PE3 sends excessive VPN routes with RD1 and attached RT1 and
RT2, while both PE1 and PE2 import VPN routes with RT1, the process
of offending VPN routes will influence performance of VRFs on PEs.
a) PE1
If quota value is not set on PE1, when the prefix limit of VPN1 VRF
is exceeded, PE1 cannot trigger VPN Prefix ORF mechanism directly,
because VPN2 VRF needs the VPN routes with RT2. Only when both VPN1
VRF and VPN2 VRF are overflow, PE1 will send VPN Prefix ORF message
to RR and send warning to operator. The message will carry the VRF
Prefix Limit = min(prefix limit of VPN1 VRF, prefix limit of VPN2
VRF), the RD value is set to 0 and the RT value is set to RT1, RT2.
RR will withdraw the offending VPN routes and control the number of
VPN routes sending to PE1.
If quota value is set on PE1, when routes associated with <RD1, PE3>
tuple pass the quota but the prefix limit of VPN1 VRF is not
exceeded, PE1 sends a warning to the operator. When the prefix limit
of VPN1 VRF is exceeded, if the VPN2 VRF does not reach its limit at
the same time, PE1 should still not send out the trigger message,
because if it does so, the VPN2 VRF can't receive the VPN routes too
(RR will filter all the VPN prefixes that contain RT1). PE1 just
discard the offending VPN routes locally. PE1 should only generate a
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BGP ROUTE-REFRESH message contains a VPN Prefix ORF entry(RD1,
min(prefix limit of VPN1 VRF, prefix limit of VPN2 VRF), comes from
PE3) when both the VRFs that import such prefixes are overflow.
b) PE2
If quota value is not set on PE2, when the prefix limit of VPN1 VRF
is exceeded, due to there is no other VRFs on PE2 need the VPN routes
with RT1, PE2 will send VPN Prefix ORF message to RR and send warning
to operator. The message will carry the prefix limit of VPN1 VRF,
the RD value is set to 0 and the RT value is set to RT1. RR will
withdraw the offending VPN routes and control the number of VPN
routes sending to PE2.
If quota value is set on PE2, due to there is only one VRF imports
VPN routes with RT1. If it overflows, it will trigger VPN Prefix ORF
(RD1, the prefix limit of VPN1 VRF, comes from PE3) mechanisms. RR
will withdraw and stop to advertise such offending VPN routes to PE2.
When PE2 overflows and PE1 does not overflow. PE2 triggers the VPN
Prefix ORF message (RD1, comes from PE3). Using Source PE and RD, RR
will only withdraw and stop to advertise VPN routes with RD1 come
from PE3 to PE2. The communication between PE2 and PE1 for VPN1 will
not be influenced.
5. VPN Prefix ORF Encoding
In this section, we defined a new ORF type called VPN Prefix Outbound
Route Filter (VPN Prefix ORF). The ORF entries are carried in the
BGP ROUTE-REFRESH message as defined in [RFC5291]. A BGP ROUTE-
REFRESH message can carry one or more ORF entries. The ROUTE-REFRESH
message which carries ORF entries contains the following fields:
* AFI (2 octets)
* SAFI (1 octet)
* When-to-refresh (1 octet): the value is IMMEDIATE or DEFER
* ORF Type (1 octet)
* Length of ORF entries (2 octets)
A VPN Prefix ORF entry contains a common part and type-specific part.
The common part is encoded as follows:
* Action (2 bits): the value is ADD, REMOVE or REMOVE-ALL
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* Match (1 bit): the value is PERMIT or DENY
* Offending VPN routes process method (1bit): if the value is set to
0, it means the sender of VPN Prefix ORF message refuse to receive
new offending VPN routes; if the value is set to 1, it means all
offending VPN routes on the sender of VPN Prefix ORF message
should be withdrawn. The default value is 0.
* Reserved (4 bits)
VPN Prefix ORF also contains type-specific part. The encoding of the
type-specific part is shown in Figure 4.
+-----------------------------------------+
| |
| Sequence (4 octets) |
| |
+-----------------------------------------+
| |
| Length (2 octets) |
| |
+-----------------------------------------+
| |
| VRF Prefix Limit (2 octets) |
| |
+-----------------------------------------+
| |
| Route Distinguisher (8 octets) |
| |
+-----------------------------------------+
| |
| Optional TLVs (variable) |
| |
+-----------------------------------------+
Figure 4: VPN Prefix ORF type-specific encoding
* Sequence: identifying the order in which RD-ORF is generated.
* Length: identifying the length of this VPN Prefix ORF entry.
* VRF Prefix Limit: carrying the prefix limt of the overflowed VRF.
* Route Distinguisher: distinguish the different user routes. The
VPN Prefix ORF filters the VPN routes it tends to send based on
Route Distinguisher. If RD is equal to 0, it means any VPN
prefixes.
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* Optional TLVs: carry the potential additional information to give
the extensibility of the VPN Prefix ORF mechanism.
Note that if the Action component of an ORF entry specifies REMOVE-
ALL, the ORF entry does not include the type-specific part.
When the BGP ROUTE-REFRESH message carries VPN Prefix ORF entries, it
must be set as follows:
* The ORF-Type MUST be set to VPN Prefix ORF.
* The AFI MUST be set to IPv4, IPv6, or Layer 2 VPN (L2VPN).
* If the AFI is set to IPv4 or IPv6, the SAFI MUST be set to MPLS-
labeled VPN address.
* If the AFI is set to L2VPN, the SAFI MUST be set to BGP EVPN.
* The Match field should be set to PERMIT when VRF Prefix Limit =
0xFFFF and RD=0; otherwise, the Match field should be set to DENY.
5.1. Source PE TLV
Source PE TLV is defined to identify the source of the VPN routes.
Using source PE and RD to filter VPN routes together can achieve more
refined route control. The source PE TLV contains the following
types:
* In single-domain or Option C cross-domain scenario, NEXT_HOP
attribute is unchanged during routing transmission, so it can be
used as source address.
Type = 1, Length = 4 octets, value = NEXT_HOP.
Type = 2, Length = 16 octets, value = NEXT_HOP.
* In Option B cross-domain scenario, NEXT_HOP attribute will be
changed by ASBRs and cannot identify the source PE. A new
Extended Community: Source PE Extended Community is needed to
preserve the source PE identification. Its value should be set by
the RR (similar with the BGP ORIGINATOR_ID attributes) or the
router that peers with the source PE (non-RR scenario), as the BGP
Router ID of the corresponding BGP session. Once set and attached
with the BGP update message, its value should not be changed along
the advertisement path.
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Type = 3, Length = 6 octets, value = the value field of Source
PE Extended Community.
In principle, when the device can extract Source PE Extended
Community from the received BGP UPDATE message, the value of Source
PE TLV should be set to Source PE Extended Community; Otherwise, the
value should be set to NEXT_HOP.
5.2. Route Target TLV
Route Target TLV is defined to identify the RT of the offending VPN
routes. RT and RD can be used together to filter VPN routes when the
source VRF contains multiple RTs, and the VPN routes with different
RTs may be assigned to different VRFs on the receiver. The encoding
of Route Target TLV is as follow:
Type = 4, Length = 8*n (n is the number of RTs that the offending
VPN routes attached) octets, value = the RT of the offending VPN
routes. If multiple RTs are included, there must be an exact
match.
6. Operation process of VPN Prefix ORF mechanism on receiver
The receiver of VPN Prefix ORF entries may be a RR or PE. As it
receives the VPN Prefix ORF entries, it will check <AFI/SAFI, ORF-
Type, Sequence, Route Distinguisher> to find if it already existed in
its ORF-Policy table. If not, the receiver will add the VPN Prefix
ORF entries into its ORF-Policy table; otherwise, the receiver will
discard it.
Before the receiver send a VPN route, it should check its ORF-Policy
table with <RD, Source PE> tuple of the VPN route. The Route
Distinguisher information can be extracted directly from the BGP
UPDATE message. The source PE information should be compared against
the Source PE Extended Community if it is contained in BGP UPDATE
message, or else the NEXT_HOP.
If there is not a related VPN Prefix ORF entry in ORF-Policy table,
the receiver will send this VPN route; otherwise, the receiver will
perform the following operations:
* If the "Offending VPN routes process method" bit is 0:
- If the RD value of this entry is 0, the receiver should
withdraw the extra VPN routes according to the value of VRF
Prefix Limit in the entry and RT, and stop sending the
corresponding VPN routes to the sender.
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- If the RD value of this entry is not 0, the receiver withdraw
the extra VPN routes according to the value of VRF Prefix
Limit, RD, RT and information in optional TLVs in the entry,
and stop sending the corresponding VPN routes to the sender.
* If the "Offending VPN routes process method" bit is 1:
- If the RD value of this entry is 0, the receiver should
withdraw all the VPN routes identified by RT, and stop sending
the corresponding VPN routes to the sender.
- If the RD value of this entry is not 0, the receiver should
withdraw all the VPN routes identified by RD, RT and
information in optional TLVs in the entry, and stop sending the
corresponding VPN routes to the sender.
7. Withdraw of VPN Prefix ORF entries
When the VPN Prefix ORF mechanism is triggered, the alarm information
will be generated and sent to the network operators. Operators
should manually configure the network to resume normal operation.
Due to devices can record the VPN Prefix ORF entries sent by each
VRF, operators can find the entries needs to be withdrawn, and
trigger the withdraw process as described in [RFC5291] manually.
After returning to normal, the device sends withdraw ORF entries to
its peer who have previously received ORF entries.
8. Applicability
We take the scenario in Section 4.1.1 as an example to illustrate how
to determine each field when the sender generates a VPN Prefix ORF
entry. We assume it is an IPv4 network. After PE1-PE4 and RR
advertising the Outbound Route Filtering Capability, each of PE1-PE4
should send a VPN Prefix ORF entry that means "PERMIT-ALL" as
follows:
* AFI is equal to IPv4
* SAFI is equal to MPLS-labeled VPN address
* When-to-refresh is equal to IMMEDIATE
* ORF Type is equal to VPN Prefix ORF
* Length of ORF entries is equal to 24
* Action is equal to ADD
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* Match is equal to PERMIT
* Offending VPN routes process method is equal to 0
* Sequence is equal to 0xFFFFFFFF
* Length is equal to 10
* VRF Prefix Limit is equal to 0xFFFF
* Route Distinguisher is equal to 0
When the VPN Prefix ORF mechanism is triggered on PE1, PE1 will
generate a VPN Prefix ORF contains the following information:
* AFI is equal to IPv4
* SAFI is equal to MPLS-labeled VPN address
* When-to-refresh is equal to IMMEDIATE
* ORF Type is equal to VPN Prefix ORF
* Length of ORF entries is equal to 40
* Action is equal to ADD
* Match is equal to DENY
* Offending VPN routes process method is equal to 0
* Sequence is equal to 1
* Length is equal to 26
* VRF Prefix Limit is equal to the prefix limit of VPN1 VRF
* Route Distinguisher is equal to RD31
* Optional TLV:
- Type is equal to 1 (Source PE TLV)
- Length is equal to 4
- value is equal to PE3's IPv4 address
- Type is equal to 4 (Route Target TLV)
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- Length is equal to 8
- value is equal to RT1
9. Implementation Considerations
Before originating an VPN Prefix ORF message, the device should
compare the list of RDs carried by VPN routes signaled for filtering
and the RDs imported by not affected VRF(s). Once they have
intersection, the VPN Prefix ORF message MUST NOT be originated.
In deployment, the quota value can be set with different granularity,
such as <PE>, <RD, Source AS>, etc. If the quota value is set to
(VRF prefix limit/the number of PEs), whenever a new PE access to the
network, the quota value should be changed.
To avoid the frequently change of the quota value, the value can be
set according to the following formula:
Quota=MIN[(Margins coefficient)*<PE,CE limit>*<Number of PEs within
the VPN, includes the possibility expansion in futures>, VRF Prefixes
Limit]
It should be noted that the above formula is only an example, the
operators can use different formulas based on actual needs in
management plane.
10. Security Considerations
A BGP speaker will maintain the VPN Prefix ORF entries in an ORF-
Policy table, this behavior consumes its memory and compute
resources. To avoid the excessive consumption of resources,
[RFC5291] specifies that a BGP speaker can only accept ORF entries
transmitted by its interested peers.
11. IANA Considerations
This document defines a new Outbound Route Filter type - VPN Prefix
Outbound Route Filter (VPN Prefix ORF). The code point is from the
"BGP Outbound Route Filtering (ORF) Types". It is recommended to set
the code point of VPN Prefix ORF to 66.
This document also define a VPN Prefix ORF TLV type under "Border
Gateway Protocol (BGP) Parameters", four TLV types are defined:
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+===========================+======+===========================+
| Registry | Type | Meaning |
+===========================+======+===========================+
|IPv4 Source PE TLV | 1 |IPv4 address for source PE.|
+---------------------------+------+---------------------------+
|IPv6 Source PE TLV | 2 |IPv6 address for source PE.|
+---------------------------+------+---------------------------+
|Source PE Extended | 3 |Source PE Extended |
|Community TLV | |Community |
+---------------------------+------+---------------------------+
|Route Target TLV | 4 |Route Target of the |
| | |offending VPN routes |
+---------------------------+------+---------------------------+
This document also requests a new Transitive Extended Community Type.
The new Transitive Extended Community Type name shall be "Source PE
Extended Community".
Under "Transitive Extended Community:"
Registry: "Source PE Extended Community"
Registration Procedure(s): First Come, First Served
0x0c Source PE Extended Community
12. Acknowledgement
Thanks Robert Raszuk, Jim Uttaro, Jakob Heitz, Jeff Tantsura, Rajiv
Asati, John E Drake, Gert Doering, Shuanglong Chen, Enke Chen,
Srihari Sangli and Igor Malyushkin for their valuable comments on
this draft.
13. Normative References
[I-D.ietf-bess-evpn-inter-subnet-forwarding]
Sajassi, A., Salam, S., Thoria, S., Drake, J. E., and J.
Rabadan, "Integrated Routing and Bridging in Ethernet VPN
(EVPN)", Work in Progress, Internet-Draft, draft-ietf-
bess-evpn-inter-subnet-forwarding-15, 26 July 2021,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-
inter-subnet-forwarding-15.txt>.
[I-D.wang-idr-vpn-routes-control-analysis]
Wang, A., Wang, W., Mishra, G. S., Wang, H., Zhuang, S.,
and J. Dong, "Analysis of VPN Routes Control in Shared BGP
Session", Work in Progress, Internet-Draft, draft-wang-
idr-vpn-routes-control-analysis-04, 6 September 2021,
<https://www.ietf.org/archive/id/draft-wang-idr-vpn-
routes-control-analysis-04.txt>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
February 2006, <https://www.rfc-editor.org/info/rfc4360>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[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, DOI 10.17487/RFC4684,
November 2006, <https://www.rfc-editor.org/info/rfc4684>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>.
[RFC5291] Chen, E. and Y. Rekhter, "Outbound Route Filtering
Capability for BGP-4", RFC 5291, DOI 10.17487/RFC5291,
August 2008, <https://www.rfc-editor.org/info/rfc5291>.
[RFC5292] Chen, E. and S. Sangli, "Address-Prefix-Based Outbound
Route Filter for BGP-4", RFC 5292, DOI 10.17487/RFC5292,
August 2008, <https://www.rfc-editor.org/info/rfc5292>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC7543] Jeng, H., Jalil, L., Bonica, R., Patel, K., and L. Yong,
"Covering Prefixes Outbound Route Filter for BGP-4",
RFC 7543, DOI 10.17487/RFC7543, May 2015,
<https://www.rfc-editor.org/info/rfc7543>.
Authors' Addresses
Wei Wang
China Telecom
Beiqijia Town, Changping District
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Beijing
Beijing, 102209
China
Email: weiwang94@foxmail.com
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
Beijing, 102209
China
Email: wangaj3@chinatelecom.cn
Haibo Wang
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing
Beijing, 100095
China
Email: rainsword.wang@huawei.com
Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring, MD 20904
United States of America
Phone: 301 502-1347
Email: gyan.s.mishra@verizon.com
Shunwan Zhuang
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing
Beijing, 100095
China
Email: zhuangshunwan@huawei.com
Jie Dong
Huawei Technologies
Huawei Building, No.156 Beiqing Rd.
Beijing
Beijing, 100095
China
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Email: jie.dong@huawei.com
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