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 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://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 13 April 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. Wang, et al. Expires 13 April 2023 [Page 1] Internet-Draft RD-ORF October 2022 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 extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are 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] Wang, et al. Expires 13 April 2023 [Page 2] Internet-Draft RD-ORF October 2022 * 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 Wang, et al. Expires 13 April 2023 [Page 3] Internet-Draft RD-ORF October 2022 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. Wang, et al. Expires 13 April 2023 [Page 4] Internet-Draft RD-ORF October 2022 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 tuple has a pre-configurated quota. * when routes associated with 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 tuple pass the quota and the prefix limit is exceeded and there is no other VRFs on offended PE need VPN routes with this 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). Wang, et al. Expires 13 April 2023 [Page 5] Internet-Draft RD-ORF October 2022 * 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 Wang, et al. Expires 13 April 2023 [Page 6] Internet-Draft RD-ORF October 2022 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 tuple imported into VRF has a quota. When routes associated with 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. Wang, et al. Expires 13 April 2023 [Page 7] Internet-Draft RD-ORF October 2022 +------------------------------------------------------------------------+ | | | | | +-------+ +-------+ | | | 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 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 Wang, et al. Expires 13 April 2023 [Page 8] Internet-Draft RD-ORF October 2022 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. Wang, et al. Expires 13 April 2023 [Page 9] Internet-Draft RD-ORF October 2022 +------------------------------------------------------------------------+ | | | | | +-------+ +-------+ | | | 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 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 Wang, et al. Expires 13 April 2023 [Page 10] Internet-Draft RD-ORF October 2022 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 Wang, et al. Expires 13 April 2023 [Page 11] Internet-Draft RD-ORF October 2022 * 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. Wang, et al. Expires 13 April 2023 [Page 12] Internet-Draft RD-ORF October 2022 * 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. Wang, et al. Expires 13 April 2023 [Page 13] Internet-Draft RD-ORF October 2022 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 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 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. Wang, et al. Expires 13 April 2023 [Page 14] Internet-Draft RD-ORF October 2022 - 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 Wang, et al. Expires 13 April 2023 [Page 15] Internet-Draft RD-ORF October 2022 * 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) Wang, et al. Expires 13 April 2023 [Page 16] Internet-Draft RD-ORF October 2022 - 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 , , 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)**, 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: Wang, et al. Expires 13 April 2023 [Page 17] Internet-Draft RD-ORF October 2022 +===========================+======+===========================+ | 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, . [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, . Wang, et al. Expires 13 April 2023 [Page 18] Internet-Draft RD-ORF October 2022 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, February 2006, . [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, 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, DOI 10.17487/RFC4684, November 2006, . [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, . [RFC5291] Chen, E. and Y. Rekhter, "Outbound Route Filtering Capability for BGP-4", RFC 5291, DOI 10.17487/RFC5291, August 2008, . [RFC5292] Chen, E. and S. Sangli, "Address-Prefix-Based Outbound Route Filter for BGP-4", RFC 5292, DOI 10.17487/RFC5292, August 2008, . [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, . [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, . Authors' Addresses Wei Wang China Telecom Beiqijia Town, Changping District Wang, et al. Expires 13 April 2023 [Page 19] Internet-Draft RD-ORF October 2022 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 Wang, et al. Expires 13 April 2023 [Page 20] Internet-Draft RD-ORF October 2022 Email: jie.dong@huawei.com Wang, et al. Expires 13 April 2023 [Page 21]