Route Distinguisher Outbound Route Filter (RD-ORF) for BGP-4
draft-wang-idr-rd-orf-07
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Wei Wang , Aijun Wang , Haibo Wang , Gyan Mishra , Shunwan Zhuang , Jie Dong | ||
| Last updated | 2021-09-07 | ||
| Replaced by | draft-wang-idr-vpn-prefix-orf | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Call For Adoption By WG Issued | |
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draft-wang-idr-rd-orf-07
IDR Working Group W. Wang
Internet-Draft A. Wang
Intended status: Standards Track China Telecom
Expires: March 12, 2022 H. Wang
Huawei Technologies
G. Mishra
Verizon Inc.
S. Zhuang
J. Dong
Huawei Technologies
September 8, 2021
Route Distinguisher Outbound Route Filter (RD-ORF) for BGP-4
draft-wang-idr-rd-orf-07
Abstract
This draft defines a new Outbound Route Filter (ORF) type, called the
Route Distinguisher ORF (RD-ORF). The described RD-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
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This Internet-Draft will expire on March 12, 2022.
Copyright Notice
Copyright (c) 2021 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Operation process of RD-ORF mechanism on sender . . . . . . . 4
4.1. Intra-domain Scenarios and Solutions . . . . . . . . . . 4
4.1.1. Scenario-1 and Solution (Unique RD, One RT) . . . . . 5
4.1.2. Scenario-2 and Solution (Unique RD, Multiple RTs) . . 6
4.1.3. Scenario-2 and Solution (Universal RD) . . . . . . . 7
5. Operation process of RD-ORF mechanism on receiver . . . . . . 8
6. Withdraw of RD-ORF entries . . . . . . . . . . . . . . . . . 8
7. RD-ORF Encoding . . . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10
11. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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 analizes the existing solutions and their limitations for these
scenarios, proposes the new RD-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:
o Route Target Constraint (RTC) as defined in [RFC4684]
o Address Prefix ORF as defined in [RFC5292]
o PE-CE edge peer Maximum Prefix
o Configure the Maximum Prefix for each VRF on edge nodes
However, there are limitations to existing solutions:
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1) Route Target Constraint
RTC can only filter the VPN routes from the uninterested VRFs, if the
"trashing routes" come from the interested VRF, filter on RTs will
erase all prefixes from this VRF.
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) PE-CE edge peer Maximum Prefix
This mechanism can only protect the edge between PE-CE, it can't be
deployed within PE that peered via RR. Depending solely on the edge
protection is dangerous, because if only one of the edge points being
comprised/error-configured/attacked, then all of PEs within domain
are under risk.
4) Configure the Maximum Prefix for each VRF on edge nodes
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
overflowing PE.
This draft defines a new ORF-type, called the Route Distinguisher ORF
(RD-ORF). Using RD-ORF mechanism, VPN routes can be controlled based
on RD. 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 RD of excessive VPN routes in this VRF, and send a RD-ORF to
its BGP peer that carrys the RD. If a BGP speaker receives a RD-ORF
entry from its BGP peer, it will filter the VPN routes it tends to
send according to the entry.
RD-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] .
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3. Terminology
The following terms are defined in this draft:
o RD: Route Distinguisher, defined in [RFC4364]
o ORF: Outbound Route Filter, defined in [RFC5291]
o AFI: Address Family Identifier, defined in [RFC4760]
o SAFI: Subsequent Address Family Identifier, defined in [RFC4760]
o EVPN: BGP/MPLS Ethernet VPN, defined in [RFC7432]
o RR: Router Reflector, provides a simple solution to the problem of
IBGP full mesh connection in large-scale IBGP implementation.
o VRF: Virtual Routing Forwarding, a virtual routing table based on
VPN instance.
4. Operation process of RD-ORF mechanism on sender
The operation of RD-ORF mechanism on each device is independent, each
of them makes a local judgement to determine whether it needs to send
RD-ORF to its peers.
When the RD-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:
o RD is allocated per VPN/per PE, each VRF only import one RT(see
Section 4.1).
o RD is allocated per VPN/per PE. Multiple RTs are associated with
such VPN routes, and be imported into different VRFs in other
devices(see Section 4.2).
o RD is allocated per VPN, each VRF imports one/multiple RTs(see
Section 4.3).
The following sections will describe solutions to the above scenarios
in detail.
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4.1.1. Scenario-1 and Solution (Unique RD, One RT)
In this scenario, RD is allocated per VPN or per PE, each VRF only
import 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 excessive VPN routes will
influence performance of VRFs on PEs. PEs and RR should have some
mechanisms to identify and control the advertisement of excessive VPN
routes.
On PE1, each VRF has a set threshold, we assume it is 80% of Maximum
Prefix of VRF. When the number of VPN1 VRF routing entries reaches
the threshold, PE1 will start monitoring the RD carried by the
received VPN routing entries. Once the number of VPN routing entries
exceed the prefix limit, PE1 will calculate the RD received the most
times during this period, the result is RD31, which is associated
with RT1. Then, PE1 will locally discards the VPN routes carry RD31
in VRF1.
Due to there is no other VRFs on it to import the VPN routes with
RT1. after local processing, PE1 will generate a BGP ROUTE-REFRESH
message contains a RD-ORF entry, and send to RR. RR will withdraw
and stop to advertise such excessive VPN routes to PE1.
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On PE2, the local processing is the same as PE1. Due to there has
other VRF on it to import the VPN routes with RT1, PE2 triggers the
RD-ORF message to RR(RD field is set to RD31) only when all the VRFs
that import RT1 are overflowed.
4.1.2. Scenario-2 and Solution (Unique RD, Multiple RTs)
In this scenario, RD is allocated per VPN or per PE. Multiple RTs
are associated with such VPN routes, and be imported into different
VRFs in other devices. We assume the network topology is shown in
Figure 2.
+------------------------------------------------------------------------+
| |
| |
| +-------+ +-------+ |
| | PE1 +----------------+ +-----------------+ PE4 | |
| +-------+ | | +-------+ |
| VPN1(RD11,RT1) | | VPN2(RD12,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, the process of excessive VPN routes will influence
performance of VRF on PEs. PEs and RR should have some mechanisms to
identify and control the advertisement of excessive VPN routes.
In this senario, both VRF1 and VRF2 import VPN route carries RT2,
which contains RD31.
On PE1, if it overflows, it will know that the RD of excessive VPN
routes is RD31 during the local processing, associated with RT1 and
RT2. There are different VRFs on PE1 import the VPN routes
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respectively with RT1 and RT2. If PE1 trigger the RD-ORF message
when VRF1 overflows, it cannot receive the VPN routes with RT2 from
PE3. The local determination of the PE can be used to inhibit the PE
from sending RD-ORF entries. PE1 will not trigger the RD-ORF message
until all VPNs that import VPN routes with RD31 are overflowed. When
RD-ORF mechanisms is triggered, PE1 will discard the overflowed VPN
routes locally and send RD-ORF entry to RR, and RR withdraws and
stops to advertise such excessive VPN routes to PE1.
On PE2, due to there only one VRF imports VPN routes with RT1. If it
overflows, it will trigger RD-ORF(RD31) mechanisms. RR will withdraw
and stop to advertise such excessive VPN routes to PE2.
4.1.3. Scenario-2 and Solution (Universal RD)
In this scenario, RD is allocated per VPN. One/Multiple RTs are
associated with such VPN routes, and be imported into different VRFs
in other devices. We assume the network topology is shown in
Figure 3.
+------------------------------------------------------------------------+
| |
| |
| +-------+ +-------+ |
| | 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 excessive VPN routes will influence performance of VRF on PEs.
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PEs and RR should have some mechanisms to identify and control the
advertisement of excessive VPN routes.
Based on previous principle, when PE2 overflows and PE1 not. PE2
triggers the RD-ORF message(RD1). RR will withdraw and stop to
advertise such excessive VPN routes to PE2. The communication among
PE2 with other PEs(PE1, PE3) for VPN1 will be influenced. But we
think it is acceptable.
5. Operation process of RD-ORF mechanism on receiver
The receiver of RD-ORF entries may be a RR or PE. As it receives the
RD-ORF entries, it will checks <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 RD-ORF entries into its ORF-Policy
table; otherwise, the receiver will discard it. Before the receiver
send a VPN route, it will check its ORF-Policy table whether there is
a related RD-ORF entry or not. If not, the receiver will send this
VPN route; otherwise, the receiver will stop sending that VPN route
to its peer.
6. Withdraw of RD-ORF entries
When the RD-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 RD-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 peers who have
previously received ORF entries.
7. RD-ORF Encoding
In this section, we defined a new ORF type called Route Distinguisher
Outbound Route Filter (RD-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:
o AFI (2 octets)
o SAFI (1 octet)
o When-to-refresh (1 octet): the value is IMMEDIATE or DEFER
o ORF Type (1 octet)
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o Length of ORF entries (2 octets)
A RD-ORF entry contains a common part and type-specific part. The
common part is encoded as follows:
o Action (2 bits): the value is ADD, REMOVE or REMOVE-ALL
o Match (1 bit): the value is PERMIT or DENY
o Reserved (5 bits)
RD-ORF also contains type-specific part. The encoding of the type-
specific part is shown in Figure 2.
+-----------------------------------------+
| |
| Sequence (4 octets) |
| |
+-----------------------------------------+
| |
| Route Distinguisher (8 octets) |
| |
+-----------------------------------------+
Figure 2: RD-ORF type-specific encoding
o Sequence: identifying the order in which RD-ORF is generated
o Route Distinguisher: distinguish the different user routes. The
RD-ORF filters the VPN routes it tends to send based on Route
Distinguisher.
Note that if the Action component of an ORF entry specifies REMOVE-
ALL, the ORF entry does not include the type-specific part. The
Sequence can uniquely identifies an RD-ORF entry. All VRFs share the
sequence field, and the corresponding sequence of RD-ORF sent by each
VRF will be recorded on the device.
When the BGP ROUTE-REFRESH message carries RD-ORF entries, it must be
set as follows:
o The ORF-Type MUST be set to RD-ORF.
o The AFI MUST be set to IPv4, IPv6, or Layer 2 VPN (L2VPN).
o If the AFI is set to IPv4 or IPv6, the SAFI MUST be set to MPLS-
labeled VPN address.
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o If the AFI is set to L2VPN, the SAFI MUST be set to BGP EVPN.
o The Match field MUST be equal to DENY.
8. Security Considerations
A BGP speaker will maintain the RD-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.
9. IANA Considerations
This document defines a new Outbound Route Filter type - Route
Distinguisher Outbound Route Filter (RD-ORF). The code point is from
the "BGP Outbound Route Filtering (ORF) Types". It is recommended to
set the code point of RD-ORF to 66.
10. Acknowledgement
Thanks Robert Raszuk, Jim Uttaro, Jakob Heitz, Jeff Tantsura, Rajiv
Asati, John E Drake, Gert Doering, Shuanglong Chen, Enke Chen and
Srihari Sangli for their valuable comments on this draft.
11. 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 EVPN", draft-
ietf-bess-evpn-inter-subnet-forwarding-15 (work in
progress), 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", draft-wang-idr-vpn-routes-control-analysis-04
(work in progress), September 2021.
[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>.
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[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>.
Authors' Addresses
Wei Wang
China Telecom
Beiqijia Town, Changping District
Beijing, Beijing 102209
China
Email: weiwang94@foxmail.com
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing, Beijing 102209
China
Email: wangaj3@chinatelecom.cn
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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
Email: jie.dong@huawei.com
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