draft-ietf-lsr-ospf-prefix-originator-06.txt   draft-ietf-lsr-ospf-prefix-originator-07.txt 
LSR Working Group A. Wang LSR Working Group A. Wang
Internet-Draft China Telecom Internet-Draft China Telecom
Intended status: Standards Track A. Lindem Intended status: Standards Track A. Lindem
Expires: January 1, 2021 Cisco Systems Expires: April 23, 2021 Cisco Systems
J. Dong J. Dong
Huawei Technologies Huawei Technologies
P. Psenak P. Psenak
K. Talaulikar K. Talaulikar
Cisco Systems Cisco Systems
June 30, 2020 October 20, 2020
OSPF Prefix Originator Extensions OSPF Prefix Originator Extensions
draft-ietf-lsr-ospf-prefix-originator-06 draft-ietf-lsr-ospf-prefix-originator-07
Abstract Abstract
This document defines OSPF extensions to include information This document defines OSPF extensions to include information
associated with the node originating a prefix along with the prefix associated with the node originating a prefix along with the prefix
advertisement. advertisement.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on January 1, 2021. This Internet-Draft will expire on April 23, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3
2.1. Prefix Source Router-ID Sub-TLV . . . . . . . . . . . . . 4 2.1. Prefix Source Router-ID Sub-TLV . . . . . . . . . . . . . 3
2.2. Prefix Originator Sub-TLV . . . . . . . . . . . . . . . . 4 2.2. Prefix Originator Sub-TLV . . . . . . . . . . . . . . . . 4
3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 5 3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
Appendix B. Special Considerations on Inter-Area Topology
Retrieval . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
Prefix attributes are advertised in OSPFv2 [RFC2328] using the Prefix attributes are advertised in OSPFv2 [RFC2328] using the
Extended Prefix Opaque Link State Advertisement (LSA) [RFC7684] and Extended Prefix Opaque Link State Advertisement (LSA) [RFC7684] and
in OSPFv3 [RFC5340] using the various Extended Prefix LSA types in OSPFv3 [RFC5340] using the various Extended Prefix LSA types
[RFC8362]. [RFC8362].
The identification of the originating router for a prefix in OSPF The identification of the originating router for a prefix in OSPF
varies by the type of the prefix and is currently not always varies by the type of the prefix and is currently not always
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This document proposes extensions to the OSPF protocol for inclusion This document proposes extensions to the OSPF protocol for inclusion
of information associated with the router originating the prefix of information associated with the router originating the prefix
along with the prefix advertisement. These extensions do not change along with the prefix advertisement. These extensions do not change
the core OSPF route computation functionality. They provide useful the core OSPF route computation functionality. They provide useful
information for topology analysis and traffic engineering, especially information for topology analysis and traffic engineering, especially
on a controller when this information is advertised as an attribute on a controller when this information is advertised as an attribute
of the prefixes via mechanisms such as Border Gateway Protocol Link- of the prefixes via mechanisms such as Border Gateway Protocol Link-
State (BGP-LS) [RFC7752]. State (BGP-LS) [RFC7752].
Applications related to use of the prefix originating node
information for topology reconstruction process on a controller and
the associated limitations are described in Appendix A and
Appendix B.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Protocol Extensions 2. Protocol Extensions
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TLV, Inter-Area-Prefix TLV, and External-Prefix TLV [RFC8362] when TLV, Inter-Area-Prefix TLV, and External-Prefix TLV [RFC8362] when
originating either an IPv4 [RFC5838] or an IPv6 prefix advertisement. originating either an IPv4 [RFC5838] or an IPv6 prefix advertisement.
The Prefix Originator Sub-TLV has the following format: The Prefix Originator Sub-TLV has the following format:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Address (4 or 16 octects) | | Router Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Prefix Originator Sub-TLV Format Figure 2: Prefix Originator Sub-TLV Format
Where: Where:
o Type: TBD1 for OSPFv2 and TBD2 for OSPFv3 o Type: TBD1 for OSPFv2 and TBD2 for OSPFv3
o Length: 4 or 16 o Length: 4 or 16
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router that originated the IPv4 or IPv6 prefix advertisement. router that originated the IPv4 or IPv6 prefix advertisement.
Such an address would be semantically equivalent to what may be Such an address would be semantically equivalent to what may be
advertised in the OSPFv2 Router Address TLV [RFC3630] or in the advertised in the OSPFv2 Router Address TLV [RFC3630] or in the
OSPFv3 Router IPv6 Address TLV [RFC5329]. OSPFv3 Router IPv6 Address TLV [RFC5329].
A prefix advertisement MAY include more than one Prefix Originator A prefix advertisement MAY include more than one Prefix Originator
sub-TLV, one corresponding to each of the Equal-Cost Multi-Path sub-TLV, one corresponding to each of the Equal-Cost Multi-Path
(ECMP) nodes that originated the given prefix. (ECMP) nodes that originated the given prefix.
A received Prefix Originator Sub-TLV that has an invalid length (not A received Prefix Originator Sub-TLV that has an invalid length (not
4 or 16) or a Reachable Address containing an invalid IPv4 or IPv6 4 or 16) or a Router Address containing an invalid IPv4 or IPv6
address (dependent on address family of the associated prefix) MUST address (dependent on address family of the associated prefix) MUST
be considered invalid and ignored. Additionally, reception of such be considered invalid and ignored. Additionally, reception of such
Sub-TLV SHOULD be logged as an error (subject to rate-limiting). Sub-TLV SHOULD be logged as an error (subject to rate-limiting).
[RFC7794] provides similar functionality for the Intermediate System [RFC7794] provides similar functionality for the Intermediate System
to Intermediate System (IS-IS) protocol. to Intermediate System (IS-IS) protocol.
3. Elements of Procedure 3. Elements of Procedure
This section describes the procedure for advertisement of the Prefix This section describes the procedure for advertisement of the Prefix
Source Router-ID and Prefix Originator Sub-TLVs along with the prefix Source Router-ID and Prefix Originator Sub-TLVs along with the prefix
advertisement. advertisement.
The OSPF Router ID of the Prefix Source Router-ID is set to the OSPF The OSPF Router ID of the Prefix Source Router-ID is set to the OSPF
Router ID of the node originating the prefix in the OSPF domain. Router ID of the node originating the prefix in the OSPF domain.
If the originating node is advertising an OSPFv2 Router Address TLV If the originating node is advertising an OSPFv2 Router Address TLV
[RFC3630] or an OSPFv3 Router IPv6 Address TLV [RFC5329], then that [RFC3630] or an OSPFv3 Router IPv6 Address TLV [RFC5329], then that
value is set in the Router Address field of the Prefix Originator value is set in the Router Address field of the Prefix Originator
Sub-TLV. When the orignating node is not advertising such an Sub-TLV. When the originating node is not advertising such an
address, implementations MAY support mechanisms to determine a address, implementations MAY support mechanisms to determine a
reachable address belonging to the originating node to set in the reachable address (e.g., advertised with the N-flag set [RFC7684] or
Router Address field. Such mechanisms are outside the scope of this N-bit set [RFC8362] and either matching the OSPF Router ID or the
document. highest IP address) belonging to the originating node to set in the
Router Address field.
Implementations MAY support the selection of specific prefixes for Implementations MAY support the selection of specific prefixes for
which the originating node information needs to be included with which the originating node information needs to be included with
their prefix advertisements. their prefix advertisements.
When an ABR generates inter-area prefix advertisements into its non- When an ABR generates inter-area prefix advertisements into its non-
backbone areas corresponding to an inter-area prefix advertisement backbone areas corresponding to an inter-area prefix advertisement
from the backbone area, the only way to determine the originating from the backbone area, the only way to determine the originating
node information is based on the Prefix Source Router-ID and Prefix node information is based on the Prefix Source Router-ID and Prefix
Originator Sub-TLVs present in the inter-area prefix advertisement Originator Sub-TLVs present in the inter-area prefix advertisement
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| 27 | Prefix Source Router-ID Sub-TLV | early allocation done | | 27 | Prefix Source Router-ID Sub-TLV | early allocation done |
| TBD2 | Prefix Originator Sub-TLV | pending | | TBD2 | Prefix Originator Sub-TLV | pending |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Code Points in OSPFv3 Extended-LSA Sub-TLVs Figure 4: Code Points in OSPFv3 Extended-LSA Sub-TLVs
6. Acknowledgement 6. Acknowledgement
Many thanks to Les Ginsberg for his suggestions on this draft. Also Many thanks to Les Ginsberg for his suggestions on this draft. Also
thanks to Jeff Tantsura, Rob Shakir, Gunter Van De Velde, Goethals thanks to Jeff Tantsura, Rob Shakir, Gunter Van De Velde, Goethals
Dirk, Smita Selot, Shaofu Peng, and John E Drake for their valuable Dirk, Smita Selot, Shaofu Peng, John E Drake and Baalajee S for their
comments. review and valuable comments.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
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R. Aggarwal, "Support of Address Families in OSPFv3", R. Aggarwal, "Support of Address Families in OSPFv3",
RFC 5838, DOI 10.17487/RFC5838, April 2010, RFC 5838, DOI 10.17487/RFC5838, April 2010,
<https://www.rfc-editor.org/info/rfc5838>. <https://www.rfc-editor.org/info/rfc5838>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-editor.org/info/rfc7752>.
Appendix A. Inter-Area Topology Retrieval Process
When an IP SDN Controller receives BGP-LS [RFC7752] information, it
should compare the prefix Network Layer Reachability Information
(NLRI) that is included in the BGP-LS NLRI. When it encounters the
same prefix but with different source router ID, it should extract
the corresponding area-ID, rebuild the link between these two source
routers in the non-backbone area. Below is one example that based on
the Figure 5 which illustrates a topology where OSPF is running in
multiple areas.
+-----------------+
|IP SDN Controller|
+--------+--------+
|
| BGP-LS
|
+---------------------+------+--------+-----+--------------+
| +--+ +--+ ++-+ ++-+ +-++ + -+ +--+|
| |S1+--------+S2+---+R1+---|R0+----+R2+---+T1+--------+T2||
| +-++ N1 +-++ ++-+ +--+ +-++ ++++ N2 +-++|
| | | | | || | |
| | | | | || | |
| +-++ +-++ ++-+ +-++ ++++ +-++|
| |S4+--------+S3+---+R3+-----------+R4+---+T3+--------+T4||
| +--+ +--+ ++-+ +-++ ++-+ +--+|
| | | |
| | | |
| Area 1 | Area 0 | Area 2 |
+---------------------+---------------+--------------------+
Figure 5: OSPF Inter-Area Prefix Originator Scenario
R0-R4 are routers in the backbone area, S1-S4 are internal routers in
area 1, and T1-T4 are internal routers in area 2. R1 and R3 are ABRs
between area 0 and area 1. R2 and R4 are ABRs between area 0 and
area 2. N1 is the network between router S1 and S2 and N2 is the
network between router T1 and T2. Ls1 is the loopback address of
Node S1 and Lt1 is the loopback address of Node T1.
Assuming we want to rebuild the connection between router S1 and
router S2 located in area 1:
a. Normally, router S1 will advertise prefix N1 within its router-
LSA.
b. When this router-LSA reaches the ABR router R1, it will convert
it into summary-LSA, add the Source Router-ID Sub-TLV and the
Prefix Originator Sub-TLV, as described in Section 3.
c. R1 then floods this extension summary-LSA to R0, which is using
the BGP-LS protocol with IP SDN Controller. The controller then
knows the prefix for N1 is from S1.
d. Router S2 will perform a similar process, and the controller will
also learn that prefix N1 is also from S2.
e. Then it can reconstruct the link between S1 and S2, using the
prefix N1. The topology within Area 1 can then be reconstructed
accordingly.
Iterating the above process continuously, the IP SDN controller can
retrieve a detailed topology that spans multiple areas.
Appendix B. Special Considerations on Inter-Area Topology Retrieval
The above topology retrieval process can be applied in the case where
each point-to-point or multi-access link connecting routers is
assigned a unique prefix. However, there are some situations where
this heuristic cannot be applied. Specifically, the cases where the
link is unnumbered or the prefix corresponding to the link is an
anycast prefix.
The Appendix A heuristic to rebuild the topology can normally be used
if all links are numbered. For anycast prefixes, if it corresponds
to the loopback interface and has a host prefix length, i.e., 32 for
IPv4 prefixes and 128 for IPv6 prefixes, Appendix A can also applied
since these anycast prefixes are not required to reconstruct the
topology.
Authors' Addresses Authors' Addresses
Aijun Wang Aijun Wang
China Telecom China Telecom
Beiqijia Town, Changping District Beiqijia Town, Changping District
Beijing 102209 Beijing 102209
China China
Email: wangaj3@chinatelecom.cn Email: wangaj3@chinatelecom.cn
Acee Lindem Acee Lindem
Cisco Systems Cisco Systems
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