< draft-ietf-lsr-ospf-prefix-originator-03.txt   draft-ietf-lsr-ospf-prefix-originator-04.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: February 28, 2020 Cisco Systems Expires: March 15, 2020 Cisco Systems
J. Dong J. Dong
Huawei Technologies Huawei Technologies
P. Psenak P. Psenak
K. Talaulikar K. Talaulikar
Cisco Systems Cisco Systems
August 27, 2019 September 12, 2019
OSPF Extension for Prefix Originator OSPF Prefix Originator Extension
draft-ietf-lsr-ospf-prefix-originator-03 draft-ietf-lsr-ospf-prefix-originator-04
Abstract Abstract
This document describes Open Shortest Path First (OSPF) v2 and OSPFv3 This document defines Open Shortest Path First (OSPF) encodings to
encodings to advertise the router-id of the originator of inter-area advertise the router-id of the originator of inter-area prefixes for
prefixes for OSPFv2 and OSPFv3 Link-State Advertisement (LSA), which OSPFv2 and OSPFv3 Link-State Advertisements (LSAs). The source
are needed in several use cases in multi-area OSPF use cases. originator is needed in several multi-area OSPF use cases.
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
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 28, 2020. This Internet-Draft will expire on March 15, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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skipping to change at page 2, line 15 skipping to change at page 2, line 15
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
2. Conventions used in this document . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Conventions used in this document . . . . . . . . . . . . . . 4 4. Inter-Area Prefix Source Advertisement Use Cases . . . . . . 4
5. Scenario Description . . . . . . . . . . . . . . . . . . . . 4 5. Prefix Source Router-ID sub-TLV . . . . . . . . . . . . . . . 5
6. Prefix Source Router-ID sub-TLV . . . . . . . . . . . . . . . 5 6. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 6
7. Extended LSA Elements of Procedure . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 10.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 7 10.2. Informative References . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 9 Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 9
Appendix B. Special Considerations on Inter-Area Topology Appendix B. Special Considerations on Inter-Area Topology
Retrieval . . . . . . . . . . . . . . . . . . . . . 9 Retrieval . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
[I-D.ietf-ospf-mpls-elc] defines mechanisms to Entropy Readable Label [I-D.ietf-ospf-mpls-elc] defines mechanisms to advertise Entropy
Depth (ERLD) for ingress Label Switching Router (LSR) to discover Readable Label Depth (ERLD) for ingress Label Switching Routers (LSR)
each LSR's capability of performing Entropy Label (EL) -based load- to discover other LSR's capability of performing Entropy Label based
balancing in Multi Protocol Label Switch (MPLS) networks. The load-balancing in MPLS networks. The ingress LSR can use this
ingress LSR can use this information to push the appropriate label information to construct the appropriate label stack for specific
stack for specific traffic, especially in segment routing traffic requirements, especially in segment routed networks and other
environments and other stacked LSPs scenarios. deployments requiring stacked LSPs.
However, in inter-area scenarios, the Area Border Router (ABR) does However, in inter-area scenarios, the Area Border Router (ABR) does
not advertise the originating OSPF router-id for inter-area prefixes. not advertise the originating OSPF router-id for inter-area prefixes.
An OSPF router in one area doesn't know where the prefixes really An OSPF router in one area doesn't know the origin area of inter-area
came from and can't determine the router that originated inter-area prefixes and can't determine the router that originated these
prefixes and then can't judge the ERLD capabilities of the prefixes or the ERLD capabilities of the destination. Therefore, it
destination. It is necessary to transfer the originator information is necessary to advertise the originator of these inter-area prefixes
of these inter-area prefixes to ensure the ingress LSR constructs the to ensure the ingress LSR can construct the appropriate label stack.
right label stack.
More generally, [RFC8476] defines a mechanism to advertise multiple More generally, [RFC8476] defines a mechanism to advertise multiple
types of supported Maximum SID Depths (MSD) at node and/or link types of supported Maximum SID Depths (MSD) at node and/or link
granularity. This information will be referred when the head-end granularity. This information will be referred when the head-end
router starts to send traffic to destination prefixes. In inter-area router starts to send traffic to destination prefixes. In inter-area
scenario, it is also necessary for the sender to learn the scenario, it is also necessary for the sender to learn the
capabilities of the receivers associated with the inter-area capabilities of the receivers associated with the inter-area
prefixes. prefixes.
There is also another scenario where knowing the originator of inter- There is another scenario where knowing the originator of inter-area
area prefixes is useful. For example, Border Gateway Protocol Link- prefixes is useful. For example, Border Gateway Protocol Link-State
State (BGP-LS) [RFC7752] describes mechanisms using the BGP protocol (BGP-LS) [RFC7752] describes mechanisms using the BGP protocol to
to advertise Link-State information. This can enable an Software advertise Link-State information. This information can enable a
Definition Network (SDN) controller to collect the underlay network Software Definition Network (SDN) controller to automatically
topology automatically. determine the underlay network topology.
But if the underlay network is divided into multiple areas and However, if the underlay network is partitioned into multiple areas
running the OSPF protocol, it is not easy for the SDN controller to and running the OSPF protocol, it is not easy for the SDN controller
rebuild the multi-area topology, because normally an ABR that to rebuild the multi-area topology since ABR that connects multiple
connects multiple areas will hide the detailed topology information areas will normally hide the detailed topology for these non-backbone
for these non-backbone areas. If only the internal routers within areas. If only the internal routers within backbone area run the
backbone area run the BGP-LS protocol, they just learn and report the BGP-LS protocol, they just learn and report the summary network
summary network information from the non-backbone areas. If the SDN information from the non-backbone areas. If the SDN controller can
controller can learn the originator of the inter-area prefixes, it is learn the originator of the inter-area prefixes, it is possible to
possible to rebuild the inter-area topology automatically. rebuild the inter-area topology.
[RFC7794] introduces the Intermediate System to Intermediate System [RFC7794] introduces the Intermediate System to Intermediate System
(IS-IS) "IPv4/IPv6 Source Router IDs" Type-Length-Value (TLV) to (IS-IS) "IPv4/IPv6 Source Router IDs" Type-Length-Value (TLV) to
advertise the source of the prefixes redistributed from a different advertise the source of prefixes leaked from a different IS-IS level.
IS-IS level. This TLV can be used in the above scenarios. Such This TLV can be used in the above scenarios. Such solution can also
solution can also be applied in networks that run the OSPF protocol, be applied in networks that run the OSPF protocol, but existing OSPF
but the related LSAs TLV must be extended. LSAs TLVs must be extended to include the router originating the
prefix.
This draft provides such solution for the OSPFv2 and OSPFv3 This draft provides such solution for the OSPFv2 and OSPFv3
protocols. protocols.
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119] . "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Terminology 3. Terminology
The following terms are used in this document: The following terms are used in this document:
o ABR: Area Border Router o ABR: Area Border Router
o ERLD: Entropy Readable Label Depth o ERLD: Entropy Readable Label Depth
o EL: Entropy Label o EL: Entropy Label
skipping to change at page 4, line 18 skipping to change at page 4, line 18
o MSD: Maximum SID Depths o MSD: Maximum SID Depths
o NLRI: Network Layer Reachability Information o NLRI: Network Layer Reachability Information
o OSPF: Open Shortest Path First o OSPF: Open Shortest Path First
o SID: Segment IDentifier o SID: Segment IDentifier
o SDN: Software Definition Network o SDN: Software Definition Network
4. Conventions used in this document 4. Inter-Area Prefix Source Advertisement Use Cases
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] .
5. Scenario Description
Figure 1 illustrates the topology scenario when OSPF is running in Figure 1 illustrates a topology where OSPF is running in multiple
multi-area. R0-R4 are routers in backbone area, S1-S4,T1-T4 are areas. R0-R4 are routers in the backbone area, S1-S4 are internal
internal routers in area 1 and area 2 respectively. R1 and R3 are routers in area 1, and T1-T4 are internal routers in area 2. R1 and
area border routers between area 0 and area 1. R2 and R4 are area R3 are ABRs between area 0 and area 1. R2 and R4 are ABRs between
border routers between area 0 and area 2. N1 is the network between area 0 and area 2. N1 is the network between router S1 and S2 and N2
router S1 and S2 and N2 is the network between router T1 and T2. Ls1 is the network between router T1 and T2. Ls1 is the loopback address
is the loopback address of Node S1 and Lt1 is the loopback address of of Node S1 and Lt1 is the loopback address of Node T1.
Node T1.
+-----------------+ +-----------------+
|IP SDN Controller| |IP SDN Controller|
+--------+--------+ +--------+--------+
| |
| BGP-LS | BGP-LS
| |
+---------------------+------+--------+-----+--------------+ +---------------------+------+--------+-----+--------------+
| +--+ +--+ ++-+ ++-+ +-++ + -+ +--+| | +--+ +--+ ++-+ ++-+ +-++ + -+ +--+|
| |S1+--------+S2+---+R1+---|R0+----+R2+---+T1+--------+T2|| | |S1+--------+S2+---+R1+---|R0+----+R2+---+T1+--------+T2||
skipping to change at page 5, line 27 skipping to change at page 4, line 50
| +-++ +-++ ++-+ +-++ ++++ +-++| | +-++ +-++ ++-+ +-++ ++++ +-++|
| |S4+--------+S3+---+R3+-----------+R4+---+T3+--------+T4|| | |S4+--------+S3+---+R3+-----------+R4+---+T3+--------+T4||
| +--+ +--+ ++-+ +-++ ++-+ +--+| | +--+ +--+ ++-+ +-++ ++-+ +--+|
| | | | | | | |
| | | | | | | |
| Area 1 | Area 0 | Area 2 | | Area 1 | Area 0 | Area 2 |
+---------------------+---------------+--------------------+ +---------------------+---------------+--------------------+
Figure 1: OSPF Inter-Area Prefix Originator Scenario Figure 1: OSPF Inter-Area Prefix Originator Scenario
If S1 wants to send traffic to prefix Lt1 that is connected T1 in If S1 wants to send traffic to prefix Lt1 that is connected to T1 in
another area, it should know the ERLD, and MSD values that are another area, it should know the ERLD and MSD values associated with
associated with the node T1, and then construct the right label stack the node T1, and then construct the right label stack at the ingress
at the ingress node for the target traffic. node for traffic destined to prefix Lt1.
In another scenario, If R0 has some method to learn the originator of In another scenario, If R0 has some method to learn the originator of
network N1 and reports such information to IP SDN controller, then it network N1 and reports such information to IP SDN controller, then it
is possible for the controller to retrieval the topology in non- is possible for the controller to reconstruct the topology in the
backbone area. The topology retrieval process and its usage non-backbone areas. The topology reconstruction process and its
limitation are described in the Appendix A and Appendix B . limitations are described in the Appendix A and Appendix B.
From the above scenarios, we can conclude it is useful to introduce From the above scenarios, we can conclude it is useful to define the
and define the prefix originator sub TLV within OSPF. OSPF prefix originator sub TLV .
6. Prefix Source Router-ID sub-TLV 5. Prefix Source Router-ID sub-TLV
[RFC7684] and [RFC8362] define the TLV extensions for OSPFv2 and [RFC7684] and [RFC8362] respectively define TLV-based LSAs for OSPFv2
OSPFv3 respectively. These documents facilitate addition of new and OSPFv3. These documents facilitate addition of new attributes
attributes for prefixes. Based on these formats, we can define new for prefixes and provide the basis for a sub-TLV to advertise the
sub-TLV to advertise the "Prefix Source Router ID", as that defined "Prefix Source Router ID". For OSPFv2, this sub-TLV is a sub-TLV of
in [RFC7794]. OSPFv2 Extended Prefix TLV which SHOULD be included in the "OSPFv2
Extended Prefix Opaque LSA" [RFC7684] for inter-area prefixes. For
OSPFv3, this sub-TLV is a sub-TLV of "Inter-Area-Prefix TLV", which
SHOULD be included in the "E-Inter-Area-Prefix-LSA" [RFC8362].
The "Prefix Source Router-ID" sub-TLV has the following format: The "Prefix Source Router-ID" 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Source Router-ID | | Prefix Source Router-ID |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
Figure 2: Prefix Source Router-ID sub-TLV Format Figure 2: Prefix Source Router-ID sub-TLV Format
o Source Router-ID Sub-TLV Type: TBD1[RFC7684] or TBD2 [RFC8362] o Source Router-ID Sub-TLV Type: TBD1 [RFC7684] or TBD2 [RFC8362]
o Length: 4 o Length: 4
o Value: Router-ID of OSPFv2/OSPFv3 source router o Value: Router-ID of OSPFv2/OSPFv3 router that is the source of the
prefix.
For OSPFv2, this sub-TLV is a sub-TLV of OSPFv2 Extended Prefix TLV, This sub-TLV provides the same functionality as the IS-IS "IPv4/IPv6
which SHOULD be included in the "OSPFv2 Extended Prefix Opaque LSA" . Source Router" TLV defined in [RFC7794].
For OSPFv3, this sub-TLV is a sub-TLV of "Inter-Area-Prefix TLV", 6. Elements of Procedure
which SHOULD be included in the "E-Inter-Area-Prefix-LSA".
7. Extended LSA Elements of Procedure When an ABR, for example R2 in Figure 1, receives a Router-LSA
advertisement in area 2, it SHOULD originate the corresponding
"OSPFv2 Extended Prefix Opaque LSA" for OSPFv2 or "E-Inter-Area-
Prefix-LSA" for OSPFv3 that includes the Source Router-ID sub-TLV for
the network prefixes. For example, to identify the source router
prefix Lt1 and other inter-area prefixes in Figure 1.
When an ABR, for example R2 in Figure 1, receives the Router-LSA When a router in another area, e.g., S1, receives such LSA, it then
announcement in area 2, it should originate the corresponding "OSPFv2 can ascertain that prefix Lt1 is associated with node T1 and obtain
Extended Prefix Opaque LSA" for OSPFv2 or "E-Inter-Area-Prefix-LSA" the ERLD or MSD value from T1's Router-Information LSA [RFC7770] and
for OSPFv3 that includes the Source Router-ID sub-TLV for the network construct the right label stack at the ingress node S1 for traffic
prefixes, e.g., for prefix Lt1, N2. etc., which identifies the source destined to prefix Lt1.
router that advertised the prefix.
When S1 in another area receives such LSA, it then can learn that When a router in another area, e.g., R0, receives such LSA, it learns
prefix Lt1 is associated with node T1, check the ERLD, or MSD value the Prefix Source Router-id and includes it in the prefix information
according to its necessity, and construct the right label stack at advertised to an SDN controller as described in
the ingress node S1 for the traffic destined to Lt1. [I-D.ietf-idr-bgp-ls-segment-routing-ext]. The SDN controller can
then use such information to build the inter-area topology according
to the process described in the Appendix A. The topology retrieval
process may not suitable for some environments as stated in
Appendix B.
When R0 receives such LSA, it learns the Prefix Source Router-id and 7. Security Considerations
includes it in the prefix information advertised to an SDN controller
as described in[I-D.ietf-idr-bgp-ls-segment-routing-ext]. The SDN
controller can then use such information to build the inter-area
topology according to the process described in the Appendix A. The
topology retrieval process may not suitable for some environments as
stated in Appendix B.
8. Security Considerations Since this document extends the "OSPFv2 Extended Prefix LSA" and
"OSPFv3 E-Inter-Area-Prefix LSA", the security considerations for
[RFC7684] and [RFC8362] are applicable.
Security concerns for OSPF are addressed in [RFC5709] Modification of the "Prefix Source Sub-TLV" could be used for a
Advertisement of the additional information defined in this document Denial-of-Service attack and could inhibit the use cases described in
introduces no new security concerns Section 4. If the OSPF domain is vulnerable to such attacks, OSPF
authentication should be used as defined for OSPFv2 in [RFC5709] and
[RFC7474] and for OSPFv3 in [RFC7166].
9. IANA Considerations Additionally, advertisement of the prefix source for inter-area
prefixes facilitates reconstruction of the OSPF topology for other
areas. Network operators may consider their topologies to be
sensitive confidential data. For OSPFv3, IPsec can be used to
provide confidentiality [RFC4552]. Since there is no standard
defined for native OSPFv2 IPsec, some form of secure tunnel is
required to provide confidentiality.
This specification defines one Prefix Source Router-ID sub-TLV as 8. IANA Considerations
described in Section 6. This value should be added to the existing
"OSPFv2 Extended Prefix TLV Sub-TLVs" registry and "OSPFv3 Extended-
LSA Sub-TLVs registry" respectively.
The following new sub-TLV is added to the registry of "OSPFv2 This specification defines the Prefix Source Router-ID sub-TLV as
Extended Prefix TLV Sub-TLVs". The allocation policy is IETF Review described in Section 5. This value should be added to the both
that defined in [RFC7684] existing "OSPFv2 Extended Prefix TLV Sub-TLVs" and "OSPFv3 Extended-
LSA Sub-TLVs" registries.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ The following sub-TLV is added to the "OSPFv2 Extended Prefix TLV
| Code Point | Description | Status | Sub-TLVs" registry. The allocation policy is IETF Review as defined
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ in [RFC7684]
| TBD | Prefix Source Sub-TLV | Allocation from IANA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
Figure 3: CodePoint in "OSPFv2 Extended Prefix TLV Sub-TLVs"
The following new sub-TLV is added to the registry of "OSPFv3 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Extended-LSA Sub-TLVs". The allocation policy is IETF Review that | Code Point | Description | Status |
defined in [RFC8362] +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | Prefix Source Sub-TLV | Allocation from IANA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Code Point in "OSPFv2 Extended Prefix TLV Sub-TLVs"
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ The following sub-TLV is added to the "OSPFv3 Extended-LSA Sub-TLVs"
| Code Point | Description | Status | registry. The allocation policy is IETF Review as defined in
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++ [RFC8362]
| TBD | Prefix Source Sub-TLV | Allocation from IANA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
Figure 4: CodePoint in "OSPFv3 Extended-LSA Sub-TLVs"
10. Acknowledgement +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code Point | Description | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | Prefix Source Sub-TLV | Allocation from IANA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Code Point in "OSPFv3 Extended-LSA Sub-TLVs"
Many thanks to Les Ginsberg for his valuable suggestions on this 9. Acknowledgement
draft. And also thanks Jeff Tantsura,Rob Shakir, Van De Velde
Gunter, Goethals Dirk, Shaofu Peng, John E Drake for their valuable
comments on this draft.
11. References Many thanks to Les Ginsberg for his suggestions on this draft. Also
thanks to Jeff Tantsura, Rob Shakir, Gunter Van De Velde, Goethals
Dirk, Shaofu Peng, and John E Drake for their valuable comments.
11.1. Normative References 10. References
10.1. 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>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M., [RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, DOI 10.17487/RFC5709, October Authentication", RFC 5709, DOI 10.17487/RFC5709, October
2009, <https://www.rfc-editor.org/info/rfc5709>. 2009, <https://www.rfc-editor.org/info/rfc5709>.
[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<https://www.rfc-editor.org/info/rfc7166>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>. 2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Ray, "North-Bound Distribution of Link-State and S. Shaffer, "Extensions to OSPF for Advertising Optional
Traffic Engineering (TE) Information Using BGP", RFC 7752, Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
DOI 10.17487/RFC7752, March 2016, February 2016, <https://www.rfc-editor.org/info/rfc7770>.
<https://www.rfc-editor.org/info/rfc7752>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>. March 2016, <https://www.rfc-editor.org/info/rfc7794>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA) F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>. 2018, <https://www.rfc-editor.org/info/rfc8362>.
[RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, [RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
"Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476, "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476,
DOI 10.17487/RFC8476, December 2018, DOI 10.17487/RFC8476, December 2018,
<https://www.rfc-editor.org/info/rfc8476>. <https://www.rfc-editor.org/info/rfc8476>.
11.2. Informative References 10.2. Informative References
[I-D.ietf-idr-bgp-ls-segment-routing-ext] [I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H., Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16 Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16
(work in progress), June 2019. (work in progress), June 2019.
[I-D.ietf-ospf-mpls-elc] [I-D.ietf-ospf-mpls-elc]
Xu, X., Kini, S., Psenak, P., Filsfils, C., and S. Xu, X., Kini, S., Psenak, P., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability and Entropy Litkowski, "Signaling Entropy Label Capability and Entropy
Readable Label-stack Depth Using OSPF", draft-ietf-ospf- Readable Label-stack Depth Using OSPF", draft-ietf-ospf-
mpls-elc-08 (work in progress), May 2019. mpls-elc-09 (work in progress), September 2019.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
Appendix A. Inter-Area Topology Retrieval Process Appendix A. Inter-Area Topology Retrieval Process
When an IP SDN Controller receives this information, it should When an IP SDN Controller receives BGP-LS [RFC7752] information, it
compare the prefix Network Layer Reachability Information (NLRI) that should compare the prefix Network Layer Reachability Information
included in the BGP-LS packet. When it encounters the same prefix (NLRI) that is included in the BGP-LS NLRI. When it encounters the
but with different source router ID, it should extract the same prefix but with different source router ID, it should extract
corresponding area-ID, rebuild the link between these two different the corresponding area-ID, rebuild the link between these two source
source routers in non-backbone area. Belows is one example that routers in the non-backbone area. Below is one example that based on
based on the Figure 1: the Figure 1:
Assuming we want to rebuild the connection between router S1 and Assuming we want to rebuild the connection between router S1 and
router S2 that locates in area 1: router S2 located in area 1:
a. Normally, router S1 will advertise prefix N1 within its router- a. Normally, router S1 will advertise prefix N1 within its router-
LSA. LSA.
b. When this router-LSA reaches the ABR router R1, it will convert b. When this router-LSA reaches the ABR router R1, it will convert
it into summary-LSA, add the Prefix Source Router-ID sub-TLV, it into summary-LSA, add the Prefix Source Router-ID sub-TLV,
which is router id of S1 in this example. which is router id of S1 in this example.
c. R1 then floods this extension summary-LSA to R0, which is running c. R1 then floods this extension summary-LSA to R0, which is using
BGP-LS protocol with IP SDN Controller. The controller then the BGP-LS protocol with IP SDN Controller. The controller then
knows the prefixes of N1 is from S1. knows the prefix for N1 is from S1.
d. Router S2 will do the similar process, and the controller will d. Router S2 will perform a similar process, and the controller will
also learn that prefixes N1 is also from S2. also learn that prefix N1 is also from S2.
e. Then it can reconstruct the link between S1 and S2, using the e. Then it can reconstruct the link between S1 and S2, using the
prefix N1. The topology within Area 1 can then be reconstructed prefix N1. The topology within Area 1 can then be reconstructed
accordingly. accordingly.
Iterating the above process continuously, the IP SDN controller can Iterating the above process continuously, the IP SDN controller can
retrieve a detailed topology that spans multiple areas. retrieve a detailed topology that spans multiple areas.
Appendix B. Special Considerations on Inter-Area Topology Retrieval Appendix B. Special Considerations on Inter-Area Topology Retrieval
The above topology retrieval process can be applied in the case where The above topology retrieval process can be applied in the case where
each link between routers is assigned a unique prefix. However, each point-to-point or multi-access link connecting routers is
there are some situations where this heuristic cannot be applied. assigned a unique prefix. However, there are some situations where
Specifically, the cases where the link is unnumbered or the prefix this heuristic cannot be applied. Specifically, the cases where the
corresponding to the link is an anycast prefix. 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 The Appendix A heuristic to rebuild the topology can normally be used
if all links are numbered. For anycast prefixes, if it corresponds 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 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 apply. 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
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