draft-ietf-ospf-segment-routing-msd-25.txt   rfc8476.txt 
OSPF Working Group J. Tantsura Internet Engineering Task Force (IETF) J. Tantsura
Internet-Draft Apstra, Inc. Request for Comments: 8476 Apstra, Inc.
Intended status: Standards Track U. Chunduri Category: Standards Track U. Chunduri
Expires: April 20, 2019 Huawei Technologies ISSN: 2070-1721 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc.
P. Psenak P. Psenak
Cisco Systems Cisco Systems
October 17, 2018 December 2018
Signaling MSD (Maximum SID Depth) using OSPF Signaling Maximum SID Depth (MSD) Using OSPF
draft-ietf-ospf-segment-routing-msd-25
Abstract Abstract
This document defines a way for an Open Shortest Path First (OSPF) This document defines a way for an Open Shortest Path First (OSPF)
Router to advertise multiple types of supported Maximum SID(Segment router to advertise multiple types of supported Maximum SID Depths
Identifier) Depths (MSDs) at node and/or link granularity. Such (MSDs) at node and/or link granularity. Such advertisements allow
advertisements allow entities (e.g., centralized controllers) to entities (e.g., centralized controllers) to determine whether a
determine whether a particular SID stack can be supported in a given particular Segment Identifier (SID) stack can be supported in a given
network. This document defines only one type of MSD, but defines an network. This document only refers to the Signaling MSD as defined
encoding that can support other MSD types. Here the term OSPF means in RFC 8491, but it defines an encoding that can support other MSD
both OSPFv2 and OSPFv3. types. Here, the term "OSPF" means both OSPFv2 and OSPFv3.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on April 20, 2019. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8476.
Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction ....................................................3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology ................................................4
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language ......................................4
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 2. Node MSD Advertisement ..........................................5
3. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5 3. Link MSD Sub-TLV ................................................6
4. Procedures for Defining and Using Node and Link MSD 4. Procedures for Defining and Using Node and Link MSD
Advertisements . . . . . . . . . . . . . . . . . . . . . . . 6 Advertisements ..................................................7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations .............................................7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations .........................................8
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 7. References ......................................................9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References .......................................9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.2. Informative References ....................................10
9.1. Normative References . . . . . . . . . . . . . . . . . . 9 Acknowledgements ..................................................11
9.2. Informative References . . . . . . . . . . . . . . . . . 9 Contributors ......................................................11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses ................................................11
1. Introduction 1. Introduction
When Segment Routing (SR) paths are computed by a centralized When Segment Routing (SR) paths are computed by a centralized
controller, it is critical that the controller learns the Maximum SID controller, it is critical that the controller learn the Maximum SID
(Segment Identifier) Depth (MSD) that can be imposed at each node/ Depth (MSD) that can be imposed at each node/link on a given SR path.
link on a given SR path to ensure that the Segment Identifier (SID) This ensures that the Segment Identifier (SID) stack depth of a
stack depth of a computed path doesn't exceed the number of SIDs the computed path doesn't exceed the number of SIDs the node is capable
node is capable of imposing. of imposing.
[I-D.ietf-pce-segment-routing] defines how to signal MSD in the Path [PCEP-EXT] defines how to signal MSD in the Path Computation Element
Computation Element communication Protocol (PCEP). However, if PCEP Communication Protocol (PCEP). However, if PCEP is not supported/
is not supported/configured on the head-end of an SR tunnel or a configured on the head-end of an SR tunnel or a Binding-SID anchor
Binding-SID anchor node and controller does not participate in IGP node, and the controller does not participate in IGP routing, it has
routing, it has no way to learn the MSD of nodes and links. BGP-LS no way of learning the MSD of nodes and links. BGP-LS (Distribution
(Distribution of Link-State and TE Information using Border Gateway of Link-State and TE Information Using BGP) [RFC7752] defines a way
Protocol) [RFC7752] defines a way to expose topology and associated to expose topology and associated attributes and capabilities of the
attributes and capabilities of the nodes in that topology to a nodes in that topology to a centralized controller. MSD signaling by
centralized controller. MSD signaling by BGP-LS has been defined in BGP-LS has been defined in [MSD-BGP]. Typically, BGP-LS is
[I-D.ietf-idr-bgp-ls-segment-routing-msd]. Typically, BGP-LS is
configured on a small number of nodes that do not necessarily act as configured on a small number of nodes that do not necessarily act as
head-ends. In order for BGP-LS to signal MSD for all the nodes and head-ends. In order for BGP-LS to signal MSD for all the nodes and
links in the network MSD is relevant, MSD capabilities SHOULD be links in the network for which MSD is relevant, MSD capabilities
advertised by every OSPF router in the network. SHOULD be advertised by every OSPF router in the network.
Other types of MSD are known to be useful. For example, Other types of MSDs are known to be useful. For example, [ELC-ISIS]
[I-D.ietf-ospf-mpls-elc] defines Readable Label Depth Capability defines Entropy Readable Label Depth (ERLD), which is used by a
(RLDC) that is used by a head-end to insert an Entropy Label (EL) at head-end to insert an Entropy Label (EL) at a depth where it can be
a depth that could be read by transit nodes. read by transit nodes.
This document defines an extension to OSPF used to advertise one or This document defines an extension to OSPF used to advertise one or
more types of MSD at node and/or link granularity. In the future it more types of MSDs at node and/or link granularity. In the future,
is expected, that new MSD-types will be defined to signal additional it is expected that new MSD-Types will be defined to signal
capabilities e.g., entropy labels, SIDs that can be imposed through additional capabilities, e.g., ELs, SIDs that can be imposed through
recirculation, or SIDs associated with another dataplane e.g., IPv6. recirculation, or SIDs associated with another data plane such
as IPv6.
MSD advertisements MAY be useful even if Segment Routing itself is MSD advertisements MAY be useful even if SR itself is not enabled.
not enabled. For example, in a non-SR MPLS network, MSD defines the For example, in a non-SR MPLS network, MSD defines the maximum label
maximum label depth. depth.
1.1. Terminology 1.1. Terminology
This memo makes use of the terms defined in [RFC7770] This memo makes use of the terms defined in [RFC7770].
BGP-LS: Distribution of Link-State and TE Information using Border BGP-LS: Distribution of Link-State and TE Information Using BGP
Gateway Protocol
OSPF: Open Shortest Path First OSPF: Open Shortest Path First
MSD: Maximum SID Depth - the number of SIDs supported by a node or a MSD: Maximum SID Depth - the number of SIDs supported by a node
link on a node or a link on a node
SID: Segment Identifier as defined in [RFC8402] SID: Segment Identifier as defined in [RFC8402]
Label Imposition: Imposition is the act of modifying and/or adding Label Imposition: Imposition is the act of modifying and/or adding
labels to the outgoing label stack associated with a packet. This labels to the outgoing label stack associated with a packet.
includes: This includes:
o replacing the label at the top of the label stack with a new label * replacing the label at the top of the label stack with a
new label
o pushing one or more new labels onto the label stack * pushing one or more new labels onto the label stack
The number of labels imposed is then the sum of the number of labels The number of labels imposed is then the sum of the number of labels
which are replaced and the number of labels which are pushed. See that are replaced and the number of labels that are pushed. See
[RFC3031] for further details. [RFC3031] for further details.
PCC: Path Computation Client PCEP: Path Computation Element Communication Protocol
PCE: Path Computation Element
PCEP: Path Computation Element Protocol
SR: Segment Routing
SID: Segment Identifier SR: Segment Routing
LSA: Link state advertisement LSA: Link State Advertisement
RI: OSPF Router Information LSA RI: Router Information
1.2. Requirements Language 1.2. 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
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Node MSD Advertisement 2. Node MSD Advertisement
The node MSD TLV within the body of the OSPF RI Opaque LSA [RFC7770] The Node MSD TLV within the body of the OSPF RI Opaque LSA [RFC7770]
is defined to carry the provisioned SID depth of the router is defined to carry the provisioned SID depth of the router
originating the RI LSA. Node MSD is the smallest MSD supported by originating the RI LSA. Node MSD is the smallest MSD supported by
the node on the set of interfaces configured for use by the the node on the set of interfaces configured for use by the
advertising IGP instance. MSD values may be learned via a hardware advertising IGP instance. MSD values may be learned via a hardware
API or may be provisioned. API or may be provisioned.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MSD-Type | MSD-Value | MSD-Type... | MSD-Value... |
| MSD-Type | MSD-Value | MSD-Type... | MSD-Value... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Node MSD TLV Figure 1: Node MSD TLV
Type: 12 Type: 12
Length: variable (multiple of 2 octets) and represents the total Length: variable (multiple of 2 octets); represents the total length
length of value field in octets. of the value field in octets.
Value: consists of one or more pairs of a 1 octet MSD-type and 1 Value: consists of one or more pairs of a 1-octet MSD-Type and
octet MSD-Value. 1-octet MSD-Value.
MSD-Type: one of the values defined in the IGP MSD-Types registry MSD-Type: one of the values defined in the "IGP MSD-Types" registry
defined in [I-D.ietf-isis-segment-routing-msd]. defined in [RFC8491].
MSD-Value: a number in the range of 0-255. For all MSD-Types, 0 MSD-Value: a number in the range of 0-255. For all MSD-Types, 0
represents lack of the ability to impose MSD stack of any depth; any represents the lack of ability to impose an MSD stack of any depth;
other value represents that of the node. This value MUST represent any other value represents that of the node. This value MUST
the lowest value supported by any link configured for use by the represent the lowest value supported by any link configured for use
advertising OSPF instance. by the advertising OSPF instance.
This TLV is applicable to OSPFv2 and to OSPFv3 and is optional. The This TLV is optional and is applicable to both OSPFv2 and OSPFv3.
scope of the advertisement is specific to the deployment. The scope of the advertisement is specific to the deployment.
When multiple Node MSD TLVs are received from a given router, the When multiple Node MSD TLVs are received from a given router, the
receiver MUST use the first occurrence of the TLV in the Router receiver MUST use the first occurrence of the TLV in the Router
Information LSA. If the Node MSD TLV appears in multiple Router Information (RI) LSA. If the Node MSD TLV appears in multiple RI
Information LSAs that have different flooding scopes, the Node MSD LSAs that have different flooding scopes, the Node MSD TLV in the RI
TLV in the Router Information LSA with the area-scoped flooding scope LSA with the area-scoped flooding scope MUST be used. If the Node
MUST be used. If the Node MSD TLV appears in multiple Router MSD TLV appears in multiple RI LSAs that have the same flooding
Information LSAs that have the same flooding scope, the Node MSD TLV scope, the Node MSD TLV in the RI LSA with the numerically smallest
in the Router Information (RI) LSA with the numerically smallest
Instance ID MUST be used and other instances of the Node MSD TLV MUST Instance ID MUST be used and other instances of the Node MSD TLV MUST
be ignored. The RI LSA can be advertised at any of the defined be ignored. The RI LSA can be advertised at any of the defined
opaque flooding scopes (link, area, or Autonomous System (AS)). For opaque flooding scopes (link, area, or Autonomous System (AS)). For
the purpose of Node MSD TLV advertisement, area-scoped flooding is the purpose of Node MSD TLV advertisement, area-scoped flooding is
RECOMMENDED. RECOMMENDED.
3. Link MSD sub-TLV 3. Link MSD Sub-TLV
The link sub-TLV is defined to carry the MSD of the interface The Link MSD sub-TLV is defined to carry the MSD of the interface
associated with the link. MSD values may be learned via a hardware associated with the link. MSD values may be learned via a hardware
API or may be provisioned. API or may be provisioned.
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MSD-Type | MSD-Value | MSD-Type... | MSD-Value... |
| MSD-Type | MSD-Value | MSD-Type... | MSD-Value... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Link MSD Sub-TLV Figure 2: Link MSD Sub-TLV
Type: Type:
For OSPFv2, the link-level MSD-Value is advertised as an optional
sub-TLV of the OSPFv2 Extended Link TLV as defined in [RFC7684]
and has a type of 6.
For OSPFv2, the Link level MSD-Value is advertised as an optional For OSPFv3, the link-level MSD-Value is advertised as an optional
Sub-TLV of the OSPFv2 Extended Link TLV as defined in [RFC7684], and sub-TLV of the E-Router-LSA TLV as defined in [RFC8362] and has a
has a type of 6. type of 9.
For OSPFv3, the Link level MSD-Value is advertised as an optional
Sub-TLV of the E-Router-LSA TLV as defined in [RFC8362], and has a
type of 9.
Length: variable and same as defined in Section 2.
Value: consists of one or more pairs of a 1 octet MSD-type and 1 Length: variable; same as defined in Section 2.
octet MSD-Value.
MSD-Type: one of the values defined in the MSD-Types registry defined Value: consists of one or more pairs of a 1-octet MSD-Type and
in [I-D.ietf-isis-segment-routing-msd]. 1-octet MSD-Value.
MSD-Value field contains Link MSD of the router originating the MSD-Type: one of the values defined in the "IGP MSD-Types" registry
corresponding LSA as specified for OSPFv2 and OSPFv3. Link MSD is a defined in [RFC8491].
number in the range of 0-255. For all MSD-Types, 0 represents lack
of the ability to impose MSD stack of any depth; any other value
represents that of the particular link when used as an outgoing
interface.
If this sub-TLV is advertised multiple times in the same OSPFv2 The MSD-Value field contains the Link MSD of the router originating
Extended Link Opaque LSA/E-Router-LSA, only the first instance of the the corresponding LSA as specified for OSPFv2 and OSPFv3. The Link
TLV MUST be used by receiving OSPF routers. This situation SHOULD be MSD is a number in the range of 0-255. For all MSD-Types, 0
logged as an error. represents the lack of ability to impose an MSD stack of any depth;
any other value represents that of the particular link when used as
an outgoing interface.
If this sub-TLV is advertised multiple times for the same link in If this sub-TLV is advertised multiple times for the same link in
different OSPF Extended Link Opaque LSAs/E-Router-LSAs originated by different OSPF Extended Link Opaque LSAs / E-Router-LSAs originated
the same OSPF router, the OSPFv2 Extended Link TLV in the OSPFv2 by the same OSPF router, the sub-TLV in the OSPFv2 Extended Link
Extended Link Opaque LSA with the smallest Opaque ID or in the OSPFv3 Opaque LSA with the smallest Opaque ID or in the OSPFv3 E-Router-LSA
E-Router-LSA with the smallest Link State ID MUST be used by with the smallest Link State ID MUST be used by receiving OSPF
receiving OSPF routers. This situation MAY be logged as a warning. routers. This situation SHOULD be logged as an error.
4. Procedures for Defining and Using Node and Link MSD Advertisements 4. Procedures for Defining and Using Node and Link MSD Advertisements
When Link MSD is present for a given MSD-type, the value of the Link When Link MSD is present for a given MSD-Type, the value of the Link
MSD MUST take precedence over the Node MSD. When a Link MSD-type is MSD MUST take precedence over the Node MSD. When a Link MSD-Type is
not signaled but the Node MSD-type is, then the Node MSD-type value not signaled but the Node MSD-Type is, then the Node MSD-Type value
MUST be considered as the MSD value for that link. MUST be considered as the MSD value for that link.
In order to increase flooding efficiency, it is RECOMMENDED that In order to increase flooding efficiency, it is RECOMMENDED that
routers with homogenous link MSD values advertise just the Node MSD routers with homogenous Link MSD values advertise just the Node MSD
value. value.
The meaning of the absence of both Node and Link MSD advertisements The meaning of the absence of both Node and Link MSD advertisements
for a given MSD-type is specific to the MSD-type. Generally it can for a given MSD-Type is specific to the MSD-Type. Generally, it can
only be inferred that the advertising node does not support only be inferred that the advertising node does not support
advertisement of that MSD-type. However, in some cases the lack of advertisement of that MSD-Type. However, in some cases the lack of
advertisement might imply that the functionality associated with the advertisement might imply that the functionality associated with the
MSD-type is not supported. The correct interpretation MUST be MSD-Type is not supported. Per [RFC8491], the correct interpretation
specified when an MSD-type is defined in MUST be specified when an MSD-Type is defined.
[I-D.ietf-isis-segment-routing-msd].
5. IANA Considerations 5. IANA Considerations
This specification updates several existing OSPF registries. This specification updates several existing OSPF registries.
IANA has allocated TLV type 12 from the OSPF Router Information (RI) IANA has allocated TLV type 12 from the "OSPF Router Information (RI)
TLVs Registry as defined by [RFC7770]. TLVs" registry as defined by [RFC7770].
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
12 Node MSD This document 12 Node MSD This document
Figure 3: RI Node MSD Figure 3: RI Node MSD
IANA has allocated sub-TLV type 6 from the OSPFv2 Extended Link TLV IANA has allocated sub-TLV type 6 from the "OSPFv2 Extended Link TLV
Sub-TLVs registry. Sub-TLVs" registry.
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
6 OSPFv2 Link MSD This document 6 OSPFv2 Link MSD This document
Figure 4: OSPFv2 Link MSD Figure 4: OSPFv2 Link MSD
IANA has allocated sub-TLV type 9 from the OSPFv3 Extended-LSA Sub- IANA has allocated sub-TLV type 9 from the "OSPFv3 Extended-LSA
TLV registry. Sub-TLVs" registry.
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
9 OSPFv3 Link MSD This document 9 OSPFv3 Link MSD This document
Figure 5: OSPFv3 Link MSD Figure 5: OSPFv3 Link MSD
6. Security Considerations 6. Security Considerations
Security concerns for OSPF are addressed in [RFC7474], [RFC4552] and Security concerns for OSPF are addressed in [RFC7474], [RFC4552], and
[RFC7166]. Further security analysis for OSPF protocol is done in [RFC7166]. Further security analysis for the OSPF protocol is done
[RFC6863]. Security considerations, as specified by [RFC7770], in [RFC6863]. Security considerations as specified by [RFC7770],
[RFC7684] and [RFC8362] are applicable to this document. [RFC7684], and [RFC8362] are applicable to this document.
Implementations MUST assure that malformed TLV and Sub-TLV defined in Implementations MUST ensure that malformed TLVs and sub-TLVs defined
this document are detected and do not provide a vulnerability for in this document are detected and do not provide a vulnerability for
attackers to crash the OSPF router or routing process. Reception of attackers to crash the OSPF router or routing process. Reception of
malformed TLV or Sub-TLV SHOULD be counted and/or logged for further malformed TLVs or sub-TLVs SHOULD be counted and/or logged for
analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be rate- further analysis. Logging of malformed TLVs and sub-TLVs SHOULD be
limited to prevent a Denial of Service (DoS) attack (distributed or rate-limited to prevent a Denial-of-Service (DoS) attack (distributed
otherwise) from overloading the OSPF control plane. or otherwise) from overloading the OSPF control plane.
Advertisement of an incorrect MSD value may have negative Advertisement of an incorrect MSD value may have negative
consequences. If the value is smaller than supported, path consequences. If the value is smaller than supported, path
computation may fail to compute a viable path. If the value is computation may fail to compute a viable path. If the value is
larger than supported, an attempt to instantiate a path that can't be larger than supported, an attempt to instantiate a path that can't be
supported by the head-end (the node performing the SID imposition) supported by the head-end (the node performing the SID imposition)
may occur. may occur.
The presence of this information also may inform an attacker of how The presence of this information may also inform an attacker of how
to induce any of the aforementioned conditions. to induce any of the aforementioned conditions.
There's no Denial of Service risk specific to this extension, and it There's no DoS risk specific to this extension, and it is not
is not vulnerable to replay attacks. vulnerable to replay attacks.
7. Contributors
The following people contributed to this document:
Les Ginsberg
Email: ginsberg@cisco.com
8. Acknowledgments
The authors would like to thank Acee Lindem, Ketan Talaulikar, Tal
Mizrahi, Stephane Litkowski and Bruno Decraene for their reviews and
valuable comments.
9. References 7. References
9.1. Normative References
[I-D.ietf-isis-segment-routing-msd] 7.1. Normative References
Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling MSD (Maximum SID Depth) using IS-IS", draft-
ietf-isis-segment-routing-msd-19 (work in progress),
October 2018.
[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>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>. <https://www.rfc-editor.org/info/rfc3031>.
[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,
2015, <https://www.rfc-editor.org/info/rfc7684>. November 2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>. February 2016, <https://www.rfc-editor.org/info/rfc7770>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, RFC 2119 Key Words", BCP 14, RFC 8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. 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,
2018, <https://www.rfc-editor.org/info/rfc8362>. April 2018, <https://www.rfc-editor.org/info/rfc8362>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>. July 2018, <https://www.rfc-editor.org/info/rfc8402>.
9.2. Informative References [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491,
DOI 10.17487/RFC8491, November 2018,
<https://www.rfc-editor.org/info/rfc8491>.
[I-D.ietf-idr-bgp-ls-segment-routing-msd] 7.2. Informative References
Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
"Signaling MSD (Maximum SID Depth) using Border Gateway
Protocol Link-State", draft-ietf-idr-bgp-ls-segment-
routing-msd-02 (work in progress), August 2018.
[I-D.ietf-ospf-mpls-elc] [ELC-ISIS] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Xu, X., Kini, S., Sivabalan, S., 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", Work in Progress,
mpls-elc-07 (work in progress), September 2018. draft-ietf-ospf-mpls-elc-07, September 2018.
[I-D.ietf-pce-segment-routing] [MSD-BGP] Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., "Signaling MSD (Maximum SID Depth) using Border Gateway
Protocol Link-State", Work in Progress, draft-ietf-idr-
bgp-ls-segment-routing-msd-02, August 2018.
[PCEP-EXT] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing", and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-12 (work in progress), June Work in Progress, draft-ietf-pce-segment-routing-14,
2018. October 2018.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>. <https://www.rfc-editor.org/info/rfc4552>.
[RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security [RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security
According to the Keying and Authentication for Routing According to the Keying and Authentication for Routing
Protocols (KARP) Design Guide", RFC 6863, Protocols (KARP) Design Guide", RFC 6863,
DOI 10.17487/RFC6863, March 2013, DOI 10.17487/RFC6863, March 2013,
<https://www.rfc-editor.org/info/rfc6863>. <https://www.rfc-editor.org/info/rfc6863>.
skipping to change at page 11, line 5 skipping to change at page 11, line 5
"Security Extension for OSPFv2 When Using Manual Key "Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>. <https://www.rfc-editor.org/info/rfc7474>.
[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>.
Acknowledgements
The authors would like to thank Acee Lindem, Ketan Talaulikar, Tal
Mizrahi, Stephane Litkowski, and Bruno Decraene for their reviews and
valuable comments.
Contributors
The following person contributed to this document:
Les Ginsberg
Email: ginsberg@cisco.com
Authors' Addresses Authors' Addresses
Jeff Tantsura Jeff Tantsura
Apstra, Inc. Apstra, Inc.
Email: jefftant.ietf@gmail.com Email: jefftant.ietf@gmail.com
Uma Chunduri Uma Chunduri
Huawei Technologies Huawei Technologies
Email: uma.chunduri@huawei.com Email: uma.chunduri@huawei.com
Sam Aldrin Sam Aldrin
Google, Inc Google, Inc.
Email: aldrin.ietf@gmail.com Email: aldrin.ietf@gmail.com
Peter Psenak Peter Psenak
Cisco Systems Cisco Systems
Email: ppsenak@cisco.com Email: ppsenak@cisco.com
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