draft-ietf-ospf-ospfv2-hbit-04.txt   draft-ietf-ospf-ospfv2-hbit-05.txt 
OSPF K. Patel OSPF K. Patel
Internet-Draft Arrcus Internet-Draft Arrcus
Intended status: Standards Track P. Pillay-Esnault Intended status: Standards Track P. Pillay-Esnault
Expires: August 1, 2018 Huawei Technologies Expires: February 2, 2019 Huawei Technologies
M. Bhardwaj M. Bhardwaj
S. Bayraktar S. Bayraktar
Cisco Systems Cisco Systems
January 28, 2018 August 1, 2018
H-bit Support for OSPFv2 H-bit Support for OSPFv2
draft-ietf-ospf-ospfv2-hbit-04 draft-ietf-ospf-ospfv2-hbit-05
Abstract Abstract
OSPFv3 defines an option field for router-LSAs known as a R-bit in OSPFv3 defines an option bit for router-LSAs known as the R-bit in
RFC5340. If the R-bit is clear, an OSPFv3 router can participate in RFC5340. If the R-bit is clear, an OSPFv3 router can participate in
OSPF topology distribution without acting as a forwarder to forward OSPF topology flooding, however it will not used as a transit router.
the transit traffic. In such cases, an OSPF router would only accept In such cases, other routers in the OSPFv3 routing domain only
traffic intended for local delivery. This draft defines R-bit install routes to allow local traffic delivery. This draft defines
functionality for OSPFv2 defined in RFC2328. the H-bit functionality to prevent other OSPFv2 routers from using
the router for transit traffic in OSPFv2 routing domains as described
in RFC 2328.
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
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on August 1, 2018. This Internet-Draft will expire on February 2, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 16 skipping to change at page 2, line 18
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. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. H-bit Support . . . . . . . . . . . . . . . . . . . . . . . . 3 3. H-bit Support . . . . . . . . . . . . . . . . . . . . . . . . 3
4. SPF Modifications . . . . . . . . . . . . . . . . . . . . . . 5 4. SPF Modifications . . . . . . . . . . . . . . . . . . . . . . 5
5. Auto Discovery and Backwards Compatibility . . . . . . . . . 5 5. Auto Discovery and Backward Compatibility . . . . . . . . . . 5
6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics . . . . . 6 6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 10.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 7 10.2. Informative References . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
OSPFv3 [RFC5340] defines an option field for router-LSAs known as a OSPFv3 [RFC5340] defines an option bit for router-LSAs known as the
R-bit. If the R-bit is clear, an OSPF router can participate in R-bit. If the R-bit is clear, an OSPFv3 router can participate in
OSPFv3 topology distribution without acting as a forwarder to forward OSPFv3 topology flooding without acting as a transit router. In such
the transit traffic. In such cases, an OSPF router would only accept cases, other routers in the OSPFv3 routing domain only install routes
traffic intended for local delivery. used for local traffic.
This functionality is particularly useful for BGP Route Reflectors This functionality is particularly useful for BGP Route Reflectors,
known as virtual Route Reflectors (vRRs) that are not in the known as virtual Route Reflectors (vRRs), that are not in the
forwarding path but are in central location such as data centers. forwarding path but are in central locations such as data centers.
Such Route Reflectors typically are used for route distribution and Such Route Reflectors typically are used for route distribution and
are not capable of forwarding data traffic. However, they need to are not capable of forwarding transit traffic. However, they need to
participate in the IGP routing for: 1) computing SPFs for Optimal learn the OSPF topology for:
Route Reflection functionality defined in
[I-D.ietf-idr-bgp-optimal-route-reflection], and 2) resolving
reachability for its Route Reflector Clients.
This draft defines R-bit functionality for OSPFv2 defined in 1. SPF computation for Optimal Route Reflection functionality as
[RFC2328] by introducing a new Router LSA bit known as a "H-bit". defined in [I-D.ietf-idr-bgp-optimal-route-reflection]
2. Reachability resolution for its Route Reflector Clients.
This draft defines the R-bit functionality equivalent for OSPFv2
defined in [RFC2328] by introducing a new router-LSA bit known as the
"H-bit".
2. Requirements Language 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119] only when "OPTIONAL" in this document are to be interpreted as described in BCP
they appear in all upper case. They may also appear in lower or 14 [RFC2119] [RFC8174] when, and only when, they appear in all
mixed case as English words, without any normative meaning. capitals, as shown here.
3. H-bit Support 3. H-bit Support
This draft defines a new Router-LSA bit known as a Host Bit or a This document defines a new router-LSA bit known as the Host Bit or
H-bit. The H-bit indicates the OSPFv2's capability of acting as a the H-bit. An OSPFv2 router advertising a router-LSA with the H-bit
transit router. When set, the OSPFv2 router indicates that the set indicates to other OSPFv2 routers in the area supporting the
transit capability is disabled. The bit value usage of the H-bit is functionality that it MUST NOT be used as a transit router. The bit
reversed as opposed to the R-bit value defined in OSPFv3 [RFC5340] to value usage of the H-bit is reversed from the R-bit defined in OSPFv3
support backward compatibility. The OSPFv2 Router LSA format is [RFC5340] to support backward compatibility. The modified OSPFv2
defined as: router-LSA format is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 1 | | LS age | Options | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID | | Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router | | Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 4, line 38 skipping to change at page 4, line 38
| TOS | 0 | TOS metric | | TOS | 0 | TOS metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID | | Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data | | Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | | ... |
bit H bit H
When set, an OSPFv2 router is a non-transit router and is When set, an OSPFv2 router is a non-transit router and is
incapable of acting as a forwarder. incapable of forwarding transit traffic.
When H-bit is set, an OSPFv2 router is a non-transit router and is When the H-bit is set, an OSPFv2 router is a non-transit router and
incapable of acting as a forwarder. In this mode, the other OSPFv2 should not be used to forward transit traffic. In this mode, the
routers SHOULD NOT use the originating OSPFv2 router for the transit other OSPFv2 routers in the area SHOULD NOT use the originating
traffic, but they will use the OSPFv2 router for data traffic OSPFv2 router for transit traffic, but MAY use the OSPFv2 router for
destined to that OSPFv2 router. An OSPFv2 router originating a local traffic destined to that OSPFv2 router.
Router LSA with the H-bit set SHOULD advertise its LINKS with MAX
Link cost as defined in Section 3 of [RFC6987]. This is to increase
the applicability of the H-bit in partial deployments where it is the
responsibility of the operator to ensure that the H-bit does not
result in routing loops.
When H-bit is set, IPv4 prefixes associated with local interfaces MAY An OSPFv2 router originating a router-LSA with the H-bit set SHOULD
be advertised in summary LSAs. Non-local IPv4 prefixes, e.g., those advertise all its non-local router links with a link cost of
advertised by other routers and installed during the SPF computation, MaxLinkMetric as defined in Section 3 of [RFC6987]. This is to
MAY be advertised in summary-LSAs if configured by policy. Likewise, increase the applicability of the H-bit to partial deployments where
when H-bit is set, only IPv4 prefixes associated with local it is the responsibility of the operator to ensure that OSPFv2
interfaces MAY be advertised in AS-external LSAs. Non-local IPv4 routers not supporting the H-bit do not install routes causing
prefixes, e.g., those exported from other routing protocols, MUST NOT routing loops.
be advertised in AS-external-LSAs. Finally, when H-bit is set, an
ABR MUST advertise a consistent H-bit setting in its self-originated When the H-bit is set, IPv4 prefixes associated with local interfaces
router-LSAs for all attached areas. in other areas MAY be advertised in summary LSAs. Non-local IPv4
prefixes, e.g., those advertised by other routers and installed
during the SPF computation, MAY be advertised in summary-LSAs if
configured by policy. Likewise, when the H-bit is set, only IPv4
prefixes associated with local interfaces MAY be advertised in AS-
external LSAs. Non-local IPv4 prefixes, e.g., those exported from
other routing protocols, MUST NOT be advertised in AS-external-LSAs.
Finally, when the H-bit is set, an Area Border Router (ABR) MUST
advertise a consistent H-bit setting in its self-originated router-
LSAs for all attached areas.
4. SPF Modifications 4. SPF Modifications
The SPF calculation described in section 16.1 [RFC2328] will be The SPF calculation described in section 16.1 [RFC2328] will be
modified to assure that the routers originating router-LSAs with the modified to ensure that the routers originating router-LSAs with the
H-bit set will not be used for transit traffic. Step 2 is modified H-bit set will not be used for transit traffic. Step 2 is modified
as follows: as follows:
2) Call the vertex just added to the 2) Call the vertex just added to the
tree vertex V. Examine the LSA tree vertex V. Examine the LSA
associated with vertex V. This is associated with vertex V. This is
a lookup in the Area A's link state a lookup in the Area A's link state
database based on the Vertex ID. If database based on the Vertex ID. If
this is a router-LSA, and the H-bit this is a router-LSA, and the H-bit
of the router-LSA is set, and of the router-LSA is set, and
skipping to change at page 5, line 42 skipping to change at page 5, line 45
and step (3) should be executed and step (3) should be executed
immediately. If this is a router-LSA, immediately. If this is a router-LSA,
and bit V of the router-LSA (see and bit V of the router-LSA (see
Section A.4.2) is set, set Area A's Section A.4.2) is set, set Area A's
TransitCapability to TRUE. In any case, TransitCapability to TRUE. In any case,
each link described by the LSA gives each link described by the LSA gives
the cost to an adjacent vertex. For the cost to an adjacent vertex. For
each described link, (say it joins each described link, (say it joins
vertex V to vertex W): vertex V to vertex W):
5. Auto Discovery and Backwards Compatibility 5. Auto Discovery and Backward Compatibility
To avoid the possibility of any routing loops due to partial To avoid the possibility of any routing loops due to partial
deployments, this draft defines a new OSPF Router Functional deployment, this document defines a OSPF Router-Information LSA
Capability known as a Host Support Capability. The value of this functional capability bit known as the Host Support capability.
capability is a bit value to be assigned by IANA from OSPF Router
Functional Capability Bits registry [RFC7770] .
The Auto Discovery via announcement of the Host Support Functional Auto Discovery via announcement of the Host Support Functional
Capability ensures that the H-bit functionality and its associated Capability ensures that the H-bit functionality and its associated
SPF changes SHOULD only take effect if all the routers in a given SPF changes SHOULD only take effect if all the routers in a given
OSPF area support this functionality. OSPF area support this functionality.
Implementations are encouraged to provide a knob to manually override Implementations are encouraged to provide a configuration parameter
enforcement of the H-bit functionality in partial deployment to manually override enforcement of the H-bit functionality in
scenarios for cases where the topology guarantees that the router partial deployments where the topology guarantees that OSPFv2 routers
supporting the H-bit will not cause routing loops. not supporting the H-bit do not compute routes resulting in routing
loops. More precisely, the advertisement of MaxLinkMetric for the
router's non-local links will prevent OSPFv2 routers not supporting
the H-bit from attempting to use it for transit traffic.
6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics 6. OSPF AS-External-LSAs/NSSA LSAs with Type 2 Metrics
When calculating the path to an OSPF AS-External-LSA or NSSA-LSA with When calculating the path to an OSPF AS-External-LSA or NSSA-LSA with
a Type-2 metric, the advertised Type-2 metric is taken as more a Type-2 metric, the advertised Type-2 metric is taken as more
significant than the OSPF intra-area or inter-area path. Hence, significant than the OSPF intra-area or inter-area path. Hence,
advertising the links with MaxLinkMetric as specified in [RFC6987] advertising the links with MaxLinkMetric as specified in [RFC6987]
does not discourage transit traffic when calculating AS external or does not discourage transit traffic when calculating AS external or
NSSA routes. Consequently, OSPF routers implementing [RFC6987] or NSSA routes. Consequently, OSPF routers implementing [RFC6987] or
this specification should advertise a Type-2 metric of LSInfinity for this specification should advertise a Type-2 metric of LSInfinity for
any self-originated AS-External-LSAs or NSSA-LSAs in situations when any self-originated AS-External-LSAs or NSSA-LSAs in situations when
the OSPF router is acting as a stub router [RFC6987] or implementing the OSPF router is acting as a stub router [RFC6987] or implementing
this specification. this specification.
7. IANA Considerations 7. IANA Considerations
This draft defines a new Router LSA bit known as a H-bit. This draft IANA is requested to create the OSPF Router-LSA bit registry with the
requests IANA to 1) Create a new OSPF Router LSA bits registry and 2) following assignments:
assign a H-bit code type from the newly allocated OSPF Router LSA bit
registry.
This draft defines a new Router Functional Capability known as a Host Value Description Reference
Support Functional Capability. This draft requests IANA to allocate 0x01 Area Border Router (B-bit) [RFC2328]
the value of this capability from the Router Functional Capability 0x02 AS Boundary Router (E-bit) [RFC2328]
Bits TLV. 0x04 Virtual Link Endpoint (V-bit) [RFC2328]
0x08 Historic (W-bit) [RFC1584]
0x10 Unconditional NSSA Translator (Nt-bit) [RFC3101]
0x20 Unassigned
0x40 Unassigned
0x80 Host (H-bit) This Document
This document also defines a new Router Functional Capability
[RFC7770] known as the Host Support Functional Capability. This
document requests IANA to allocate the value of this capability from
the Router Functional Capability Bits TLV.
8. Security Considerations 8. Security Considerations
This document introduces no new security considerations above and This document introduces no new security considerations beyond those
beyond those already specified in [RFC2328] and [RFC5340]. already specified in [RFC6987], [RFC2328], and [RFC5340].
9. Acknowledgements 9. Acknowledgements
The authors would like to acknowledge Hasmit Grover for discovery of The authors would like to acknowledge Hasmit Grover for discovery of
the limitation in [RFC6987], Acee Lindem, Abhay Roy, David Ward, the limitation in [RFC6987], Acee Lindem, Abhay Roy, David Ward,
Burjiz Pithawala and Michael Barnes for their comments. Burjiz Pithawala and Michael Barnes for their comments.
10. Change Log 10. References
Initial Version: April 23 2015
11. References
11.1. Normative 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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998, DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>. <https://www.rfc-editor.org/info/rfc2328>.
[RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, DOI 10.17487/RFC3101, January 2003,
<https://www.rfc-editor.org/info/rfc3101>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>. <https://www.rfc-editor.org/info/rfc5340>.
[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>.
11.2. Informative References [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>.
10.2. Informative References
[I-D.ietf-idr-bgp-optimal-route-reflection] [I-D.ietf-idr-bgp-optimal-route-reflection]
Raszuk, R., Cassar, C., Aman, E., Decraene, B., Litkowski, Raszuk, R., Cassar, C., Aman, E., Decraene, B., and K.
S., and K. Wang, "BGP Optimal Route Reflection (BGP-ORR)", Wang, "BGP Optimal Route Reflection (BGP-ORR)", draft-
draft-ietf-idr-bgp-optimal-route-reflection-13 (work in ietf-idr-bgp-optimal-route-reflection-16 (work in
progress), January 2017. progress), April 2018.
[RFC1584] Moy, J., "Multicast Extensions to OSPF", RFC 1584,
DOI 10.17487/RFC1584, March 1994,
<https://www.rfc-editor.org/info/rfc1584>.
[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 6987, McPherson, "OSPF Stub Router Advertisement", RFC 6987,
DOI 10.17487/RFC6987, September 2013, DOI 10.17487/RFC6987, September 2013,
<https://www.rfc-editor.org/info/rfc6987>. <https://www.rfc-editor.org/info/rfc6987>.
Authors' Addresses Authors' Addresses
Keyur Patel Keyur Patel
Arrcus Arrcus
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