Internet DRAFT - draft-ietf-ospf-rfc2370bis
draft-ietf-ospf-rfc2370bis
Internet Draft Lou Berger (LabN)
Obsoletes: 2370 Igor Bryskin (Adva)
Category: Standards Track Alex Zinin (Alcatel)
Expiration Date: November 8, 2008 Original Author:
Rob Coltun (Acoustra Productions)
May 8, 2008
The OSPF Opaque LSA Option
draft-ietf-ospf-rfc2370bis-05.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document defines enhancements to the OSPF protocol to support a
new class of link-state advertisements (LSA) called Opaque LSAs.
Opaque LSAs provide a generalized mechanism to allow for the future
extensibility of OSPF. Opaque LSAs consist of a standard LSA header
followed by application-specific information. The information field
may be used directly by OSPF or by other applications. Standard OSPF
link-state database flooding mechanisms are used to distribute Opaque
LSAs to all or some limited portion of the OSPF topology.
This document replaces RFC 2370 and adds to it a mechanism to enable
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an OSPF router to validate AS-scope opaque LSAs originated outside of
the router's OSPF area.
Table of Contents
1 Conventions used in this document ......................... 3
2 Introduction .............................................. 3
2.1 Organization Of This Document ............................. 3
2.2 Acknowledgments ........................................... 4
3 The Opaque LSA ............................................ 4
3.1 Flooding Opaque LSAs ...................................... 5
3.2 Modifications To The Neighbor State Machine ............... 6
4 Protocol Data Structures .................................. 7
4.1 Additions To The OSPF Neighbor Structure .................. 8
5 Inter-Area Considerations ................................. 8
6 Management Considerations ................................. 9
7 Backward Compatibility .................................... 9
8 Security Considerations ................................... 10
9 IANA Considerations ....................................... 11
10 References ................................................ 12
10.1 Normative References ...................................... 12
10.2 Informative References .................................... 12
11 Author's Addresses ........................................ 13
12 Appendix A: OSPF Data formats ............................. 13
12.1 The Options Field ......................................... 13
12.2 The Opaque LSA ............................................ 15
13 Full Copyright Statement .................................. 16
14 Intellectual Property ..................................... 16
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1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction
Over the last several years the OSPF routing protocol [OSPF] has been
widely deployed throughout the Internet. As a result of this
deployment and the evolution of networking technology, OSPF has been
extended to support many options; this evolution will obviously
continue.
This document defines enhancements to the OSPF protocol to support a
new class of link-state advertisements (LSA) called Opaque LSAs.
Opaque LSAs provide a generalized mechanism to allow for the future
extensibility of OSPF. The information contained in Opaque LSAs may
be used directly by OSPF or indirectly by some application wishing to
distribute information throughout the OSPF domain. The exact use of
Opaque LSAs is beyond the scope of this document.
Opaque LSAs consist of a standard LSA header followed by a 32-bit
aligned application-specific information field. Like any other LSA,
the Opaque LSA uses the link-state database distribution mechanism
for flooding this information throughout the topology. The link-
state type field of the Opaque LSA identifies the LSA's range of
topological distribution. This range is referred to as the Flooding
Scope.
It is envisioned that an implementation of the Opaque option provides
an application interface for 1) encapsulating application-specific
information in a specific Opaque type, 2) sending and receiving
application-specific information, and 3) if required, informing the
application of the change in validity of previously received
information when topological changes are detected.
2.1. Organization Of This Document
This document first defines the three types of Opaque LSAs followed
by a description of OSPF packet processing. The packet processing
sections include modifications to the flooding procedure and to the
neighbor state machine. Appendix A then gives the packet formats.
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2.2. Acknowledgments
We would like to thank Acee Lindem for his detailed review and useful
feedback. The handling of AS-scope opaque LSAs described in this
document is taken from draft-bryskin-ospf-lsa-
type11-validation-00.txt.
3. The Opaque LSA
Opaque LSAs are types 9, 10, and 11 link-state advertisements.
Opaque LSAs consist of a standard LSA header followed by a 32-bit
aligned application-specific information field. Standard link-state
database flooding mechanisms are used for distribution of Opaque
LSAs. The range of topological distribution (i.e., the flooding
scope) of an Opaque LSA is identified by its link-state type. This
section documents the flooding of Opaque LSAs.
The flooding scope associated with each Opaque link-state type is
defined as follows.
o Link-state type-9 denotes a link-local scope. Type-9 Opaque
LSAs are not flooded beyond the local (sub)network.
o Link-state type-10 denotes an area-local scope. Type-10 Opaque
LSAs are not flooded beyond the borders of their associated area.
o Link-state type-11 denotes that the LSA is flooded throughout
the Autonomous System (AS). The flooding scope of type-11
LSAs are equivalent to the flooding scope of AS-external (type-5)
LSAs. Specifically, type-11 Opaque LSAs are 1) flooded
throughout all transit areas, 2) not flooded into stub areas or
Not-So-Stubby Areas (NSSAs), see [NSSA], from the backbone and
3) not originated by routers into their connected stub areas
or NSSAs. As with type-5 LSAs, if a type-11 Opaque LSA is
received in a stub area or NSSA from a neighboring router
within the stub area or NSSA the LSA is rejected.
The link-state ID of the Opaque LSA is divided into an Opaque type
field (the first 8 bits) and a type-specific ID (the remaining 24
bits). The packet format of the Opaque LSA is given in Appendix A.
Section 7 describes Opaque type allocation and assignment.
The responsibility for proper handling of the Opaque LSA's flooding
scope is placed on both the sender and receiver of the LSA. The
receiver must always store a valid received Opaque LSA in its link-
state database. The receiver must not accept Opaque LSAs that
violate the flooding scope (e.g., a type-11 (domain-wide) Opaque LSA
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is not accepted in a stub area or NSSA). The flooding scope effects
both the synchronization of the link-state database and the flooding
procedure.
The following describes the modifications to these procedures that
are necessary to insure conformance to the Opaque LSA's Scoping
Rules.
3.1. Flooding Opaque LSAs
The flooding of Opaque LSAs MUST follow the rules of Flooding Scope
as specified in this section. Section 13 of [OSPF] describes the
OSPF flooding procedure. Those procedures MUST be followed as
defined except where modified in this section. The following
describes the Opaque LSA's type-specific flooding restrictions.
o If the Opaque LSA is type-9 (the flooding scope is link-local)
and the interface that the LSA was received on is not the same
as the target interface (e.g., the interface associated with a
particular target neighbor), the Opaque LSA MUST be discarded
and not acknowledged. An implementation SHOULD keep track of
the IP interface associated with each Opaque LSA having a
link-local flooding scope.
o If the Opaque LSA is type-10 (the flooding scope is area-local)
and the area associated with the Opaque LSA (as identified
during origination or from a received LSA's associated OSPF
packet header) is not the same as the area associated with the
target interface, the Opaque LSA MUST be discarded and not
acknowledged. An implementation SHOULD keep track of the OSPF
area associated with each Opaque LSA having an area-local
flooding scope.
o If the Opaque LSA is type-11 (the LSA is flooded throughout the
AS) and the target interface is associated with a stub area or
NSSA, the Opaque LSA MUST NOT be flooded out the interface. A
type-11 Opaque LSA that is received on an interface associated
with a stub area or NSSA MUST be discarded and not acknowledged
(the neighboring router has flooded the LSA in error).
When opaque-capable routers and non-opaque-capable OSPF routers are
mixed together in a routing domain, the Opaque LSAs are typically not
flooded to the non-opaque-capable routers. As a general design
principle, optional OSPF advertisements are only flooded to those
routers that understand them.
An opaque-capable router learns of its neighbor's opaque capability
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at the beginning of the "Database Exchange Process" (see Section 10.6
of [OSPF], receiving Database Description packets from a neighbor in
state ExStart). A neighbor is opaque-capable if and only if it sets
the O-bit in the Options field of its Database Description packets;
the O-bit SHOULD NOT be set and MUST be ignored when received in
packets other than Database Description packets. Using the O-bit in
OSPF packets other than Database Description packets will result in
interoperability issues. The setting of the O-bit is a "SHOULD NOT"
rather than a "MUST NOT" to remain compatible with earlier
specifications.
In the next step of the Database Exchange process, Opaque LSAs are
included in the Database summary list that is sent to the neighbor
(see Sections 3.2 below and 10.3 of [OSPF]) when the neighbor is
opaque capable.
When flooding Opaque-LSAs to adjacent neighbors, an opaque-capable
router looks at the neighbor's opaque capability. Opaque LSAs are
only flooded to opaque-capable neighbors. To be more precise, in
Section 13.3 of [OSPF], Opaque LSAs MUST be placed on the link-state
retransmission lists of opaque-capable neighbors and MUST NOT be
placed on the link-state retransmission lists of non-opaque-capable
neighbors. However, when sending Link State Update packets as
multicasts, a non-opaque-capable neighbor may (inadvertently) receive
Opaque LSAs. The non-opaque-capable router will then simply discard
the LSA (see Section 13 of [OSPF], receiving LSAs having unknown LS
types).
Information contained in received opaque LSAs SHOULD only be used
when the router originating the LSA is reachable. As mentioned in
[OSPFv3], reachability validation MAY be done less frequently than
every SPF calculation. Additionally, routers processing received
opaque LSAs MAY choose to give priority to processing base OSPF LSA
types over opaque LSA types.
3.2. Modifications To The Neighbor State Machine
The state machine as it exists in section 10.3 of [OSPF] remains
unchanged except for the action associated with State: ExStart,
Event: NegotiationDone which is where the Database summary list is
built. To incorporate the Opaque LSA in OSPF this action is changed
to the following.
State(s): ExStart
Event: NegotiationDone
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New state: Exchange
Action: The router MUST list the contents of its entire area
link-state database in the neighbor Database summary
list. The area link-state database consists of the
Router LSAs, Network LSAs, Summary LSAs, type-9 opaque
LSAs, and type-10 opaque LSAs contained in the area
structure, along with AS External and type-11 Opaque
LSAs contained in the global structure. AS External
and type-11 Opaque LSAs MUST be omitted from a
virtual neighbor's Database summary list. AS External
LSAs and type-11 Opaque LSAs MUST be omitted from the
Database summary list if the area has been configured
as a stub area or NSSA (see Section 3.6 of [OSPF]).
Type-9 Opaque LSAs MUST be omitted from the Database
summary list if the interface associated with the
neighbor is not the interface associated with the Opaque
LSA (as noted upon reception).
Any advertisement whose age is equal to MaxAge MUST be
omitted from the Database summary list. It MUST instead
be added to the neighbor's link-state retransmission
list. A summary of the Database summary list will be
sent to the neighbor in Database Description packets.
Only one Database Description Packet is allowed to be
outstanding at any one time. For more detail on the
sending and receiving of Database Description packets,
see Sections 10.6 and 10.8 of [OSPF].
4. Protocol Data Structures
The Opaque option is described herein in terms of its operation on
various protocol data structures. These data structures are included
for explanatory uses only. They are not intended to constrain an
implementation. In addition to the data structures listed below, this
specification references the various data structures (e.g., OSPF
neighbors) defined in [OSPF].
In an OSPF router, the following item is added to the list of global
OSPF data structures described in Section 5 of [OSPF]:
o Opaque capability. Indicates whether the router is running the
Opaque option (i.e., capable of storing Opaque LSAs). Such a
router will continue to inter-operate with non-opaque-capable
OSPF routers.
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4.1. Additions To The OSPF Neighbor Structure
The OSPF neighbor structure is defined in Section 10 of [OSPF]. In
an opaque-capable router, the following items are added to the OSPF
neighbor structure:
o Neighbor Options. This field was already defined in the OSPF
specification. However, in opaque-capable routers there is a new
option which indicates the neighbor's Opaque capability. This new
option is learned in the Database Exchange process through
reception of the neighbor's Database Description packets and
determines whether Opaque LSAs are flooded to the neighbor. For a
more detailed explanation of the flooding of the Opaque LSA see
section 3 of this document.
5. Inter-Area Considerations
As defined above, link-state type-11 opaque LSAs are flooded
throughout the Autonomous System (AS). One issue related to such AS
scoped Opaque LSAs is that there must be a way for OSPF routers in
remote areas to check availability of the LSA originator.
Specifically, if an OSPF router originates a type-11 LSA and, after
that, goes out of service, OSPF routers located outside of the
originator's OSPF area have no way of detecting this fact and may use
the stale information for a considerable period of time (up to 60
minutes). This could prove to be suboptimal for some applications and
may result in others not functioning.
Type-9 opaque LSAs and type-10 opaque LSAs do not have this problem
as a receiving router can detect if the advertising router is
reachable within the LSA's respective flooding scope. In the case of
type-9 LSAs, the originating router must be an OSPF neighbor in
Exchange state or greater. In the case of type-10 Opaque LSAs, the
intra-area SPF calculation will determine the advertising router's
reachability.
There is a parallel issue in OSPF for the AS scoped AS-external-LSAs
(type-5 LSAs). OSPF addresses this by using AS border information
advertised in AS boundary router (ASBR) summary-LSAs (type-4 LSAs),
see [OSPF] Section 16.4. This same mechanism is reused by this
document for type-11 opaque LSAs.
To enable OSPF routers in remote areas to check availability of the
originator of link-state type-11 opaque LSAs, the originators
advertise themselves as ASBRs. This will enable routers to track the
reachability of the LSA originator either directly via the SPF
calculation (for routers in the same area) or indirectly via type-4
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LSAs originated by ABRs (for routers in other areas). It is important
to note that per [OSPF] this solution does not apply to OSPF stub
areas or NSSAs as AS scoped opaque LSAs are not flooded into these
area types.
The procedures related to inter-area opaque LSAs are as follows:
(1) An OSPF router that is configured to originate AS-scope opaque
LSAs will advertise itself as an ASBR and MUST follow the
requirements related to setting of the Options field E-bit in
OSPF LSA headers as specified in [OSPF].
(2) When processing a received type-11 Opaque LSA, the router MUST
look up the routing table entries (potentially one per attached
area) for the AS boundary router (ASBR) that originated the LSA.
If no entries exist for router ASBR (i.e., the ASBR is
unreachable), the router MUST do nothing with this LSA. It also
MUST discontinue using all Opaque LSAs injected into the network
by the same originator whenever it is detected that the
originator is unreachable.
6. Management Considerations
The updated OSPF MIB, [RFC4750], provides explicit support for opaque
LSAs and SHOULD be used to support implementations of this document.
See Section 12.3 of [RFC4750] for details. In addition to that
section, implementations supporting [RFC4750] will also include
opaque LSAs in all appropriate generic LSA objects, e.g.,
ospfOriginateNewLsas, and ospfLsdbTable.
7. Backward Compatibility
The solution proposed in this document introduces no interoperability
issues. In the case that a non-opaque-capable neighbor receives
Opaque LSAs, per [OSPF], the non-opaque-capable router will simply
discard the LSA.
Note that OSPF routers that implement [RFC2370] will continue using
stale type-11 LSAs even when the LSA originator implements the Inter-
area procedures described in Section 6 of this document.
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8. Security Considerations
There are two types of issues that need be addressed when looking at
protecting routing protocols from misconfigurations and malicious
attacks. The first is authentication and certification of routing
protocol information. The second is denial of service attacks
resulting from repetitive origination of the same router
advertisement or origination of a large number of distinct
advertisements resulting in database overflow. Note that both of
these concerns exist independently of a router's support for the
Opaque option.
To address the authentication concerns, OSPF protocol exchanges are
authenticated. OSPF supports multiple types of authentication; the
type of authentication in use can be configured on a per network
segment basis. One of OSPF's authentication types, namely the
Cryptographic authentication option, is believed to be secure against
passive attacks and provide significant protection against active
attacks. When using the Cryptographic authentication option, each
router appends a "message digest" to its transmitted OSPF packets.
Receivers then use the shared secret key and received digest to
verify that each received OSPF packet is authentic.
The quality of the security provided by the Cryptographic
authentication option depends completely on the strength of the
message digest algorithm (MD5 is currently the only message digest
algorithm specified), the strength of the key being used, and the
correct implementation of the security mechanism in all communicating
OSPF implementations. It also requires that all parties maintain the
secrecy of the shared secret key. None of the standard OSPF
authentication types provide confidentiality. Nor do they protect
against traffic analysis. For more information on the standard OSPF
security mechanisms, see Sections 8.1, 8.2, and Appendix D of [OSPF].
Repetitive origination of advertisements is addressed by OSPF by
mandating a limit on the frequency that new instances of any
particular LSA can be originated and accepted during the flooding
procedure. The frequency at which new LSA instances may be
originated is set equal to once every MinLSInterval seconds, whose
value is 5 seconds (see Section 12.4 of [OSPF]). The frequency at
which new LSA instances are accepted during flooding is once every
MinLSArrival seconds, whose value is set to 1 (see Section 13,
Appendix B and G.5 of [OSPF]).
Proper operation of the OSPF protocol requires that all OSPF routers
maintain an identical copy of the OSPF link-state database. However,
when the size of the link-state database becomes very large, some
routers may be unable to keep the entire database due to resource
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shortages; we term this "database overflow". When database overflow
is anticipated, the routers with limited resources can be
accommodated by configuring OSPF stub areas and NSSAs. [OVERFLOW]
details a way of gracefully handling unanticipated database
overflows.
In the case of type-11 Opaque LSAs, this document reuses an ASBR
tracking mechanism that is already employed in basic OSPF for type-5
LSAs. Therefore, applying it to type-11 Opaque LSAs does not create
any threats that are not already known for type-5 LSAs.
9. IANA Considerations
This document updates the requirements for the OSPF Opaque LSA type
registry, see http://www.iana.org/assignments/ospf-opaque-types.
Three changes are requested. The first is for references to
[RFC2370] to be replaced with references to this document. The second
change is for the Opaque type values in the range of 128-255 to be
reserved for "Private Use" as defined in [RFC2434]. The final change
is for the reference for registry value 1, Traffic Engineering LSA,
to be updated to [RFC3630].
With these changes integrated, the registry should read:
Open Shortest Path First (OSPF) Opaque Link-State
Advertisements (LSA) Option Types
Registries included below:
- Opaque Link-State Advertisements (LSA) Option Types
Registry Name: Opaque Link-State Advertisements (LSA) Option Types
Reference: [This document]
Range Registration Procedures Notes
-------- ------------------------------------------ --------
0-127 IETF Consensus
128-255 Private Use
Registry:
Value Opaque Type Reference
------- ------------------------------------------ ---------
1 Traffic Engineering LSA [RFC3630]
2 Sycamore Optical Topology Descriptions [Moy]
3 grace-LSA [RFC3623]
4 Router Information (RI) [RFC4970]
5-127 Unassigned
128-255 Private Use
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10. References
10.1. Normative References
[DEMD] Moy, J., "Extending OSPF to Support Demand Circuits", RFC
1793, April 1995.
[OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to indicate
requirements levels", RFC 2119, March 1997.
[RFC2434] Narten, T., Alvestrand, H., "Guidelines for Writing an
IANA Considerations Section in RFCs ", RFC 2434, October
1998.
[RFC4750] Joyal, D., et al., "OSPF Version 2 Management Information
Base", RFC 4750, November 2006.
10.2. Informative References
[MOSPF] Moy, J., "Multicast Extensions to OSPF", RFC 1584, March
1994.
[NSSA] Murphy P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, January 2003.
[OSPF-MT] Psenak, P., et al., "Multi-Topology (MT) Routing in OSPF",
draft-ietf-ospf-mt-, January 2007.
[OSPFv3] Coltun, R., et al. "OSPF for IPv6",
draft-ietf-ospf-ospfv3-update-21.txt, April 2008.
[OVERFLOW] Moy, J., "OSPF Database Overflow", RFC 1765, March 1995.
[RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370,
July 1998.
[RFC3630] Katz, D., Kompella, K., Yeund, D., "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC4576] Rosen, E., et al., "Using a Link State Advertisement
(LSA) Options Bit to Prevent Looping in BGP/MPLS IP
Virtual Private Networks (VPNs)", RFC 4576, June 2006.
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11. Author's Addresses
Lou Berger
LabN Consulting, L.L.C.
Email: lberger@labn.net
Igor Bryskin
ADVA Optical Networking Inc
7926 Jones Branch Drive
Suite 615
McLean, VA - 22102
Email: ibryskin@advaoptical.com
Alex Zinin
Alcatel
Email: zinin@psg.com
Original Author:
Rob Coltun
Acoustra Productions
12. Appendix A: OSPF Data formats
This appendix describes the format of the Options Field followed by
the packet format of the Opaque LSA.
12.1. The Options Field
The OSPF Options field is present in OSPF Hello packets, Database
Description packets and all link-state advertisements. The Options
field enables OSPF routers to support (or not support) optional
capabilities, and to communicate their capability level to other OSPF
routers. Through this mechanism routers of differing capabilities can
be mixed within an OSPF routing domain.
When used in Hello packets, the Options field allows a router to
reject a neighbor because of a capability mismatch. Alternatively,
when capabilities are exchanged in Database Description packets a
router can choose not to flood certain link-state advertisements to a
neighbor because of its reduced functionality. Lastly, listing
capabilities in link-state advertisements allows routers to forward
traffic around reduced functionality routers by excluding them from
parts of the routing table calculation.
All eight bits of the OSPF Options field have been assigned, although
only the O-bit is described completely by this document. Each bit is
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described briefly below. Routers SHOULD reset (i.e., clear)
unrecognized bits in the Options field when sending Hello packets or
Database Description packets and when originating link-state
advertisements. Conversely, routers encountering unrecognized Option
bits in received Hello Packets, Database Description packets or link-
state advertisements SHOULD ignore the capability and process the
packet/advertisement normally.
+--------------------------------------+
| DN | O | DC | EA | N/P | MC | E | MT |
+--------------------------------------+
The Options Field
MT-bit
This bit describes the router's multi-topology link-excluding
capability, as described in [OSPF-MT].
E-bit
This bit describes the way AS-external-LSAs are flooded, as
described in Sections 3.6, 9.5, 10.8 and 12.1.2 of [OSPF].
MC-bit
This bit describes whether IP multicast datagrams are forwarded
according to the specifications in [MOSPF].
N/P-bit
This bit describes the handling of Type-7 LSAs, as specified in
[NSSA].
DC-bit
This bit describes the router's handling of demand circuits, as
specified in [DEMD].
EA-bit
This bit describes the router's willingness to receive and
forward External-Attributes-LSAs. While defined, the
documents specifying this bit have all expired. The use
of this bit may be deprecated in the future.
O-bit
This bit describes the router's willingness to receive and
forward Opaque-LSAs as specified in this document.
DN-bit
This bit is used to prevent looping in BGP/MPLS IP VPNs,
as specified in [RFC4576].
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12.2. The Opaque LSA
Opaque LSAs are Type 9, 10, and 11 link-state advertisements. These
advertisements MAY be used directly by OSPF or indirectly by some
application wishing to distribute information throughout the OSPF
domain. The function of the Opaque LSA option is to provide for
future OSPF extensibility.
Opaque LSAs contain some number of octets (of application-specific
data) padded to 32-bit alignment. Like any other LSA, the Opaque LSA
uses the link-state database distribution mechanism for flooding this
information throughout the topology. However, the Opaque LSA has a
flooding scope associated with it so that the scope of flooding may
be link-local (type-9), area-local (type-10) or the entire OSPF
routing domain (type-11). Section 3 of this document describes the
flooding procedures for the Opaque LSA.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 9, 10, or 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Type | Opaque ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Opaque Information |
+ +
| ... |
Link-State Type
The link-state type of the Opaque LSA identifies the LSA's range of
topological distribution. This range is referred to as the Flooding
Scope. The following explains the flooding scope of each of the
link-state types.
o A value of 9 denotes a link-local scope. Opaque LSAs with a
link-local scope MUST NOT be flooded beyond the local
(sub)network.
o A value of 10 denotes an area-local scope. Opaque LSAs with a
Berger, Bryskin & Zinin Standards Track [Page 15]
Internet-Draft draft-ietf-ospf-rfc2370bis-05.txt May 8, 2008
area-local scope MUST NOT be flooded beyond their area of
origin.
o A value of 11 denotes that the LSA is flooded throughout the
Autonomous System (e.g., has the same scope as type-5 LSAs).
Opaque LSAs with AS-wide scope MUST NOT be flooded into stub
areas or NSSAs.
Syntax Of The Opaque LSA's Link-State ID
The link-state ID of the Opaque LSA is divided into an Opaque Type
field (the first 8 bits) and an Opaque ID (the remaining 24 bits).
See section 7 of this document for a description of Opaque type
allocation and assignment.
13. Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Copies of IPR disclosures made to the IETF Secretariat and any
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specification can be obtained from the IETF on-line IPR repository
Berger, Bryskin & Zinin Standards Track [Page 16]
Internet-Draft draft-ietf-ospf-rfc2370bis-05.txt May 8, 2008
at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention
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Acknowledgement
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Berger, Bryskin & Zinin Standards Track [Page 17]
Generated on: Thu May 8 16:11:50 EDT 2008
