Internet DRAFT - draft-chen-ospf-abnormal-state-info
draft-chen-ospf-abnormal-state-info
Internet Engineering Task Force H. Chen
Internet-Draft Futurewei
Intended status: Standards Track 31 January 2024
Expires: 3 August 2024
OSPF Abnormal State Information
draft-chen-ospf-abnormal-state-info-11
Abstract
This document describes a couple of options for an OSPF router to
advertise its abnormal state information in a routing domain.
Status of This Memo
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This Internet-Draft will expire on 3 August 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Conventions Used in This Document . . . . . . . . . . . . . . 3
4. OSPF Router State Information LSA . . . . . . . . . . . . . . 3
4.1. OSPFv2 Router State Information (RSI) Opaque LSA . . . . 3
4.2. OSPFv3 Router State Information (RSI) Opaque LSA . . . . 4
4.3. OSPF Router State Information (RSI) TLV . . . . . . . . . 4
5. Attach RSI TLV to Router Inforamtion LSA . . . . . . . . . . 6
6. Notify Other Systems . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
There may be some states that are not normal in an OSPF router, which
include the state that a link state advertisement (LSA) stays in a
retransmission list on the router for more than a given time period
such as more than hello dead interval, and may include the state that
a database description (DD) packet does not get acknowledged for a
given period of time.
If a link state advertisement (LSA) with a topology change in a
router can not get through over an OSPF interface for a given time
period, some of the routers in the routing domain may have different
view of the real network topology, thus routing loops may occur and
some traffic may get dropped.
It is useful for an OSPF router in a routing domain to advertise its
abnormal state information to other routers, or notify some systems
such as an event management or monitoring system for its abnormal
state.
This document describes a couple of options for an OSPF router to
advertise its abnormal state information in a routing domain.
2. Terminology
This document uses terminologies defined in RFC 4970, RFC 2328, and
RFC 2740.
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3. 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 RFC 2119.
4. OSPF Router State Information LSA
OSPF routers MAY advertise their state information in a area-scoped
or AS-scoped router state information LSA with a router state
informatioin TLV.
4.1. OSPFv2 Router State Information (RSI) Opaque LSA
OSPFv2 routers will advertise an area-scoped or AS-scoped Router
State Information Opaque-LSA [RFC 2370], which has an Opaque type of
5 and Opaque ID of 0.
The RSI LSA will be originated initially by an OSPF router when an
OSPF instance is created and re-originated in every refresh interval
(LSRefreshTime) with the current state information of the router.
When the current state information changes, the RSI LSA will also be
originated.
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 | 10/11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- TLVs -+
| ... |
Figure 1: OSPFv2 Router State Information Opaque LSA
The format of the TLVs within the body of a RSI LSA is the same as
the format used by the Traffic Engineering Extensions to OSPF [RFC
3630]. The LSA payload consists of one or more nested Type/Length/
Value (TLV) triplets. The format of each TLV is:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: TLV Format
The Length field defines the length of the value portion in octets
(thus a TLV with no value portion would have a length of 0). The TLV
is padded to 4-octet alignment; padding is not included in the length
field (so a 3-octet value would have a length of 3, but the total
size of the TLV would be 8 octets). Nested TLVs are also 32-bit
aligned. For example, a 1-byte value would have the length field set
to 1, and 3 octets of padding would be added to the end of the value
portion of the TLV. Unrecognized types are ignored.
4.2. OSPFv3 Router State Information (RSI) Opaque LSA
TBD.
4.3. OSPF Router State Information (RSI) TLV
A router advertising a RSI LSA MAY include the Router State
Information TLV. If included, it MUST be the first TLV in the LSA.
Additionally, the TLV MUST accurately reflect the OSPF router's state
information in the scope advertised.
The format of the Router State Information TLV is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (1) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| State Information sub-TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Router State Information TLV
Type: A 2-octet field set to 1.
Length: A 2-octet field that indicates the length of the value
portion in octets and will be the total number of octets that
state information sub-TLVs use.
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Value: A variable length sequence of router state information sub-
TLVs.
The format of the Router State Information LSA retranmission time
sub-TLV is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (1) | Length (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSA retransmission time | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Retranmission Time Sub-TLV
Type: A 2-octet field set to 1.
Length: A 2-octet field that indicates the length of the value
portion in octets and will be 2.
Value: A 2-octet field set to the current maximum time (in seconds)
that an LSA stays in a retransmission list in a router.
The format of the sub-TLV for the maximum time that a Database
Description packet is not acknowledged is illustrated below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (2) | Length (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max time DD not acked | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Maximum DD Time Sub-TLV
Type: A 2-octet field set to 2.
Length: A 2-octet field that indicates the length of the value
portion in octets and will be 2.
Value: A 2-octet field set to the current maximum time (in seconds)
for which a DD packet is not acknowledged in a router.
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5. Attach RSI TLV to Router Inforamtion LSA
Instead of using a Router State Information LSA to advertise the
abnormal state information for a router, we may use the existing
Router Information LSA defined in RFC 4970 to advertise the state
information through adding the Router State Information (RSI) TLV
into the Router Inforamtion LSA.
When a Router State Information (RSI) TLV is put into a Router
Information LSA, the type of the TLV may be different from the one
mentioned in the section above.
6. Notify Other Systems
An OSPF router may also notify other systems such as an event
management system about its abnormal state when the abnormal state
occurs in the router.
7. Security Considerations
The mechanism described in this document does not raise any new
security issues for the OSPF protocols.
8. IANA Considerations
tb
9. Acknowledgement
The author would like to thank people for their valuable comments on
this draft.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370,
DOI 10.17487/RFC2370, July 1998,
<https://www.rfc-editor.org/info/rfc2370>.
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[RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
RFC 2740, DOI 10.17487/RFC2740, December 1999,
<https://www.rfc-editor.org/info/rfc2740>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July
2007, <https://www.rfc-editor.org/info/rfc4970>.
10.2. Informative References
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
July 2008, <https://www.rfc-editor.org/info/rfc5250>.
Author's Address
Huaimo Chen
Futurewei
Boston, MA,
United States of America
Email: Huaimo.chen@futurewei.com
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