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Internet Engineering Task Force                                  H. Chen
Internet-Draft                                                 Futurewei
Intended status: Standards Track                         October 2, 2019
Expires: April 4, 2020


                    OSPF Abnormal State Information
               draft-chen-ospf-abnormal-state-info-03.txt

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

   This Internet-Draft is submitted to IETF in full conformance with the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   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  . . . . . 5
     4.3.  OSPF Router State Information (RSI) TLV . . . . . . . . . . 5
   5.  Attach RSI TLV to Router Inforamtion LSA  . . . . . . . . . . . 6
   6.  Notify Other Systems  . . . . . . . . . . . . . . . . . . . . . 7
   7.  Security  Considerations  . . . . . . . . . . . . . . . . . . . 7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   9.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 7
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8

































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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.


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.



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   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                             -+
       |                             ...                               |


                  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:

        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...                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                  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



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   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                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Type     A 16-bit field set to 1.

       Length   A 16-bit 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.

       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:












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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 (1)           |           Length (2)          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Max LSA retransmission time  |            Padding            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Type     A 16-bit field set to 1.

       Length   A 16-bit field that indicates the length of the value
                portion in octets and will be 2.

       Value    A 16-bit 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            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Type     A 16-bit field set to 2.

       Length   A 16-bit field that indicates the length of the value
                portion in octets and will be 2.

       Value    A 16-bit field set to the current maximum time
                (in seconds) for which a DD packet is not acknowledged
                in a router.



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



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   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


Author's Address

   Huaimo Chen
   Futurewei
   Boston, MA
   US

   Email: Huaimo.chen@futurewei.com


























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