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Request For Comments - RFC2452

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Network Working Group                                      M. Daniele
Request for Comments: 2452                Compaq Computer Corporation
Category: Standards Track                               December 1998

               IP Version 6 Management Information Base
                 for the Transmission Control Protocol

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.


   This document is one in the series of documents that define various
   MIB objects for IPv6.  Specifically, this document is the MIB module
   which defines managed objects for implementations of the Transmission
   Control Protocol (TCP) over IP Version 6 (IPv6).

   This document also recommends a specific policy with respect to the
   applicability of RFC 2012 for implementations of IPv6.  Namely, that
   most of managed objects defined in RFC 2012 are independent of which
   IP versions underlie TCP, and only the TCP connection information is
   IP version-specific.

   This memo defines an experimental portion of the Management
   Information Base (MIB) for use with network management protocols in
   IPv6-based internets.

1.  Introduction

   A management system contains: several (potentially many) nodes, each
   with a processing entity, termed an agent, which has access to
   management instrumentation; at least one management station; and, a
   management protocol, used to convey management information between
   the agents and management stations.  Operations of the protocol are
   carried out under an administrative framework which defines
   authentication, authorization, access control, and privacy policies.

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RFC 2452                    TCP MIB for IPv6               December 1998

   Management stations execute management applications which monitor and
   control managed elements.  Managed elements are devices such as
   hosts, routers, terminal servers, etc., which are monitored and
   controlled via access to their management information.

   Management information is viewed as a collection of managed objects,
   residing in a virtual information store, termed the Management
   Information Base (MIB).  Collections of related objects are defined
   in MIB modules.  These modules are written using a subset of OSI's
   Abstract Syntax Notation One (ASN.1) [1], termed the Structure of
   Management Information (SMI) [2].

2.  Overview

   This document is one in the series of documents that define various
   MIB objects, and statements of conformance, for IPv6.  This document
   defines the required instrumentation for implementations of TCP over

3.  Transparency of IP versions to TCP

   The fact that a particular TCP connection uses IPv6 as opposed to
   IPv4, is largely invisible to a TCP implementation.  A "TCPng" did
   not need to be defined, implementations simply need to support IPv6

   As such, the managed objects already defined in [TCP MIB] are
   sufficient for managing TCP in the presence of IPv6.  These objects
   are equally applicable whether the managed node supports IPv4 only,
   IPv6 only, or both IPv4 and IPv6.

   For example, tcpActiveOpens counts "The number of times TCP
   connections have made a direct transition to the SYN-SENT state from
   the CLOSED state", regardless of which version of IP is used between
   the connection endpoints.

   Stated differently, TCP implementations don't need separate counters
   for IPv4 and for IPv6.

4.  Representing TCP Connections

   The exception to the statements in section 3 is the tcpConnTable.
   Since IPv6 addresses cannot be represented with the IpAddress syntax,
   not all TCP connections can be represented in the tcpConnTable
   defined in [TCP MIB].

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RFC 2452                    TCP MIB for IPv6               December 1998

   This memo defines a new, separate table to represent only those TCP
   connections between IPv6 endpoints.  TCP connections between IPv4
   endpoints continue to be represented in tcpConnTable [TCP MIB].  (It
   is not possible to establish a TCP connection between an IPv4
    endpoint and an IPv6 endpoint.)

   A different approach would have been to define a new table to
   represent all TCP connections regardless of IP version.  This would
   require changes to [TCP MIB] and hence to existing (IPv4-only) TCP
   implementations.  The approach suggested in this memo has the
   advantage of leaving IPv4-only implementations intact.

   It is assumed that the objects defined in this memo will eventually
   be defined in an update to [TCP MIB].  For this reason, the module
   identity is assigned under the experimental portion of the MIB.

5.  Conformance

   This memo contains conformance statements to define conformance to
   this MIB for TCP over IPv6 implementations.

6.  Definitions


   mib-2, experimental                  FROM SNMPv2-SMI
   Ipv6Address, Ipv6IfIndexOrZero       FROM IPV6-TC;

   LAST-UPDATED "9801290000Z"
        "       Mike Daniele

                Postal: Compaq Computer Corporation
                        110 Spitbrook Rd
                        Nashua, NH 03062.

                Phone:  +1 603 884 1423
                Email:  daniele@zk3.dec.com"
        "The MIB module for entities implementing TCP over IPv6."
   ::= { experimental 86 }

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RFC 2452                    TCP MIB for IPv6               December 1998

-- objects specific to TCP for IPv6

tcp      OBJECT IDENTIFIER ::= { mib-2 6 }

-- the TCP over IPv6 Connection table

-- This connection table contains information about this
-- entity's existing TCP connections between IPv6 endpoints.
-- Only connections between IPv6 addresses are contained in
-- this table.  This entity's connections between IPv4
-- endpoints are contained in tcpConnTable.

ipv6TcpConnTable OBJECT-TYPE
   SYNTAX      SEQUENCE OF Ipv6TcpConnEntry
   MAX-ACCESS  not-accessible
   STATUS      current
        "A table containing TCP connection-specific information,
         for only those connections whose endpoints are IPv6 addresses."
   ::= { tcp 16 }

ipv6TcpConnEntry OBJECT-TYPE
   SYNTAX      Ipv6TcpConnEntry
   MAX-ACCESS  not-accessible
   STATUS      current
        "A conceptual row of the ipv6TcpConnTable containing
         information about a particular current TCP connection.
         Each row of this table is transient, in that it ceases to
         exist when (or soon after) the connection makes the transition
         to the CLOSED state.

         Note that conceptual rows in this table require an additional
         index object compared to tcpConnTable, since IPv6 addresses
         are not guaranteed to be unique on the managed node."
   INDEX   { ipv6TcpConnLocalAddress,
             ipv6TcpConnIfIndex }
   ::= { ipv6TcpConnTable 1 }

Ipv6TcpConnEntry ::=
   SEQUENCE { ipv6TcpConnLocalAddress    Ipv6Address,
              ipv6TcpConnLocalPort       INTEGER (0..65535),
              ipv6TcpConnRemAddress      Ipv6Address,
              ipv6TcpConnRemPort         INTEGER (0..65535),
              ipv6TcpConnIfIndex         Ipv6IfIndexOrZero,

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RFC 2452                    TCP MIB for IPv6               December 1998

              ipv6TcpConnState           INTEGER }

ipv6TcpConnLocalAddress OBJECT-TYPE
   SYNTAX     Ipv6Address
   MAX-ACCESS not-accessible
   STATUS     current
        "The local IPv6 address for this TCP connection. In
         the case of a connection in the listen state which
         is willing to accept connections for any IPv6
         address associated with the managed node, the value
         ::0 is used."
   ::= { ipv6TcpConnEntry 1 }

ipv6TcpConnLocalPort OBJECT-TYPE
   SYNTAX     INTEGER (0..65535)
   MAX-ACCESS not-accessible
   STATUS     current
        "The local port number for this TCP connection."
   ::= { ipv6TcpConnEntry 2 }

ipv6TcpConnRemAddress OBJECT-TYPE
   SYNTAX     Ipv6Address
   MAX-ACCESS not-accessible
   STATUS     current
        "The remote IPv6 address for this TCP connection."
   ::= { ipv6TcpConnEntry 3 }

ipv6TcpConnRemPort OBJECT-TYPE
   SYNTAX     INTEGER (0..65535)
   MAX-ACCESS not-accessible
   STATUS     current
        "The remote port number for this TCP connection."
   ::= { ipv6TcpConnEntry 4 }

ipv6TcpConnIfIndex OBJECT-TYPE
   SYNTAX     Ipv6IfIndexOrZero
   MAX-ACCESS not-accessible
   STATUS     current
        "An index object used to disambiguate conceptual rows in
         the table, since the connection 4-tuple may not be unique.

         If the connection's remote address (ipv6TcpConnRemAddress)
         is a link-local address and the connection's local address

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RFC 2452                    TCP MIB for IPv6               December 1998

         (ipv6TcpConnLocalAddress) is not a link-local address, this
         object identifies a local interface on the same link as
         the connection's remote link-local address.

         Otherwise, this object identifies the local interface that
         is associated with the ipv6TcpConnLocalAddress for this
         TCP connection.  If such a local interface cannot be determined,
         this object should take on the value 0.  (A possible example
         of this would be if the value of ipv6TcpConnLocalAddress is ::0.)

         The interface identified by a particular non-0 value of this
         index is the same interface as identified by the same value
         of ipv6IfIndex.

         The value of this object must remain constant during the life
         of the TCP connection."
   ::= { ipv6TcpConnEntry 5 }

ipv6TcpConnState OBJECT-TYPE
        deleteTCB(12) }
   MAX-ACCESS read-write
   STATUS     current
        "The state of this TCP connection.

         The only value which may be set by a management station is
         deleteTCB(12).  Accordingly, it is appropriate for an agent
         to return an error response (`badValue' for SNMPv1, 'wrongValue'
         for SNMPv2) if a management station attempts to set this
         object to any other value.

         If a management station sets this object to the value
         deleteTCB(12), then this has the effect of deleting the TCB
         (as defined in RFC 793) of the corresponding connection on
         the managed node, resulting in immediate termination of the

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RFC 2452                    TCP MIB for IPv6               December 1998

         As an implementation-specific option, a RST segment may be
         sent from the managed node to the other TCP endpoint (note
         however that RST segments are not sent reliably)."
   ::= { ipv6TcpConnEntry 6 }

-- conformance information

ipv6TcpConformance OBJECT IDENTIFIER ::= { ipv6TcpMIB 2 }

ipv6TcpCompliances OBJECT IDENTIFIER ::= { ipv6TcpConformance 1 }
ipv6TcpGroups      OBJECT IDENTIFIER ::= { ipv6TcpConformance 2 }

-- compliance statements

   STATUS  current
        "The compliance statement for SNMPv2 entities which
         implement TCP over IPv6."
   MODULE  -- this module
   MANDATORY-GROUPS { ipv6TcpGroup }
   ::= { ipv6TcpCompliances 1 }

   OBJECTS   { -- these are defined in this module
               -- ipv6TcpConnLocalAddress (not-accessible)
               -- ipv6TcpConnLocalPort (not-accessible)
               -- ipv6TcpConnRemAddress (not-accessible)
               -- ipv6TcpConnRemPort (not-accessible)
               -- ipv6TcpConnIfIndex (not-accessible)
               ipv6TcpConnState }
   STATUS    current
        "The group of objects providing management of
         TCP over IPv6."
   ::= { ipv6TcpGroups 1 }


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RFC 2452                    TCP MIB for IPv6               December 1998

7.  Acknowledgments

   This memo is a product of the IPng work group, and benefited
   especially from the contributions of the following working group

      Dimitry Haskin          Bay Networks
      Margaret Forsythe       Epilogue
      Tim Hartrick            Mentat
      Frank Solensky          FTP
      Jack McCann             DEC

8.  References

   [1]           Information processing systems - Open Systems
                 Interconnection - Specification of Abstract Syntax
                 Notation One (ASN.1), International Organization for
                 Standardization.  International Standard 8824,
                 (December, 1987).

   [2]           McCloghrie, K., Editor, "Structure of Management
                 Information for version 2 of the Simple Network
                 Management Protocol (SNMPv2)", RFC 1902, January 1996.

   [TCP MIB]     SNMPv2 Working Group, McCloghrie, K., Editor, "SNMPv2
                 Management Information Base for the Transmission
                 Control Protocol using SMIv2", RFC 2012, November 1996.

   [IPV6 MIB TC] Haskin, D., and S. Onishi, "Management Information
                 Base for IP Version 6: Textual Conventions and General
                 Group", RFC 2465, December 1998.

   [IPV6]        Deering, S., and R. Hinden, "Internet Protocol, Version
                 6 (IPv6) Specification", RFC 2460, December 1998.

   [RFC2274]     Blumenthal, U., and B. Wijnen, "The User-Based Security
                 Model for Version 3 of the Simple Network Management
                 Protocol (SNMPv3)", RFC 2274, January 1998.

   [RFC2275]     Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
                 Access Control Model for the Simple Network Management
                 Protocol (SNMP)", RFC 2275, January 1998.

9.  Security Considerations

   This MIB contains a management object that has a MAX-ACCESS clause of
   read-write and/or read-create.  In particular, it is possible to
   delete individual TCP control blocks (i.e., connections).

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RFC 2452                    TCP MIB for IPv6               December 1998

   Consequently, anyone having the ability to issue a SET on this object
   can impact the operation of the node.

   There are a number of managed objects in this MIB that may be
   considered to contain sensitive information in some environments.
   For example, the MIB identifies the active TCP connections on the
   node.  Although this information might be considered sensitive in
   some environments (i.e., to identify ports on which to launch
   denial-of-service or other attacks), there are already other ways of
   obtaining similar information.  For example, sending a random TCP
   packet to an unused port prompts the generation of a TCP reset

   Therefore, it may be important in some environments to control read
   and/or write access to these objects and possibly to even encrypt the
   values of these object when sending them over the network via SNMP.
   Not all versions of SNMP provide features for such a secure
   environment.  SNMPv1 by itself does not provide encryption or strong

   It is recommended that the implementors consider the security
   features as provided by the SNMPv3 framework.  Specifically, the use
   of the User-based Security Model [RFC2274] and the View-based Access
   Control Model [RFC2275] is recommended.

   It is then a customer/user responsibility to ensure that the SNMP
   entity giving access to an instance of this MIB, is properly
   configured to give access to those objects only to those principals
   (users) that have legitimate rights to access them.

10. Author's Address

   Mike Daniele
   Compaq Computer Corporation
   110 Spit Brook Rd
   Nashua, NH 03062

   Phone: +1-603-884-1423
   EMail: daniele@zk3.dec.com

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RFC 2452                    TCP MIB for IPv6               December 1998

11.  Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an

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