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rfc:rfc4898

Network Working Group M. Mathis Request for Comments: 4898 J. Heffner Category: Standards Track Pittsburgh Supercomputing Center

                                                       R. Raghunarayan
                                                         Cisco Systems
                                                              May 2007
                    TCP Extended Statistics MIB

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 IETF Trust (2007).

Abstract

 This document describes extended performance statistics for TCP.
 They are designed to use TCP's ideal vantage point to diagnose
 performance problems in both the network and the application.  If a
 network-based application is performing poorly, TCP can determine if
 the bottleneck is in the sender, the receiver, or the network itself.
 If the bottleneck is in the network, TCP can provide specific
 information about its nature.

Table of Contents

 1. Introduction ....................................................2
 2. The Internet-Standard Management Framework ......................2
 3. Overview ........................................................2
    3.1. MIB Initialization and Persistence .........................4
    3.2. Relationship to TCP Standards ..............................4
    3.3. Diagnosing SYN-Flood Denial-of-Service Attacks .............6
 4. TCP Extended Statistics MIB .....................................7
 5. Security Considerations ........................................69
 6. IANA Considerations ............................................70
 7. Normative References ...........................................70
 8. Informative References .........................................72
 9. Contributors ...................................................73
 10. Acknowledgments ...............................................73

Mathis, et al. Standards Track [Page 1] RFC 4898 TCP Extended Statistics MIB May 2007

1. Introduction

 This document describes extended performance statistics for TCP.
 They are designed to use TCP's ideal vantage point to diagnose
 performance problems in both the network and the application.  If a
 network-based application is performing poorly, TCP can determine if
 the bottleneck is in the sender, the receiver, or the network itself.
 If the bottleneck is in the network, TCP can provide specific
 information about its nature.
 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.
 The Simple Network Management Protocol (SNMP) objects defined in this
 document extend TCP MIB, as specified in RFC 4022 [RFC4022].  In
 addition to several new scalars and other objects, it augments two
 tables and makes one clarification to RFC 4022.  Existing management
 stations for the TCP MIB are expected to be fully compatible with
 these clarifications.

2. The Internet-Standard Management Framework

 For a detailed overview of the documents that describe the current
 Internet-Standard Management Framework, please refer to section 7 of
 RFC 3410 [RFC3410].
 Managed objects are accessed via a virtual information store, termed
 the Management Information Base or MIB.  MIB objects are generally
 accessed through the Simple Network Management Protocol (SNMP).
 Objects in the MIB are defined using the mechanisms defined in the
 Structure of Management Information (SMI).  This memo specifies a MIB
 module that is compliant to the SMIv2, which is described in STD 58,
 RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
 [RFC2580].

3. Overview

 The TCP-ESTATS-MIB defined in this memo consists of two groups of
 scalars, seven tables, and two notifications:
  • The first group of scalars contain statistics of the TCP protocol

engine not covered in RFC 4022. This group consists of the single

    scalar tcpEStatsListenerTableLastChange, which provides management
    stations with an easier mechanism to validate their listener
    caches.

Mathis, et al. Standards Track [Page 2] RFC 4898 TCP Extended Statistics MIB May 2007

  • The second group of scalars consist of knobs to enable and disable

information collection by the tables containing connection-related

    statistics/information.  For example, the tcpEStatsControlPath
    object controls the activation of the tcpEStatsPathTable.  The
    tcpEStatsConnTableLatency object determines how long connection
    table rows are retained after a TCP connection transitions into
    the closed state.
  • The tcpEStatsListenerTable augments tcpListenerTable in TCP-MIB

[RFC4022] to provide additional information on the active TCP

    listeners on a device.  It supports objects to monitor and
    diagnose SYN-flood denial-of-service attacks as described below.
  • The tcpEStatsConnectIdTable augments the tcpConnectionTable in

TCP-MIB [RFC4022] to provide a mapping between connection 4-tuples

    (which index tcpConnectionTable) and an integer connection index,
    tcpEStatsConnectIndex.  The connection index is used to index into
    the five remaining tables in this MIB module, and is designed to
    facilitate rapid polling of multiple objects associated with one
    TCP connection.
  • The tcpEStatsPerfTable contains objects that are useful for

measuring TCP performance and first check problem diagnosis.

  • The tcpEStatsPathTable contains objects that can be used to infer

detailed behavior of the Internet path, such as the extent that

    there are segment losses or reordering, etc.
  • The tcpEStatsStackTable contains objects that are most useful for

determining how well the TCP control algorithms are coping with

    this particular path.
  • The tcpEStatsAppTable provides objects that are useful for

determining if the application using TCP is limiting TCP

    performance.
  • The tcpEStatsTuneTable provides per-connection controls that can

be used to work around a number of common problems that plague TCP

    over some paths.
  • The two notifications defined in this MIB module are

tcpEStatsEstablishNotification, indicating that a new connection

    has been accepted (or established, see below), and
    tcpEStatsCloseNotification, indicating that an existing connection
    has recently closed.

Mathis, et al. Standards Track [Page 3] RFC 4898 TCP Extended Statistics MIB May 2007

3.1. MIB Initialization and Persistence

 The TCP protocol itself is specifically designed not to preserve any
 state whatsoever across system reboots, and enforces this by
 requiring randomized Initial Sequence numbers and ephemeral ports
 under any conditions where segments from old connections might
 corrupt new connections following a reboot.
 All of the objects in the MIB MUST have the same persistence
 properties as the underlying TCP implementation.  On a reboot, all
 zero-based counters MUST be cleared, all dynamically created table
 rows MUST be deleted, and all read-write objects MUST be restored to
 their default values.  It is assumed that all TCP implementation have
 some initialization code (if nothing else, to set IP addresses) that
 has the opportunity to adjust tcpEStatsConnTableLatency and other
 read-write scalars controlling the creation of the various tables,
 before establishing the first TCP connection.  Implementations MAY
 also choose to make these control scalars persist across reboots.
 The ZeroBasedCounter32 and ZeroBasedCounter64 objects in the listener
 and connection tables are initialized to zero when the table row is
 created.
 The tcpEStatsConnTableLatency object determines how long connection
 table rows are retained after a TCP connection transitions into the
 closed state, to permit reading final connection completion
 statistics.  In RFC 4022 (TCP-MIB), the discussion of
 tcpConnectionTable row latency (page 9) the words "soon after" are
 understood to mean after tcpEStatsConnTableLatency, such that all
 rows of all tables associated with one connection are retained at
 least tcpEStatsConnTableLatency after connection close.  This
 clarification to RFC 4022 only applies when TCP-ESTATS-MIB is
 implemented.  If TCP-ESTATS-MIB is not implemented, RFC 4022 permits
 an unspecified delay between connection close and row deletion.

3.2. Relationship to TCP Standards

 There are more than 70 RFCs and other documents that specify various
 aspects of the Transmission Control Protocol (TCP) [RFC4614].  While
 most protocols are completely specified in one or two documents, this
 has not proven to be feasible for TCP.  TCP implements a reliable
 end-to-end data transport service over a very weakly constrained IP
 datagram service.  The essential problem that TCP has to solve is
 balancing the applications need for fast and reliable data transport
 against the need to make fair, efficient, and equitable use of
 network resources, with only sparse information about the state of
 the network or its capabilities.

Mathis, et al. Standards Track [Page 4] RFC 4898 TCP Extended Statistics MIB May 2007

 TCP maintains this balance through the use of many estimators and
 heuristics that regulate various aspects of the protocol.  For
 example, RFC 2988 describes how to calculate the retransmission timer
 (RTO) from the average and variance of the network round-trip-time
 (RTT), as estimated from the round-trip time sampled on some data
 segments.  Although these algorithms are standardized, they are a
 compromise which is optimal for only common Internet environments.
 Other estimators might yield better results (higher performance or
 more efficient use of the network) in some environments, particularly
 under uncommon conditions.
 It is the consensus of the community that nearly all of the
 estimators and heuristics used in TCP might be improved through
 further research and development.  For this reason, nearly all TCP
 documents leave some latitude for future improvements, for example,
 by the use of "SHOULD" instead of "MUST" [RFC2119].  Even standard
 algorithms that are required because they critically effect fairness
 or the dynamic stability of Internet congestion control, include some
 latitude for evolution.  As a consequence, there is considerable
 diversity in the details of the TCP implementations actually in use
 today.
 The fact that the underlying algorithms are not uniform makes it
 difficult to tightly specify a MIB.  We could have chosen the point
 of view that the MIB should publish precisely defined metrics of the
 network path, even if they are different from the estimators in use
 by TCP.  This would make the MIB more useful as a measurement tool,
 but less useful for understanding how any specific TCP implementation
 is interacting with the network path and upper protocol layers.  We
 chose instead to have the MIB expose the estimators and important
 states variables of the algorithms in use, without constraining the
 TCP implementation.
 As a consequence, the MIB objects are defined in terms of fairly
 abstract descriptions (e.g., round-trip time), but are intended to
 expose the actual estimators or other state variables as they are
 used in TCP implementations, possibly transformed (e.g., scaled or
 otherwise adjusted) to match the spirit of the object descriptions in
 this document.
 This may mean that MIB objects may not be exactly comparable between
 two different TCP implementations.  A general management station can
 only assume the abstract descriptions, which are useful for a general
 assessment of how TCP is functioning.  To a TCP implementer with
 detailed knowledge about the TCP implementation on a specific host,
 this MIB might be useful for debugging or evaluating the algorithms
 in their implementation.

Mathis, et al. Standards Track [Page 5] RFC 4898 TCP Extended Statistics MIB May 2007

 Under no conditions is this MIB intended to constrain TCP to use (or
 exclude) any particular estimator, heuristic, algorithm, or
 implementation.

3.3. Diagnosing SYN-Flood Denial-of-Service Attacks

 The tcpEStatsListenerTable is specifically designed to provide
 information that is useful for diagnosing SYN-flood Denial-of-Service
 attacks, where a server is overwhelmed by forged or otherwise
 malicious connection attempts.  There are several different
 techniques that can be used to defend against SYN-flooding but none
 are standardized [Edd06].  These different techniques all have the
 same basic characteristics that are instrumentable with a common set
 of objects, even though the techniques differ greatly in the details.
 All SYN-flood defenses avoid allocating significant resources (memory
 or CPU) to incoming (passive open) connections until the connections
 meet some liveness criteria (to defend against forged IP source
 addresses) and the server has sufficient resources to process the
 incoming request.  Note that allocating resources is an
 implementation-specific event that may not correspond to an
 observable protocol event (e.g., segments on the wire).  There are
 two general concepts that can be applied to all known SYN-flood
 defenses.  There is generally a well-defined event when a connection
 is allocated full resources, and a "backlog" -- a queue of embryonic
 connections that have been allocated only partial resources.
 In many implementations, incoming TCP connections are allocated
 resources as a side effect of the POSIX [POSIX] accept() call.  For
 this reason we use the terminology "accepting a connection" to refer
 to this event: committing sufficient network resources to process the
 incoming request.  Accepting a connection typically entails
 allocating memory for the protocol control block [RFC793], the per-
 connection table rows described in this MIB and CPU resources, such
 as process table entries or threads.
 Note that it is not useful to accept connections before they are
 ESTABLISHED, because this would create an easy opportunity for
 Denial-of-Service attacks, using forged source IP addresses.
 The backlog consists of connections that are in SYN-RCVD or
 ESTABLISHED states, that have not been accepted.  For purposes of
 this MIB, we assume that these connections have been allocated some
 resources (e.g., an embryonic protocol control block), but not full
 resources (e.g., do not yet have MIB table rows).

Mathis, et al. Standards Track [Page 6] RFC 4898 TCP Extended Statistics MIB May 2007

 Note that some SYN-Flood defenses dispense with explicit SYN-RCVD
 state by cryptographically encoding the state in the ISS (initial
 sequence number sent) of the SYN-ACK (sometimes called a syn-cookie),
 and then using the sequence number of the first ACK to reconstruct
 the SYN-RCVD state before transitioning to the ESTABLISHED state.
 For these implementations there is no explicit representation of the
 SYN-RCVD state, and the backlog only consists of connections that are
 ESTABLISHED and are waiting to be ACCEPTED.
 Furthermore, most SYN-flood defenses have some mechanism to throttle
 connections that might otherwise overwhelm this endpoint.  They
 generally use some combination of discarding incoming SYNs and
 discarding connections already in the backlog.  This does not cause
 all connections from legitimate clients to fail, as long as the
 clients retransmit the SYN or first ACK as specified in RFC 793.
 Most diversity in SYN flood defenses arise from variations in these
 algorithms to limit load, and therefore cannot be instrumented with a
 common standard MIB.
 The Listen Table instruments all passively opened TCP connections in
 terms of observable protocol events (e.g., sent and received
 segments) and resource allocation events (entering the backlog and
 being accepted).  This approach eases generalization to SYN-flood
 mechanisms that use alternate TCP state transition diagrams and
 implicit mechanisms to encode some states.

4. TCP Extended Statistics MIB

 This MIB module IMPORTS definitions from [RFC2578], [RFC2579],
 [RFC2580], [RFC2856], [RFC4022], and [RFC4502].  It uses REFERENCE
 clauses to refer to [RFC791], [RFC793], [RFC1122], [RFC1191],
 [RFC1323], [RFC2018], [RFC2581], [RFC2861], [RFC2883], [RFC2988],
 [RFC3168], [RFC3260], [RFC3517], [RFC3522], and [RFC3742].
 TCP-ESTATS-MIB DEFINITIONS ::= BEGIN
 IMPORTS
        MODULE-IDENTITY, Counter32, Integer32, Unsigned32,
        Gauge32, OBJECT-TYPE, mib-2,
        NOTIFICATION-TYPE
            FROM SNMPv2-SMI                 -- [RFC2578]
        MODULE-COMPLIANCE, OBJECT-GROUP, NOTIFICATION-GROUP
            FROM SNMPv2-CONF                -- [RFC2580]
        ZeroBasedCounter32
            FROM RMON2-MIB                  -- [RFC4502]
        ZeroBasedCounter64
            FROM HCNUM-TC                   -- [RFC2856]
        TEXTUAL-CONVENTION,
        DateAndTime, TruthValue, TimeStamp

Mathis, et al. Standards Track [Page 7] RFC 4898 TCP Extended Statistics MIB May 2007

            FROM SNMPv2-TC                  -- [RFC2579]
        tcpListenerEntry, tcpConnectionEntry
            FROM TCP-MIB;                   -- [RFC4022]
 tcpEStatsMIB MODULE-IDENTITY
     LAST-UPDATED "200705180000Z"    -- 18 May 2007
     ORGANIZATION "IETF TSV Working Group"
     CONTACT-INFO
         "Matt Mathis
         John Heffner
         Web100 Project
         Pittsburgh Supercomputing Center
         300 S. Craig St.
         Pittsburgh, PA 15213
         Email: mathis@psc.edu, jheffner@psc.edu
         Rajiv Raghunarayan
         Cisco Systems Inc.
         San Jose, CA 95134
         Phone: 408 853 9612
         Email: raraghun@cisco.com
         Jon Saperia
         84 Kettell Plain Road
         Stow, MA 01775
         Phone: 617-201-2655
         Email: saperia@jdscons.com "
     DESCRIPTION
         "Documentation of TCP Extended Performance Instrumentation
          variables from the Web100 project.  [Web100]
          All of the objects in this MIB MUST have the same
          persistence properties as the underlying TCP implementation.
          On a reboot, all zero-based counters MUST be cleared, all
          dynamically created table rows MUST be deleted, and all
          read-write objects MUST be restored to their default values.
          It is assumed that all TCP implementation have some
          initialization code (if nothing else to set IP addresses)
          that has the opportunity to adjust tcpEStatsConnTableLatency
          and other read-write scalars controlling the creation of the
          various tables, before establishing the first TCP
          connection.  Implementations MAY also choose to make these
          control scalars persist across reboots.
          Copyright (C) The IETF Trust (2007).  This version
          of this MIB module is a part of RFC 4898; see the RFC
          itself for full legal notices."

Mathis, et al. Standards Track [Page 8] RFC 4898 TCP Extended Statistics MIB May 2007

     REVISION "200705180000Z"    -- 18 May 2007
     DESCRIPTION
         "Initial version, published as RFC 4898."
         ::= { mib-2 156 }
 tcpEStatsNotifications OBJECT IDENTIFIER ::= { tcpEStatsMIB 0 }
 tcpEStatsMIBObjects    OBJECT IDENTIFIER ::= { tcpEStatsMIB 1 }
 tcpEStatsConformance   OBJECT IDENTIFIER ::= { tcpEStatsMIB 2 }
 tcpEStats             OBJECT IDENTIFIER ::= { tcpEStatsMIBObjects 1 }
 tcpEStatsControl      OBJECT IDENTIFIER ::= { tcpEStatsMIBObjects 2 }
 tcpEStatsScalar       OBJECT IDENTIFIER ::= { tcpEStatsMIBObjects 3 }
  1. -
  2. - Textual Conventions
  3. -
 TcpEStatsNegotiated  ::= TEXTUAL-CONVENTION
    STATUS             current
    DESCRIPTION
        "Indicates if some optional TCP feature was negotiated.
         Enabled(1) indicates that the feature was successfully
         negotiated on, which generally requires both hosts to agree
         to use the feature.
         selfDisabled(2) indicates that the local host refused the
         feature because it is not implemented, configured off, or
         refused for some other reason, such as the lack of
         resources.
         peerDisabled(3) indicates that the local host was willing
         to negotiate the feature, but the remote host did not
         do so."
    SYNTAX INTEGER {
                 enabled(1),
                 selfDisabled(2),
                 peerDisabled(3)
         }
  1. -
  2. - TCP Extended statistics scalars
  3. -
 tcpEStatsListenerTableLastChange OBJECT-TYPE
     SYNTAX     TimeStamp
     MAX-ACCESS read-only
     STATUS     current
     DESCRIPTION

Mathis, et al. Standards Track [Page 9] RFC 4898 TCP Extended Statistics MIB May 2007

            "The value of sysUpTime at the time of the last
             creation or deletion of an entry in the tcpListenerTable.
             If the number of entries has been unchanged since the
             last re-initialization of the local network management
             subsystem, then this object contains a zero value."
     ::= { tcpEStatsScalar 3 }
  1. - ================================================================
  2. -
  3. - The tcpEStatsControl Group
  4. -
  1. - The scalar objects in this group are used to control the
  2. - activation and deactivation of the TCP Extended Statistics
  3. - tables and notifications in this module.
  4. -
 tcpEStatsControlPath  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
         "Controls the activation of the TCP Path Statistics
         table.
         A value 'true' indicates that the TCP Path Statistics
         table is active, while 'false' indicates that the
         table is inactive."
     DEFVAL          { false }
     ::= { tcpEStatsControl 1 }
 tcpEStatsControlStack  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
         "Controls the activation of the TCP Stack Statistics
         table.
         A value 'true' indicates that the TCP Stack Statistics
         table is active, while 'false' indicates that the
         table is inactive."
     DEFVAL          { false }
     ::= { tcpEStatsControl 2 }
 tcpEStatsControlApp  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-write

Mathis, et al. Standards Track [Page 10] RFC 4898 TCP Extended Statistics MIB May 2007

     STATUS          current
     DESCRIPTION
         "Controls the activation of the TCP Application
         Statistics table.
         A value 'true' indicates that the TCP Application
         Statistics table is active, while 'false' indicates
         that the table is inactive."
     DEFVAL          { false }
     ::= { tcpEStatsControl 3 }
 tcpEStatsControlTune  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
         "Controls the activation of the TCP Tuning table.
         A value 'true' indicates that the TCP Tuning
         table is active, while 'false' indicates that the
         table is inactive."
     DEFVAL          { false }
     ::= { tcpEStatsControl 4 }
 tcpEStatsControlNotify  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
         "Controls the generation of all notifications defined in
         this MIB.
         A value 'true' indicates that the notifications
         are active, while 'false' indicates that the
         notifications are inactive."
     DEFVAL          { false }
     ::= { tcpEStatsControl 5 }
 tcpEStatsConnTableLatency OBJECT-TYPE
     SYNTAX          Unsigned32
     UNITS           "seconds"
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
         "Specifies the number of seconds that the entity will
          retain entries in the TCP connection tables, after the
          connection first enters the closed state.  The entity
          SHOULD provide a configuration option to enable

Mathis, et al. Standards Track [Page 11] RFC 4898 TCP Extended Statistics MIB May 2007

          customization of this value.  A value of 0
          results in entries being removed from the tables as soon as
          the connection enters the closed state.  The value of
          this object pertains to the following tables:
            tcpEStatsConnectIdTable
            tcpEStatsPerfTable
            tcpEStatsPathTable
            tcpEStatsStackTable
            tcpEStatsAppTable
            tcpEStatsTuneTable"
     DEFVAL { 0 }
     ::= { tcpEStatsControl 6 }
  1. - ================================================================
  2. -
  3. - Listener Table
  4. -
 tcpEStatsListenerTable OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsListenerEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table contains information about TCP Listeners,
         in addition to the information maintained by the
         tcpListenerTable RFC 4022."
     ::= { tcpEStats 1 }
 tcpEStatsListenerEntry OBJECT-TYPE
     SYNTAX       TcpEStatsListenerEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in the table contains information about
         a specific TCP Listener."
     AUGMENTS { tcpListenerEntry }
     ::= { tcpEStatsListenerTable 1 }
 TcpEStatsListenerEntry ::= SEQUENCE {
         tcpEStatsListenerStartTime         TimeStamp,
         tcpEStatsListenerSynRcvd           ZeroBasedCounter32,
         tcpEStatsListenerInitial           ZeroBasedCounter32,
         tcpEStatsListenerEstablished       ZeroBasedCounter32,
         tcpEStatsListenerAccepted          ZeroBasedCounter32,
         tcpEStatsListenerExceedBacklog     ZeroBasedCounter32,
         tcpEStatsListenerHCSynRcvd         ZeroBasedCounter64,
         tcpEStatsListenerHCInitial         ZeroBasedCounter64,
         tcpEStatsListenerHCEstablished     ZeroBasedCounter64,

Mathis, et al. Standards Track [Page 12] RFC 4898 TCP Extended Statistics MIB May 2007

         tcpEStatsListenerHCAccepted        ZeroBasedCounter64,
         tcpEStatsListenerHCExceedBacklog   ZeroBasedCounter64,
         tcpEStatsListenerCurConns          Gauge32,
         tcpEStatsListenerMaxBacklog        Unsigned32,
         tcpEStatsListenerCurBacklog        Gauge32,
         tcpEStatsListenerCurEstabBacklog   Gauge32
 }
 tcpEStatsListenerStartTime   OBJECT-TYPE
     SYNTAX     TimeStamp
     MAX-ACCESS read-only
     STATUS     current
     DESCRIPTION
         "The value of sysUpTime at the time this listener was
         established.  If the current state was entered prior to
         the last re-initialization of the local network management
         subsystem, then this object contains a zero value."
     ::= { tcpEStatsListenerEntry 1 }
 tcpEStatsListenerSynRcvd OBJECT-TYPE
     SYNTAX     ZeroBasedCounter32
     MAX-ACCESS read-only
     STATUS     current
     DESCRIPTION
         "The number of SYNs which have been received for this
         listener.  The total number of failed connections for
         all reasons can be estimated to be tcpEStatsListenerSynRcvd
         minus tcpEStatsListenerAccepted and
         tcpEStatsListenerCurBacklog."
     ::= { tcpEStatsListenerEntry 2 }
 tcpEStatsListenerInitial     OBJECT-TYPE
    SYNTAX     ZeroBasedCounter32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The total number of connections for which the Listener
        has allocated initial state and placed the
        connection in the backlog.  This may happen in the
        SYN-RCVD or ESTABLISHED states, depending on the
        implementation."
     ::= { tcpEStatsListenerEntry 3 }
 tcpEStatsListenerEstablished OBJECT-TYPE
     SYNTAX     ZeroBasedCounter32
     MAX-ACCESS read-only
     STATUS     current
     DESCRIPTION

Mathis, et al. Standards Track [Page 13] RFC 4898 TCP Extended Statistics MIB May 2007

         "The number of connections that have been established to
         this endpoint (e.g., the number of first ACKs that have
         been received for this listener)."
     ::= { tcpEStatsListenerEntry 4 }
 tcpEStatsListenerAccepted    OBJECT-TYPE
    SYNTAX     ZeroBasedCounter32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The total number of connections for which the Listener
        has successfully issued an accept, removing the connection
        from the backlog."
     ::= { tcpEStatsListenerEntry 5 }
 tcpEStatsListenerExceedBacklog OBJECT-TYPE
    SYNTAX     ZeroBasedCounter32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The total number of connections dropped from the
       backlog by this listener due to all reasons.  This
       includes all connections that are allocated initial
       resources, but are not accepted for some reason."
     ::= { tcpEStatsListenerEntry 6 }
 tcpEStatsListenerHCSynRcvd OBJECT-TYPE
     SYNTAX     ZeroBasedCounter64
     MAX-ACCESS read-only
     STATUS     current
     DESCRIPTION
         "The number of SYNs that have been received for this
         listener on systems that can process (or reject) more
         than 1 million connections per second.  See
         tcpEStatsListenerSynRcvd."
     ::= { tcpEStatsListenerEntry 7 }
 tcpEStatsListenerHCInitial     OBJECT-TYPE
    SYNTAX     ZeroBasedCounter64
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The total number of connections for which the Listener
        has allocated initial state and placed the connection
        in the backlog on systems that can process (or reject)
        more than 1 million connections per second.  See
        tcpEStatsListenerInitial."
     ::= { tcpEStatsListenerEntry 8 }

Mathis, et al. Standards Track [Page 14] RFC 4898 TCP Extended Statistics MIB May 2007

 tcpEStatsListenerHCEstablished OBJECT-TYPE
     SYNTAX     ZeroBasedCounter64
     MAX-ACCESS read-only
     STATUS     current
     DESCRIPTION
         "The number of connections that have been established to
         this endpoint on systems that can process (or reject) more
         than 1 million connections per second.  See
         tcpEStatsListenerEstablished."
     ::= { tcpEStatsListenerEntry 9 }
 tcpEStatsListenerHCAccepted    OBJECT-TYPE
    SYNTAX     ZeroBasedCounter64
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The total number of connections for which the Listener
        has successfully issued an accept, removing the connection
        from the backlog on systems that can process (or reject)
        more than 1 million connections per second.  See
        tcpEStatsListenerAccepted."
     ::= { tcpEStatsListenerEntry 10 }
 tcpEStatsListenerHCExceedBacklog OBJECT-TYPE
    SYNTAX     ZeroBasedCounter64
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The total number of connections dropped from the
       backlog by this listener due to all reasons on
       systems that can process (or reject) more than
       1 million connections per second.  See
       tcpEStatsListenerExceedBacklog."
     ::= { tcpEStatsListenerEntry 11 }
 tcpEStatsListenerCurConns   OBJECT-TYPE
    SYNTAX     Gauge32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The current number of connections in the ESTABLISHED
        state, which have also been accepted.  It excludes
        connections that have been established but not accepted
        because they are still subject to being discarded to
        shed load without explicit action by either endpoint."
     ::= { tcpEStatsListenerEntry 12 }
 tcpEStatsListenerMaxBacklog OBJECT-TYPE

Mathis, et al. Standards Track [Page 15] RFC 4898 TCP Extended Statistics MIB May 2007

    SYNTAX     Unsigned32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The maximum number of connections allowed in the
        backlog at one time."
     ::= { tcpEStatsListenerEntry 13 }
 tcpEStatsListenerCurBacklog OBJECT-TYPE
    SYNTAX     Gauge32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The current number of connections that are in the backlog.
        This gauge includes connections in ESTABLISHED or
        SYN-RECEIVED states for which the Listener has not yet
        issued an accept.
        If this listener is using some technique to implicitly
        represent the SYN-RECEIVED states (e.g., by
        cryptographically encoding the state information in the
        initial sequence number, ISS), it MAY elect to exclude
        connections in the SYN-RECEIVED state from the backlog."
     ::= { tcpEStatsListenerEntry 14 }
 tcpEStatsListenerCurEstabBacklog OBJECT-TYPE
    SYNTAX     Gauge32
    MAX-ACCESS read-only
    STATUS     current
    DESCRIPTION
       "The current number of connections in the backlog that are
        in the ESTABLISHED state, but for which the Listener has
        not yet issued an accept."
     ::= { tcpEStatsListenerEntry 15 }
  1. - ================================================================
  2. -
  3. - TCP Connection ID Table
  4. -
 tcpEStatsConnectIdTable    OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsConnectIdEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table maps information that uniquely identifies
         each active TCP connection to the connection ID used by

Mathis, et al. Standards Track [Page 16] RFC 4898 TCP Extended Statistics MIB May 2007

         other tables in this MIB Module.  It is an extension of
         tcpConnectionTable in RFC 4022.
         Entries are retained in this table for the number of
         seconds indicated by the tcpEStatsConnTableLatency
         object, after the TCP connection first enters the closed
         state."
     ::= { tcpEStats 2 }
 tcpEStatsConnectIdEntry  OBJECT-TYPE
     SYNTAX       TcpEStatsConnectIdEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in this table maps a TCP connection
         4-tuple to a connection index."
     AUGMENTS { tcpConnectionEntry }
     ::= { tcpEStatsConnectIdTable 1 }
 TcpEStatsConnectIdEntry ::= SEQUENCE {
         tcpEStatsConnectIndex             Unsigned32
 }
 tcpEStatsConnectIndex  OBJECT-TYPE
     SYNTAX          Unsigned32 (1..4294967295)
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
         "A unique integer value assigned to each TCP Connection
         entry.
         The RECOMMENDED algorithm is to begin at 1 and increase to
         some implementation-specific maximum value and then start
         again at 1 skipping values already in use."
     ::= { tcpEStatsConnectIdEntry 1 }
  1. - ================================================================
  2. -
  3. - Basic TCP Performance Statistics
  4. -
 tcpEStatsPerfTable    OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsPerfEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table contains objects that are useful for

Mathis, et al. Standards Track [Page 17] RFC 4898 TCP Extended Statistics MIB May 2007

         measuring TCP performance and first line problem
         diagnosis.  Most objects in this table directly expose
         some TCP state variable or are easily implemented as
         simple functions (e.g., the maximum value) of TCP
         state variables.
         Entries are retained in this table for the number of
         seconds indicated by the tcpEStatsConnTableLatency
         object, after the TCP connection first enters the closed
         state."
     ::= { tcpEStats 3 }
 tcpEStatsPerfEntry  OBJECT-TYPE
     SYNTAX       TcpEStatsPerfEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in this table has information about the
         characteristics of each active and recently closed TCP
         connection."
    INDEX { tcpEStatsConnectIndex }
    ::= { tcpEStatsPerfTable 1 }
 TcpEStatsPerfEntry ::= SEQUENCE {
         tcpEStatsPerfSegsOut                ZeroBasedCounter32,
         tcpEStatsPerfDataSegsOut            ZeroBasedCounter32,
         tcpEStatsPerfDataOctetsOut          ZeroBasedCounter32,
         tcpEStatsPerfHCDataOctetsOut        ZeroBasedCounter64,
         tcpEStatsPerfSegsRetrans            ZeroBasedCounter32,
         tcpEStatsPerfOctetsRetrans          ZeroBasedCounter32,
         tcpEStatsPerfSegsIn                 ZeroBasedCounter32,
         tcpEStatsPerfDataSegsIn             ZeroBasedCounter32,
         tcpEStatsPerfDataOctetsIn           ZeroBasedCounter32,
         tcpEStatsPerfHCDataOctetsIn         ZeroBasedCounter64,
         tcpEStatsPerfElapsedSecs            ZeroBasedCounter32,
         tcpEStatsPerfElapsedMicroSecs       ZeroBasedCounter32,
         tcpEStatsPerfStartTimeStamp         DateAndTime,
         tcpEStatsPerfCurMSS                 Gauge32,
         tcpEStatsPerfPipeSize               Gauge32,
         tcpEStatsPerfMaxPipeSize            Gauge32,
         tcpEStatsPerfSmoothedRTT            Gauge32,
         tcpEStatsPerfCurRTO                 Gauge32,
         tcpEStatsPerfCongSignals            ZeroBasedCounter32,
         tcpEStatsPerfCurCwnd                Gauge32,
         tcpEStatsPerfCurSsthresh            Gauge32,
         tcpEStatsPerfTimeouts               ZeroBasedCounter32,
         tcpEStatsPerfCurRwinSent            Gauge32,

Mathis, et al. Standards Track [Page 18] RFC 4898 TCP Extended Statistics MIB May 2007

         tcpEStatsPerfMaxRwinSent            Gauge32,
         tcpEStatsPerfZeroRwinSent           ZeroBasedCounter32,
         tcpEStatsPerfCurRwinRcvd            Gauge32,
         tcpEStatsPerfMaxRwinRcvd            Gauge32,
         tcpEStatsPerfZeroRwinRcvd           ZeroBasedCounter32,
         tcpEStatsPerfSndLimTransRwin        ZeroBasedCounter32,
         tcpEStatsPerfSndLimTransCwnd        ZeroBasedCounter32,
         tcpEStatsPerfSndLimTransSnd         ZeroBasedCounter32,
         tcpEStatsPerfSndLimTimeRwin         ZeroBasedCounter32,
         tcpEStatsPerfSndLimTimeCwnd         ZeroBasedCounter32,
         tcpEStatsPerfSndLimTimeSnd          ZeroBasedCounter32
     }
  1. -
  2. - The following objects provide statistics on aggregate
  3. - segments and data sent on a connection. These provide a
  4. - direct measure of the Internet capacity consumed by a
  5. - connection.
  6. -
 tcpEStatsPerfSegsOut  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The total number of segments sent."
     ::= { tcpEStatsPerfEntry 1 }
 tcpEStatsPerfDataSegsOut  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of segments sent containing a positive length
         data segment."
     ::= { tcpEStatsPerfEntry 2 }
 tcpEStatsPerfDataOctetsOut  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets of data contained in transmitted
         segments, including retransmitted data.  Note that this does
         not include TCP headers."
     ::= { tcpEStatsPerfEntry 3 }

Mathis, et al. Standards Track [Page 19] RFC 4898 TCP Extended Statistics MIB May 2007

 tcpEStatsPerfHCDataOctetsOut  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter64
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets of data contained in transmitted
         segments, including retransmitted data, on systems that can
         transmit more than 10 million bits per second.  Note that
         this does not include TCP headers."
     ::= { tcpEStatsPerfEntry 4 }
 tcpEStatsPerfSegsRetrans  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of segments transmitted containing at least some
         retransmitted data."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 5 }
 tcpEStatsPerfOctetsRetrans  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets retransmitted."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 6 }
 tcpEStatsPerfSegsIn  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The total number of segments received."
     ::= { tcpEStatsPerfEntry 7 }
 tcpEStatsPerfDataSegsIn  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of segments received containing a positive

Mathis, et al. Standards Track [Page 20] RFC 4898 TCP Extended Statistics MIB May 2007

         length data segment."
     ::= { tcpEStatsPerfEntry 8 }
 tcpEStatsPerfDataOctetsIn  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets contained in received data segments,
         including retransmitted data.  Note that this does not
         include TCP headers."
     ::= { tcpEStatsPerfEntry 9 }
 tcpEStatsPerfHCDataOctetsIn  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter64
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets contained in received data segments,
         including retransmitted data, on systems that can receive
         more than 10 million bits per second.  Note that this does
         not include TCP headers."
     ::= { tcpEStatsPerfEntry 10 }
 tcpEStatsPerfElapsedSecs  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "seconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The seconds part of the time elapsed between
         tcpEStatsPerfStartTimeStamp and the most recent protocol
         event (segment sent or received)."
     ::= { tcpEStatsPerfEntry 11 }
 tcpEStatsPerfElapsedMicroSecs  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "microseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The micro-second part of time elapsed between
         tcpEStatsPerfStartTimeStamp to the most recent protocol
         event (segment sent or received).  This may be updated in
         whatever time granularity is the system supports."
     ::= { tcpEStatsPerfEntry 12 }

Mathis, et al. Standards Track [Page 21] RFC 4898 TCP Extended Statistics MIB May 2007

 tcpEStatsPerfStartTimeStamp  OBJECT-TYPE
     SYNTAX          DateAndTime
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Time at which this row was created and all
         ZeroBasedCounters in the row were initialized to zero."
     ::= { tcpEStatsPerfEntry 13 }
  1. -
  2. - The following objects can be used to fit minimal
  3. - performance models to the TCP data rate.
  4. -
 tcpEStatsPerfCurMSS  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current maximum segment size (MSS), in octets."
     REFERENCE
        "RFC 1122, Requirements for Internet Hosts - Communication
         Layers"
     ::= { tcpEStatsPerfEntry 14 }
 tcpEStatsPerfPipeSize  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The TCP senders current estimate of the number of
         unacknowledged data octets in the network.
         While not in recovery (e.g., while the receiver is not
         reporting missing data to the sender), this is precisely the
         same as 'Flight size' as defined in RFC 2581, which can be
         computed as SND.NXT minus SND.UNA. [RFC793]
         During recovery, the TCP sender has incomplete information
         about the state of the network (e.g., which segments are
         lost vs reordered, especially if the return path is also
         dropping TCP acknowledgments).  Current TCP standards do not
         mandate any specific algorithm for estimating the number of
         unacknowledged data octets in the network.
         RFC 3517 describes a conservative algorithm to use SACK

Mathis, et al. Standards Track [Page 22] RFC 4898 TCP Extended Statistics MIB May 2007

         information to estimate the number of unacknowledged data
         octets in the network. tcpEStatsPerfPipeSize object SHOULD
         be the same as 'pipe' as defined in RFC 3517 if it is
         implemented. (Note that while not in recovery the pipe
         algorithm yields the same values as flight size).
         If RFC 3517 is not implemented, the data octets in flight
         SHOULD be estimated as SND.NXT minus SND.UNA adjusted by
         some measure of the data that has left the network and
         retransmitted data.  For example, with Reno or NewReno style
         TCP, the number of duplicate acknowledgment is used to
         count the number of segments that have left the network.
         That is,
         PipeSize=SND.NXT-SND.UNA+(retransmits-dupacks)*CurMSS"
     REFERENCE
        "RFC 793, RFC 2581, RFC 3517"
     ::= { tcpEStatsPerfEntry 15 }
 tcpEStatsPerfMaxPipeSize  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum value of tcpEStatsPerfPipeSize, for this
         connection."
     REFERENCE
        "RFC 793, RFC 2581, RFC 3517"
     ::= { tcpEStatsPerfEntry 16 }
 tcpEStatsPerfSmoothedRTT  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The smoothed round trip time used in calculation of the
         RTO. See SRTT in [RFC2988]."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPerfEntry 17 }
 tcpEStatsPerfCurRTO  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 23] RFC 4898 TCP Extended Statistics MIB May 2007

        "The current value of the retransmit timer RTO."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPerfEntry 18 }
 tcpEStatsPerfCongSignals  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of multiplicative downward congestion window
         adjustments due to all forms of congestion signals,
         including Fast Retransmit, Explicit Congestion Notification
         (ECN), and timeouts.  This object summarizes all events that
         invoke the MD portion of Additive Increase Multiplicative
         Decrease (AIMD) congestion control, and as such is the best
         indicator of how a cwnd is being affected by congestion.
         Note that retransmission timeouts multiplicatively reduce
         the window implicitly by setting ssthresh, and SHOULD be
         included in tcpEStatsPerfCongSignals.  In order to minimize
         spurious congestion indications due to out-of-order
         segments, tcpEStatsPerfCongSignals SHOULD be incremented in
         association with the Fast Retransmit algorithm."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPerfEntry 19 }
 tcpEStatsPerfCurCwnd  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current congestion window, in octets."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPerfEntry 20 }
 tcpEStatsPerfCurSsthresh  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current slow start threshold in octets."
     REFERENCE
        "RFC 2581, TCP Congestion Control"

Mathis, et al. Standards Track [Page 24] RFC 4898 TCP Extended Statistics MIB May 2007

     ::= { tcpEStatsPerfEntry 21 }
 tcpEStatsPerfTimeouts  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of times the retransmit timeout has expired when
         the RTO backoff multiplier is equal to one."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPerfEntry 22 }
  1. -
  2. - The following objects instrument receiver window updates
  3. - sent by the local receiver to the remote sender. These can
  4. - be used to determine if the local receiver is exerting flow
  5. - control back pressure on the remote sender.
  6. -
 tcpEStatsPerfCurRwinSent  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The most recent window advertisement sent, in octets."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 23 }
 tcpEStatsPerfMaxRwinSent  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum window advertisement sent, in octets."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 24 }
 tcpEStatsPerfZeroRwinSent  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of acknowledgments sent announcing a zero

Mathis, et al. Standards Track [Page 25] RFC 4898 TCP Extended Statistics MIB May 2007

         receive window, when the previously announced window was
         not zero."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 25 }
  1. -
  2. - The following objects instrument receiver window updates
  3. - from the far end-system to determine if the remote receiver
  4. - has sufficient buffer space or is exerting flow-control
  5. - back pressure on the local sender.
  6. -
 tcpEStatsPerfCurRwinRcvd  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The most recent window advertisement received, in octets."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 26 }
 tcpEStatsPerfMaxRwinRcvd  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum window advertisement received, in octets."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 27 }
 tcpEStatsPerfZeroRwinRcvd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of acknowledgments received announcing a zero
         receive window, when the previously announced window was
         not zero."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 28 }
  1. -

Mathis, et al. Standards Track [Page 26] RFC 4898 TCP Extended Statistics MIB May 2007

  1. - The following optional objects can be used to quickly
  2. - identify which subsystems are limiting TCP performance.
  3. - There are three parallel pairs of instruments that measure
  4. - the extent to which TCP performance is limited by the
  5. - announced receiver window (indicating a receiver
  6. - bottleneck), the current congestion window or
  7. - retransmission timeout (indicating a path bottleneck) and
  8. - all others events (indicating a sender bottleneck).
  9. -
  10. - These instruments SHOULD be updated every time the TCP
  11. - output routine stops sending data. The elapsed time since
  12. - the previous stop is accumulated into the appropriate
  13. - object as determined by the previous stop reason (e.g.,
  14. - stop state). The current stop reason determines which timer
  15. - will be updated the next time TCP output stops.
  16. -
  17. - Since there is no explicit stop at the beginning of a
  18. - timeout, it is necessary to retroactively reclassify the
  19. - previous stop as 'Congestion Limited'.
  20. -
 tcpEStatsPerfSndLimTransRwin  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of transitions into the 'Receiver Limited' state
         from either the 'Congestion Limited' or 'Sender Limited'
         states.  This state is entered whenever TCP transmission
         stops because the sender has filled the announced receiver
         window, i.e., when SND.NXT has advanced to SND.UNA +
         SND.WND - 1 as described in RFC 793."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsPerfEntry 31 }
 tcpEStatsPerfSndLimTransCwnd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of transitions into the 'Congestion Limited'
         state from either the 'Receiver Limited' or 'Sender
         Limited' states.  This state is entered whenever TCP
         transmission stops because the sender has reached some
         limit defined by congestion control (e.g., cwnd) or other
         algorithms (retransmission timeouts) designed to control
         network traffic.  See the definition of 'CONGESTION WINDOW'

Mathis, et al. Standards Track [Page 27] RFC 4898 TCP Extended Statistics MIB May 2007

         in RFC 2581."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPerfEntry 32 }
 tcpEStatsPerfSndLimTransSnd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of transitions into the 'Sender Limited' state
         from either the 'Receiver Limited' or 'Congestion Limited'
         states.  This state is entered whenever TCP transmission
         stops due to some sender limit such as running out of
         application data or other resources and the Karn algorithm.
         When TCP stops sending data for any reason, which cannot be
         classified as Receiver Limited or Congestion Limited, it
         MUST be treated as Sender Limited."
     ::= { tcpEStatsPerfEntry 33 }
 tcpEStatsPerfSndLimTimeRwin  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The cumulative time spent in the 'Receiver Limited' state.
         See tcpEStatsPerfSndLimTransRwin."
     ::= { tcpEStatsPerfEntry 34 }
 tcpEStatsPerfSndLimTimeCwnd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The cumulative time spent in the 'Congestion Limited'
         state.  See tcpEStatsPerfSndLimTransCwnd.  When there is a
         retransmission timeout, it SHOULD be counted in
         tcpEStatsPerfSndLimTimeCwnd (and not the cumulative time
         for some other state.)"
     ::= { tcpEStatsPerfEntry 35 }
 tcpEStatsPerfSndLimTimeSnd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current

Mathis, et al. Standards Track [Page 28] RFC 4898 TCP Extended Statistics MIB May 2007

     DESCRIPTION
        "The cumulative time spent in the 'Sender Limited' state.
         See tcpEStatsPerfSndLimTransSnd."
     ::= { tcpEStatsPerfEntry 36 }
  1. - ================================================================
  2. -
  3. - Statistics for diagnosing path problems
  4. -
 tcpEStatsPathTable    OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsPathEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table contains objects that can be used to infer
         detailed behavior of the Internet path, such as the
         extent that there is reordering, ECN bits, and if
         RTT fluctuations are correlated to losses.
         Entries are retained in this table for the number of
         seconds indicated by the tcpEStatsConnTableLatency
         object, after the TCP connection first enters the closed
         state."
     ::= { tcpEStats 4 }
 tcpEStatsPathEntry  OBJECT-TYPE
     SYNTAX       TcpEStatsPathEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in this table has information about the
         characteristics of each active and recently closed TCP
         connection."
    INDEX { tcpEStatsConnectIndex }
    ::= { tcpEStatsPathTable 1 }
 TcpEStatsPathEntry ::= SEQUENCE {
         tcpEStatsPathRetranThresh           Gauge32,
         tcpEStatsPathNonRecovDAEpisodes     ZeroBasedCounter32,
         tcpEStatsPathSumOctetsReordered     ZeroBasedCounter32,
         tcpEStatsPathNonRecovDA             ZeroBasedCounter32,
         tcpEStatsPathSampleRTT              Gauge32,
         tcpEStatsPathRTTVar                 Gauge32,
         tcpEStatsPathMaxRTT                 Gauge32,
         tcpEStatsPathMinRTT                 Gauge32,
         tcpEStatsPathSumRTT                 ZeroBasedCounter32,

Mathis, et al. Standards Track [Page 29] RFC 4898 TCP Extended Statistics MIB May 2007

         tcpEStatsPathHCSumRTT               ZeroBasedCounter64,
         tcpEStatsPathCountRTT               ZeroBasedCounter32,
         tcpEStatsPathMaxRTO                 Gauge32,
         tcpEStatsPathMinRTO                 Gauge32,
         tcpEStatsPathIpTtl                  Unsigned32,
         tcpEStatsPathIpTosIn                OCTET STRING,
         tcpEStatsPathIpTosOut               OCTET STRING,
         tcpEStatsPathPreCongSumCwnd         ZeroBasedCounter32,
         tcpEStatsPathPreCongSumRTT          ZeroBasedCounter32,
         tcpEStatsPathPostCongSumRTT         ZeroBasedCounter32,
         tcpEStatsPathPostCongCountRTT       ZeroBasedCounter32,
         tcpEStatsPathECNsignals             ZeroBasedCounter32,
         tcpEStatsPathDupAckEpisodes         ZeroBasedCounter32,
         tcpEStatsPathRcvRTT                 Gauge32,
         tcpEStatsPathDupAcksOut             ZeroBasedCounter32,
         tcpEStatsPathCERcvd                 ZeroBasedCounter32,
         tcpEStatsPathECESent                ZeroBasedCounter32
     }
  1. -
  2. - The following optional objects can be used to infer segment
  3. - reordering on the path from the local sender to the remote
  4. - receiver.
  5. -
 tcpEStatsPathRetranThresh  OBJECT-TYPE
     SYNTAX          Gauge32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of duplicate acknowledgments required to trigger
         Fast Retransmit.  Note that although this is constant in
         traditional Reno TCP implementations, it is adaptive in
         many newer TCPs."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPathEntry 1 }
 tcpEStatsPathNonRecovDAEpisodes  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of duplicate acknowledgment episodes that did
         not trigger a Fast Retransmit because ACK advanced prior to
         the number of duplicate acknowledgments reaching
         RetranThresh.

Mathis, et al. Standards Track [Page 30] RFC 4898 TCP Extended Statistics MIB May 2007

         In many implementations this is the number of times the
         'dupacks' counter is set to zero when it is non-zero but
         less than RetranThresh.
         Note that the change in tcpEStatsPathNonRecovDAEpisodes
         divided by the change in tcpEStatsPerfDataSegsOut is an
         estimate of the frequency of data reordering on the forward
         path over some interval."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPathEntry 2 }
 tcpEStatsPathSumOctetsReordered  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The sum of the amounts SND.UNA advances on the
         acknowledgment which ends a dup-ack episode without a
         retransmission.
         Note the change in tcpEStatsPathSumOctetsReordered divided
         by the change in tcpEStatsPathNonRecovDAEpisodes is an
         estimates of the average reordering distance, over some
         interval."
     ::= { tcpEStatsPathEntry 3 }
 tcpEStatsPathNonRecovDA  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Duplicate acks (or SACKS) that did not trigger a Fast
         Retransmit because ACK advanced prior to the number of
         duplicate acknowledgments reaching RetranThresh.
         In many implementations, this is the sum of the 'dupacks'
         counter, just before it is set to zero because ACK advanced
         without a Fast Retransmit.
         Note that the change in tcpEStatsPathNonRecovDA divided by
         the change in tcpEStatsPathNonRecovDAEpisodes is an
         estimate of the average reordering distance in segments
         over some interval."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPathEntry 4 }

Mathis, et al. Standards Track [Page 31] RFC 4898 TCP Extended Statistics MIB May 2007

  1. -
  2. - The following optional objects instrument the round trip
  3. - time estimator and the retransmission timeout timer.
  4. -
 tcpEStatsPathSampleRTT  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The most recent raw round trip time measurement used in
         calculation of the RTO."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 11 }
 tcpEStatsPathRTTVar  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The round trip time variation used in calculation of the
         RTO.  See RTTVAR in [RFC2988]."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 12 }
 tcpEStatsPathMaxRTT  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum sampled round trip time."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 13 }
 tcpEStatsPathMinRTT  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The minimum sampled round trip time."
     REFERENCE

Mathis, et al. Standards Track [Page 32] RFC 4898 TCP Extended Statistics MIB May 2007

        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 14 }
 tcpEStatsPathSumRTT  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The sum of all sampled round trip times.
         Note that the change in tcpEStatsPathSumRTT divided by the
         change in tcpEStatsPathCountRTT is the mean RTT, uniformly
         averaged over an enter interval."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 15 }
 tcpEStatsPathHCSumRTT  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter64
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The sum of all sampled round trip times, on all systems
         that implement multiple concurrent RTT measurements.
         Note that the change in tcpEStatsPathHCSumRTT divided by
         the change in tcpEStatsPathCountRTT is the mean RTT,
         uniformly averaged over an enter interval."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 16 }
 tcpEStatsPathCountRTT  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of round trip time samples included in
         tcpEStatsPathSumRTT and tcpEStatsPathHCSumRTT."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 17 }
 tcpEStatsPathMaxRTO  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"

Mathis, et al. Standards Track [Page 33] RFC 4898 TCP Extended Statistics MIB May 2007

     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum value of the retransmit timer RTO."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 18 }
 tcpEStatsPathMinRTO  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The minimum value of the retransmit timer RTO."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsPathEntry 19 }
  1. -
  2. - The following optional objects provide information about
  3. - how TCP is using the IP layer.
  4. -
 tcpEStatsPathIpTtl  OBJECT-TYPE
     SYNTAX          Unsigned32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of the TTL field carried in the most recently
         received IP header.  This is sometimes useful to detect
         changing or unstable routes."
     REFERENCE
        "RFC 791, Internet Protocol"
     ::= { tcpEStatsPathEntry 20 }
 tcpEStatsPathIpTosIn  OBJECT-TYPE
     SYNTAX          OCTET STRING (SIZE(1))
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of the IPv4 Type of Service octet, or the IPv6
         traffic class octet, carried in the most recently received
         IP header.
         This is useful to diagnose interactions between TCP and any
         IP layer packet scheduling and delivery policy, which might
         be in effect to implement Diffserv."

Mathis, et al. Standards Track [Page 34] RFC 4898 TCP Extended Statistics MIB May 2007

     REFERENCE
        "RFC 3260, New Terminology and Clarifications for Diffserv"
     ::= { tcpEStatsPathEntry 21 }
 tcpEStatsPathIpTosOut  OBJECT-TYPE
     SYNTAX          OCTET STRING (SIZE(1))
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of the IPv4 Type Of Service octet, or the IPv6
         traffic class octet, carried in the most recently
         transmitted IP header.
         This is useful to diagnose interactions between TCP and any
         IP layer packet scheduling and delivery policy, which might
         be in effect to implement Diffserv."
     REFERENCE
        "RFC 3260, New Terminology and Clarifications for Diffserv"
     ::= { tcpEStatsPathEntry 22 }
  1. -
  2. - The following optional objects characterize the congestion
  3. - feedback signals by collecting statistics on how the
  4. - congestion events are correlated to losses, changes in RTT
  5. - and other protocol events.
  6. -
 tcpEStatsPathPreCongSumCwnd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The sum of the values of the congestion window, in octets,
         captured each time a congestion signal is received.  This
         MUST be updated each time tcpEStatsPerfCongSignals is
         incremented, such that the change in
         tcpEStatsPathPreCongSumCwnd divided by the change in
         tcpEStatsPerfCongSignals is the average window (over some
         interval) just prior to a congestion signal."
     ::= { tcpEStatsPathEntry 23 }
 tcpEStatsPathPreCongSumRTT  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 35] RFC 4898 TCP Extended Statistics MIB May 2007

        "Sum of the last sample of the RTT (tcpEStatsPathSampleRTT)
         prior to the received congestion signals.  This MUST be
         updated each time tcpEStatsPerfCongSignals is incremented,
         such that the change in tcpEStatsPathPreCongSumRTT divided by
         the change in tcpEStatsPerfCongSignals is the average RTT
         (over some interval) just prior to a congestion signal."
     ::= { tcpEStatsPathEntry 24 }
 tcpEStatsPathPostCongSumRTT  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Sum of the first sample of the RTT (tcpEStatsPathSampleRTT)
         following each congestion signal.  Such that the change in
         tcpEStatsPathPostCongSumRTT divided by the change in
         tcpEStatsPathPostCongCountRTT is the average RTT (over some
         interval) just after a congestion signal."
     ::= { tcpEStatsPathEntry 25 }
 tcpEStatsPathPostCongCountRTT  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "milliseconds"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of RTT samples included in
         tcpEStatsPathPostCongSumRTT such that the change in
         tcpEStatsPathPostCongSumRTT divided by the change in
         tcpEStatsPathPostCongCountRTT is the average RTT (over some
         interval) just after a congestion signal."
     ::= { tcpEStatsPathEntry 26 }
  1. -
  2. - The following optional objects can be used to detect other
  3. - types of non-loss congestion signals such as source quench
  4. - or ECN.
  5. -
 tcpEStatsPathECNsignals  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of congestion signals delivered to the TCP
         sender via explicit congestion notification (ECN).  This is
         typically the number of segments bearing Echo Congestion

Mathis, et al. Standards Track [Page 36] RFC 4898 TCP Extended Statistics MIB May 2007

         Experienced (ECE) bits, but
         should also include segments failing the ECN nonce check or
         other explicit congestion signals."
     REFERENCE
        "RFC 3168, The Addition of Explicit Congestion Notification
         (ECN) to IP"
     ::= { tcpEStatsPathEntry 27 }
  1. -
  2. - The following optional objects are receiver side
  3. - instruments of the path from the sender to the receiver. In
  4. - general, the receiver has less information about the state
  5. - of the path because the receiver does not have a robust
  6. - mechanism to infer the sender's actions.
  7. -
 tcpEStatsPathDupAckEpisodes  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of Duplicate Acks Sent when prior Ack was not
         duplicate.  This is the number of times that a contiguous
         series of duplicate acknowledgments have been sent.
         This is an indication of the number of data segments lost
         or reordered on the path from the remote TCP endpoint to
         the near TCP endpoint."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPathEntry 28 }
 tcpEStatsPathRcvRTT  OBJECT-TYPE
     SYNTAX          Gauge32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The receiver's estimate of the Path RTT.
         Adaptive receiver window algorithms depend on the receiver
         to having a good estimate of the path RTT."
     ::= { tcpEStatsPathEntry 29 }
 tcpEStatsPathDupAcksOut  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 37] RFC 4898 TCP Extended Statistics MIB May 2007

        "The number of duplicate ACKs sent.  The ratio of the change
         in tcpEStatsPathDupAcksOut to the change in
         tcpEStatsPathDupAckEpisodes is an indication of reorder or
         recovery distance over some interval."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsPathEntry 30 }
 tcpEStatsPathCERcvd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of segments received with IP headers bearing
         Congestion Experienced (CE) markings."
     REFERENCE
        "RFC 3168, The Addition of Explicit Congestion Notification
         (ECN) to IP"
     ::= { tcpEStatsPathEntry 31 }
 tcpEStatsPathECESent  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Number of times the Echo Congestion Experienced (ECE) bit
         in the TCP header has been set (transitioned from 0 to 1),
         due to a Congestion Experienced (CE) marking on an IP
         header.  Note that ECE can be set and reset only once per
         RTT, while CE can be set on many segments per RTT."
     REFERENCE
        "RFC 3168, The Addition of Explicit Congestion Notification
         (ECN) to IP"
     ::= { tcpEStatsPathEntry 32 }
  1. - ================================================================
  2. -
  3. - Statistics for diagnosing stack algorithms
  4. -
 tcpEStatsStackTable    OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsStackEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table contains objects that are most useful for
         determining how well some of the TCP control
         algorithms are coping with this particular

Mathis, et al. Standards Track [Page 38] RFC 4898 TCP Extended Statistics MIB May 2007

         path.
         Entries are retained in this table for the number of
         seconds indicated by the tcpEStatsConnTableLatency
         object, after the TCP connection first enters the closed
         state."
     ::= { tcpEStats 5 }
 tcpEStatsStackEntry  OBJECT-TYPE
     SYNTAX       TcpEStatsStackEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in this table has information about the
         characteristics of each active and recently closed TCP
         connection."
    INDEX { tcpEStatsConnectIndex }
    ::= { tcpEStatsStackTable 1 }
 TcpEStatsStackEntry ::= SEQUENCE {
         tcpEStatsStackActiveOpen            TruthValue,
         tcpEStatsStackMSSSent               Unsigned32,
         tcpEStatsStackMSSRcvd               Unsigned32,
         tcpEStatsStackWinScaleSent          Integer32,
         tcpEStatsStackWinScaleRcvd          Integer32,
         tcpEStatsStackTimeStamps            TcpEStatsNegotiated,
         tcpEStatsStackECN                   TcpEStatsNegotiated,
         tcpEStatsStackWillSendSACK          TcpEStatsNegotiated,
         tcpEStatsStackWillUseSACK           TcpEStatsNegotiated,
         tcpEStatsStackState                 INTEGER,
         tcpEStatsStackNagle                 TruthValue,
         tcpEStatsStackMaxSsCwnd             Gauge32,
         tcpEStatsStackMaxCaCwnd             Gauge32,
         tcpEStatsStackMaxSsthresh           Gauge32,
         tcpEStatsStackMinSsthresh           Gauge32,
         tcpEStatsStackInRecovery            INTEGER,
         tcpEStatsStackDupAcksIn             ZeroBasedCounter32,
         tcpEStatsStackSpuriousFrDetected    ZeroBasedCounter32,
         tcpEStatsStackSpuriousRtoDetected   ZeroBasedCounter32,
         tcpEStatsStackSoftErrors            ZeroBasedCounter32,
         tcpEStatsStackSoftErrorReason       INTEGER,
         tcpEStatsStackSlowStart             ZeroBasedCounter32,
         tcpEStatsStackCongAvoid             ZeroBasedCounter32,
         tcpEStatsStackOtherReductions       ZeroBasedCounter32,
         tcpEStatsStackCongOverCount         ZeroBasedCounter32,
         tcpEStatsStackFastRetran            ZeroBasedCounter32,
         tcpEStatsStackSubsequentTimeouts    ZeroBasedCounter32,

Mathis, et al. Standards Track [Page 39] RFC 4898 TCP Extended Statistics MIB May 2007

         tcpEStatsStackCurTimeoutCount       Gauge32,
         tcpEStatsStackAbruptTimeouts        ZeroBasedCounter32,
         tcpEStatsStackSACKsRcvd             ZeroBasedCounter32,
         tcpEStatsStackSACKBlocksRcvd        ZeroBasedCounter32,
         tcpEStatsStackSendStall             ZeroBasedCounter32,
         tcpEStatsStackDSACKDups             ZeroBasedCounter32,
         tcpEStatsStackMaxMSS                Gauge32,
         tcpEStatsStackMinMSS                Gauge32,
         tcpEStatsStackSndInitial            Unsigned32,
         tcpEStatsStackRecInitial            Unsigned32,
         tcpEStatsStackCurRetxQueue          Gauge32,
         tcpEStatsStackMaxRetxQueue          Gauge32,
         tcpEStatsStackCurReasmQueue         Gauge32,
         tcpEStatsStackMaxReasmQueue         Gauge32
     }
  1. -
  2. - The following objects reflect TCP options carried on the
  3. - SYN or SYN-ACK. These options are used to provide
  4. - additional protocol parameters or to enable various
  5. - optional TCP features or algorithms.
  6. -
  7. - Except as noted, the TCP protocol does not permit these
  8. - options to change after the SYN exchange.
  9. -
 tcpEStatsStackActiveOpen  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "True(1) if the local connection traversed the SYN-SENT
         state, else false(2)."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsStackEntry 1 }
 tcpEStatsStackMSSSent  OBJECT-TYPE
     SYNTAX          Unsigned32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value sent in an MSS option, or zero if none."
     REFERENCE
        "RFC 1122, Requirements for Internet Hosts - Communication
         Layers"
     ::= { tcpEStatsStackEntry 2 }

Mathis, et al. Standards Track [Page 40] RFC 4898 TCP Extended Statistics MIB May 2007

 tcpEStatsStackMSSRcvd  OBJECT-TYPE
     SYNTAX          Unsigned32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value received in an MSS option, or zero if none."
     REFERENCE
        "RFC 1122, Requirements for Internet Hosts - Communication
         Layers"
     ::= { tcpEStatsStackEntry 3 }
 tcpEStatsStackWinScaleSent  OBJECT-TYPE
     SYNTAX          Integer32 (-1..14)
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of the transmitted window scale option if one was
         sent; otherwise, a value of -1.
         Note that if both tcpEStatsStackWinScaleSent and
         tcpEStatsStackWinScaleRcvd are not -1, then Rcv.Wind.Scale
         will be the same as this value and used to scale receiver
         window announcements from the local host to the remote
         host."
     REFERENCE
        "RFC 1323, TCP Extensions for High Performance"
     ::= { tcpEStatsStackEntry 4 }
 tcpEStatsStackWinScaleRcvd  OBJECT-TYPE
     SYNTAX          Integer32 (-1..14)
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of the received window scale option if one was
         received; otherwise, a value of -1.
         Note that if both tcpEStatsStackWinScaleSent and
         tcpEStatsStackWinScaleRcvd are not -1, then Snd.Wind.Scale
         will be the same as this value and used to scale receiver
         window announcements from the remote host to the local
         host."
     REFERENCE
        "RFC 1323, TCP Extensions for High Performance"
     ::= { tcpEStatsStackEntry 5 }
 tcpEStatsStackTimeStamps  OBJECT-TYPE
     SYNTAX          TcpEStatsNegotiated
     MAX-ACCESS      read-only

Mathis, et al. Standards Track [Page 41] RFC 4898 TCP Extended Statistics MIB May 2007

     STATUS          current
     DESCRIPTION
        "Enabled(1) if TCP timestamps have been negotiated on,
         selfDisabled(2) if they are disabled or not implemented on
         the local host, or peerDisabled(3) if not negotiated by the
         remote hosts."
     REFERENCE
        "RFC 1323, TCP Extensions for High Performance"
     ::= { tcpEStatsStackEntry 6 }
 tcpEStatsStackECN  OBJECT-TYPE
     SYNTAX          TcpEStatsNegotiated
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Enabled(1) if Explicit Congestion Notification (ECN) has
         been negotiated on, selfDisabled(2) if it is disabled or
         not implemented on the local host, or peerDisabled(3) if
         not negotiated by the remote hosts."
     REFERENCE
        "RFC 3168, The Addition of Explicit Congestion Notification
         (ECN) to IP"
     ::= { tcpEStatsStackEntry 7 }
 tcpEStatsStackWillSendSACK  OBJECT-TYPE
     SYNTAX          TcpEStatsNegotiated
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Enabled(1) if the local host will send SACK options,
         selfDisabled(2) if SACK is disabled or not implemented on
         the local host, or peerDisabled(3) if the remote host did
         not send the SACK-permitted option.
         Note that SACK negotiation is not symmetrical.  SACK can
         enabled on one side of the connection and not the other."
     REFERENCE
        "RFC 2018, TCP Selective Acknowledgement Options"
     ::= { tcpEStatsStackEntry 8 }
 tcpEStatsStackWillUseSACK  OBJECT-TYPE
     SYNTAX          TcpEStatsNegotiated
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Enabled(1) if the local host will process SACK options,
         selfDisabled(2) if SACK is disabled or not implemented on
         the local host, or peerDisabled(3) if the remote host sends

Mathis, et al. Standards Track [Page 42] RFC 4898 TCP Extended Statistics MIB May 2007

         duplicate ACKs without SACK options, or the local host
         otherwise decides not to process received SACK options.
         Unlike other TCP options, the remote data receiver cannot
         explicitly indicate if it is able to generate SACK options.
         When sending data, the local host has to deduce if the
         remote receiver is sending SACK options.  This object can
         transition from Enabled(1) to peerDisabled(3) after the SYN
         exchange.
         Note that SACK negotiation is not symmetrical.  SACK can
         enabled on one side of the connection and not the other."
     REFERENCE
        "RFC 2018, TCP Selective Acknowledgement Options"
     ::= { tcpEStatsStackEntry 9 }
  1. -
  2. - The following two objects reflect the current state of the
  3. - connection.
  4. -
 tcpEStatsStackState  OBJECT-TYPE
     SYNTAX          INTEGER {
        tcpESStateClosed(1),
        tcpESStateListen(2),
        tcpESStateSynSent(3),
        tcpESStateSynReceived(4),
        tcpESStateEstablished(5),
        tcpESStateFinWait1(6),
        tcpESStateFinWait2(7),
        tcpESStateCloseWait(8),
        tcpESStateLastAck(9),
        tcpESStateClosing(10),
        tcpESStateTimeWait(11),
        tcpESStateDeleteTcb(12)
     }
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "An integer value representing the connection state from the
         TCP State Transition Diagram.
         The value listen(2) is included only for parallelism to the
         old tcpConnTable, and SHOULD NOT be used because the listen
         state in managed by the tcpListenerTable.
         The value DeleteTcb(12) is included only for parallelism to
         the tcpConnTable mechanism for terminating connections,

Mathis, et al. Standards Track [Page 43] RFC 4898 TCP Extended Statistics MIB May 2007

         although this table does not permit writing."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsStackEntry 10 }
 tcpEStatsStackNagle  OBJECT-TYPE
     SYNTAX          TruthValue
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "True(1) if the Nagle algorithm is being used, else
         false(2)."
     REFERENCE
        "RFC 1122, Requirements for Internet Hosts - Communication
         Layers"
     ::= { tcpEStatsStackEntry 11 }
  1. -
  2. - The following objects instrument the overall operation of
  3. - TCP congestion control and data retransmissions. These
  4. - instruments are sufficient to fit the actual performance to
  5. - an updated macroscopic performance model [RFC2581] [Mat97]
  6. - [Pad98].
  7. -
 tcpEStatsStackMaxSsCwnd  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum congestion window used during Slow Start, in
         octets."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 12 }
 tcpEStatsStackMaxCaCwnd  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum congestion window used during Congestion
         Avoidance, in octets."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 13 }

Mathis, et al. Standards Track [Page 44] RFC 4898 TCP Extended Statistics MIB May 2007

 tcpEStatsStackMaxSsthresh  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum slow start threshold, excluding the initial
         value."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 14 }
 tcpEStatsStackMinSsthresh  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The minimum slow start threshold."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 15 }
 tcpEStatsStackInRecovery  OBJECT-TYPE
     SYNTAX          INTEGER {
        tcpESDataContiguous(1),
        tcpESDataUnordered(2),
        tcpESDataRecovery(3)
     }
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "An integer value representing the state of the loss
         recovery for this connection.
         tcpESDataContiguous(1) indicates that the remote receiver
         is reporting contiguous data (no duplicate acknowledgments
         or SACK options) and that there are no unacknowledged
         retransmissions.
         tcpESDataUnordered(2) indicates that the remote receiver is
         reporting missing or out-of-order data (e.g., sending
         duplicate acknowledgments or SACK options) and that there
         are no unacknowledged retransmissions (because the missing
         data has not yet been retransmitted).
         tcpESDataRecovery(3) indicates that the sender has
         outstanding retransmitted data that is still

Mathis, et al. Standards Track [Page 45] RFC 4898 TCP Extended Statistics MIB May 2007

         unacknowledged."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 16 }
 tcpEStatsStackDupAcksIn  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of duplicate ACKs received."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 17 }
 tcpEStatsStackSpuriousFrDetected  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of acknowledgments reporting out-of-order
         segments after the Fast Retransmit algorithm has already
         retransmitted the segments. (For example as detected by the
         Eifel algorithm).'"
     REFERENCE
        "RFC 3522, The Eifel Detection Algorithm for TCP"
     ::= { tcpEStatsStackEntry 18 }
 tcpEStatsStackSpuriousRtoDetected  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of acknowledgments reporting segments that have
         already been retransmitted due to a Retransmission Timeout."
     ::= { tcpEStatsStackEntry 19 }
  1. -
  2. - The following optional objects instrument unusual protocol
  3. - events that probably indicate implementation problems in
  4. - the protocol or path.
  5. -
 tcpEStatsStackSoftErrors  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 46] RFC 4898 TCP Extended Statistics MIB May 2007

        "The number of segments that fail various consistency tests
         during TCP input processing.  Soft errors might cause the
         segment to be discarded but some do not.  Some of these soft
         errors cause the generation of a TCP acknowledgment, while
         others are silently discarded."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsStackEntry 21 }
 tcpEStatsStackSoftErrorReason  OBJECT-TYPE
     SYNTAX          INTEGER {
        belowDataWindow(1),
        aboveDataWindow(2),
        belowAckWindow(3),
        aboveAckWindow(4),
        belowTSWindow(5),
        aboveTSWindow(6),
        dataCheckSum(7),
        otherSoftError(8)
     }
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "This object identifies which consistency test most recently
         failed during TCP input processing.  This object SHOULD be
         set every time tcpEStatsStackSoftErrors is incremented.  The
         codes are as follows:
         belowDataWindow(1) - All data in the segment is below
         SND.UNA. (Normal for keep-alives and zero window probes).
         aboveDataWindow(2) - Some data in the segment is above
         SND.WND. (Indicates an implementation bug or possible
         attack).
         belowAckWindow(3) - ACK below SND.UNA. (Indicates that the
         return path is reordering ACKs)
         aboveAckWindow(4) - An ACK for data that we have not sent.
         (Indicates an implementation bug or possible attack).
         belowTSWindow(5) - TSecr on the segment is older than the
         current TS.Recent (Normal for the rare case where PAWS
         detects data reordered by the network).
         aboveTSWindow(6) - TSecr on the segment is newer than the
         current TS.Recent. (Indicates an implementation bug or
         possible attack).

Mathis, et al. Standards Track [Page 47] RFC 4898 TCP Extended Statistics MIB May 2007

         dataCheckSum(7) - Incorrect checksum.  Note that this value
         is intrinsically fragile, because the header fields used to
         identify the connection may have been corrupted.
         otherSoftError(8) - All other soft errors not listed
         above."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsStackEntry 22 }
  1. -
  2. - The following optional objects expose the detailed
  3. - operation of the congestion control algorithms.
  4. -
 tcpEStatsStackSlowStart  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of times the congestion window has been
         increased by the Slow Start algorithm."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 23 }
 tcpEStatsStackCongAvoid  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of times the congestion window has been
         increased by the Congestion Avoidance algorithm."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 24 }
 tcpEStatsStackOtherReductions  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of congestion window reductions made as a result
         of anything other than AIMD congestion control algorithms.
         Examples of non-multiplicative window reductions include
         Congestion Window Validation [RFC2861] and experimental
         algorithms such as Vegas [Bra94].

Mathis, et al. Standards Track [Page 48] RFC 4898 TCP Extended Statistics MIB May 2007

         All window reductions MUST be counted as either
         tcpEStatsPerfCongSignals or tcpEStatsStackOtherReductions."
     REFERENCE
        "RFC 2861, TCP Congestion Window Validation"
     ::= { tcpEStatsStackEntry 25 }
 tcpEStatsStackCongOverCount  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of congestion events that were 'backed out' of
         the congestion control state machine such that the
         congestion window was restored to a prior value.  This can
         happen due to the Eifel algorithm [RFC3522] or other
         algorithms that can be used to detect and cancel spurious
         invocations of the Fast Retransmit Algorithm.
         Although it may be feasible to undo the effects of spurious
         invocation of the Fast Retransmit congestion events cannot
         easily be backed out of tcpEStatsPerfCongSignals and
         tcpEStatsPathPreCongSumCwnd, etc."
     REFERENCE
        "RFC 3522, The Eifel Detection Algorithm for TCP"
     ::= { tcpEStatsStackEntry 26 }
 tcpEStatsStackFastRetran  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of invocations of the Fast Retransmit algorithm."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 27 }
 tcpEStatsStackSubsequentTimeouts  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of times the retransmit timeout has expired after
         the RTO has been doubled.  See Section 5.5 of RFC 2988."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsStackEntry 28 }

Mathis, et al. Standards Track [Page 49] RFC 4898 TCP Extended Statistics MIB May 2007

 tcpEStatsStackCurTimeoutCount  OBJECT-TYPE
     SYNTAX          Gauge32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current number of times the retransmit timeout has
         expired without receiving an acknowledgment for new data.
         tcpEStatsStackCurTimeoutCount is reset to zero when new
         data is acknowledged and incremented for each invocation of
         Section 5.5 of RFC 2988."
     REFERENCE
        "RFC 2988, Computing TCP's Retransmission Timer"
     ::= { tcpEStatsStackEntry 29 }
 tcpEStatsStackAbruptTimeouts  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of timeouts that occurred without any
         immediately preceding duplicate acknowledgments or other
         indications of congestion.  Abrupt Timeouts indicate that
         the path lost an entire window of data or acknowledgments.
         Timeouts that are preceded by duplicate acknowledgments or
         other congestion signals (e.g., ECN) are not counted as
         abrupt, and might have been avoided by a more sophisticated
         Fast Retransmit algorithm."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsStackEntry 30 }
 tcpEStatsStackSACKsRcvd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of SACK options received."
     REFERENCE
        "RFC 2018, TCP Selective Acknowledgement Options"
     ::= { tcpEStatsStackEntry 31 }
 tcpEStatsStackSACKBlocksRcvd  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of SACK blocks received (within SACK options)."

Mathis, et al. Standards Track [Page 50] RFC 4898 TCP Extended Statistics MIB May 2007

     REFERENCE
        "RFC 2018, TCP Selective Acknowledgement Options"
     ::= { tcpEStatsStackEntry 32 }
 tcpEStatsStackSendStall  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of interface stalls or other sender local
         resource limitations that are treated as congestion
         signals."
     ::= { tcpEStatsStackEntry 33 }
 tcpEStatsStackDSACKDups  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of duplicate segments reported to the local host
         by D-SACK blocks."
     REFERENCE
        "RFC 2883, An Extension to the Selective Acknowledgement
         (SACK) Option for TCP"
     ::= { tcpEStatsStackEntry 34 }
  1. -
  2. - The following optional objects instrument path MTU
  3. - discovery.
  4. -
 tcpEStatsStackMaxMSS  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum MSS, in octets."
     REFERENCE
        "RFC 1191, Path MTU discovery"
     ::= { tcpEStatsStackEntry 35 }
 tcpEStatsStackMinMSS  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 51] RFC 4898 TCP Extended Statistics MIB May 2007

        "The minimum MSS, in octets."
     REFERENCE
        "RFC 1191, Path MTU discovery"
     ::= { tcpEStatsStackEntry 36 }
  1. -
  2. - The following optional initial value objects are useful for
  3. - conformance testing instruments on application progress and
  4. - consumed network resources.
  5. -
 tcpEStatsStackSndInitial  OBJECT-TYPE
     SYNTAX          Unsigned32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Initial send sequence number.  Note that by definition
         tcpEStatsStackSndInitial never changes for a given
         connection."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsStackEntry 37 }
 tcpEStatsStackRecInitial  OBJECT-TYPE
     SYNTAX          Unsigned32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "Initial receive sequence number.  Note that by definition
         tcpEStatsStackRecInitial never changes for a given
         connection."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsStackEntry 38 }
  1. -
  2. - The following optional objects instrument the senders
  3. - buffer usage, including any buffering in the application
  4. - interface to TCP and the retransmit queue. All 'buffer
  5. - memory' instruments are assumed to include OS data
  6. - structure overhead.
  7. -
 tcpEStatsStackCurRetxQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current

Mathis, et al. Standards Track [Page 52] RFC 4898 TCP Extended Statistics MIB May 2007

     DESCRIPTION
        "The current number of octets of data occupying the
         retransmit queue."
     ::= { tcpEStatsStackEntry 39 }
 tcpEStatsStackMaxRetxQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum number of octets of data occupying the
         retransmit queue."
     ::= { tcpEStatsStackEntry 40 }
 tcpEStatsStackCurReasmQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current number of octets of sequence space spanned by
         the reassembly queue.  This is generally the difference
         between rcv.nxt and the sequence number of the right most
         edge of the reassembly queue."
     ::= { tcpEStatsStackEntry 41 }
 tcpEStatsStackMaxReasmQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum value of tcpEStatsStackCurReasmQueue"
     ::= { tcpEStatsStackEntry 42 }
  1. - ================================================================
  2. -
  3. - Statistics for diagnosing interactions between
  4. - applications and TCP.
  5. -
 tcpEStatsAppTable    OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsAppEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table contains objects that are useful for
         determining if the application using TCP is

Mathis, et al. Standards Track [Page 53] RFC 4898 TCP Extended Statistics MIB May 2007

         limiting TCP performance.
         Entries are retained in this table for the number of
         seconds indicated by the tcpEStatsConnTableLatency
         object, after the TCP connection first enters the closed
         state."
     ::= { tcpEStats 6 }
 tcpEStatsAppEntry  OBJECT-TYPE
     SYNTAX       TcpEStatsAppEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in this table has information about the
         characteristics of each active and recently closed TCP
         connection."
    INDEX { tcpEStatsConnectIndex }
    ::= { tcpEStatsAppTable 1 }
 TcpEStatsAppEntry ::= SEQUENCE {
         tcpEStatsAppSndUna                  Counter32,
         tcpEStatsAppSndNxt                  Unsigned32,
         tcpEStatsAppSndMax                  Counter32,
         tcpEStatsAppThruOctetsAcked         ZeroBasedCounter32,
         tcpEStatsAppHCThruOctetsAcked       ZeroBasedCounter64,
         tcpEStatsAppRcvNxt                  Counter32,
         tcpEStatsAppThruOctetsReceived      ZeroBasedCounter32,
         tcpEStatsAppHCThruOctetsReceived    ZeroBasedCounter64,
         tcpEStatsAppCurAppWQueue            Gauge32,
         tcpEStatsAppMaxAppWQueue            Gauge32,
         tcpEStatsAppCurAppRQueue            Gauge32,
         tcpEStatsAppMaxAppRQueue            Gauge32
     }
  1. -
  2. - The following objects provide throughput statistics for the
  3. - connection including sequence numbers and elapsed
  4. - application data. These permit direct observation of the
  5. - applications progress, in terms of elapsed data delivery
  6. - and elapsed time.
  7. -
 tcpEStatsAppSndUna  OBJECT-TYPE
     SYNTAX          Counter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 54] RFC 4898 TCP Extended Statistics MIB May 2007

        "The value of SND.UNA, the oldest unacknowledged sequence
         number.
         Note that SND.UNA is a TCP state variable that is congruent
         to Counter32 semantics."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsAppEntry 1 }
 tcpEStatsAppSndNxt  OBJECT-TYPE
     SYNTAX          Unsigned32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of SND.NXT, the next sequence number to be sent.
         Note that tcpEStatsAppSndNxt is not monotonic (and thus not
         a counter) because TCP sometimes retransmits lost data by
         pulling tcpEStatsAppSndNxt back to the missing data."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsAppEntry 2 }
 tcpEStatsAppSndMax  OBJECT-TYPE
     SYNTAX          Counter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The farthest forward (right most or largest) SND.NXT value.
         Note that this will be equal to tcpEStatsAppSndNxt except
         when tcpEStatsAppSndNxt is pulled back during recovery."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsAppEntry 3 }
 tcpEStatsAppThruOctetsAcked  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets for which cumulative acknowledgments
         have been received.  Note that this will be the sum of
         changes to tcpEStatsAppSndUna."
     ::= { tcpEStatsAppEntry 4 }
 tcpEStatsAppHCThruOctetsAcked  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter64
     UNITS           "octets"

Mathis, et al. Standards Track [Page 55] RFC 4898 TCP Extended Statistics MIB May 2007

     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets for which cumulative acknowledgments
         have been received, on systems that can receive more than
         10 million bits per second.  Note that this will be the sum
         of changes in tcpEStatsAppSndUna."
     ::= { tcpEStatsAppEntry 5 }
 tcpEStatsAppRcvNxt  OBJECT-TYPE
     SYNTAX          Counter32
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The value of RCV.NXT.  The next sequence number expected on
         an incoming segment, and the left or lower edge of the
         receive window.
         Note that RCV.NXT is a TCP state variable that is congruent
         to Counter32 semantics."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsAppEntry 6 }
 tcpEStatsAppThruOctetsReceived  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets for which cumulative acknowledgments
         have been sent.  Note that this will be the sum of changes
         to tcpEStatsAppRcvNxt."
     ::= { tcpEStatsAppEntry 7 }
 tcpEStatsAppHCThruOctetsReceived  OBJECT-TYPE
     SYNTAX          ZeroBasedCounter64
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The number of octets for which cumulative acknowledgments
         have been sent, on systems that can transmit more than 10
         million bits per second.  Note that this will be the sum of
         changes in tcpEStatsAppRcvNxt."
     ::= { tcpEStatsAppEntry 8 }
 tcpEStatsAppCurAppWQueue  OBJECT-TYPE

Mathis, et al. Standards Track [Page 56] RFC 4898 TCP Extended Statistics MIB May 2007

     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current number of octets of application data buffered
         by TCP, pending first transmission, i.e., to the left of
         SND.NXT or SndMax.  This data will generally be transmitted
         (and SND.NXT advanced to the left) as soon as there is an
         available congestion window (cwnd) or receiver window
         (rwin).  This is the amount of data readily available for
         transmission, without scheduling the application.  TCP
         performance may suffer if there is insufficient queued
         write data."
     ::= { tcpEStatsAppEntry 11 }
 tcpEStatsAppMaxAppWQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The maximum number of octets of application data buffered
         by TCP, pending first transmission.  This is the maximum
         value of tcpEStatsAppCurAppWQueue.  This pair of objects can
         be used to determine if insufficient queued data is steady
         state (suggesting insufficient queue space) or transient
         (suggesting insufficient application performance or
         excessive CPU load or scheduler latency)."
     ::= { tcpEStatsAppEntry 12 }
 tcpEStatsAppCurAppRQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION
        "The current number of octets of application data that has
         been acknowledged by TCP but not yet delivered to the
         application."
     ::= { tcpEStatsAppEntry 13 }
 tcpEStatsAppMaxAppRQueue  OBJECT-TYPE
     SYNTAX          Gauge32
     UNITS           "octets"
     MAX-ACCESS      read-only
     STATUS          current
     DESCRIPTION

Mathis, et al. Standards Track [Page 57] RFC 4898 TCP Extended Statistics MIB May 2007

        "The maximum number of octets of application data that has
         been acknowledged by TCP but not yet delivered to the
         application."
     ::= { tcpEStatsAppEntry 14 }
  1. - ================================================================
  2. -
  3. - Controls for Tuning TCP
  4. -
 tcpEStatsTuneTable    OBJECT-TYPE
     SYNTAX      SEQUENCE OF TcpEStatsTuneEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     DESCRIPTION
         "This table contains per-connection controls that can
         be used to work around a number of common problems that
         plague TCP over some paths.  All can be characterized as
         limiting the growth of the congestion window so as to
         prevent TCP from overwhelming some component in the
         path.
         Entries are retained in this table for the number of
         seconds indicated by the tcpEStatsConnTableLatency
         object, after the TCP connection first enters the closed
         state."
     ::= { tcpEStats 7 }
 tcpEStatsTuneEntry  OBJECT-TYPE
     SYNTAX       TcpEStatsTuneEntry
     MAX-ACCESS   not-accessible
     STATUS       current
     DESCRIPTION
         "Each entry in this table is a control that can be used to
         place limits on each active TCP connection."
    INDEX { tcpEStatsConnectIndex }
    ::= { tcpEStatsTuneTable 1 }
 TcpEStatsTuneEntry ::= SEQUENCE {
         tcpEStatsTuneLimCwnd                Unsigned32,
         tcpEStatsTuneLimSsthresh            Unsigned32,
         tcpEStatsTuneLimRwin                Unsigned32,
         tcpEStatsTuneLimMSS                 Unsigned32
     }
 tcpEStatsTuneLimCwnd  OBJECT-TYPE
     SYNTAX          Unsigned32

Mathis, et al. Standards Track [Page 58] RFC 4898 TCP Extended Statistics MIB May 2007

     UNITS           "octets"
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
        "A control to set the maximum congestion window that may be
         used, in octets."
     REFERENCE
        "RFC 2581, TCP Congestion Control"
     ::= { tcpEStatsTuneEntry 1 }
 tcpEStatsTuneLimSsthresh  OBJECT-TYPE
     SYNTAX          Unsigned32
     UNITS           "octets"
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
        "A control to limit the maximum queue space (in octets) that
         this TCP connection is likely to occupy during slowstart.
         It can be implemented with the algorithm described in
         RFC 3742 by setting the max_ssthresh parameter to twice
         tcpEStatsTuneLimSsthresh.
         This algorithm can be used to overcome some TCP performance
         problems over network paths that do not have sufficient
         buffering to withstand the bursts normally present during
         slowstart."
     REFERENCE
        "RFC 3742, Limited Slow-Start for TCP with Large Congestion
         Windows"
     ::= { tcpEStatsTuneEntry 2 }
 tcpEStatsTuneLimRwin  OBJECT-TYPE
     SYNTAX          Unsigned32
     UNITS           "octets"
     MAX-ACCESS      read-write
     STATUS          current
     DESCRIPTION
        "A control to set the maximum window advertisement that may
         be sent, in octets."
     REFERENCE
        "RFC 793, Transmission Control Protocol"
     ::= { tcpEStatsTuneEntry 3 }
 tcpEStatsTuneLimMSS  OBJECT-TYPE
     SYNTAX          Unsigned32
     UNITS           "octets"
     MAX-ACCESS      read-write

Mathis, et al. Standards Track [Page 59] RFC 4898 TCP Extended Statistics MIB May 2007

     STATUS          current
     DESCRIPTION
        "A control to limit the maximum segment size in octets, that
         this TCP connection can use."
     REFERENCE
        "RFC 1191, Path MTU discovery"
     ::= { tcpEStatsTuneEntry 4 }
  1. - ================================================================
  2. -
  3. - TCP Extended Statistics Notifications Group
  4. -
 tcpEStatsEstablishNotification NOTIFICATION-TYPE
     OBJECTS     {
                   tcpEStatsConnectIndex
                 }
     STATUS      current
     DESCRIPTION
         "The indicated connection has been accepted
         (or alternatively entered the established state)."
     ::= { tcpEStatsNotifications 1 }
 tcpEStatsCloseNotification NOTIFICATION-TYPE
     OBJECTS     {
                   tcpEStatsConnectIndex
                 }
     STATUS      current
     DESCRIPTION
         "The indicated connection has left the
         established state"
     ::= { tcpEStatsNotifications 2 }
  1. - ================================================================
  2. -
  3. - Conformance Definitions
  4. -
    tcpEStatsCompliances   OBJECT IDENTIFIER
         ::= { tcpEStatsConformance 1 }
    tcpEStatsGroups        OBJECT IDENTIFIER
         ::= { tcpEStatsConformance 2 }
  1. -
  2. - Compliance Statements
  3. -
   tcpEStatsCompliance MODULE-COMPLIANCE

Mathis, et al. Standards Track [Page 60] RFC 4898 TCP Extended Statistics MIB May 2007

      STATUS current
      DESCRIPTION
          "Compliance statement for all systems that implement TCP
          extended statistics."
      MODULE -- this module
          MANDATORY-GROUPS {
                             tcpEStatsListenerGroup,
                             tcpEStatsConnectIdGroup,
                             tcpEStatsPerfGroup,
                             tcpEStatsPathGroup,
                             tcpEStatsStackGroup,
                             tcpEStatsAppGroup
                           }
          GROUP tcpEStatsListenerHCGroup
          DESCRIPTION
              "This group is mandatory for all systems that can
               wrap the values of the 32-bit counters in
               tcpEStatsListenerGroup in less than one hour."
          GROUP tcpEStatsPerfOptionalGroup
          DESCRIPTION
              "This group is optional for all systems."
          GROUP tcpEStatsPerfHCGroup
          DESCRIPTION
              "This group is mandatory for systems that can
              wrap the values of the 32-bit counters in
              tcpEStatsPerfGroup in less than one hour.
              Note that any system that can attain 10 Mb/s
              can potentially wrap 32-Bit Octet counters in
              under one hour."
          GROUP tcpEStatsPathOptionalGroup
          DESCRIPTION
              "This group is optional for all systems."
          GROUP tcpEStatsPathHCGroup
          DESCRIPTION
              "This group is mandatory for systems that can
              wrap the values of the 32-bit counters in
              tcpEStatsPathGroup in less than one hour.
              Note that any system that can attain 10 Mb/s
              can potentially wrap 32-Bit Octet counters in
              under one hour."
          GROUP tcpEStatsStackOptionalGroup

Mathis, et al. Standards Track [Page 61] RFC 4898 TCP Extended Statistics MIB May 2007

          DESCRIPTION
              "This group is optional for all systems."
          GROUP tcpEStatsAppHCGroup
          DESCRIPTION
              "This group is mandatory for systems that can
              wrap the values of the 32-bit counters in
              tcpEStatsStackGroup in less than one hour.
              Note that any system that can attain 10 Mb/s
              can potentially wrap 32-Bit Octet counters in
              under one hour."
          GROUP tcpEStatsAppOptionalGroup
          DESCRIPTION
              "This group is optional for all systems."
          GROUP tcpEStatsTuneOptionalGroup
          DESCRIPTION
              "This group is optional for all systems."
          GROUP tcpEStatsNotificationsGroup
          DESCRIPTION
              "This group is optional for all systems."
          GROUP tcpEStatsNotificationsCtlGroup
          DESCRIPTION
              "This group is mandatory for systems that include the
               tcpEStatsNotificationGroup."
    ::= { tcpEStatsCompliances 1 }
  1. - ================================================================
  2. -
  3. - Units of Conformance
  4. -

tcpEStatsListenerGroup OBJECT-GROUP

          OBJECTS {
               tcpEStatsListenerTableLastChange,
               tcpEStatsListenerStartTime,
               tcpEStatsListenerSynRcvd,
               tcpEStatsListenerInitial,
               tcpEStatsListenerEstablished,
               tcpEStatsListenerAccepted,
               tcpEStatsListenerExceedBacklog,
               tcpEStatsListenerCurConns,
               tcpEStatsListenerMaxBacklog,
               tcpEStatsListenerCurBacklog,

Mathis, et al. Standards Track [Page 62] RFC 4898 TCP Extended Statistics MIB May 2007

               tcpEStatsListenerCurEstabBacklog
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsListener group includes objects that
               provide valuable statistics and debugging
               information for TCP Listeners."
       ::= { tcpEStatsGroups 1 }
     tcpEStatsListenerHCGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsListenerHCSynRcvd,
               tcpEStatsListenerHCInitial,
               tcpEStatsListenerHCEstablished,
               tcpEStatsListenerHCAccepted,
               tcpEStatsListenerHCExceedBacklog
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsListenerHC group includes 64-bit
                counters in tcpEStatsListenerTable."
       ::= { tcpEStatsGroups 2 }
     tcpEStatsConnectIdGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsConnTableLatency,
               tcpEStatsConnectIndex
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsConnectId group includes objects that
               identify TCP connections and control how long TCP
               connection entries are retained in the tables."
       ::= { tcpEStatsGroups 3 }
     tcpEStatsPerfGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsPerfSegsOut, tcpEStatsPerfDataSegsOut,
               tcpEStatsPerfDataOctetsOut,
               tcpEStatsPerfSegsRetrans,
               tcpEStatsPerfOctetsRetrans, tcpEStatsPerfSegsIn,
               tcpEStatsPerfDataSegsIn,
               tcpEStatsPerfDataOctetsIn,
               tcpEStatsPerfElapsedSecs,
               tcpEStatsPerfElapsedMicroSecs,
               tcpEStatsPerfStartTimeStamp, tcpEStatsPerfCurMSS,
               tcpEStatsPerfPipeSize, tcpEStatsPerfMaxPipeSize,
               tcpEStatsPerfSmoothedRTT, tcpEStatsPerfCurRTO,

Mathis, et al. Standards Track [Page 63] RFC 4898 TCP Extended Statistics MIB May 2007

               tcpEStatsPerfCongSignals, tcpEStatsPerfCurCwnd,
               tcpEStatsPerfCurSsthresh, tcpEStatsPerfTimeouts,
               tcpEStatsPerfCurRwinSent,
               tcpEStatsPerfMaxRwinSent,
               tcpEStatsPerfZeroRwinSent,
               tcpEStatsPerfCurRwinRcvd,
               tcpEStatsPerfMaxRwinRcvd,
               tcpEStatsPerfZeroRwinRcvd
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsPerf group includes those objects that
               provide basic performance data for a TCP connection."
       ::= { tcpEStatsGroups 4 }
     tcpEStatsPerfOptionalGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsPerfSndLimTransRwin,
               tcpEStatsPerfSndLimTransCwnd,
               tcpEStatsPerfSndLimTransSnd,
               tcpEStatsPerfSndLimTimeRwin,
               tcpEStatsPerfSndLimTimeCwnd,
               tcpEStatsPerfSndLimTimeSnd
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsPerf group includes those objects that
               provide basic performance data for a TCP connection."
       ::= { tcpEStatsGroups 5 }
     tcpEStatsPerfHCGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsPerfHCDataOctetsOut,
               tcpEStatsPerfHCDataOctetsIn
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsPerfHC group includes 64-bit
               counters in the tcpEStatsPerfTable."
       ::= { tcpEStatsGroups 6 }
     tcpEStatsPathGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsControlPath,
               tcpEStatsPathRetranThresh,
               tcpEStatsPathNonRecovDAEpisodes,
               tcpEStatsPathSumOctetsReordered,

Mathis, et al. Standards Track [Page 64] RFC 4898 TCP Extended Statistics MIB May 2007

               tcpEStatsPathNonRecovDA
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsPath group includes objects that
               control the creation of the tcpEStatsPathTable,
               and provide information about the path
               for each TCP connection."
       ::= { tcpEStatsGroups 7 }
     tcpEStatsPathOptionalGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsPathSampleRTT, tcpEStatsPathRTTVar,
               tcpEStatsPathMaxRTT, tcpEStatsPathMinRTT,
               tcpEStatsPathSumRTT, tcpEStatsPathCountRTT,
               tcpEStatsPathMaxRTO, tcpEStatsPathMinRTO,
               tcpEStatsPathIpTtl, tcpEStatsPathIpTosIn,
               tcpEStatsPathIpTosOut,
               tcpEStatsPathPreCongSumCwnd,
               tcpEStatsPathPreCongSumRTT,
               tcpEStatsPathPostCongSumRTT,
               tcpEStatsPathPostCongCountRTT,
               tcpEStatsPathECNsignals,
               tcpEStatsPathDupAckEpisodes, tcpEStatsPathRcvRTT,
               tcpEStatsPathDupAcksOut, tcpEStatsPathCERcvd,
               tcpEStatsPathECESent
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsPath group includes objects that
               provide additional information about the path
               for each TCP connection."
       ::= { tcpEStatsGroups 8 }
   tcpEStatsPathHCGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsPathHCSumRTT
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsPathHC group includes 64-bit
               counters in the tcpEStatsPathTable."
       ::= { tcpEStatsGroups 9 }
     tcpEStatsStackGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsControlStack,
               tcpEStatsStackActiveOpen, tcpEStatsStackMSSSent,

Mathis, et al. Standards Track [Page 65] RFC 4898 TCP Extended Statistics MIB May 2007

               tcpEStatsStackMSSRcvd, tcpEStatsStackWinScaleSent,
               tcpEStatsStackWinScaleRcvd,
               tcpEStatsStackTimeStamps, tcpEStatsStackECN,
               tcpEStatsStackWillSendSACK,
               tcpEStatsStackWillUseSACK, tcpEStatsStackState,
               tcpEStatsStackNagle, tcpEStatsStackMaxSsCwnd,
               tcpEStatsStackMaxCaCwnd,
               tcpEStatsStackMaxSsthresh,
               tcpEStatsStackMinSsthresh,
               tcpEStatsStackInRecovery, tcpEStatsStackDupAcksIn,
               tcpEStatsStackSpuriousFrDetected,
               tcpEStatsStackSpuriousRtoDetected
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsConnState group includes objects that
               control the creation of the tcpEStatsStackTable,
               and provide information about the operation of
               algorithms used within TCP."
       ::= { tcpEStatsGroups 10 }
     tcpEStatsStackOptionalGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsStackSoftErrors,
               tcpEStatsStackSoftErrorReason,
               tcpEStatsStackSlowStart, tcpEStatsStackCongAvoid,
               tcpEStatsStackOtherReductions,
               tcpEStatsStackCongOverCount,
               tcpEStatsStackFastRetran,
               tcpEStatsStackSubsequentTimeouts,
               tcpEStatsStackCurTimeoutCount,
               tcpEStatsStackAbruptTimeouts,
               tcpEStatsStackSACKsRcvd,
               tcpEStatsStackSACKBlocksRcvd,
               tcpEStatsStackSendStall, tcpEStatsStackDSACKDups,
               tcpEStatsStackMaxMSS, tcpEStatsStackMinMSS,
               tcpEStatsStackSndInitial,
               tcpEStatsStackRecInitial,
               tcpEStatsStackCurRetxQueue,
               tcpEStatsStackMaxRetxQueue,
               tcpEStatsStackCurReasmQueue,
               tcpEStatsStackMaxReasmQueue
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsConnState group includes objects that
               provide additional information about the operation of
               algorithms used within TCP."

Mathis, et al. Standards Track [Page 66] RFC 4898 TCP Extended Statistics MIB May 2007

       ::= { tcpEStatsGroups 11 }
     tcpEStatsAppGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsControlApp,
               tcpEStatsAppSndUna, tcpEStatsAppSndNxt,
               tcpEStatsAppSndMax, tcpEStatsAppThruOctetsAcked,
               tcpEStatsAppRcvNxt,
               tcpEStatsAppThruOctetsReceived
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsConnState group includes objects that
               control the creation of the tcpEStatsAppTable,
               and provide information about the operation of
               algorithms used within TCP."
       ::= { tcpEStatsGroups 12 }
   tcpEStatsAppHCGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsAppHCThruOctetsAcked,
               tcpEStatsAppHCThruOctetsReceived
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsStackHC group includes 64-bit
               counters in the tcpEStatsStackTable."
       ::= { tcpEStatsGroups 13 }
     tcpEStatsAppOptionalGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsAppCurAppWQueue,
               tcpEStatsAppMaxAppWQueue,
               tcpEStatsAppCurAppRQueue,
               tcpEStatsAppMaxAppRQueue
          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsConnState group includes objects that
               provide additional information about how applications
               are interacting with each TCP connection."
       ::= { tcpEStatsGroups 14 }
     tcpEStatsTuneOptionalGroup  OBJECT-GROUP
          OBJECTS {
               tcpEStatsControlTune,
               tcpEStatsTuneLimCwnd, tcpEStatsTuneLimSsthresh,
               tcpEStatsTuneLimRwin, tcpEStatsTuneLimMSS

Mathis, et al. Standards Track [Page 67] RFC 4898 TCP Extended Statistics MIB May 2007

          }
          STATUS current
          DESCRIPTION
               "The tcpEStatsConnState group includes objects that
               control the creation of the tcpEStatsConnectionTable,
               which can be used to set tuning parameters
               for each TCP connection."
       ::= { tcpEStatsGroups 15 }
     tcpEStatsNotificationsGroup      NOTIFICATION-GROUP
          NOTIFICATIONS {
                        tcpEStatsEstablishNotification,
                        tcpEStatsCloseNotification
          }
          STATUS   current
          DESCRIPTION
              "Notifications sent by a TCP extended statistics agent."
       ::= { tcpEStatsGroups 16 }
     tcpEStatsNotificationsCtlGroup  OBJECT-GROUP
          OBJECTS {
                        tcpEStatsControlNotify
          }
          STATUS   current
          DESCRIPTION
              "The tcpEStatsNotificationsCtl group includes the
               object that controls the creation of the events
               in the tcpEStatsNotificationsGroup."
       ::= { tcpEStatsGroups 17 }
    END

Mathis, et al. Standards Track [Page 68] RFC 4898 TCP Extended Statistics MIB May 2007

5. Security Considerations

 There are a number of management objects defined in this MIB module
 with a MAX-ACCESS clause of read-write and/or read-create.  Such
 objects may be considered sensitive or vulnerable in some network
 environments.  The support for SET operations in a non-secure
 environment without proper protection can have a negative effect on
 network operations.  These are the tables and objects and their
 sensitivity/vulnerability:
  • Changing tcpEStatsConnTableLatency or any of the control objects

in the tcpEStatsControl group (tcpEStatsControlPath,

    tcpEStatsControlStack, tcpEStatsControlApp, tcpEStatsControlTune)
    may affect the correctness of other management applications
    accessing this MIB.  Generally, local policy should only permit
    limited write access to these controls (e.g., only by one
    management station or only during system configuration).
  • The objects in the tcpEStatsControlTune group

(tcpEStatsTuneLimCwnd, tcpEStatsTuneLimSsthresh,

    tcpEStatsTuneLimRwin) can be used to limit resources consumed by
    TCP connections or to limit TCP throughput.  An attacker might
    manipulate these objects to reduce performance to levels below the
    minimum acceptable for a particular application.
 Some of the readable objects in this MIB module (i.e., objects with a
 MAX-ACCESS other than not-accessible) may be considered sensitive or
 vulnerable in some network environments.  It is thus important to
 control even GET and/or NOTIFY access to these objects and possibly
 to even encrypt the values of these objects when sending them over
 the network via SNMP.  These are the tables and objects and their
 sensitivity/vulnerability:
  • All objects which expose TCP sequence numbers (tcpEStatsAppSndUna,

tcpEStatsAppSndNxt, tcpEStatsAppSndMax, tcpEStatsStackSndInitial,

    tcpEStatsAppRcvNxt, and tcpEStatsStackRecInitial) might make it
    easier for an attacker to forge in sequence TCP segments to
    disrupt TCP connections.
  • Nearly all objects in this (or any other) MIB may be used to

estimate traffic volumes, which may reveal unanticipated

    information about an organization to the outside world.
 SNMP versions prior to SNMPv3 did not include adequate security.
 Even if the network itself is secure (for example by using IPsec),
 even then, there is no control as to who on the secure network is
 allowed to access and GET/SET (read/change/create/delete) the objects
 in this MIB module.

Mathis, et al. Standards Track [Page 69] RFC 4898 TCP Extended Statistics MIB May 2007

 It is RECOMMENDED that implementers consider the security features as
 provided by the SNMPv3 framework (see [RFC3410], section 8),
 including full support for the SNMPv3 cryptographic mechanisms (for
 authentication and privacy).
 Further, deployment of SNMP versions prior to SNMPv3 is NOT
 RECOMMENDED.  Instead, it is RECOMMENDED to deploy SNMPv3 and to
 enable cryptographic security.  It is then a customer/operator
 responsibility to ensure that the SNMP entity giving access to an
 instance of this MIB module is properly configured to give access to
 the objects only to those principals (users) that have legitimate
 rights to indeed GET or SET (change/create/delete) them.

6. IANA Considerations

 The MIB module in this document uses the following IANA-assigned
 OBJECT IDENTIFIER values recorded in the SMI Numbers registry:
        Descriptor        OBJECT IDENTIFIER value
        ------------      -----------------------
        tcpEStatsMIB      { mib-2 156 }

7. Normative References

 [RFC791]   Postel, J., "Internet Protocol", STD 5, RFC 791, September
            1981.
 [RFC793]   Postel, J., "Transmission Control Protocol", STD 7, RFC
            793, September 1981.
 [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
            Communication Layers", STD 3, RFC 1122, October 1989.
 [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
            November 1990.
 [RFC1323]  Jacobson, V., Braden, R., and D. Borman, "TCP Extensions
            for High Performance", RFC 1323, May 1992.
 [RFC2018]  Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP
            Selective Acknowledgment Options", RFC 2018, October 1996.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

Mathis, et al. Standards Track [Page 70] RFC 4898 TCP Extended Statistics MIB May 2007

 [RFC2578]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
            Rose, M., and S. Waldbusser, "Structure of Management
            Information Version 2 (SMIv2)", STD 58, RFC 2578, April
            1999.
 [RFC2579]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
            Rose, M., and S. Waldbusser, "Textual Conventions for
            SMIv2", RFC 2579, STD 58, April 1999.
 [RFC2580]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
            Rose, M., and S. Waldbusser, "Conformance Statements for
            SMIv2", RFC 2580, STD 58, April 1999.
 [RFC2581]  Allman, M., Paxson, V., and W. Stevens, "TCP Congestion
            Control", RFC 2581, April 1999.
 [RFC2856]  Bierman, A., McCloghrie, K., and R. Presuhn, "Textual
            Conventions for Additional High Capacity Data Types", RFC
            2856, June 2000.
 [RFC2883]  Floyd, S., Mahdavi, J., Mathis, M., and M. Podolsky, "An
            Extension to the Selective Acknowledgement (SACK) Option
            for TCP", RFC 2883, July 2000.
 [RFC2988]  Paxson, V. and M. Allman, "Computing TCP's Retransmission
            Timer", RFC 2988, November 2000.
 [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
            of Explicit Congestion Notification (ECN) to IP", RFC
            3168, September 2001.
 [RFC3517]  Blanton, E., Allman, M., Fall, K., and L. Wang, "A
            Conservative Selective Acknowledgment (SACK)-based Loss
            Recovery Algorithm for TCP", RFC 3517, April 2003.
 [RFC4022]  Raghunarayan, R., Ed., "Management Information Base for
            the Transmission Control Protocol (TCP)", RFC 4022, March
            2005.
 [RFC4502]  Waldbusser, S., "Remote Network Monitoring Management
            Information Base Version 2", RFC 4502, May 2006.

Mathis, et al. Standards Track [Page 71] RFC 4898 TCP Extended Statistics MIB May 2007

8. Informative References

 [Mat97]    M. Mathis, J. Semke, J. Mahdavi, T. Ott, "The Macroscopic
            Behavior of the TCP Congestion Avoidance Algorithm",
            Computer Communication Review, volume 27, number 3, July
            1997.
 [Bra94]    Brakmo, L., O'Malley, S., "TCP Vegas, New Techniques for
            Congestion Detection and Avoidance", SIGCOMM'94, London,
            pp 24-35, October 1994.
 [Edd06]    Eddy, W., "TCP SYN Flooding Attacks and Common
            Mitigations", Work in Progress, May 2007.
 [POSIX]    Portable Operating System Interface, IEEE Std 1003.1
 [Pad98]    Padhye, J., Firoiu, V., Towsley, D., Kurose, J., "Modeling
            TCP Throughput: A Simple Model and its Empirical
            Validation", SIGCOMM'98.
 [Web100]   Mathis, M., J. Heffner, R. Reddy, "Web100: Extended TCP
            Instrumentation for Research, Education and Diagnosis",
            ACM Computer Communications Review, Vol 33, Num 3, July
            2003.
 [RFC2861]  Handley, M., Padhye, J., and S. Floyd, "TCP Congestion
            Window Validation", RFC 2861, June 2000.
 [RFC3260]  Grossman, D., "New Terminology and Clarifications for
            Diffserv", RFC 3260, April 2002.
 [RFC3410]  Case, J., Mundy, R., Partain, D. and B. Stewart,
            "Introduction and Applicability Statements for Internet-
            Standard Management Framework", RFC 3410, December 2002.
 [RFC3522]  Ludwig, R. and M. Meyer, "The Eifel Detection Algorithm
            for TCP", RFC 3522, April 2003.
 [RFC3742]  Floyd, S., "Limited Slow-Start for TCP with Large
            Congestion Windows", RFC 3742, March 2004.
 [RFC4614]  Duke M., Braden, R., Eddy, W., Blanton, E.  "A Roadmap for
            Transmission Control Protocol (TCP) Specification
            Documents", RFC 4614, September 2006.

Mathis, et al. Standards Track [Page 72] RFC 4898 TCP Extended Statistics MIB May 2007

9. Contributors

 The following people contributed text that was incorporated into this
 document:
 Jon Saperia <saperia@jdscons.com> converted Web100 internal
 documentation into a true MIB.
 Some of the objects in this document were moved from an early version
 of the TCP-MIB by Bill Fenner, et al.
 Some of the object descriptions are based on an earlier unpublished
 document by Jeff Semke.

10. Acknowledgments

 This document is a product of the Web100 project (www.web100.org), a
 joint effort of Pittsburgh Supercomputing Center (www.psc.edu),
 National Center for Atmospheric Research (www.ncar.ucar.edu), and
 National Center for Supercomputer Applications (www.ncsa.edu).
 It would not have been possible without all of the hard work by the
 entire Web100 team, especially Peter O'Neal, who read and reread the
 entire document several times; Janet Brown and Marla Meehl, who
 patiently managed the unmanageable.  The Web100 project would not
 have been successful without all of the early adopters who suffered
 our bugs to provide many good suggestions and insights into their
 needs for TCP instrumentation.
 Web100 was supported by the National Science Foundation under Grant
 No. 0083285 and a research grant from Cisco Systems.
 We would also like to thank all of the people who built experimental
 implementations of this MIB from early versions and provided us with
 constructive feedback:  Glenn Turner at AARnet, Kristine Adamson at
 IBM, and Xinyan Zan at Microsoft.
 And last, but not least, we would like to thank Dan Romascanu, our
 "MIB Doctor" and Bert Wijnen, the Operations Area Director, for
 patiently steering us through the MIB review process.

Mathis, et al. Standards Track [Page 73] RFC 4898 TCP Extended Statistics MIB May 2007

Authors' Addresses

 Matt Mathis
 Pittsburgh Supercomputing Center
 300 S. Craig St.
 Pittsburgh, PA 15213
 Phone: 412-268-4960
 EMail: mathis@psc.edu
 John Heffner
 Pittsburgh Supercomputing Center
 300 S. Craig St.
 Pittsburgh, PA 15213
 Phone: 412-268-4960
 EMail: jheffner@psc.edu
 Rajiv Raghunarayan
 Cisco Systems Inc.
 San Jose, CA 95134
 Phone: 408 853 9612
 EMail: raraghun@cisco.com

Mathis, et al. Standards Track [Page 74] RFC 4898 TCP Extended Statistics MIB May 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
 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
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Mathis, et al. Standards Track [Page 75]

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