Diameter Maintenance and Extensions (DIME)              J. Korhonen, Ed.
Internet-Draft                                                  Broadcom
Intended status: Standards Track                         S. Donovan, Ed.
Expires: January 4, April 30, 2015                                      B. Campbell
                                                                  Oracle
                                                               L. Morand
                                                             Orange Labs
                                                            July 3,
                                                        October 27, 2014

                Diameter Overload Indication Conveyance
                      draft-ietf-dime-ovli-03.txt
                      draft-ietf-dime-ovli-04.txt

Abstract

   This specification documents a Diameter Overload Control (DOC) base
   solution and the dissemination of the overload report information.

Requirements

   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 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on January 4, April 30, 2015.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology and Abbreviations . . . . . . . . . . . . . . . .   4   3
   3.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .   4   5
     3.1.  Overload Control Endpoints (Non normative)  Piggybacking Principle  . . . . . . .   6
     3.2.  Piggybacking Principle (Non normative) . . . . . . . . .  10
     3.3. .   7
     3.2.  DOIC Capability Announcement (Non normative)  . . . . . .  11
     3.4.  DOIC Overload Condition Reporting (Non normative) . . . .  12
     3.5.  DOIC Extensibility (Non normative) . . . .   8
     3.3.  DOIC Overload Condition Reporting . . . . . . .  13
     3.6.  Simplified Example Architecture (Non normative) . . . . .  14
     3.7.  Considerations for Applications Integrating the   9
     3.4.  DOIC
           Solution (Non normative) Extensibility  . . . . . . . . . . . . . . . .  15
       3.7.1.  Application Classification  (Non normative) . . .  10
     3.5.  Simplified Example Architecture . .  15
       3.7.2.  Application Type Overload Implications  (Non
               normative) . . . . . . . . . . .  11
   4.  Solution Procedures . . . . . . . . . .  16
       3.7.3.  Request Transaction Classification  (Non normative) .  18
       3.7.4.  Request Type Overload Implications  (Non normative) .  18
   4.  Solution Procedures (Normative) . . . . . . . . .  12
     4.1.  Capability Announcement . . . . . .  20
     4.1.  Capability Announcement (Normative) . . . . . . . . . . .  20  12
       4.1.1.  Reacting Node Behavior (Normative)  . . . . . . . . .  20 . . . . . .  12
       4.1.2.  Reporting Node Behavior  (Normative) . . . . . . . .  21 . . . . . . .  12
       4.1.3.  Agent Behavior  (Normative)  . . . . . . . . . . . . .  22 . . . . . .  13
     4.2.  Overload Report Processing (Normative)  . . . . . . . . .  22 . . . . . .  14
       4.2.1.  Overload Control State (Normative)  . . . . . . . . .  22 . . . . . .  14
       4.2.2.  Reacting Node Behavior  (Normative)  . . . . . . . . .  24 . . . . . .  18
       4.2.3.  Reporting Node Behavior  (Normative) . . . . . . . .  26
       4.2.4.  Agent Behavior  (Normative) . . . . . . .  18
     4.3.  Protocol Extensibility  . . . . . .  26
     4.3.  Protocol Extensibility (Normative) . . . . . . . . . . .  27  20
   5.  Loss Algorithm (Normative)  . . . . . . . . . . . . . . . . .  28
     5.1.  Overview (Non normative) . . . . . .  21
     5.1.  Overview  . . . . . . . . . .  28
     5.2.  Use of OC-Reduction-Percentage AVP . . . . . . . . . . .  29
     5.3. . . .  21
     5.2.  Reporting Node Behavior (Normative) . . . . . . . . . . .  29
     5.4. . . . . . .  22
     5.3.  Reacting Node Behavior (Normative)  . . . . . . . . . . .  29 . . . . . .  22
   6.  Attribute Value Pairs (Normative) . . . . . . . . . . . . . .  30 . . . . . .  23
     6.1.  OC-Supported-Features AVP . . . . . . . . . . . . . . . .  31  23
     6.2.  OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . .  31  24
     6.3.  OC-OLR AVP  . . . . . . . . . . . . . . . . . . . . . . .  32  24
     6.4.  OC-Sequence-Number AVP  . . . . . . . . . . . . . . . . .  33  25
     6.5.  OC-Validity-Duration AVP  . . . . . . . . . . . . . . . .  33  25
     6.6.  OC-Report-Type AVP  . . . . . . . . . . . . . . . . . . .  34  25
     6.7.  OC-Reduction-Percentage AVP . . . . . . . . . . . . . . .  35  26
     6.8.  Attribute Value Pair flag rules . . . . . . . . . . . . .  35  27
   7.  Error Response Codes  . . . . . . . . . . . . . . . . . . . .  36  27
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  36  28
     8.1.  AVP codes . . . . . . . . . . . . . . . . . . . . . . . .  36  28
     8.2.  New registries  . . . . . . . . . . . . . . . . . . . . .  37  28
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  37  29
     9.1.  Potential Threat Modes  . . . . . . . . . . . . . . . . .  37  29
     9.2.  Denial of Service Attacks . . . . . . . . . . . . . . . .  38  30
     9.3.  Non-Compliant Nodes . . . . . . . . . . . . . . . . . . .  39  30
     9.4.  End-to End-Security Issues  . . . . . . . . . . . . . . .  39  31
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  40  32
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  40  32
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  40  32
     11.2.  Informative References . . . . . . . . . . . . . . . . .  41  32
   Appendix A.  Issues left for future specifications  . . . . . . .  41  33
     A.1.  Additional traffic abatement algorithms . . . . . . . . .  41  33
     A.2.  Agent Overload  . . . . . . . . . . . . . . . . . . . . .  41  33
     A.3.  DIAMETER_TOO_BUSY clarifications  New Error Diagnostic AVP  . . . . . . . . . . . .  42
   Appendix B.  Examples . . . .  33
   Appendix B.  Deployment Considerations  . . . . . . . . . . . . .  34
   Appendix C.  Requirements Conformance Analysis  . . . . .  42
     B.1.  Mix of Destination-Realm routed requests and Destination-
           Host routed requests . . . .  34
   Appendix D.  Considerations for Applications Integrating the DOIC
                Solution . . . . . . . . . . . . . .  42
   Appendix C.  Restructuring of -02 version of the draft . . . . .  45
   Authors' Addresses . . .  34
     D.1.  Application Classification  . . . . . . . . . . . . . . .  34
     D.2.  Application Type Overload Implications  . . . . . . . . .  35
     D.3.  Request Transaction Classification  . . . . . . . . . . .  36
     D.4.  Request Type Overload Implications  . . . . . . . . . . .  37
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . .  48 .  38

1.  Introduction

   This specification defines a base solution for Diameter Overload
   Control (DOC), refered referred to as Diameter Overload Indication Conveyance
   (DOIC).  The requirements for the solution are described and
   discussed in the corresponding design requirements document
   [RFC7068].  Note that the overload control solution defined in this
   specification does not address all the requirements listed in
   [RFC7068].  A number of overload control related features are left
   for the future specifications.  See Appendix A for a list of
   extensions that are currently being considered.  See Appendix C for
   an analysis of the conformance to the requirements specified in
   [RFC7068].

   The solution defined in this specification addresses Diameter
   overload control between two endpoints (see Section 3.1). Diameter nodes that support the DOIC
   solution.  Furthermore, the solution which is designed to apply to
   existing and future Diameter applications, requires no changes to the
   Diameter base protocol [RFC6733] and is deployable in environments
   where some Diameter nodes do not implement the Diameter overload
   control solution defined in this specification.

2.  Terminology and Abbreviations

   Abatement
      Reaction to receipt of an overload report resulting in a reduction
      in traffic sent to the reporting node.  Abatement actions include
      diversion and throttling.

   Abatement Algorithm

      An algorithm mechanism requested by reporting nodes and used by reacting
      nodes to reduce the amount of traffic sent during an occurrence of
      overload control.

   Throttling

      Throttling is the reduction of the number

   Diversion

      Abatement of requests traffic sent to an
      entity.  Throttling can include a client dropping requests, or an
      agent rejecting requests with appropriate error responses.
      Clients and agents can also choose to redirect throttled requests
      to some other entity or entities capable of handling them.

      Editor's note: Propose to add reporting node by a definition of Abatement reacting node
      in response to include
      both throttling and diversion (redirecting receipt of messages) actions.
      Then an overload report.  The abatement is
      achieved by diverting traffic from the reporting node to modify this definition another
      Diameter node that is able to include just process the rejecting request.

   Host-Routed Request

      The set of requests and adding that a definition of diversion.

   Reporting Node

      A Diameter reacting node that generates an overload report.  (This may or
      may not knows will be served by a
      particular host, either due to the overloaded node.)

   Reacting Node

      A Diameter node that consumes and acts upon presence of a report.  Note that
      "act upon" does not necessarily mean Destination-Host
      AVP, or by some other local knowledge on the part of the reacting node applies an
      abatement algorithm; it might decide to delegate that downstream,
      in which case it also becomes a "reporting node".
      node.

   Overload Control State (OCS)

      State

      Reporting and reacting node internally maintained state describing an occurrence
      occurrences of overload control maintained by
      reporting and reacting nodes. control.

   Overload Report (OLR)

      A set of AVPs

      Information sent by a reporting node indicating the start or start,
      continuation or end of an occurrence of overload control.

   Reacting Node

      A Diameter node that acts upon an overload report.

   Realm-Routed Request

      The set of requests that a reacting node does not know the host
      that will service the request.

   Reporting Node

      A Diameter node that generates an overload report.  (This may or
      may not be the overloaded node.)

   Throttling

      Throttling is the reduction of the number of requests sent to an
      entity.  Throttling can include a Diameter Client or Diameter
      Server dropping requests, or a Diameter Agent rejecting requests
      with appropriate error responses.  In extreme cases reporting
      nodes can also throttle requests when the requested reductions in
      traffic does not sufficiently address the overload scenario.

3.  Solution Overview

   The Diameter Overload Information Conveyance (DOIC) mechanism solution allows
   Diameter nodes to request other nodes to perform overload abatement
   actions, that is, actions to reduce the load offered to the
   overloaded node or realm.

   A Diameter node that supports DOIC is known as a "DOIC endpoint". node".  Any
   Diameter node can act as a DOIC endpoint, node, including clients, servers, and
   agents.  DOIC endpoints nodes are further divided into "Reporting Nodes" and
   "Reacting Nodes."  A reporting node requests overload abatement by
   sending an Overload Report (OLR) to one or more reacting nodes.

   A reacting node consumes acts upon OLRs, and performs whatever actions are
   needed to fulfill fulfil the abatement requests included in the OLRs.  A
   Reporting node may report overload on its own behalf, or on behalf of
   other (typically upstream) nodes.  Likewise, a reacting node may
   perform overload abatement on its own behalf, or on behalf of other
   (typically downstream) nodes.

   A node's role as a DOIC endpoint node is independent of its Diameter role.
   For example, Diameter relay Relay and proxy agents Proxy Agents may act as DOIC
   endpoints, nodes,
   even though they are not endpoints in the Diameter sense.  Since
   Diameter enables bi-directional applications, where Diameter
   servers Servers
   can send requests towards Diameter clients, Clients, a given Diameter node can
   simultaneously act as a reporting node and a reacting node.

   Likewise, a relay or proxy agent may act as a reacting node from the
   perspective of upstream nodes, and a reporting node from the
   perspective of downstream nodes.

   DOIC endpoints nodes do not generate new messages to carry DOIC related
   information.  Rather, they "piggyback" DOIC information over existing
   Diameter messages by inserting new AVPs into existing Diameter
   requests and responses.  Nodes indicate support for DOIC, and any
   needed DOIC parameters by inserting an OC_Supported_Features AVP
   (Section 6.2) into existing requests and responses.  Reporting nodes
   send OLRs by inserting OC-OLR AVPs (Section 6.3).

   A given OLR applies to the Diameter realm and application of the
   Diameter message that carries it.  If a reporting node supports more
   than one realm and/or application, it reports independently for each
   combination of realm and application.  Similarly, OC-Feature-Vector
   AVPs apply the OC-Supported-
   Features AVP applies to the realm and application of the enclosing
   message.  This implies that a node may support DOIC for one
   application and/or realm, but not another, and may indicate different
   DOIC parameters for each application and realm for which it supports
   DOIC.

   Reacting nodes perform overload abatement according to an agreed-upon
   abatement algorithm.  An abatement algorithm defines the meaning of
   the parameters of an OLR, OLR and the procedures required for overload
   abatement.  This document specifies a single must-support algorithm,
   namely the "loss" algorithm Section (Section 5).  Future specifications may
   introduce new algorithms.

   Overload conditions may vary in scope.  For example, a single
   Diameter node may be overloaded, in which case reacting nodes may
   reasonably attempt to send throttled requests to other destinations or via
   other agents.  On the other hand, an entire Diameter realm may be
   overloaded, in which case such attempts would do harm.  DOIC OLRs
   have a concept of "report type" (Section 6.6), where the type defines
   such behaviors.  Report types are extensible.  This document defines
   report types for overload of a specific server, and for overload of
   an entire realm.

   While a reporting node sends OLRs

   A report of type host is sent to "adjacent" reacting nodes, nodes
   that are "adjacent" indicate the overload of a specific
   server for DOIC purposes may not be adjacent from the application-id indicated in the transaction.  When
   receiving an OLR of type host, a
   Diameter, or transport, reacting node applies overload
   abatement to what is referred to in this document as host-routed
   requests.  This is the set of requests that the reacting node knows
   will be served by a particular host, either due to the presence of a
   Destination-Host AVP, or by some other local knowledge on the part of
   the reacting node.  The reacting node applies overload abatement on
   those host-routed requests which the reacting node knows will be
   served by the server that matches the Origin-Host AVP of the received
   message that contained the received OLR of type host.

   A report type of realm is sent to indicate the overload of all
   servers in a realm for the application-id.  When receiving an OLR of
   type realm, a reacting node applies overload abatement to what is
   referred to in this document as realm-routed requests.  This is the
   set of requests that are not host-routed as defined in the previous
   paragraph.

   While a reporting node sends OLRs to "adjacent" reacting nodes, nodes
   that are "adjacent" for DOIC purposes may not be adjacent from a
   Diameter, or transport, perspective.  For example, one or more
   Diameter agents that do not support DOIC may exist between a given
   pair of reporting and reacting nodes, as long as those agents pass
   unknown AVPs through unmolested. unchanged.  The report types described in this
   document can safely pass through non-supporting agents.  This may not
   be true for report types defined in future specifications.  Documents
   that introduce new report types MUST describe any limitations on
   their use across non-supporting agents.

3.1.  Overload Control Endpoints (Non normative)  Piggybacking Principle

   The overload control solution can AVPs defined in this specification have been
   designed to be considered as an overlay piggybacked on top of an arbitrary Diameter network.  The existing application messages.
   This is made possible by adding overload control information
   is exchanged over on a "DOIC association" established between two
   communication endpoints.  The endpoints, namely top-level AVPs, the "reacting node"
   OC-OLR AVP and the "reporting node" do not need to be adjacent Diameter peer
   nodes, nor they need to be OC-Supported-Features AVP, as optional AVPs into
   existing commands when the end-to-end Diameter nodes in a typical
   "client-server" deployment with multiple intermediate Diameter agent
   nodes corresponding Command Code Format (CCF)
   specification allows adding new optional AVPs (see Section 1.3.4 of
   [RFC6733]).

   Reacting nodes indicate support for DOIC by including the OC-
   Supported-Features AVP in between.  The overload control endpoints are all request messages originated or relayed
   by the two
   Diameter reacting node.

   Reporting nodes that decide to exchange indicate support for DOIC by including the OC-
   Supported-Features AVP in all answer messages originated or relayed
   by the reporting node.  Reporting nodes also include overload control information
   between each other.  How reports
   using the endpoints are determined OC-OLR AVP in answer messages.

      Note: There is specific to
   a deployment, a no new Diameter node role in that deployment and local
   configuration. application defined to carry
      overload related AVPs.  The following diagrams illustrate the concept of DOIC AVPs are carried in existing
      Diameter Overload
   Endpoints and how they differ from application messages.

   Note that the standard [RFC6733] defined
   client, overload control solution does not have fixed server
   and agent Diameter nodes. client roles.  The following DOIC node role is determined based on the key to
   the elements in
   message type: whether the diagrams:

   C  Diameter client as defined in [RFC6733].

   S  Diameter server as defined in [RFC6733].

   A  Diameter agent, in either message is a relay request (i.e. sent by a
   "reacting node") or proxy mode, as defined in
      [RFC6733].

   DEP  Diameter Overload Endpoint as defined in this document.  In the
      following figures an answer (i.e. send by a DEP may terminate two different DOIC
      associations being "reporting node").
   Therefore, in a reporter and reactor at typical "client-server" deployment, the same time. Diameter Session  A
   Client MAY report its overload condition to the Diameter session as defined in [RFC6733].

   DOIC Association  A DOIC association exists between two Server for
   any Diameter
      Overload Endpoints.  One Server initiated message exchange.  An example of the endpoints such
   is the overload reporter
      and Diameter Server requesting a re-authentication from a Diameter
   Client.

3.2.  DOIC Capability Announcement

   The DOIC solution supports the ability for Diameter nodes to
   determine if other is the overload reactor.

   Figure 1 illustrates nodes in the most basic configuration where path of a client request support the
   solution.  This capability is
   connected directly referred to a server.  In this case, the Diameter session
   and the as DOIC association are both between the client Capability
   Announcement (DCA) and server.

      +-----+            +-----+
      |  C  |            |  S  |
      +-----+            +-----+
      | DEP |            | DEP |
      +--+--+            +--+--+
         |                  |
         |                  |
         |{Diameter Session}|
         |                  |
         |{DOIC Association}|
         |                  |

                      Figure 1: Basic DOIC deployment

   In Figure 2 there is an agent that is not participating directly separate from Diameter Capability Exchange.

   The DCA solution uses the OC-Supported-Features AVPs to indicate the
   Diameter overload features supported.

   The first node in the exchange path of overload reports.  As a result, the Diameter session
   and request that supports the
   DOIC association are still established between the client and solution inserts the server.

      +-----+            +-----+            +-----+
      |  C  |            |  A  |            |  S  |
      +-----+            +--+--+            +-----+
      | DEP |               |               | DEP |
      +--+--+               |               +--+--+
         |                  |                  |
         |                  |                  |
         |----------{Diameter Session}---------|
         |                  |                  |
         |----------{DOIC Association}---------|
         |                  |                  |

          Figure 2: DOIC deployment with non participating agent

   Figure 3 illustrates OC-Supported-Feature AVP in the case where request
   message.  This includes an indication that it supports the client does not support
   Diameter overload.  In loss
   overload abatement algorithm defined in this case, the DOIC association specification (see
   Section 5).  This ensures that there is at least one commonly
   supported overload abatement algorithm between the
   agent reporting node and
   the server.  The agent handles reacting nodes in the role path of the reactor for
   overload reports generated by request.

      DOIC must support deployments where Diameter Clients and/or
      Diameter Servers do not support the server.

      +-----+            +-----+            +-----+
      |  C  |            |  A  |            |  S  |
      +--+--+            +-----+            +-----+
         |               | DEP |            | DEP |
         |               +--+--+            +--+--+
         |                  |                  |
         |                  |                  |
         |----------{Diameter Session}---------|
         |                  |                  |
         |                  |{DOIC Association}|
         |                  |                  |

   Figure 3: DOIC deployment with non-DOIC client and DOIC enabled agent solution.  In Figure 4 there this
      scenario, it is a assumed that Diameter Agents that support the DOIC association between
      solution will handle overload abatement for the client and non supporting
      Diameter nodes.  In this case the
   agent and a second DOIC association between the agent and will insert the server.
   One use case requiring this configuration is when OC-
      Supporting-Features AVP in requests that do not already contain
      one, telling the agent reporting node that there is
   serving as a SFE for a DOIC node that
      will handle overload abatement.

   The reporting node inserts the OC-Supported-Feature AVP in all answer
   messages to requests that contained the OC-Supported-Feature AVP.
   The contents of the reporting node's OC-Supported-Feature AVP
   indicate the set of servers.

      +-----+            +-----+            +-----+
      |  C  |            |  A  |            |  S  |
      +-----+            +-----+            +-----+
      | DEP |            | DEP |            | DEP |
      +--+--+            +--+--+            +--+--+
         |                  |                  |
         |                  |                  |
         |----------{Diameter Session}---------|
         |                  |                  |
         |{DOIC Association}|{DOIC Association}|
         |                  |                and/or
         |----------{DOIC Association}---------|
         |                  |                  |

            Figure 4: A deployment where all nodes support DOIC

   Figure 5 illustrates a deployment where some clients support Diameter overload control and some do not.  In this case features supported by the agent must
   reporting node with one exception.

   The reporting node only includes an indication of support Diameter overload control for one
   overload abatement algorithm.  This is the non supporting client.  It
   might also need to have a DOIC association with algorithm that the server, as shown
   here,
   reporting node intends to handle use should it enter an overload for a server farm and/or for managing Realm
   overload.

      +-----+            +-----+            +-----+            +-----+
      | C1  |            | C2  |            |  A  |            |  S  |
      +-----+            +--+--+            +-----+            +-----+
      | DEP |               |               | DEP |            | DEP |
      +--+--+               |               +--+--+            +--+--+
         |                  |                  |                  |
         |                  |                  |                  |
         |-------------------{Diameter Session}-------------------|
         |                  |                  |                  |
         |                  |--------{Diameter Session}-----------|
         |                  |                  |                  |
         |---------{DOIC Association}----------|{DOIC Association}|
         |                  |                  |                and/or
         |-------------------{DOIC Association}-------------------|
         |                  |                  |                  |

     Figure 5: A deployment with DOIC and non-DOIC supporting clients

   Editor's note: Propose condition
   or requests to remove C1, which use while it actually is already shown in a
   previous figure.  Have this focus just on an overload condition.
   Reacting nodes can use the non supporting client
   scenario.

   Figure 6 illustrates a deployment where some agents support Diameter indicated overload control and others do not.

      +-----+            +-----+            +-----+            +-----+
      |  C  |            |  A  |            |  A  |            |  S  |
      +-----+            +--+--+            +-----+            +-----+
      | DEP |               |               | DEP |            | DEP |
      +--+--+               |               +--+--+            +--+--+
         |                  |                  |                  |
         |                  |                  |                  |
         |-------------------{Diameter Session}-------------------|
         |                  |                  |                  |
         |                  |                  |                  |
         |---------{DOIC Association}----------|{DOIC Association}|
         |                  |                  |                and/or
         |-------------------{DOIC Association}-------------------|
         |                  |                  |                  |

      Figure 6: A deployment with DOIC and non-DOIC supporting agents

   Editor's note: Propose abatement algorithm to add a non supporting server scenario.

3.2.  Piggybacking Principle (Non normative)

   The
   prepare for possible overload control AVPs reports and must use the indicated
   overload abatement algorithm if traffic reduction is actually
   requested.

      Note that the loss algorithm defined in this specification have been
   designed to be piggybacked on top of existing application message
   exchanges.  This document is made possible a
      stateless abatement algorithm.  As a result it does not require
      any actions by adding overload control top
   level AVPs, the OC-OLR AVP and reacting nodes prior to the OC-Supported-Features AVP as
   optional AVPs into existing commands when receipt of an overload
      report.  Stateful abatement algorithms that base the corresponding Command
   Code Format (CCF) specification allows adding new optional AVPs (see
   Section 1.3.4 abatement
      logic on a history of [RFC6733]).

   Reacting request messages sent might require reacting
      nodes indicate support for DOIC by including the OC-
   Supported-Features AVP all request messages originated or relayed to maintain state to ensure that overload reports can be
      properly handled.

   The individual features supported by the Diameter node.

   Reporting nodes indicate support for DOIC by including the OC-
   Supported-Features AVP nodes are indicated in all answer messages originated or relayed
   by
   the Diameter node.  Reporting nodes also include overload reports
   using OC-Feature-Vector AVP.  Any semantics associated with the OC-OLR AVP in answer messages.

      Note: There is no new Diameter application
   features will be defined to carry
      overload related AVPs.  The DOIC AVPs are carried in existing
      Diameter application messages.

   Note extension specifications that introduce
   the overload control solution does not have fixed server
   and client roles. features.

   The endpoint role is determined based on DCA mechanism must also support the
   message type: whether scenario where the message is a request (i.e. sent set of
   features supported by the sender of a
   "reacting node") or an answer (i.e. send request and by a "reporting node").
   Therefore, agents in the
   path of a typical "client-server" deployment, request differ.  In this case, the "client" MAY
   report its overload condition agent updates the OC-
   Supported-Feature AVP to reflect the "server" for any server
   initiated message exchange.  An example mixture of such is the server
   requesting a re-authentication from a client.

3.3.  DOIC Capability Announcement (Non normative) two sets of
   supported features.

      The DOIC solutions supports the ability for Diameter nodes logic to determine if other nodes in the path content of a request support the
   solution.  This capability modified OC-Supported-
      Feature AVP is refered to as DOIC Capability
   Announcement (DCA) out-of-scope for this specification and is separate from Diameter Capability Exchange.

   The DCA mechanism is built around the piggybacking principle used for
   transporting Diameter overload AVPs.  This includes both DCA AVPs and
   AVPs associated with Diameter overload reports.  This allows for the
   DCA AVPs left to
      implementation decisions.  Care must be carried across Diameter nodes that do taken not support the to introduce
      interoperability issues for downstream or upstream DOIC solution.

   The DCA mechanism nodes.

3.3.  DOIC Overload Condition Reporting

   As with DOIC Capability Announcement, Overload Condition Reporting
   uses the OC-Supported-Features new AVPs (Section 6.3) to indicate the
   Diameter an overload features supported. condition.

   The first node in OC-OLR AVP is referred to as an overload report.  The OC-OLR AVP
   includes the path type of report, a Diameter request that supports the
   DOIC solution inserts the OC-Supported-Feature AVP in sequence number, the request
   message.  This includes an indication length of time
   that it supports the loss
   overload report is valid and abatement algorithm specific AVPs.

   Two types of overload reports are defined in this specification (see
   Section 5).  This insures that there document, host
   reports and realm reports.

   A report of type host is at least one commonly
   supported overload abatement algorithm between sent to indicate the reporting overload of a specific
   Diameter node and for the reacting nodes application-id indicated in the path transaction.
   When receiving an OLR of the request.

      DOIC must support deployments where Diameter Clients and/or
      Diameter servers do not support the DOIC solution.  In this
      scenario, it is assumed that Diameter Agents that support the DOIC
      solution will handle type host, a reacting node applies overload
   abatement for the non supporting
      clients.  In to what is referred to in this case the DOIC agent will insert document as host-routed
   requests.  This is the OC-
      Supporting-Features AVP in set of requests that do not already contain
      one, telling the reporting reacting node that there is a DOIC node that knows
   will handle overload abatement.

   The reporting node inserts the OC-Supported-Feature AVP in all answer
   messages be served by a particular host, either due to requests that contained the OC-Supported-Feature AVP.
   The contents presence of a
   Destination-Host AVP, or by some other local knowledge on the reporting node's OC-Supported-Feature AVP
   indicate the set part of Diameter overload features supported by
   the
   reporting node with one exception. reacting node.  The reporting reacting node only includes an indication of support for one applies overload abatement algorithm.  This is the algorithm that on
   those host-routed requests which the
   reporting reacting node intends to use should it enter an overload condition.
   Reacting nodes can use knows will be
   served by the indicated overload abatement algorithm to
   prepare for possible overload reports.

      Note server that matches the loss algorithm defined in this document is a
      stateless abatement algorithm.  As a result it does not require
      any actions by reacting nodes prior to the receipt Origin-Host AVP of an overload
      report.  Stateful abatement algorithms the received
   message that base contained the abatement
      logic on a history received OLR of request messages sent might require reacting
      nodes to maintain state to insure that overload type host.

   Realm reports can be
      properly handled.

   The individual features supported by the DOIC nodes are apply to realm-routed requests for a specific realm as
   indicated in the OC-Feature-Vector Destination-Realm AVP.  Any semantics associated with the
   features will be defined in extension specifications that introduce
   the features.

   The DCA mechanism must also support the scenario where

   Reporting nodes are responsible for determining the set need for a
   reduction of
   features supported by traffic.  The method for making this determination is
   implementation specific and depend on the sender type of a request and overload report
   being generated.  A host report, for instance, will generally be
   generated by agents in the
   path tracking utilization of a request differ.  In this case, resources required by the agent updates host
   to handle transactions for the OC-
   Supported-Feature AVP Diameter application.  A realm report
   will generally impact the traffic sent to reflect multiple hosts and, as
   such, will typically require tracking the mixture capacity of the two sets of
   supported features.

      The logic servers
   able to determine handle realm-routed requests for the content of application.

   Once a reporting node determines the modified OC-Supported-
      Feature AVP is out-of-scope need for this specification and is left to
      implementation decisions.  Care must be taken a reduction in doing so not to
      introduce interoperability issues for downstream or upstream DOIC
      nodes.

3.4.  DOIC Overload Condition Reporting (Non normative)

   As with DOIC Capability Announcement, Overload Condition Reporting traffic,
   it uses new the DOIC defined AVPs (Section 6.3) to indicate an overload report on the condition.  These AVPs
   are included in answer messages sent or relayed by the reporting
   node.  The OC-OLR AVP reporting node indicates the overload abatement algorithm
   that is referred to as an overload report. be used to handle the traffic reduction in the OC-
   Supported-Features AVP.  The OC-OLR AVP
   includes is used to communicate
   information about the type requested reduction.

   Reacting nodes, upon receipt of report, an overload report ID, report, are responsible
   for applying the length of
   time that abatement algorithm to traffic impacted by the report
   overload report.  The method used for that abatement is valid and dependent on
   the abatement algorithm.  The loss abatement algorithm specific AVPs.

   Two types of overload reports are is defined in
   this document, host
   reports and realm reports.

   Host reports apply to traffic that is sent to a specific Diameter
   host.  The applies document (Section 5).  Other abatement algorithms can be defined
   in extensions to requests that contain the Destination-Host AVP
   that contains a DiameterIdentity that matches DOIC solutions.

   As the conditions that lead to the generation of the overload
   report.  These requests are referred to as host-routed requests.  A
   host report also applies to realm-routed requests, requests that do
   not have a Destination-Host AVP, when the selected route for the
   request is a connection to
   change the impacted host.

   Realm reporting node can send new overload reports apply to realm-routed requests for a specific realm as
   indicated in the Destination-Realm AVP.

   Reporting nodes are responsible for determining requesting
   greater reduction if the need for a condition gets worse or less reduction of traffic.  The method for making this determination is
   implementation specific and depend on if
   the type of condition improves.  The reporting node sends an overload report
   being generated.  A host report, for instance, will generally be
   generated by tracking utilization
   with a duration of resources required by the host
   to handle transactions for the the Diameter application.  A realm
   report will generally impact the traffic sent zero to multiple hosts and,
   as such, will typically require tracking indicate that the capacity overload condition has
   ended and use of the servers
   able to handle realm-routed requests for the application.

   Once a reporting abatement algorithm is no longer needed.

   The reacting node also determines when the need for a reduction in traffic,
   it uses the DOIC defined AVPs to overload report expires
   based on the condition.  These AVPs
   are included in answer messages sent or relayed by the reporting
   node.  The reporting node indicates the overload abatement algorithm
   that is to be used to handle the traffic reduction in the OC-
   Supported-Features AVP.  The OC-OLR AVP is used to communicate
   information about the requested reduction.

   Reacting nodes, upon receipt of an overload report, are responsible
   for applying the abatement algorithm to traffic impacted by the
   overload report.  The method used for that abatement is dependent on
   the abatement algorithm.  The loss abatement algorithm is defined in
   this document (Section 5).  Other abatement algorithms can be defined
   in extensions to the DOIC solutions.

   As the conditions that lead to the generation of the overload report
   change the reporting node can send new overload reports requesting
   greater reduction if the condition gets worse or less reduction if
   the condition improves.  The reporting node sends an overload report
   with a duration of zero to indicate that the overlaod condition has
   ended and use of the abatement algorithm is no longer needed.

   The reacting node also determines when the overload report expires
   based on the OC-Validaty-Duration AVP OC-Validity-Duration AVP in the overload report and
   stops applying the abatement algorithm when the report expires.

3.5.

3.4.  DOIC Extensibility (Non normative)

   The DOIC solutions solution is designed to be extensible.  This extensibility
   is based on existing Diameter based extensibility mechanisms.

   There are multiple categories of extensions that are expected.  This
   includes the definition of new overload abatement algorithms, the
   definition of new report types and new definitions of the scope of
   messages impacted by an overload report.

   The DOIC solution uses the OC-Supported-Features AVP for DOIC nodes
   to communicate supported features.  The specific features supported
   by the DOIC node are indicated in the OC-Feature-Vector AVP.  DOIC
   extensions must define new values for the OC-Feature-Vector AVP.

   DOIC extensions also have the ability to add new AVPs to the OC-
   Supported-Features AVP, if additional information about the new
   feature is required to be communicate.

   Overload abatement algorithms required.

   Reporting nodes use the OC-OLR AVP to communicate overload occurances.
   occurrences.  This AVP can also be extended to add new AVPs allowing
   a reporting nodes to communicate additional information about
   handling an overload condition.

   If necessary, new extensions can also define new top level top-level AVPs.  It
   is, however, recommended that DOIC extensions use the OC-Supported-
   Features and OC-OLR to carry all DOIC related AVPs.

3.6.

3.5.  Simplified Example Architecture (Non normative)

   Figure 7 1 illustrates the simplified architecture for Diameter
   overload information conveyance.  See Section 3.1 for more discussion
   and details how different Diameter nodes fit into the architecture
   from the DOIC point of view.

    Realm X                                  Same or other Realms
   <--------------------------------------> <---------------------->

      +--^-----+                 : (optional) :
      |Diameter|                 :            :
      |Server A|--+     .--.     : +---^----+ :     .--.
      +--------+  |   _(    `.   : |Diameter| :   _(    `.   +---^----+
                  +--(        )--:-|  Agent |-:--(        )--|Diameter|
      +--------+  | ( `  .  )  ) : +-----^--+ : ( `  .  )  ) | Client |
      |Diameter|--+  `--(___.-'  :            :  `--(___.-'  +-----^--+
      |Server B|                 :            :
      +---^----+                 :            :

                          End-to-end Overload Indication
             1)  <----------------------------------------------->
                             Diameter Application Y

                  Overload Indication A    Overload Indication A'
             2)  <----------------------> <---------------------->
                 standard base protocol   standard base protocol

     Figure 7: 1: Simplified architecture choices for overload indication
                                 delivery

   In Figure 7, 1, the Diameter overload indication can be conveyed (1)
   end-to-end between servers and clients or (2) between servers and
   Diameter agent inside the realm and then between the Diameter agent
   and the clients when the Diameter agent acting as back-to-back-agent
   for DOIC purposes.

3.7.  Considerations for Applications Integrating the DOIC clients.

4.  Solution (Non
      normative)

   THis Procedures

   This section outlines considerations to be taken into account when
   integrating the normative behavior associated with the DOIC solution into Diameter applications.

3.7.1.  Application Classification (Non normative)

   The following is a classification of Diameter applications and
   requests.  This discussion is meant
   solution.

4.1.  Capability Announcement

   This section defines DOIC Capability Announcement (DCA) behavior.

4.1.1.  Reacting Node Behavior

   A reacting node MUST include the OC-Supported-Features AVP in all
   request messages.

   A reacting node MAY include the OC-Feature-Vector AVP with an
   indication of the loss algorithm.  A reacting node MUST include the
   OC-Feature-Vector AVP to indicate support for abatement algorithms in
   addition to document factors that play
   into decisions made by the Diameter identity responsible loss algorithm.

   A reacting node SHOULD indicate support for handling
   overload reports.

   Section 8.1 of [RFC6733] defines two state machines all other DOIC features
   it supports.

      Not all DOIC features will necessarily apply to all transactions.
      For instance, there may be a future extension that imply two
   types of applications, session-less and session-based only applies to
      session based applications.

   The primary difference between these types of applications  A reacting node that supports this
      extension can choose to not include it for non session based
      applications.

   An OC-Supported-Features AVP in answer messages indicates there is a
   reporting node for the
   lifetime of Session-Ids.

   For session-based applications, transaction.  The reacting node MAY take
   action based on the Session-Id is used to tie
   multiple requests into a single session.

   In session-less applications, features indicated in the lifetime of OC-Feature-Vector AVP.

      Note that the Session-Id loss abatement algorithm is a
   single Diameter transaction, i.e. the session is implicitly
   terminated after a single Diameter transaction only feature
      described in this document and a new Session-Id
   is generated for each Diameter request.

   For the purposes of this discussion, session-less applications are
   further divided into two types of applications:

   Stateless applications:

      Requests within a stateless application have no relationship to
      each other.  The 3GPP defined S13 application it does not require action to be
      taken when there is an example active overload report.  This behavior is
      described in Section 4.2 and Section 5.

4.1.2.  Reporting Node Behavior

   Upon receipt of a
      stateless application [S13], --> where only request message, a Diameter command reporting node determines if
   there is
      defined between a client and a server and no state is maintained
      between two consecutive transactions.

   Pseudo-session applications:

      Applications that do not rely reacting node for the transaction based on the Session-Id AVP for
      correlation presence of application messages related to
   the same session
      but use other session-related information OC-Supported-Features AVP.

   If the request message contains an OC-Supported-Features AVP then the
   reporting node MUST include the OC-Supported-Features AVP in the Diameter requests
   answer message for this purpose.  The 3GPP defined Cx application [Cx] is an
      example of a pseudo-session application. that transaction.

   The Credit-Control application reporting node MUST NOT include the OC-Supported-Features AVP,
   OC-OLR AVP or any other overload control AVPs defined in [RFC4006] is an example of
   a Diameter session-based application.

   The handling of overload reports must take the type of application
   into consideration, as discussed extension
   drafts in Section 3.7.2.

3.7.2.  Application Type Overload Implications (Non normative)

   This section discusses considerations response messages for mitigating overload
   reported by a Diameter entity.  This discussion focuses on transactions where the type
   of application.  Section 3.7.3 discusses considerations for handling
   various request types when
   message does not include the target server is known to be OC-Supported-Features AVP.  Lack of the
   OC-Supported-Features AVP in an
   overloaded state.

   These discussions assume that the strategy request message indicates that there
   is no reacting node for mitigating the
   reported transaction.

   Based on the content of the OC-Supported-Features AVP in the request
   message, the reporting node knows what overload control functionality
   is to reduce supported by the overall workload sent to reacting node.  The reporting node then acts
   accordingly for the
   overloaded entity. subsequent answer messages it initiates.

   The concept of applying overload treatment to
   requests targeted reporting node MUST indicate support for an overloaded Diameter entity is inherent to
   this discussion. one and only one
   abatement algorithm in the OC-Feature-Vector AVP.  The method used to reduce offered load is not
   specified here but could include routing requests to another Diameter
   entity known to abatement
   algorithm included MUST be able from the set of abatement algorithms
   contained in the request message's OC-Supported-Features AVP.  The
   abatement algorithm included MUST indicate the abatement algorithm
   the reporting node wants the reacting node to handle them, or it could mean rejecting
   certain requests.  For a Diameter agent, rejecting requests will
   usually mean generating appropriate Diameter error responses.  For a
   Diameter client, rejecting requests will depend upon use when the application. reporting
   node enters an overload condition.

   For example, it could mean giving an indication to the entity
   requesting ongoing overload state, a reacting node MUST keep the Diameter service
   algorithm that was selected by the network is busy and to try
   again later.

   Stateless applications:

      By definition there is no relationship between individual requests reporting node in further requests
   towards the reporting node.  The reporting node SHOULD NOT change the
   selected algorithm during a stateless application.  As period of time that it is in an overload
   condition and, as a result, when a request is sent
      or relayed to an overloaded Diameter entity - either a Diameter
      Server or a Diameter Agent - the sending or relaying entity can
      choose to OC-OLR AVPs in answer
   messages.

   The reporting node SHOULD indicate support for other DOIC features
   defined in extension drafts that it supports and that apply to the overload treatment
   transaction.

      Note that not all DOIC features will apply to any request targeted for all Diameter
      applications or deployment scenarios.  The features included in
      the overloaded entity.

   Pseudo-session applications:

      For pseudo-session applications, there is an implied ordering of
      requests.  As OC-Feature-Vector AVP are based on local reporting node
      policy.

4.1.3.  Agent Behavior

   Diameter agents that support DOIC MUST ensure that all messages have
   the OC-Supporting-Features AVP.  If a result, decisions about which requests towards an
      overloaded entity to reject could take message handled by the command code of DOIC
   agent does not include the
      request into consideration.  This generally means that
      transactions later in OC-Supported-Features AVP then the sequence of transactions should be given
      more favorable treatment than messages earlier in DOIC
   agent inserts the sequence.
      This is because more work has AVP.  If the message already been done by has the Diameter
      network for those transactions that occur later AVP then the
   agent either leaves it unchanged in the sequence.
      Rejecting them could result relayed message or modifies
   it to reflect a mixed set of DOIC features.

   An agent MAY modify the OC-Supported-Features AVP carried in increasing answer
   messages.

      For instance, if the load on agent supports a superset of the network
      as features
      reported by the transactions earlier in reacting node then the sequence agent might also need choose, based
      on local policy, to be
      repeated.

   Session-based applications:

      Overload handling for session-based applications must take into
      consideration the work load associated with setting up and
      maintaining a session.  As such, the entity sending requests
      towards an overloaded Diameter entity for a session-based
      application might tend to reject new session requests prior to
      rejecting intra-session requests.  In addition, session ending
      requests might be given a lower probability of being rejected as
      rejecting session ending requests could result in session status
      being out of sync between the Diameter clients and servers.
      Application designers advertise that would decide to reject mid-session
      requests will need superset of features to consider whether the rejection invalidates
      reporting node.

      If the session and any resulting session clean-up procedures.

3.7.3.  Request Transaction Classification (Non normative)

   Independent Request:

      An independent request is not correlated to any other requests
      and, as such, agent modifies the lifetime of OC-Supported-Features AVP sent to the session-id is constrained
      reporting node then it might also need to an
      individual transaction.

   Session-Initiating Request:

      A session-initiating request is modify the initial message that
      establishes OC-Supported-
      Features AVP sent to a Diameter session.  The ACR message defined reacting node in
      [RFC6733] is the subsequent answer
      message, as it cannot send an example indication of a session-initiating request.

   Correlated Session-Initiating Request:

      There support for features
      that are cases when multiple session-initiated requests must be
      correlated and managed not supported by the same Diameter server.  It reacting node.

      Editor's note: There is notably an open issue on the case wording around agent
      behavior in the 3GPP PCC architecture [PCC], where multiple
      apparently independent Diameter application sessions are actually
      correlated and must this case that needs to be handled by the same Diameter server.

   Intra-Session Request:

      An intra session request is a request that uses the same Session-
      Id than the one used in a previous request.  An intra session
      request generally needs to be delivered resolved prior to the server that handled
      the session creating request finishing
      this document.

4.2.  Overload Report Processing

4.2.1.  Overload Control State

   Both reacting and reporting nodes maintain Overload Control State
   (OCS) for active overload conditions.

4.2.1.1.  Overload Control State for Reacting Nodes

   A reacting node SHOULD maintain the session.  The STR message
      defined in [RFC6733] is an example of an intra-session requests.

   Pseudo-Session Requests:

      Pseudo-session requests are independent following OCS per supported
   Diameter application:

   o  A host-type OCS entry for each Destination-Host to which it sends
      host-type requests and do not use
      the same Session-Id but are correlated

   o  A realm-type OCS entry for each Destination-Realm to which it
      sends realm-type requests.

   A host-type OCS entry is identified by other session-related
      information contained in the request.  There exists Diameter
      applications that define an expected ordering pair of transactions.
      This sequencing Application-Id and
   Host-Id.

   A realm-type OCS entry is identified by the pair of independent transactions results in a pseudo
      session. Application-Id
   and Realm-Id.

   The AIR, MAR host-type and SAR requests in realm-type OCS entries MAY include the 3GPP defined Cx
      [Cx] application are examples following
   information (the actual information stored is an implementation
   decision):

   o  Sequence number (as received in OC-OLR)
   o  Time of pseudo-session requests.

3.7.4.  Request Type Overload Implications (Non normative)

   The request classes identified expiry (derived from OC-Validity-Duration AVP received in Section 3.7.3 have implications on
   decisions about which requests should be throttled first.  The
   following list
      the OC-OLR AVP and time of reception of request treatment regarding throttling is provided
   as guidelines for application designers when implementing the
   Diameter overload control mechanism described message carrying OC-
      OLR AVP)

   o  Selected Abatement Algorithm (as received in this document.  The
   exact behavior regarding throttling is a matter of local policy,
   unless specifically defined OC-Supported-Features
      AVP)

   o  Abatement Algorithm specific input data (as received within the
      OC-OLR AVP, for example, OC-Reduction-Percentage for the application.

   Independent requests:

      Independent requests can be given equal treatment when making
      throttling decisions.

   Session-initiating requests:

      Session-initiating requests represent more work than independent
      or intra-session requests.  Moreover, session-initiating requests
      are typically followed Loss
      abatement algorithm)

4.2.1.2.  Overload Control State for Reporting Nodes

   A reporting node SHOULD maintain OCS entries per supported Diameter
   application, per supported (and eventually selected) Abatement
   Algorithm and per report-type.

   An OCS entry is identified by other session-related requests.  As
      such, as the main objective pair of Application-Id and
   Abatement Algorithm.

   The OCS entry for a given pair of Application and Abatement Algorithm
   MAY include the overload control information (the actual information stored is to reduce
      the total an
   implementation decision):

   o  Report type

   o  Sequence number of requests sent to

   o  Validity Duration

   o  Expiration Time

   o  Algorithm specific input data (for example, the overloaded entity,
      throttling decisions might favor allowing intra-session requests
      over session-initiating requests.  Individual session-initiating
      requests can be given equal treatment when making throttling
      decisions.

   Correlated session-initiating requests:

      A Request that results in a new binding, where Reduction
      Percentage for the binding Loss Abatement Algorithm)

4.2.1.3.  Reacting Node Maintenance of Overload Control State

   When a reacting node receives an OC-OLR AVP, it MUST determine if it
   is used for routing an existing or new overload condition.

      For the remainder of subsequent session-initiating requests this section the term OLR referres to the same
      server, represents more work load than other requests.  As such,
      these requests might be throttled more frequently than other
      request types.

   Pseudo-session requests:

      Throttling decisions for pseudo-session requests can take into
      consideration where individual requests fit into
      combination of the overall
      sequence contents of requests within the pseudo session.  Requests that are
      earlier in received OC-OLR AVP and the sequence might be throttled more aggressively than
      requests that occur later
      abatement algorithm indicated in the sequence.

   Intra-session requests

      There are two classes of intra-sessions requests. received OC-Supported-
      Features AVP.

   The first class
      consists of requests OLR is for an existing overload condition if the reacting node
   has an OCS that terminate matches the received OLR.

   For a session.  The second one
      contains host report-type this means it matches the set of requests that are used by app-id and host-id
   in an existing host OCS entry.

   For a realm report-type this means it matches the Diameter client app-id and server realm-id
   in an existing realm OCS entry.

   If the OLR is for an existing overload condition then it MUST
   determine if the OLR is a retransmission or an update to maintain the ongoing session state.  Session
      terminating requests should be throttled less aggressively existing
   OLR.

   If the sequence number for the received OLR is greater than the
   sequence number stored in
      order to gracefully terminate sessions, allow clean-up of the
      related resources (e.g. session state) and get rid of matching OCS entry then the need reacting
   node MUST update the matching OCS entry.

   If the sequence number for
      other intra-session requests, reducing the session management
      impact on received OLR is less than or equal to
   the overloaded entity. sequence number in the matching OCS entry then the reacting node
   MUST silently ignore the received OLR.  The default handling of other
      intra-session requests might be to treat them equally when making
      throttling decisions.  There might also matching OCS MUST NOT be application level
      considerations whether some request types are favored over others.

4.  Solution Procedures (Normative)

   This section outlines the normative behavior associated with
   updated in this case.

   If the DOIC
   solution.

4.1.  Capability Announcement (Normative)

   This section defines DOIC Capability Announcement (DCA) behavior.

   The DCA procedures are used to indicate support for DOIC and support received OLR is for DOIC features.  The DOIC features include a new overload abatement
   algorithms supported.  It might also include condition then the reacting
   node MUST generate a new report types or
   other extensions documented OCS entry for the overload condition.

   For a host report-type this means it creates on OCS entry with the
   app-id of the application-id in the future.

   Diameter nodes indicate support for DOIC by including received message and host-id of
   the OC-
   Supported-Features AVP Origin-Host in messages sent or handled by the node.

   Diameter agents that support DOIC MUST ensure received message.

      Note: This solution assumes that all messages have the OC-Supporting-Features AVP.  If a Origin-Host AVP in the answer
      message handled included by the DOIC
   agent does reporting node is not include changed along the OC-Supported-Features AVP then
      path to the DOIC
   agent inserts reacting node.

   For a realm report-type this means it creates on OCS entry with the AVP.  If
   app-id of the message already has application-id in the AVP then received message and realm-id of
   the
   agent either leaves it unchanged Origin-Realm in the relayed message or modifies
   it to reflect received message.

   If the received OLR contains a mixed set validity duration of DOIC features.

4.1.1.  Reacting Node Behavior (Normative)

   A reacting node MUST include zero ("0") then
   the OC-Supported-Features AVP in all
   request messages.

   A reacting node MUST include the OC-Feature-Vector AVP with an
   indication of update the loss algorithm.

   A reacting node SHOULD indicate support for all other DOIC features OCS entry as being expired.

      Note that it supports.

   An OC-Supported-Features AVP in answer messages indicates is not necessarily appropriate to delete the OCS
      entry, as there is a
   reporting node for recommended behavior that the transaction.  The reacting node MAY take
   action based on the features indicated in the OC-Feature-Vector AVP.

      Note that the loss abatement algorithm is the only feature
      described in this document and it does not require action
      slowly returns to be
      taken by the full traffic when ending an overload abatement
      period.

   The reacting node except does not delete an OCS when the receiving an answer
   message also has that does not contain an overload report.  This behavior is described in Section 4.2 and
      Section 5.

4.1.2. OC-OLR AVP (i.e. absence of OLR
   means "no change").

4.2.1.4.  Reporting Node Behavior (Normative)

   Upon receipt Maintenance of a request message, a Overload Control State

   A reporting node determines if
   there is SHOULD create a reacting node for the transaction based on the presence of
   the OC-Supported-Features AVP.

   Based on new OCS entry when entering an
   overload condition.

      If the content reporting node knows through absence of the OC-Supported-Features OC-Supported-
      Features AVP in the request
   message, received messages that there are no reacting nodes
      supporting DOIC then the reporting node knows what can choose to not create
      OCS entries.

   When generating a new OCS entry the sequence number MAY be set to any
   value if there is no unexpired overload control functionality
   supported by report for previous overload
   conditions sent to any reacting node(s).  The reporting node then acts
   accordingly for the subsequent answer messages it initiates.

   If the reqeust message contains an OC-Supported-Features AVP then the
   reporting node MUST include same application and
   report-type.

   When generating sequence numbers for new overload conditions, the OC-Supported-Features AVP new
   sequence number MUST be greater than any sequence number in an active
   (unexpired) overload report previously sent by the
   answer message for that transaction.

   The reporting node node.
   This property MUST indicate support for one and only one
   abatement algorithm in hold over a reboot of the OC-Feature-Vector AVP. reporting node.

   The abatement
   algorithm included reporting node MUST be from update an OCS entry when it needs to adjust
   the set validity duration of abatement algorithms
   contained in the request messages OC-Supported-Features AVP.  The
   abatement algorithm included indicates the abatement algorithm overload condition at reacting nodes.

      For instance, if the reporting node wants the wishes to instruct reacting node
      nodes to use when continue overload abatement for a longer period of time
      that originally communicated.  This also applies if the reporting
      node
   enters an wishes to shorten the period of time that overload condition.

   The abatement
      is to continue.

   A reporting node MUST NOT change update the selected abatement algorithm during a
   period of time that it is in an overload condition and, as a result,
   is sending OC-OLR AVPs in answer messages.

   The active
   OCS entry.

   A reporting node SHOULD indicate support for other DOIC features MUST update an OCS entry when it
   supports and that apply wishes to adjust
   any abatement algorithm specific parameters, including the transaction.

      Note that not all DOIC features will apply reduction
   percentage used for the Loss abatement algorithm.

      For instance, if the reporting node wishes to all Diameter
      applications change the reduction
      percentage either higher, if the overload condition has worsened,
      or deployment scenarios.  The features included in lower, if the overload condition has improved, then the OC-Feature-Vector AVP is based on local
      reporting node policy. would update the appropriate OCS entry.

   The reporting node MUST NOT include update the OC-Supported-Features AVP,
   OC-OLR AVP or any other overload control AVPs defined in extension
   drafts in response messages for transactions where sequence number associated with
   the request
   message does not include OCS entry anytime the OC-Supported-Features AVP.  Lack contents of the
   OC-Supported-Features AVP OCS entry are changed.
   This will result in a new sequence number being sent to reacting
   nodes, instructing the request message indicates that there
   is no reacting nodes to process the OC-OLR AVP.

   A reporting node for SHOULD update an OCS entry with a validity duration
   of zero ("0") when the transaction.

   An agent MAY modify overload condition ends.

      If the OC-Supported-Features AVP carried reporting node knows that the OCS entries in answer
   messages.

4.1.3.  Agent Behavior (Normative)

   Editor's note -- Need to add this section.

4.2.  Overload Report Processing (Normative)

4.2.1.  Overload Control State (Normative)

   Both the reacting and reporting
      nodes maintain are near expiration then the reporting node can decide to
      delete the OCS entry.

   The reporting node MUST keep an overload control state
   (OCS) for each endpoint (a host or a realm) they communicate OCS entry with and
   both endpoints have announced support for DOIC.  See Sections 6.1 and
   4.1 a validity duration of
   zero ("0") for discussion about how a period of time long enough to ensure that any non-
   expired reacting node's OCS entry created as a result of the support for DOIC overload
   condition in the reporting node is determined.

4.2.1.1.  Overload Control State for deleted.

4.2.2.  Reacting Nodes

   A Node Behavior

   When a reacting node maintains the following OCS per supported Diameter
   application:

   o  A host-type Overload Control State for each Destination-Host
      towards which it sends host-type requests and

   o  A realm-type Overload Control State for each Destination-Realm
      towards which a request it sends realm-type requests.

   A host-type Overload Control State may be identified by MUST determine if that
   request matches an active OCS.

   If the pair of
   Application-Id request matches and Destination-Host.  A realm-type Overload Control
   State may be identified by active OCS then the pair of Application-Id and
   Destination-Realm. reacting node MUST
   apply abatement treatment on the request.  The host-type/realm-type Overload Control State abatement treatment
   applied depends on the abatement algorithm stored in the OCS.

   For the Loss abatement algorithm defined in this specification, see
   Section 5 for a given pair of Application and Destination-Host / Destination-
   Realm could include the following information:

   o  Sequence number (as received abatement logic applied.

   If the abatement treatment results in OC-OLR)

   o  Time throttling of expiry (deviated from validity duration as received in OC-
      OLR the request and time of reception)

   o  Selected Abatement Algorithm (as received in OC-Supported-
      Features)

   o  Algorithm specific input data (as received within OC-OLR, e.g.
      Reduction Percentage for Loss)

4.2.1.2.  Overload Control States for Reporting Nodes

   A reporting
   if the reacting node maintains per supported Diameter application and per
   supported (and eventually selected) Abatement Algorithm is an Overload
   Control State.

   An Overload Control State may be identified by agent then the pair of
   Application-Id and supported Abatement Algorithm.

   The Overload Control State for a given pair of Application and
   Abatement Algorithm could include agent MUST send an
   appropriate error as defined in section Section 7.

   In the information:

   o  Sequence number

   o  Validity Duration and Expiry Time

   o  Algorithm specific input data (e.g.  Reduction Percentage for
      Loss)

   Overload Control States for reporting nodes containing a case that the OCS entry validity duration of 0 sec. should not expire before any previously sent
   (stale) OLR expires or has timed out at any reacting node.

   Editor's note: This statement is unclear and contradictory with other
   statements.  A a
   validity timer duration of zero seconds indicates ("0"), meaning that it the reporting node
   has explicitly signaled the end of the overload condition has ended and then
   abatement is no longer requested.

4.2.1.3.  Maintaining Overload Control State

   Reacting nodes create associated with the overload abatement MUST be ended in a host-type OCS identified by OCS-Id = (app-
   id,host-id) when receiving an answer message of application app-id
   containing
   controlled fashion.

4.2.3.  Reporting Node Behavior

   The operation on the reporting node is straight forward.

   If there is an Orig-Host of host-id and a host-type active OCS entry then the reporting node SHOULD
   include the OC-OLR AVP unless
   such host-type OCS already exists.

   Reacting nodes create a realm-type OCS identified by OCS-Id = (app-
   id,realm-id) when receiving an in all answer message of application app-id
   containing an Orig-Realm of realm-id and a realm-type OC-OLR messages to requests that
   contain the OC-Supported-Features AVP
   unless such realm type OCS already exists.

   Reacting nodes delete an and that match the active OCS when it expires (i.e. when current time
   minus reception time is greater than validity duration).

   Editor's note: Reacting nodes also delete on
   entry.

      A request matches if the application-id in the request matches the
      application-id in any active OCS with an updated OLR
   is received with a validity duration of zero.

   Reacting nodes update entry and if the report-type in
      the host-type OCS identified entry matches a report-type supported by OCS-Id = (app-
   id,host-id) when receiving an answer message of application app-id
   containing an Orig-Host the reporting
      node as indicated in the OC-Supported-Features AVP.

   The contents of host-id and a host-type the OC-OLR AVP with a
   sequence number higher than MUST contain all information necessary
   for the stored sequence number.

   Reacting nodes update abatement algorithm indicated in the OC-Supported-Features
   AVP that is also included in the realm-type OCS identified by OCS-Id = (app-
   id,realm-id) when receiving an answer message of application app-id
   containing message.

   A reporting node MAY choose to not resend an Orig-Realm of realm-id and overload report to a realm-type OC-OLR AVP with
   a sequence number higher than the stored sequence number.

   Reacting nodes do not delete an OCS when receiving an answer message
   reacting node if it can guarantee that does not contain an OC-OLR AVP (i.e. absence of OLR means "no
   change").

   Reporting nodes create an OCS identified by OCS-Id = (app-id,Alg)
   when receiving a request of application app-id containing an OC-
   Supported-Features AVP indicating support of this overload report is
   already active in the Abatement Algorithm
   Alg (which reacting node.

      Note - In some cases (e.g. when there are one or more agents in
      the path between reporting node selects) while being overloaded, unless
   such OCS already exists.

   Reporting nodes delete an OCS and reacting nodes, or when it expires.

   Editor's note: Reporting nodes should send updated overload
      reports
   with a validity duration of zero for a period of time after an OCS
   expires or is removed due to the overload condition ending.

   Reporting nodes update the OCS identified are discarded by OCS-Id = (app-id,Alg)
   when they detect the need to modify the requested amount of
   application app-id traffic reduction.

4.2.2.  Reacting Node Behavior (Normative)

   Once a reacting node receives an OC-OLR AVP from a reporting node, it
   applies traffic abatement based on the selected algorithm with nodes) the reporting node and may
      not be able to guarantee that the current overload condition.  The reacting node
   learns has received the
      report.

   A reporting node MUST NOT send overload reports of a type that has
   not been advertised as supported abatement algorithms directly
   from by the received answer message containing reacting node.

      Note that a reacting node advertises support for the host and
      realm report types by including the OC-Supported-Features
   AVP.

   The received OC-Supported-Features AVP does not change in
      the existing
   overload condition and/or traffic abatement algorithm settings if the
   OC-Sequence-Number AVP contains a value that is equal to the
   previously received/recorded value.  If the OC-Supported-Features AVP
   is received for the first time request.  Support for other report types must be explicitly
      indicated by new feature bits in the OC-Feature-Vector AVP.

   A reporting node or the OC-
   Sequence-Number AVP value is less than the previously received/
   recorded value (and is outside the valid overflow window), then the
   sequence number is stale (e.g. an intentional or unintentional
   replay) and SHOULD be silently discarded.

   As described in Section 6.3, MAY rely on the OC-OLR OC-Validity-Duration AVP contains the necessary
   information values for
   the implicit overload condition control state cleanup on the reporting reacting node.

   From the OC-Report-Type AVP contained in the OC-OLR AVP,
   However, it is RECOMMENDED that the reacting reporting node learns whether the overload condition report concerns a specific
   host (as identified by the Origin-Host AVP of the answer message
   containing the OC-OLR AVP) or the entire realm (as identified by always explicitly
   indicates the
   Origin-Realm AVP end of the answer message containing the OC-OLR AVP). a overload condition.

   The reacting reporting node learns the Diameter application to which SHOULD indicate the end of an overload report applies from the Application-ID occurrence
   by sending a new OLR with OC-Validity-Duration set to a value of the answer message
   containing the OC-OLR AVP. zero
   ("0").  The reacting reporting node MUST use this
   information as an input for its traffic abatement algorithm.  The
   idea is SHOULD ensure that the all reacting node applies different handling of nodes
   receive the
   traffic abatement, whether updated overload report.

      All OLRs sent request messages are targeted to a
   specific host (identified have an expiration time calculated by adding the Diameter-Host AVP
      validity-duration contained in the request) or OLR to any host in a realm (when only the Destination-Realm AVP is
   present in time the request).  Note that future specifications MAY define
   new OC-Report-Type AVP values that imply different handling of the
   OC-OLR AVP.  For example, in a form of new additional AVPs inside message was
      sent.  Transit time for the
   Grouped OC-OLR AVP that would define report target in a finer
   granularity than just a host.

      Editor's note: OLR can be safely ignored.  The above behavior for Realm reports is
      inconsistent with
      reporting node can ensure that all reacting nodes have received
      the definition of realm reports OLR by continuing to send it in section
      Section 6.6.

   If answer messages until the OC-OLR AVP is received
      expiration time for the first time, the reacting node
   MUST create all OLRs sent for that overload control state associated with the related realm
   or condition have
      expired.

   When a specific host in the realm identified in the message carrying reporting node sends an OLR, it effectively delegates any
   necessary throttling to downstream nodes.  Therefore, the OC-OLR AVP, as described in Section 4.2.1.

   If reporting
   node SHOULD NOT apply throttling to the value set of the OC-Sequence-Number AVP contained in the received
   OC-OLR AVP is equal messages to or less than which the value stored in an existing
   overload control state,
   OLR applies.  That is, the received OC-OLR AVP same candidate set of messages SHOULD NOT
   be silently
   discarded.  If the value of the OC-Sequence-Number AVP contained in
   the received OC-OLR AVP is greater than throttled multiple times.

   However, when the value stored in reporting node sends and OLR downstream, it MAY
   still be responsible to apply other abatement methods such as
   diversion.  The reporting node might also need to throttle requests
   for reasons other then overload.  For example, an
   existing overload control state agent or there is no previously recorded
   sequence number, the reacting server
   might have a configured rate limit for each client, and throttle
   requests that exceed that limit, even if such requests had already
   been candidates for throttling by downstream nodes.

   This document assumes that there is a single source for realm-reports
   for a given realm, or that if multiple nodes can send realm reports,
   that each such node MUST update has full knowledge of the overload control state associated with the realm or of the specific
   entire realm.  A reacting node in cannot distinguish between receiving
   realm-reports from a single node, or from multiple nodes.

      Editor's Note: There is not yet consensus on the realm.

   When above two
      paragraphs.  Two alternatives are under consideration --
      synchronization of sequence numbers and attribution of reports.
      If no consensus is reached then it will be left to be addressed as
      an extension.

4.3.  Protocol Extensibility

   The overload control state is created or updated, the reacting
   node MUST apply the solution can be extended, e.g. with new traffic
   abatement requested in algorithms, new report types or other new functionality.

   When defining a new extension a new feature bit MUST be defined for
   the OC-OLR AVP
   using OC-Feature-Vector.  This feature bit is used to communicate
   support for the algorithm announced new feature.

   The extension MAY define new AVPs for use in the OC-Supported-Features AVP
   contained DOIC Capability
   Announcement and for use in DOIC Overload reporting.  These new AVPs
   SHOULD be defined to be extensions to the received answer message along with the OC-Supported-Features and
   OC-OLR AVP.

   The validity duration of the overload information contained AVPs defined in the
   OC-OLR this document.

   It should be noted that [RFC6733] defined Grouped AVP extension
   mechanisms apply.  This allows, for example, defining a new feature
   that is either explicitly indicated in the OC-Validity-Duration
   AVP or is implicitly equals mandatory to the default value (5 seconds) if the
   OC-Validity-Duration AVP is absent. be understood even when piggybacked on an
   existing application.

   The reacting node MUST maintain
   the validity duration handling of feature bits in the OC-Feature-Vector AVP that are
   not associated with overload control state.  Once abatement algorithms MUST be specified
   by the
   validity duration times out, extensions that define the reacting node features.

   When defining new report type values, the corresponding specification
   MUST assume define the
   overload condition reported in a previous OC-OLR AVP has ended.

   A value semantics of zero ("0") received in the OC-Validity-Duration in an
   updated overload new report indicates that the overload condition has
   ended types and that how they affect
   the overload state is no longer valid.

   In OC-OLR AVP handling.  The specification MUST also reserve a
   corresponding new feature bit in the case that OC-Feature-Vector AVP.

   The OC-OLR AVP can be expanded with optional sub-AVPs only if a
   legacy DOIC implementation can safely ignore them without breaking
   backward compatibility for the validity duration expires or is explicitly
   signaled as being no longer valid given OC-Report-Type AVP value.  If
   the state associated with new sub-AVPs imply new semantics for handling the
   overload indicated
   report type, then a new OC-Report-Type AVP value MUST be removed and any abatement associated with defined.

   New features (feature bits in the
   overload OC-Feature-Vector AVP) and report
   types (in the OC-Report-Type AVP) MUST be ended in a controlled fashion.  After
   removing the overload state the sequence number registered with IANA.  As
   with any Diameter specification, new AVPs MUST NOT also be used registered
   with IANA.  See Section 8 for
   future comparisons of sequence numbers.

4.2.3.  Reporting Node Behavior (Normative)

   A reporting node is a Diameter node inserting an OC-OLR AVP in a the required procedures.

5.  Loss Algorithm

   This section documents the Diameter message in order to inform a reacting node about an overload
   condition and request Diameter traffic abatement. loss abatement
   algorithm.

5.1.  Overview

   The operation on DOIC specification supports the reporting node is straight forward. ability for multiple overload
   abatement algorithms to be specified.  The
   reporting node learns the capabilities abatement algorithm used
   for any instance of overload is determined by the reacting node when it
   receives the OC-Supported-Features AVP as part of any Diameter
   request message.  If the reporting node shares at least one common
   feature with the reacting node, then the DOIC can be enabled between
   these two endpoints.  See Overload
   Capability Announcement process documented in Section 4.1 for further discussion on 4.1.

   The loss algorithm described in this section is the
   capability and feature announcement between two endpoints.

   When a traffic reduction default algorithm
   that must be supported by all Diameter nodes that support DOIC.

   The loss algorithm is required due designed to an overload condition be a straightforward and
   the stateless
   overload control solution abatement algorithm.  It is supported used by the sender of the
   Diameter request, the reporting node MUST include an OC-Supported-
   Features AVP and an OC-OLR AVP nodes to
   request a percentage reduction in the corresponding Diameter answer. amount of traffic sent.  The OC-OLR AVP contains the required
   traffic reduction and impacted by the OC-
   Supported-Features AVP indicates requested reduction depends on the traffic type of
   overload report.

   Reporting nodes use a strategy of applying abatement algorithm logic to
   apply.  This algorithm MUST be one the
   requested percentage of request messages sent (or handled in the algorithms advertised case
   of agents) by the request sender.

   A reporting reacting node MAY rely on the OC-Validity-Duration AVP values for that are impacted by the implicit overload control
   report.

   From a conceptual level, the logic at the reacting node could be
   outlined as follows.

   1.  An overload report is received and the associated overload state cleanup on
       is either saved or updated (if required) by the reacting node.
   However, it

   2.  A new Diameter request is RECOMMENDED generated by the application running on
       the reacting node.

   3.  The reacting node determines that an active overload report
       applies to the reporting request, as indicated by the corresponding OCS
       entry.

   4.  The reacting node always explicitly
   indicates determines if abatement should be applied to
       the end of request.  One approach that could be taken for each request
       is to select a overload condition. random number between 1 and 100.  If the random
       number is less than the indicated reduction percentage then the
       request is given abatement treatment, otherwise the request is
       given normal routing treatment.

5.2.  Reporting Node Behavior

   The method a reporting node SHOULD indicate nodes uses to determine the end amount of traffic
   reduction required to address an overload occurrence
   by sending condition is an
   implementation decision.

   When a new OLR with OC-Validity-Duration set reporting node that has selected the loss abatement algorithm
   determines the need to request a value of zero
   ("0"). traffic reduction it includes an OC-
   OLR AVP in response messages as described in Section 4.2.3.

   The reporting node SHOULD insure that all reacting nodes
   receive MUST indicate a percentage reduction in the updated OC-
   Reduction-Percentage AVP.

   The reporting node MAY change the reduction percentage in subsequent
   overload report.

4.2.4.  Agent Behavior (Normative)

   Editor's note -- Need reports.  When doing so the reporting node must conform to add this section.

4.3.  Protocol Extensibility (Normative)

   The
   overload control solution can be extended, e.g. with new traffic
   abatement algorithms, new report types or other new functionality. handing specified in Section 4.2.3.

   When defining a new extension the reporting node determines it no longer needs a new feature bit MUST be defined for reduction in
   traffic the OC-Feature-Vector.  This feature bit is used to communicate
   support for reporting node SHOULD send an overload report indicating
   the new feature.

   The extention may also define new AVPs for use in DOIC Capability
   Anouncement and for use overload report is no longer valid, as specified in DOIC Overload reporting.  These new AVP
   should be defined to be extensions
   Section 4.2.3.

5.3.  Reacting Node Behavior

   The method a reacting node uses to the OC-Supported-Features and determine which request messages
   are given abatement treatment is an implementation decision.

   When receiving an OC-OLR AVPs defined in this document.

   It should be noted that [RFC6733] defined Grouped AVP extension
   mechanisms apply.  This allows, for example, defining a new feature
   that is mandatory to be understood even when piggybacked on an
   existing applications.  More specifically, answer message where the sub-AVPs inside algorithm
   indicated in the OC-Supported-Features and OC-OLR AVP MAY have the M-bit set.
   However, when overload control AVPs are piggybacked on top of an
   existing applications, setting M-bit in sub-AVPs is NOT RECOMMENDED.

   The handling of feature bits in the OC-Feature-Vector AVP that are
   not associated with overload abatement algorithms MUST be specified
   by the extensions that define the features.

   When defining new report type values, loss algorithm, the corresponding specification
   reacting node MUST define apply abatement treatment to the semantics requested
   percentage of request messages sent.

      Note: the new report types and how they affect
   the OC-OLR AVP handling.  The specification MUST also reserve loss algorithm is a
   corresponding new feature, see the OC-Supported-Features and OC-
   Feature-Vector AVPs.

   The OC-OLR AVP can be expanded with optional sub-AVPs only if stateless algorithm.  As a
   legacy implementation can safely ignore them without breaking
   backward compatibility for result,
      the given OC-Report-Type AVP value implied
   report handling semantics.  If reacting node does not guarantee that there will be an
      absolute reduction in traffic sent.  Rather, it guarantees that
      the requested percentage of new sub-AVPs imply new semantics requests will be given abatement
      treatment.

   When applying overload abatement treatment for handling the indicated report type, then a new OC-Report-Type AVP
   value load abatement
   algorithm, the reacting node MUST be defined.

   New features (feature bits in abate, either by throttling or
   diversion, the OC-Feature-Vector AVP) and report
   types (in requested percentage of requests that would have
   otherwise been sent to the OC-Report-Type AVP) MUST be registered with IANA.  As
   with any Diameter specification, new AVPs MUST also be registered
   with IANA.  See Section 8 for reporting host or realm.

   If reacting node comes out of the required procedures.

5.  Loss Algorithm (Normative)

   This section documents 100 percent traffic reduction as a
   result of the Diameter overload loss abatement
   algorithm.

5.1.  Overview (Non normative)

   The DOIC specification supports report timing out, the ability for multiple overload
   abatement algorithms following concerns are
   RECOMMENDED to be specified. applied.  The abatement algorithm used reacting node sending the traffic
   should be conservative and, for any instance of example, first send "probe" messages
   to learn the overload is determined condition of the overloaded node before
   converging to any traffic amount/rate decided by the Diameter Overload
   Capability Announcement process documented sender.  Similar
   concerns apply in Section 4.1.

   The loss algorithm described in this section is the default algorithm
   that must be supported by all Diameter nodes that support DOIC.

   The loss algorithm is designed to be a straightforward and stateless
   overload abatement algorithm.  It is used by reporting nodes to
   request a percentage reduction in the amount of traffic sent.  The
   traffic impacted by cases when the requested reduction depends on overload report times out unless
   the type of previous overload report.

   Reporting nodes use a strategy of applying abatement logic to report stated 0 percent reduction.

   If the
   requested percentage of request reacting node does not receive an OLR in messages sent (or handled in to the case
   of agents) by
   formerly overloaded node then the reacting node that are impacted by the overload
   report.

   From a conceptual level, SHOULD slowly
   increase the logic at rate of traffic sent to the reacting node could be
   outlined as follows.  In this discussion assume overloaded node.

   It is suggested that the reacting node is also decrease the sending node.

   1.  An overload report amount of traffic
   given abatement treatment by 20% each second until the reduction is received
   completely removed and the associated overload state no traffic is saved by the reacting node.

   2.  A new Diameter request given abatement treatment.

      The goal of this behavior is generated by to reduce the application running on probability of overload
      condition thrashing where an immediate transition from 100%
      reduction to 0% reduction results in the reacting node.

   3.  The reacting reporting node determines that moving
      quickly back into an active overload report
       applies to condition.

6.  Attribute Value Pairs

   This section describes the request.

   4.  The reacting node determines if abatement should be applied to
       the request.  One approach that could be taken would be to select
       a random number between 1 encoding and 100.  If semantics of the random number is less
       than Diameter
   Overload Indication Attribute Value Pairs (AVPs) defined in this
   document.

   A new application specification can incorporate the indicated reduction percentage then overload control
   mechanism specified in this document by making it mandatory to
   implement for the request application and referencing this specification
   normatively.  It is given
       abatement treatment, otherwise the request is given normal
       routing treatment.

5.2.  Use responsibility of OC-Reduction-Percentage AVP

   A reporting node using the loss algorithm must use the OC-Reduction-
   Percentage AVP (Section 6.7 Diameter application
   designers to indicated the desired percentage of
   traffic reduction.)

      Editor's note: define how overload control mechanisms works on that
   application.

6.1.  OC-Supported-Features AVP

   The above duplicates what OC-Supported-Features AVP (AVP code TBD1) is type of Grouped and
   serves two purposes.  First, it announces a node's support for the
   DOIC solution in general.  Second, it contains the OC-Reduction-
      Percentage description of the
   supported DOIC features of the sending node.  The OC-Supported-
   Features AVP section can probably MUST be removed.

5.3.  Reporting Node Behavior (Normative)

   The method included in every Diameter request message a reporting nodes uses
   DOIC supporting node sends.

      OC-Supported-Features ::= < AVP Header: TBD1 >
                                [ OC-Feature-Vector ]
                              * [ AVP ]

   The OC-Feature-Vector sub-AVP is used to determine announce the amount of traffic
   reduction required to address an overload condition is an
   implementation decision.

   When a reporting node that has selected DOIC features
   supported by the loss abatement algorithm
   determines DOIC node, in the need to request form of a traffic reduction it must include an
   OC-OLR AVP in all response messages.

   The reporting node must indicate a percentage reduction flag bits field in which
   each bit announces one feature or capability supported by the OC-
   Reduction-Percentage AVP.

   The reporting node may change
   (see Section 6.2).  The absence of the reduction percentage in subsequent
   overload reports.  When doing so OC-Feature-Vector AVP
   indicates that only the reporting node must conform to
   overload report handing specified default traffic abatement algorithm described
   in Section 4.2.3. this specification is supported.

6.2.  OC-Feature-Vector AVP

   The OC-Feature-Vector AVP (AVP code TBD6) is type of Unsigned64 and
   contains a 64 bit flags field of announced capabilities of a DOIC
   node.  The value of zero (0) is reserved.

   The following capabilities are defined in this document:

   OLR_DEFAULT_ALGO (0x0000000000000001)

      When this flag is set by the reporting DOIC node determines it no longer needs a reduction in means that the default
      traffic abatement (loss) algorithm is supported.

6.3.  OC-OLR AVP

   The OC-OLR AVP (AVP code TBD2) is type of Grouped and contains the reporting node should send
   information necessary to convey an overload report indicating
   the on an overload report is no longer valid, as specified in
   Section 4.2.3.

5.4.  Reacting Node Behavior (Normative)
   condition at the reporting node.  The method a OC-OLR AVP does not explicitly
   contain all information needed by the reacting node uses to determine which decide whether
   a subsequent request messages
   are given abatement treatment is an implementation decision.

   When receiving an OC-OLR in an answer message where must undergo a throttling process with the algorithm
   indicated in
   received reduction percentage.  The value of the OC-Supported-Features OC-Report-Type AVP
   within the OC-OLR AVP indicates which implicit information is
   relevant for this decision (see Section 6.6).  The application the loss algorithm,
   OC-OLR AVP applies to is the
   reacting node must attempt to apply abatement treatment to same as the
   requested percentage of request messages sent.

      Note: Application-Id found in the loss algorithm
   Diameter message header.  The host or realm the OC-OLR AVP concerns
   is determined from the Origin-Host AVP and/or Origin-Realm AVP found
   in the encapsulating Diameter command.  The OC-OLR AVP is intended to
   be sent only by a stateless algorithm.  As reporting node.

      OC-OLR ::= < AVP Header: TBD2 >
                 < OC-Sequence-Number >
                 < OC-Report-Type >
                 [ OC-Reduction-Percentage ]
                 [ OC-Validity-Duration ]
               * [ AVP ]

   Note that if a result,
      the Diameter command were to contain multiple OC-OLR AVPs
   they all MUST have different OC-Report-Type AVP value.  OC-OLR AVPs
   with unknown values SHOULD be silently discarded by reacting node does not guarantee that there will nodes
   and the event SHOULD be an
      absolute reduction logged.

6.4.  OC-Sequence-Number AVP

   The OC-Sequence-Number AVP (AVP code TBD3) is type of Unsigned64.
   Its usage in traffic sent.  Rather, it guarantees that the requested percentage context of new requests will be given abatement
      treatment.

   If reacting node comes out overload control is described in
   Section 4.2.

   From the functionality point of view, the 100 percent traffic reduction OC-Sequence-Number AVP MUST
   be used as a
   result non-volatile increasing counter for a sequence of the
   overload report timing out, the following concerns are
   RECOMMENDED to be applied.  The reacting node sending the traffic
   should be conservative and, reports between two DOIC nodes for example, first send "probe" messages
   to learn the same overload condition of the overloaded node before
   converging
   occurrence.  The sequence number is only required to any traffic amount/rate decided by the sender.  Similar
   concerns apply in all cases when be unique
   between two DOIC nodes.  Sequence numbers are treated in a uni-
   directional manner, i.e. two sequence numbers on each direction
   between two DOIC nodes are not related or correlated.

6.5.  OC-Validity-Duration AVP

   The OC-Validity-Duration AVP (AVP code TBD4) is type of Unsigned32
   and indicates in milliseconds the overload report times out unless validity time of the previous overload report stated 0 percent reduction.

      Editor's note: Need to add additional guidance to slowly increase
      the rate
   report.  The number of traffic sent to avoid milliseconds is measured after reception of
   the first OC-OLR AVP with a sudden spike given value of OC-Sequence-Number AVP.
   The default value for the OC-Validity-Duration AVP is 5000 (i.e., 5
   seconds).  When the OC-Validity-Duration AVP is not present in traffic, the
   OC-OLR AVP, the default value applies.  Validity duration with values
   above 86400 (i.e.; 24 hours) MUST NOT be used.  Invalid duration
   values are treated as if the spike in traffic could OC-Validity-Duration AVP were not
   present and result in oscillation of the need for
      overload control.

   If the reacting node does not receive a default value being used.

   Editor's note: There is an OLR in messages sent open discussion on whether to have an
   upper limit on the formally overloaded node then the reacting node should slowly
   increase the rate OC-Validity-Duration value, beyond that which can
   be indicated by an Unsigned32.

   A timeout of traffic sent to the overloaded node.

   It is suggested overload report has specific concerns that need to
   be taken into account by the reacting DOIC node decrease acting on the amount earlier received
   overload report(s).  Section 6.7 discusses the impacts of timeout in
   the scope of the traffic
   given abatement treatment by 20% each second until the reduction is
   completely removed and no traffic is given abatement treatment. algorithms.

6.6.  OC-Report-Type AVP

   The goal of this behavior OC-Report-Type AVP (AVP code TBD5) is to reduce the probability type of Enumerated.  The
   value of overload
      condition thrashing where an immediate transition from 100%
      reduction to 0% reduction results in the reporting node moving
      quickly back into an overload condition.

6.  Attribute Value Pairs (Normative)

   This section AVP describes what the encoding and semantics overload report concerns.  The
   following values are initially defined:

   0  A host report.  The overload treatment should apply to requests
      for which all of the Diameter
   Overload Indication Attribute Value Pairs (AVPs) defined following conditions are true:

      Either the Destination-Host AVP is present in this
   document.

   When added to existing commands, both OC-Feature-Vector the request and OC-OLR
   AVPs SHOULD have its
      value matches the M-bit flag cleared to avoid backward
   compatibility issues.

   A new application specification can incorporate value of the overload control
   mechanism specified in this document by making it mandatory to
   implement for Origin-Host AVP of the application and referencing this specification
   normatively.  In such a case, received
      message that contained the OC-Feature-Vector and OC-OLR AVPs
   reused in newly defined Diameter applications SHOULD have AVP; or the M-bit
   flag set.  However, it Destination-Host is
      not present in the responsibility request but the value of the Diameter
   application designers peer identity
      associated with the connection used to define how overload control mechanisms works
   on that application.

6.1.  OC-Supported-Features AVP

   The OC-Supported-Features AVP (AVP code TBD1) is type of Grouped and
   serves for two purposes.  First, it announces a node's support for send the DOIC in general.  Second, it contains request matches
      the description value of the
   supported DOIC features Origin-Host AVP of the sending node. received message that
      contained the OC-OLR AVP.

      The OC-Supported-
   Features value of the Destination-Realm AVP MUST be included in every Diameter message a DOIC
   supporting node sends.

      OC-Supported-Features ::= < AVP Header: TBD1 >
                                [ OC-Feature-Vector ]
                              * [ the request matches the
      value of the Origin-Realm AVP ]

   The OC-Feature-Vector sub-AVP is used to announce of the DOIC features
   supported by received message that
      contained the OC-OLR AVP.

      The value of the endpoint, Application-ID in the form Diameter Header of a flag bits field in which
   each bit announces one feature or capability supported by the node
   (see Section 6.2).  The absence
      request matches the value of the OC-Feature-Vector AVP
   indicates Application-ID of the Diameter
      Header of the received message that only contained the default traffic abatement algorithm described
   in this specification is supported. OC-OLR AVP.

   1  A reacting node includes this AVP to indicate its capabilities realm report.  The overload treatment should apply to a
   reporting node.  For example, the endpoint (reacting node) may
   indicate requests
      for which (future defined) traffic abatement algorithms it
   supports in addition to all of the default.

   During following conditions are true:

      The Destination-Host AVP is absent in the message exchange requestand the overload control endpoints express
   their common set value of supported capabilities.  The reacting node
   includes
      the OC-Supported-Features AVP peer identity associated with the connection used to send the
      request does not match a server that announces what it
   supports. could serve the request.

      The reporting node that sends value of the answer also includes Destination-Realm AVP in the
   OC-Supported-Features request matches the
      value of the Origin-Realm AVP of the received message that describes
      contained the capabilities it
   supports. OC-OLR AVP.

      The set value of capabilities advertised by the reporting node
   depends on local policies.  At least one of Application-ID in the announced
   capabilities MUST match.  If there is no single matching capability
   the reacting node MUST act as if it does not implement DOIC and cease
   inserting any DOIC related AVPs into any Diameter messages with this
   specific reacting node.

      Editor's note: The last sentence conflicts with Header of the last sentence
      two paragraphs up.  In reality, there will always be at least one
      matching capability as all nodes supporting DOIC must support
      request matches the
      loss algorithm.  Suggest removing value of the last sentence.

6.2.  OC-Feature-Vector AVP Application-ID of the Diameter
      Header of the received message that contained the OC-OLR AVP.

   The OC-Feature-Vector OC-Report-Type AVP (AVP code TBD6) is type of Unsigned64 and
   contains envisioned to be useful for situations
   where a 64 bit flags field of announced capabilities of an reacting node needs to apply different overload control endpoint.  The value of zero (0) is reserved.

   The following capabilities are defined in this document:

   OLR_DEFAULT_ALGO (0x0000000000000001)

      When this flag is set treatments
   for different overload contexts.  For example, the reacting node(s)
   might need to throttle differently requests sent to a specific server
   (identified by the overload control endpoint it means
      that Destination-Host AVP in the default traffic abatement (loss) algorithm is supported.

6.3.  OC-OLR request) and requests
   that can be handled by any server in a realm.

6.7.  OC-Reduction-Percentage AVP

   The OC-OLR OC-Reduction-Percentage AVP (AVP code TBD2) TBD8) is type of Grouped Unsigned32
   and contains describes the
   necessary information percentage of the traffic that the sender is
   requested to convey an overload report. reduce, compared to what it otherwise would send.  The OC-OLR
   OC-Reduction-Percentage AVP
   does not explicitly contain all information needed by the reacting
   node applies to decide whether a subsequent request must undergo a throttling
   process with the received reduction percentage.  The value of the OC-
   Report-Type AVP within the OC-OLR AVP indicates which implicit
   information is relevant for default (loss) algorithm
   specified in this decision (see Section 6.6).  The
   application specification.  However, the OC-OLR AVP applies to is the same as the Application-
   Id found in can be reused for
   future abatement algorithms, if its semantics fit into the Diameter message header. new
   algorithm.

   The identity value of the OC-OLR Reduction-Percentage AVP
   concerns is determined from the Origin-Host AVP (and Origin-Realm AVP
   as well) found from the encapsulating Diameter command. between zero (0) and one
   hundred (100).  Values greater than 100 are ignored.  The OC-OLR
   AVP value of
   100 means that all traffic is intended to be sent only by a throttled, i.e. the reporting node.

      OC-OLR ::= < AVP Header: TBD2 >
                 < OC-Sequence-Number >
                 < OC-Report-Type >
                 [ OC-Reduction-Percentage ]
                 [ OC-Validity-Duration ]
               * [ AVP ]
   node is under a severe load and ceases to process any new messages.
   The OC-Validity-Duration AVP indicates the validity time value of 0 means that the
   overload report associated with reporting node is in a specific sequence number, measured
   after reception of the OC-OLR AVP.  The validity time MUST NOT be
   updated after reception of subsequent OC-OLR AVPs with stable state and
   has no need for the same
   sequence number. reacting node to apply any traffic abatement.
   The default value for of the OC-Validity-Duration OC-Reduction-Percentage AVP
   value is 5 (i.e., 5 seconds). 0.  When the OC-Validity-Duration
   OC-Reduction-Percentage AVP is not present in the OC-OLR AVP, overload report,
   the default value applies.

   Note that if a Diameter command were to contain multiple OC-OLR AVPs
   they all MUST have different OC-Report-Type

6.8.  Attribute Value Pair flag rules

                                                         +---------+
                                                         |AVP flag |
                                                         |rules    |
                                                         +----+----+
                              AVP value.  OC-OLR AVPs
   with unknown values SHOULD be silently discarded and   Section              |    |MUST|
       Attribute Name         Code  Defined  Value Type  |MUST| NOT|
      +--------------------------------------------------+----+----+
      |OC-Supported-Features  TBD1  x.x      Grouped     |    | V  |
      +--------------------------------------------------+----+----+
      |OC-OLR                 TBD2  x.x      Grouped     |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Sequence-Number     TBD3  x.x      Unsigned64  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Validity-Duration   TBD4  x.x      Unsigned32  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Report-Type         TBD5  x.x      Enumerated  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Reduction                                      |    |    |
      |  -Percentage          TBD8  x.x      Unsigned32  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Feature-Vector      TBD6  x.x      Unsigned64  |    | V  |
      +--------------------------------------------------+----+----+

   As described in the event SHOULD
   be logged.

      Editor's note: Need to specify what happens when two reports of Diameter base protocol [RFC6733], the same type are received.

6.4.  OC-Sequence-Number AVP

   The OC-Sequence-Number M-bit
   setting for a given AVP (AVP code TBD3) is type of Unsigned64.
   Its usage in relevant to an application and each
   command within that application that includes the context of AVP.

   The Diameter overload control is described in
   Section 4.2.

   From the functionality point of view, the OC-Sequence-Number AVP MUST AVPs SHOULD always be sent with the
   M-bit cleared when used as a non-volatile increasing counter between two overload
   control endpoints.  The sequence number is only required within existing Diameter applications to be unique
   between two overload control endpoints.  Sequence numbers are treated
   avoid backward compatibility issues.  Otherwise, when reused in a uni-directional manner, i.e. two sequence numbers on each
   direction between two endpoints are not newly
   defined Diameter applications, the DOC related or correlated. AVPs SHOULD have the
   M-bit set.

7.  Error Response Codes

   When generating sequence numbers, a DOIC node rejects a Diameter request due to overload, the new sequence number DOIC
   node MUST be
   greater than any sequence number in select an active overload report
   previously sent by the reporting node. appropriate error response code.  This property MUST hold over
   a reboot of the reporting node.

6.5.  OC-Validity-Duration AVP

   The OC-Validity-Duration AVP (AVP code TBD4)
   determination is type of Unsigned32
   and indicates in seconds made based on the validity time probability of the request
   succeeding if retried on a different path.

   A reporting node rejecting a Diameter request due to an overload report.
   The number of seconds is measured after reception of the first OC-OLR
   AVP with
   condition SHOULD send a given value of OC-Sequence-Number AVP.  The default value
   for DIAMETER-TOO-BUSY error response, if it can
   assume that the OC-Validity-Duration AVP is 5 (i.e., 5 seconds).  When same request may succeed on a different path.

   If a reporting node knows or assumes that the
   OC-Validity-Duration AVP is same request will not present in the OC-OLR AVP, the
   default value applies.  Validity duration with values above 86400
   (i.e.; 24 hours) MUST NOT
   succeed on a different path, DIAMETER_UNABLE_TO_COMPLY error response
   SHOULD be used.  Invalid duration values are
   treated as  Retrying would consume valuable resources during an
   occurrence of overload.

      For instance, if the OC-Validity-Duration AVP were not present and
   result in request arrived at the default value being used.

   A timeout of reporting node without
      a Destination-Host AVP then the overload report has specific concerns reporting node might determine
      that need to
   be taken into account by there is an alternative Diameter node that could successfully
      process the endpoint acting on request and that retrying the earlier received
   overload report(s).  Section 6.7 discusses transaction would not
      negatively impact the impacts of timeout reporting node.  DIAMETER_TOO_BUSY would be
      sent in this case.

      For instance, if the scope of request arrived at the traffic abatement algorithms.

   When a reporting node has recovered from overload, it SHOULD
   invalidate any existing overload reports in with a timely matter.  This
   can be achieved by sending an updated overload report (meaning the
   OLR contains a new sequence number)
      Destination-Host AVP populated with its own Diameter identity then
      the OC-Validity-Duration AVP
   value set to zero ("0").  If reporting node can assume that retrying the overload report is about request would
      result in it coming to expire
   naturally, the same reporting node MAY choose to simply let it do so. node.
      DIAMETER_UNABLE_TO_COMPLY would be sent in this case.

      A reacting node MUST invalidate and remove second example is when an overload report agent that
   expires without an explicit overload report containing an OC-
   Validity-Duration value set to zero ("0").

6.6.  OC-Report-Type AVP

   The OC-Report-Type AVP (AVP code TBD5) is type of Enumerated.  The
   value of supports the AVP describes what DOIC solution
      is performing the overload report concerns.  The
   following values are initially defined:

   0  A host report.  The overload treatment should apply to requests
      for which all role of the following conditions a reacting node for a non supporting
      client.  Requests that are true:

      Either rejected as a result of DOIC throttling
      by the Destination-Host agent in this scenario would generally be rejected with a
      DIAMETER_UNABLE_TO_COMPLY response code.

8.  IANA Considerations

8.1.  AVP is present codes

   New AVPs defined by this specification are listed in Section 6.  All
   AVP codes allocated from the request 'Authentication, Authorization, and its
      value matches the value of the Origin-Host
   Accounting (AAA) Parameters' AVP of Codes registry.

8.2.  New registries

   Two new registries are needed under the received
      message that contained 'Authentication,
   Authorization, and Accounting (AAA) Parameters' registry.

   Section 6.2 defines a new "Overload Control Feature Vector" registry
   including the OC-OLR AVP; or initial assignments.  New values can be added into the Destination-Host is
      not present in
   registry using the request but the value of peer identity
      associated with the connection used to send the request matches
      the value of the Origin-Host AVP of the received message that
      contained the OC-OLR AVP.

      The value of Specification Required policy [RFC5226].  See
   Section 6.2 for the Destination-Realm AVP initial assignment in the request matches the
      value of registry.

   Section 6.6 defines a new "Overload Report Type" registry with its
   initial assignments.  New types can be added using the Origin-Realm AVP of Specification
   Required policy [RFC5226].

9.  Security Considerations

   This mechanism gives Diameter nodes the received message ability to request that
      contained the OC-OLR AVP.

      The value of the Application-ID in the
   downstream nodes send fewer Diameter Header requests.  Nodes do this by
   exchanging overload reports that directly affect this reduction.
   This exchange is potentially subject to multiple methods of attack,
   and has the
      request matches the value of potential to be used as a Denial-of-Service (DoS) attack
   vector.

   Overload reports may contain information about the Application-ID topology and
   current status of the a Diameter
      Header network.  This information is
   potentially sensitive.  Network operators may wish to control
   disclosure of the received message that contained the OC-OLR AVP.

   1  A realm report.  The overload treatment should apply reports to requests unauthorized parties to avoid its
   use for which all of the following conditions are true: competitive intelligence or to target attacks.

   Diameter does not include features to provide end-to-end
   authentication, integrity protection, or confidentiality.  This may
   cause complications when sending overload reports between non-
   adjacent nodes.

9.1.  Potential Threat Modes

   The Destination-Host AVP is absent Diameter protocol involves transactions in the request.

      The value form of the Destination-Realm AVP in the request matches the
      value of the Origin-Realm AVP of the received message requests
   and answers exchanged between clients and servers.  These clients and
   servers may be peers, that
      contained the OC-OLR AVP.

      The value of the Application-ID in is,they may share a direct transport (e.g.
   TCP or SCTP) connection, or the messages may traverse one or more
   intermediaries, known as Diameter Header of the
      request matches the value Agents.  Diameter nodes use TLS,
   DTLS, or IPSec to authenticate peers, and to provide confidentiality
   and integrity protection of traffic between peers.  Nodes can make
   authorization decisions based on the Application-ID of peer identities authenticated at
   the transport layer.

   When agents are involved, this presents an effectively hop-by-hop
   trust model.  That is, a Diameter
      Header of the received message client or server can authorize an
   agent for certain actions, but it must trust that contained agent to make
   appropriate authorization decisions about its peers, and so on.

   Since confidentiality and integrity protection occurs at the OC-OLR AVP.

      Editor's note:
   transport layer.  Agents can read, and perhaps modify, any part of a
   Diameter message, including an overload report.

   There is still are several ways an open issue on attacker might attempt to exploit the definition of
      Realm reports and whether what
   overload control mechanism.  An unauthorized third party might inject
   an overload report types should be supported.
      There is consensus that host reports should be supported.  There into the network.  If this third party is discussion on Realm reports upstream
   of an agent, and Realm-Routed-Request reports.
      The above definition applies to Realm-Routed-Request reports where
      Realm reports are defined that agent fails to apply to all requests that match the
      realm, independent of proper authorization
   policies, downstream nodes may mistakenly trust the presence, absence or value of report.  This
   attack is at least partially mitigated by the
      Destination-Host AVP.

   The default value assumption that nodes
   include overload reports in Diameter answers but not in requests.
   This requires an attacker to have knowledge of the OC-Report-Type AVP is 0 (i.e. the host
   report).

   The OC-Report-Type AVP original request
   in order to construct a response.  Therefore, implementations SHOULD
   validate that an answer containing an overload report is envisioned a properly
   constructed response to be useful for situations
   where a reacting node needs pending request prior to apply different acting on the
   overload treatments
   for different "types" of overload. report.

   A similar attack involves an otherwise authorized Diameter node that
   sends an inappropriate overload report.  For example, the reacting node(s)
   might need to throttle differently requests sent to a specific server
   (identified by the Destination-Host AVP in for
   the request) and requests realm "example.com" might send an overload report indicating that can be handled by any server in
   a realm.  The example in
   Appendix B.1 illustrates this usage.

6.7.  OC-Reduction-Percentage AVP

   The OC-Reduction-Percentage AVP (AVP code TBD8) competitor's realm "example.net" is type of Unsigned32
   and describes the percentage of overloaded.  If other nodes act
   on the traffic report, they may falsely believe that the sender "example.net" is
   requested to reduce, compared to what it otherwise would send.  The
   OC-Reduction-Percentage AVP applies to
   overloaded, effectively reducing that realm's capacity.  Therefore,
   it's critical that nodes validate that an overload report received
   from a peer actually falls within that peer's responsibility before
   acting on the default (loss) algorithm
   specified in this specification.  However, report or forwarding the AVP can be reused for
   future abatement algorithms, if its semantics fit into the new
   algorithm.

   The value of the Reduction-Percentage AVP is between zero (0) and one
   hundred (100).  Values greater than 100 are ignored.  The value of
   100 means that all traffic is report to be throttled, i.e. the reporting
   node is under other peers.  For
   example, an overload report from a severe load and ceases peer that applies to process any new messages.
   The value of 0 means a realm not
   handled by that the reporting node peer is suspect.

   An attacker might use the information in an overload report to assist
   in certain attacks.  For example, an attacker could use information
   about current overload conditions to time a stable state and
   has no need DoS attack for maximum
   effect, or use subsequent overload reports as a feedback mechanism to
   learn the other endpoint results of a previous or ongoing attack.

9.2.  Denial of Service Attacks

   Diameter overload reports can cause a node to apply any traffic abatement.
   The default value cease sending some or
   all Diameter requests for an extended period.  This makes them a
   tempting vector for DoS tacks.  Furthermore, since Diameter is almost
   always used in support of the OC-Reduction-Percentage AVP other protocols, a DoS attack on Diameter
   is 0. likely to impact those protocols as well.  Therefore, Diameter
   nodes MUST NOT honor or forward overload reports from unauthorized or
   otherwise untrusted sources.

9.3.  Non-Compliant Nodes

   When the
   OC-Reduction-Percentage AVP is not present in the a Diameter node sends an overload report,
   the default value applies.

6.8.  Attribute Value Pair flag rules
                                                         +---------+
                                                         |AVP flag |
                                                         |rules    |
                                                         +----+----+
                              AVP   Section              |    |MUST|
       Attribute Name         Code  Defined  Value Type  |MUST| NOT|
      +--------------------------------------------------+----+----+
      |OC-Supported-Features  TBD1  x.x      Grouped     |    | V  |
      +--------------------------------------------------+----+----+
      |OC-OLR                 TBD2  x.x      Grouped     |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Sequence-Number     TBD3  x.x      Unsigned64  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Validity-Duration   TBD4  x.x      Unsigned32  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Report-Type         TBD5  x.x      Enumerated  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Reduction                                      |    |    |
      |  -Percentage          TBD8  x.x      Unsigned32  |    | V  |
      +--------------------------------------------------+----+----+
      |OC-Feature-Vector      TBD6  x.x      Unsigned64  |    | V  |
      +--------------------------------------------------+----+----+

   As described it cannot assume that
   all nodes will comply.  A non-compliant node might continue to send
   requests with no reduction in load.  Requirement 28 [RFC7068]
   indicates that the overload control solution cannot assume that all
   Diameter base protocol [RFC6733], the M-bit
   setting for nodes in a given AVP is relevant to an application network are necessarily trusted, and each
   command within that application that includes
   malicious nodes not be allowed to take advantage of the AVP.

   The Diameter overload
   control AVPs SHOULD always be sent with the
   M-bit cleared when used within existing Diameter applications mechanism to
   avoid backward compatibility issues.  Otherwise, when reused in newly
   defined Diameter applications, the DOC related AVPs SHOULD have get more than their fair share of service.

   In the
   M-bit set.

7.  Error Response Codes

   Editor's note: This section depends on resolution absence of issue #27.

8.  IANA Considerations

8.1.  AVP codes

   New AVPs defined by this specification are listed in Section 6.  All
   AVP codes allocated an overload control mechanism, Diameter nodes need
   to implement strategies to protect themselves from the 'Authentication, Authorization, floods of
   requests, and
   Accounting (AAA) Parameters' AVP Codes registry.

8.2.  New registries

   Three new registries are needed under the 'Authentication,
   Authorization, and Accounting (AAA) Parameters' registry.

   Section 6.2 defines to make sure that a new "Overload Control Feature Vector" registry
   including the initial assignments.  New values disproportionate load from one
   source does not prevent other sources from receiving service.  For
   example, a Diameter server might reject a certain percentage of
   requests from sources that exceed certain limits.  Overload control
   can be added into the
   registry using the Specification Required policy [RFC5226].  See
   Section 6.2 thought of as an optimization for such strategies, where
   downstream nodes never send the initial assignment excess requests in the registry.

   Section 6.6 defines a new "Overload Report Type" registry with its
   initial assignments.  New types can be added using first place.
   However, the Specification
   Required policy [RFC5226].

9.  Security Considerations

   This presence of an overload control mechanism gives Diameter nodes does not
   remove the ability need for these other protection strategies.

9.4.  End-to End-Security Issues

   The lack of end-to-end security features makes it far more difficult
   to request that
   downstream nodes send fewer Diameter requests.  Nodes do this by
   exchanging establish trust in overload reports that directly affect this reduction.
   This exchange is potentially subject to multiple methods of attack,
   and has originate from non-
   adjacent nodes.  Any agents in the potential to be used as a Denial-of-Service (DoS) attack
   vector.

   Overload reports message path may contain information about the topology insert or modify
   overload reports.  Nodes must trust that their adjacent peers perform
   proper checks on overload reports from their peers, and
   current status of so on,
   creating a Diameter network.  This information is
   potentially sensitive. transitive-trust requirement extending for potentially
   long chains of nodes.  Network operators may wish to control
   disclosure of must determine if this
   transitive trust requirement is acceptable for their deployments.
   Nodes supporting Diameter overload reports to unauthorized parties control MUST give operators the
   ability to avoid its
   use for competitive intelligence or select which peers are trusted to target attacks.

   Diameter does not include features deliver overload
   reports, and whether they are trusted to provide end-to-end
   authentication, integrity protection, or confidentiality.  This may
   cause complications when sending forward overload reports between non-
   adjacent
   from non-adjacent nodes.

9.1.  Potential Threat Modes

   The lack of end-to-end confidentiality protection means that any
   Diameter protocol involves transactions agent in the form path of an overload report can view the
   contents of requests
   and answers exchanged between clients and servers.  These clients and
   servers may be peers, that is,they may share a direct transport (e.g.
   TCP or SCTP) connection, or report.  In addition to the messages may traverse one or more
   intermediaries, known as Diameter Agents.  Diameter nodes use TLS,
   DTLS, or IPSec requirement to authenticate peers, and select
   which peers are trusted to provide confidentiality
   and integrity protection of traffic between peers.  Nodes can make
   authorization decisions based on the peer identities authenticated at
   the transport layer.

   When agents send overload reports, operators MUST be
   able to select which peers are involved, this presents authorized to receive reports.  A node
   MUST not send an effectively hop-by-hop
   trust model.  That is, overload report to a Diameter client or server can authorize peer not authorized to receive
   it.  Furthermore, an agent for certain actions, but it must trust MUST remove any overload reports that agent to make
   appropriate authorization decisions about its peers, and so on.

   Since confidentiality and integrity protection occurs at the
   transport layer.  Agents can read, and perhaps modify, any part of
   might have been inserted by other nodes before forwarding a Diameter message, including an overload report.

   There are several ways an attacker might attempt
   message to exploit the
   overload control mechanism.  An unauthorized third party might inject
   an overload report into the network.  If this third party is upstream
   of an agent, and a peer that agent fails to apply proper authorization
   policies, downstream nodes may mistakenly trust the report.  This
   attack is at least partially mitigated by the assumption that nodes
   include overload reports in Diameter answers but not in requests.
   This requires an attacker authorized to have knowledge receive overload reports.

   At the time of this writing, the original request
   in order to construct a response.  Therefore, implementations SHOULD
   validate that an answer containing an overload report DIME working group is a properly
   constructed response studying
   requirements for adding end-to-end security
   [I-D.ietf-dime-e2e-sec-req] features to a pending request prior Diameter.  These features,
   when they become available, might make it easier to acting on the establish trust
   in non-adjacent nodes for overload report.

   A similar attack involves an otherwise authorized Diameter node control purposes.  Readers should
   be reminded, however, that
   sends an inappropriate overload report.  For example, a server for the realm "example.com" might send an overload report indicating control mechanism encourages
   Diameter agents to modify AVPs in, or insert additional AVPs into,
   existing messages that
   a competitor's realm "example.net" is overloaded.  If are originated by other nodes act
   on the report, they may falsely believe that "example.net" nodes.  If end-to-end
   security is enabled, there is
   overloaded, effectively reducing that realm's capacity.  Therefore,
   it's critical that nodes validate that an overload report received
   from a peer actually falls within that peer's responsibility before
   acting on the report or forwarding the report to other peers.  For
   example, an overload report from an peer that applies to a realm not
   handled by risk that peer is suspect.

   An attacker might use the information in an overload report to assist
   in certain attacks.  For example, an attacker such modification could use information
   about current
   violate integrity protection.  The details of using any future
   Diameter end-to-end security mechanism with overload conditions control will
   require careful consideration, and are beyond the scope of this
   document.

10.  Contributors

   The following people contributed substantial ideas, feedback, and
   discussion to time a DoS attack this document:

   o  Eric McMurry

   o  Hannes Tschofenig

   o  Ulrich Wiehe

   o  Jean-Jacques Trottin

   o  Maria Cruz Bartolome

   o  Martin Dolly

   o  Nirav Salot

   o  Susan Shishufeng

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for maximum
   effect, or use subsequent overload reports as a feedback mechanism to
   learn the results of a previous or ongoing attack.

9.2.  Denial of Service Attacks

   Diameter overload reports can cause a node in RFCs to cease sending some or
   all Diameter requests Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an extended period.  This makes them a
   tempting vector for DoS tacks.  Furthermore, since Diameter is almost
   always used
              IANA Considerations Section in support of other protocols, a DoS attack RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
              Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, June 2010.

   [RFC6733]  Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
              "Diameter Base Protocol", RFC 6733, October 2012.

11.2.  Informative References

   [Cx]       3GPP, , "ETSI TS 129 229 V11.4.0", August 2013.

   [I-D.ietf-dime-e2e-sec-req]
              Tschofenig, H., Korhonen, J., Zorn, G., and K. Pillay,
              "Diameter AVP Level Security: Scenarios and Requirements",
              draft-ietf-dime-e2e-sec-req-00 (work in progress),
              September 2013.

   [PCC]      3GPP, , "ETSI TS 123 203 V11.12.0", December 2013.

   [RFC4006]  Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
              Loughney, "Diameter Credit-Control Application", RFC 4006,
              August 2005.

   [RFC5729]  Korhonen, J., Jones, M., Morand, L., and T. Tsou,
              "Clarifications on the Routing of Diameter
   is likely to impact those protocols as well.  Therefore, Diameter
   nodes MUST NOT honor or forward overload reports from unauthorized or
   otherwise untrusted sources.

9.3.  Non-Compliant Nodes

   When a Diameter node sends an overload report, it cannot assume that
   all nodes will comply.  A non-compliant node might continue to send
   requests with no reduction in load.  Requirement 28 Requests Based
              on the Username and the Realm", RFC 5729, December 2009.

   [RFC7068]
   indicates that  McMurry, E. and B. Campbell, "Diameter Overload Control
              Requirements", RFC 7068, November 2013.

   [S13]      3GPP, , "ETSI TS 129 272 V11.9.0", December 2012.

Appendix A.  Issues left for future specifications

   The base solution for the overload control solution cannot assume that all
   Diameter nodes in a network are necessarily trusted, and that
   malicious nodes does not be allowed to take advantage cover all
   possible use cases.  A number of solution aspects were intentionally
   left for future specification and protocol work.

A.1.  Additional traffic abatement algorithms

   This specification describes only means for a simple loss based
   algorithm.  Future algorithms can be added using the overload
   control mechanism designed
   solution extension mechanism.  The new algorithms need to get more than their fair share of service.

   In be
   registered with IANA.  See Sections 6.1 and 8 for the absence of an overload control mechanism, required IANA
   steps.

A.2.  Agent Overload

   This specification focuses on Diameter nodes need
   to implement strategies endpoint (server or client)
   overload.  A separate extension will be required to protect themselves from floods outline the
   handling of
   requests, and the case of agent overload.

A.3.  New Error Diagnostic AVP

   The proposal was made to make sure that a disproportionate load from one
   source does not prevent other sources from receiving service.  For
   example, a Diameter server might reject add a certain percentage of
   requests from sources that exceed certain limits.  Overload control
   can new Error Diagnostic AVP to supplement
   the error responces to be thought of as an optimization able to indicate that overload was the
   reason for such strategies, where
   downstream nodes never send the excess rejection of the message.

Appendix B.  Deployment Considerations

   Non supporting agents

      Due to the way that realm-routed requests are handled in Diameter
      networks, with the first place.
   However, server selection for the presence of request done by an overload control mechanism does not
   remove the need for these other protection strategies.

9.4.  End-to End-Security Issues

   The lack of end-to-end security features makes
      agent, it far more difficult
   to establish trust in overload reports is recommended that originate from non-
   adjacent nodes.  Any deployments enable all agents that
      do server selection to support the DOIC solution prior to enabling
      the DOIC solution in the message path may insert or modify
   overload reports.  Nodes must trust Diameter network.

   Topology hiding interactions

      There exist proxies that their adjacent peers perform
   proper checks on overload reports from their peers, and so on,
   creating a transitive-trust requirement extending for potentially
   long chains of nodes.  Network operators must determine if this
   transitive trust requirement implement what is acceptable for their deployments.
   Nodes supporting Diameter overload control MUST give operators the
   ability to select which peers are trusted to deliver overload
   reports, and whether they are trusted referred to forward overload reports
   from non-adjacent nodes.

   The lack of end-to-end confidentiality protection means that any
   Diameter as Topology
      Hiding.  This can include cases where the agent modifies the
      Origin-Host in answer messages.  The behavior of the path DOIC solution
      is not well understood when this happens.  As such, the DOIC
      solution does not address this scenario.

Appendix C.  Requirements Conformance Analysis

   This section contains the result of an overload report can view the
   contents analysis of that report.  In addition to the requirement to select
   which peers are trusted DOIC solutions
   conformance to send overload reports, operators MUST the requirements defined in [RFC7068].

   To be
   able to select which peers are authorized to receive reports.  A node
   MUST not send an overload report completed.

Appendix D.  Considerations for Applications Integrating the DOIC
             Solution

   This section outlines considerations to be taken into account when
   integrating the DOIC solution into Diameter applications.

D.1.  Application Classification

   The following is a peer not authorized classification of Diameter applications and
   request types.  This discussion is meant to receive
   it.  Furthermore, an agent MUST remove any overload reports document factors that
   might have been inserted
   play into decisions made by other nodes before forwarding a the Diameter
   message to a peer that is not authorized to receive identity responsible for
   handling overload reports.

   At

   Section 8.1 of [RFC6733] defines two state machines that imply two
   types of applications, session-less and session-based applications.
   The primary difference between these types of applications is the time
   lifetime of this writing, Session-Ids.

   For session-based applications, the DIME working group Session-Id is studying
   requirements for adding end-to-end security

   [I-D.ietf-dime-e2e-sec-req] features to Diameter.  These features,
   when they become available, might make it easier used to establish trust tie
   multiple requests into a single session.

   The Credit-Control application defined in non-adjacent nodes for overload control purposes.  Readers should
   be reminded, however, that the overload control mechanism encourages [RFC4006] is an example of
   a Diameter agents to modify AVPs in, or insert additional AVPs into,
   existing messages that are originated by other nodes.  If end-to-end
   security session-based application.

   In session-less applications, the lifetime of the Session-Id is enabled, there a
   single Diameter transaction, i.e. the session is implicitly
   terminated after a risk that such modification could
   violate integrity protection.  The details of using any future single Diameter end-to-end security mechanism with overload control will
   require careful consideration, transaction and are beyond a new Session-Id
   is generated for each Diameter request.

   For the scope purposes of this
   document.

10.  Contributors

   The following people contributed substantial ideas, feedback, and
   discussion discussion, session-less applications are
   further divided into two types of applications:

   Stateless applications:

      Requests within a stateless application have no relationship to this document:

   o  Eric McMurry

   o  Hannes Tschofenig

   o  Ulrich Wiehe

   o  Jean-Jacques Trottin

   o  Maria Cruz Bartolome

   o  Martin Dolly

   o  Nirav Salot

   o  Susan Shishufeng

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing
      each other.  The 3GPP defined S13 application is an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
              Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, June 2010.

   [RFC6733]  Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
              "Diameter Base Protocol", RFC 6733, October 2012.

11.2.  Informative References

   [Cx]       3GPP, , "ETSI TS 129 229 V11.4.0", August 2013.

   [I-D.ietf-dime-e2e-sec-req]
              Tschofenig, H., Korhonen, J., Zorn, G., and K. Pillay,
              "Diameter AVP Level Security: Scenarios and Requirements",
              draft-ietf-dime-e2e-sec-req-00 (work in progress),
              September 2013.

   [PCC]      3GPP, , "ETSI TS 123 203 V11.12.0", December 2013.

   [RFC4006]  Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., example of a
      stateless application [S13], where only a Diameter command is
      defined between a client and J.
              Loughney, "Diameter Credit-Control Application", RFC 4006,
              August 2005.

   [RFC5729]  Korhonen, J., Jones, M., Morand, L., a server and T. Tsou,
              "Clarifications no state is maintained
      between two consecutive transactions.

   Pseudo-session applications:

      Applications that do not rely on the Routing Session-Id AVP for
      correlation of Diameter Requests Based
              on application messages related to the Username and same session
      but use other session-related information in the Realm", RFC 5729, December 2009.

   [RFC7068]  McMurry, E. and B. Campbell, "Diameter Overload Control
              Requirements", RFC 7068, November 2013.

   [S13]      3GPP, , "ETSI TS 129 272 V11.9.0", December 2012.

Appendix A.  Issues left Diameter requests
      for future specifications this purpose.  The base solution for the overload control does not cover all
   possible use cases.  A number 3GPP defined Cx application [Cx] is an
      example of solution aspects were intentionally
   left for future specification and protocol work.

A.1.  Additional traffic abatement algorithms

   This specification describes only means for a simple loss based
   algorithm.  Future algorithms can be added using the designed
   solution extension mechanism. pseudo-session application.

   The new algorithms need to be
   registered with IANA.  See Sections 6.1 and 8 for handling of overload reports must take the required IANA
   steps.

A.2.  Agent type of application
   into consideration, as discussed in Appendix D.2.

D.2.  Application Type Overload Implications

   This specification section discusses considerations for mitigating overload
   reported by a Diameter entity.  This discussion focuses on Diameter endpoint (server or client)
   overload.  A separate extension will be required to outline the
   handling the case of agent overload.

A.3.  DIAMETER_TOO_BUSY clarifications

   The current [RFC6733] behavior in a case type
   of DIAMETER_TOO_BUSY is
   somewhat under specified.  For example, there is no information how
   long application.  Appendix D.3 discusses considerations for handling
   various request types when the specific Diameter node target server is willing known to be unavailable.  A
   specification updating [RFC6733] should clarify in an
   overloaded state.

   These discussions assume that the handling of
   DIAMETER_TOO_BUSY from strategy for mitigating the error answer initiating Diameter node
   point of view and from
   reported overload is to reduce the original request initiating Diameter node
   point of view.  Further, overall workload sent to the inclusion
   overloaded entity.  The concept of possible additional
   information providing AVPs should be discussed and possible be
   recommended applying overload treatment to be used.

Appendix B.  Examples

B.1.  Mix of Destination-Realm routed
   requests and Destination-Host
      routed targeted for an overloaded Diameter entity is inherent to
   this discussion.  The method used to reduce offered load is not
   specified here but could include routing requests to another Diameter allows a client
   entity known to optionally select the destination server
   of be able to handle them, or it could mean rejecting
   certain requests.  For a request, even if there are agents between Diameter agent, rejecting requests will
   usually mean generating appropriate Diameter error responses.  For a
   Diameter client, rejecting requests will depend upon the client and application.
   For example, it could mean giving an indication to the
   server.  The client does this using entity
   requesting the Destination-Host AVP.  In
   cases where Diameter service that the client does not care if network is busy and to try
   again later.

   Stateless applications:

      By definition there is no relationship between individual requests
      in a specific server receives stateless application.  As a result, when a request is sent
      or relayed to an overloaded Diameter entity - either a Diameter
      Server or a Diameter Agent - the request, it sending or relaying entity can omit Destination-Host and route
      choose to apply the overload treatment to any request using targeted for
      the Destination-Realm and Application Id, effectively letting overloaded entity.

   Pseudo-session applications:

      For pseudo-session applications, there is an
   agent select the server.

   Clients commonly send mixtures implied ordering of Destination-Host and Destination-
   Realm routed
      requests.  For example, in an application that uses user
   sessions,  As a client typically won't care result, decisions about which server handles a
   session-initiating requests.  But once the session is initiated, the
   client will send all subsequent requests in that session towards an
      overloaded entity to reject could take the same
   server.  Therefore it would send command code of the initial
      request with no
   Destination-Host AVP.  If it receives a successful answer, the client
   would copy the Origin-Host value from the answer message into a
   Destination-Host AVP consideration.  This generally means that
      transactions later in each subsequent request the sequence of transactions should be given
      more favorable treatment than messages earlier in the session.

   An agent sequence.
      This is because more work has very limited options in applying overload abatement to
   requests that contain Destination-Host AVPs.  It typically cannot
   route already been done by the request to a different server than Diameter
      network for those transactions that occur later in the one identified sequence.
      Rejecting them could result in
   Destination-Host.  It's only remaining options are to throttle such
   requests locally, or to send an overload report back towards increasing the
   client so load on the client can throttle network
      as the requests.  The second choice is
   usually more efficient, since it prevents any throttled requests from
   being sent transactions earlier in the first place, and removes the agent's sequence might also need to send
   errors back to the client for each dropped request.

   On the other hand, an agent has much more leeway to apply overload
   abatement for requests that do not contain Destination-Host AVPs.  If
   the agent has multiple servers in its peer table be
      repeated.

   Session-based applications:

      Overload handling for session-based applications must take into
      consideration the given realm work load associated with setting up and application, it can route such
      maintaining a session.  As such, the entity sending requests to other, less
      towards an overloaded
   servers.

   If the overload severity increases, the agent may reach Diameter entity for a point where
   there is not sufficient capacity across all servers session-based
      application might tend to handle even
   realm-routed reject new session requests prior to
      rejecting intra-session requests.  In this case, the realm itself can addition, session ending
      requests might be
   considered overloaded.  The agent may need given a lower probability of being rejected as
      rejecting session ending requests could result in session status
      being out of sync between the client Diameter clients and servers.
      Application designers that would decide to throttle
   realm-routed reject mid-session
      requests in addition will need to Destination-Host routed
   requests.  The overload severity may be different for each server,
   and consider whether the severity for rejection invalidates
      the realm at session and any resulting session clean-up procedures.

D.3.  Request Transaction Classification

   Independent Request:

      An independent request is likely not correlated to be different than for any specific server.  Therefore, an agent may need to forward, or
   originate, multiple overload reports with differing ReportType and
   Reduction-Percentage values.

   Figure 8 illustrates such a mixed-routing scenario.  In this example,
   the servers S1, S2, and S3 handle other requests for
      and, as such, the realm "realm".
   Any lifetime of the three can handle requests session-id is constrained to an
      individual transaction.

   Session-Initiating Request:

      A session-initiating request is the initial message that are not part
      establishes a Diameter session.  The ACR message defined in
      [RFC6733] is an example of a user
   session (i.e. routed session-initiating request.

   Correlated Session-Initiating Request:

      There are cases when multiple session-initiated requests must be
      correlated and managed by Destination-Realm).  But once a session the same Diameter server.  It is
   established, all requests notably
      the case in that session the 3GPP PCC architecture [PCC], where multiple
      apparently independent Diameter application sessions are actually
      correlated and must go to be handled by the same Diameter server.

        Client     Agent      S1        S2        S3
           |         |         |         |         |
           |(1) Request (DR:realm)       |         |
           |-------->|         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |Agent selects S1   |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |(2) Request (DR:realm)       |
           |         |-------->|         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |S1 overloaded, returns OLR
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |(3) Answer (OR:realm,OH:S1,OLR:RT=DH)
           |         |<--------|         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |sees OLR,routes DR traffic to S2&S3
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |(4) Answer (OR:realm,OH:S1, OLR:RT=DH) |
           |<--------|         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |Client throttles requests with DH:S1   |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |(5) Request (DR:realm)       |         |
           |-------->|         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |Agent selects S2   |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |(6) Request (DR:realm)       |
           |         |------------------>|         |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |S2 is overloaded...
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |(7) Answer (OH:S2, OLR:RT=DH)|
           |         |<------------------|         |
           |         |         |         |         |
           |         |         |         |         |
           |         |Agent sees OLR, realm now overloaded
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |(8) Answer (OR:realm,OH:S2, OLR:RT=DH, OLR: RT=R)
           |<--------|         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |Client throttles DH:S1, DH:S2, and DR:realm
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |
           |         |         |         |         |

      Figure 8: Mix of Destination-Host and Destination-Realm Routed
                                 Requests

   1.  The client sends a request with no Destination-Host AVP (that is,
       a Destination-Realm routed request.)

   2.  The agent follows local policy to select a server from its peer
       table.  In this case, the agent selects S2 and forwards the
       request.

   3.  S1 is overloaded.  It sends a answer indicating success, but also
       includes an overload report.  Since the overload report only
       applies to S1, the ReportType is "Destination-Host".

   4.  The agent sees the overload report, and records that S1 is
       overloaded by the value in the Reduction-Percentage AVP.  It
       begins diverting the indicated percentage of realm-routed traffic
       from S1 to S2 and S3.  Since it can't divert Destination-Host
       routed traffic, it forwards the overload report to the client.
       This effectively delegates the throttling of traffic with
       Destination-Host:S1 to the client.

   5.  The client sends another Destination-Realm routed request.

   6.  The agent selects S2, and forwards the request.

   7.  It turns out that S2 is also overloaded, perhaps due to all that
       traffic it took over for S1.  S2 returns an successful answer
       containing an overload report.  Since this report only applies to
       S2, the ReportType is "Destination-Host".

   8.  The agent sees that S2 is also overloaded by the value in
       Reduction-Percentage.  This value

   Intra-Session Request:

      An intra session request is probably different than the
       value from S1's report.  The agent diverts the remaining traffic
       to S3 as best as it can, but it calculates a request that uses the remaining
       capacity across all three servers is no longer sufficient to
       handle all of the realm-routed traffic.  This means the realm
       itself is overloaded.  The realm's overload percentage is most
       likely different same Session-
      Id than that for either S1 or S2.  The agent
       forward's S2's report back to the client one used in the Diameter answer.
       Additionally, the agent generates a new report for previous request.  An intra session
      request generally needs to be delivered to the realm of
       "realm", and inserts server that report into the answer.  The client
       throttles requests with Destination-Host:S1 at one rate, requests
       with Destination-Host:S2 at another rate, and requests with no
       Destination-Host AVP at yet a third rate.  (Since S3 has not
       indicated overload, the client does not throttle requests with
       Destination-Host:S3.)

Appendix C.  Restructuring of -02 version of the draft

   This section captures the initial plan for restructuring the DOIC
   specification from the -02 version to handled
      the new -03 version.

   1. Introduction (non normative)
      -- Existing Text from section 1. --
   2. Terminology and Abbreviations (non normative)
      -- Existing Text from section 2. --
   3. Solution Overview (Non normative)
      -- Existing text from section 3. --
     3.1 Overload Control Endpoints (Non normative)
         -- New text leveraging text from existing section 5.1 --
     3.2 Piggybacking Principle (Non normative)
         -- Existing text from existing section 5.2, with enhancements --
     3.3 DOIC Capability Discovery (Non normative)
         -- New text leveraging text from existing section 5.3 --
     3.4 DOIC Overload Condition Reporting (Non normative)
         -- New text --
     3.5 DOIC Extensibility (Non normative)
         -- New text leveraging text from existing Section 5.4 --
     3.5 Simplified Example Architecture (Non normative)
         -- Existing text from section 3.1.6, with enhancements --
     3.6 Considerations session creating request for Applications Integrating the DOIC Solution (Non normative)
         -- New text --
       3.6.1. Application Classification  (Non normative)
              -- Existing text from section 3.1.1 --
       3.6.2. Application Type Overload Implications  (Non normative)
              -- Existing text from section 3.1.2 --
       3.6.3. Request Transaction Classification  (Non normative)
              -- Existing text from section 3.1.3 --
       3.6.4. session.  The STR message
      defined in [RFC6733] is an example of an intra-session requests.

   Pseudo-Session Requests:

      Pseudo-session requests are independent requests and do not use
      the same Session-Id but are correlated by other session-related
      information contained in the request.  There exists Diameter
      applications that define an expected ordering of transactions.
      This sequencing of independent transactions results in a pseudo
      session.  The AIR, MAR and SAR requests in the 3GPP defined Cx
      [Cx] application are examples of pseudo-session requests.

D.4.  Request Type Overload Implications  (Non normative)
              -- Existing text from section 3.1.4 --
   4. Solution Procedures (Normative)
     4.1 Capability Announcement (Normative)
        -- Existing text from section 5.3 --
       4.1.1. Reacting Node Behavior (Normative)
            -- Existing text from section 5.3.1 --
       4.1.2. Reporting Node Behavior  (Normative)
            -- Existing text from section 5.3.2 --
       4.1.3. Agent Behavior  (Normative)
            -- Existing text from section 5.3.3 --
     4.2. Overload Report Processing (Normative)
       4.2.1. Overload Control State (Normative)
            -- Existing text from section 5.5.1 --
       4.2.2. Reacting Node Behavior  (Normative)
            -- Existing text from section 5.5.2 --
       4.2.3. Reporting Node Behavior  (Normative)
            -- Existing text from section 5.5.3 --
       4.2.4. Agent Behavior  (Normative)
            -- Existing text from section 5.5.4 --
     4.3. Protocol Extensibility (Normative)
        -- Existing text from section 5.4 --
   5. Loss Algorithm (Normative)
      -- New text pulling from information spread through

   The request classes identified in Appendix D.3 have implications on
   decisions about which requests should be throttled first.  The
   following list of request treatment regarding throttling is provided
   as guidelines for application designers when implementing the
   Diameter overload control mechanism described in this document.  The
   exact behavior regarding throttling is a matter of local policy,
   unless specifically defined for the document --
     5.1. Overview (Non normative)
          -- New text pulling from information spread through application.

   Independent requests:

      Independent requests can generally be given equal treatment when
      making throttling decisions, unless otherwise indicated by
      application requirements or local policy.

   Session-initiating requests:

      Session-initiating requests often represent more work than
      independent or intra-session requests.  Moreover, session-
      initiating requests are typically followed by other session-
      related requests.  Since the document --
     5.2. Reporting Node Behavior (Normative)
          -- New text pulling from information spread through main objective of the document --
     5.3. Reacting Node Behavior (Normative)
          -- New text pulling from information spread through overload
      control is to reduce the document --
   6. Attribute Value Pairs (Normative)
      -- Existing text from section 4. --
     6.1. OC-Supported-Features AVP
          -- Existing text from section 4.1 --
     6.2. OC-Feature-Vector AVP
          -- Existing text from section 4.2 --
     6.3. OC-OLR AVP
          -- Existing text from section 4.3 --
     6.4. OC-Sequence-Number AVP
          -- Existing text from section 4.4 --
     6.5. OC-Validity-Duration AVP
          -- Existing text from section 4.5 --
     6.6. OC-Report-Type AVP
          -- Existing text from section 4.6 --
     6.7. OC-Reduction-Percentage AVP
          -- Existing text from section 4.7 --
     6.8. Attribute Value Pair flag rules
          -- Existing text from section 4.8 --
   7. Error Response Codes
          -- New text based on resolution total number of issue --
   8. IANA Considerations
      -- Existing text from section 7. --
     8.1. AVP codes
          -- Existing text from section 7.1 --
     8.2. New registries
          -- Existing text from section 7.2 --
   9. Security Considerations
       -- Existing text from section 8. --
     9.1. Potential Threat Modes
           -- Existing text from section 8.1 --
     9.2. Denial requests sent to the
      overloaded entity, throttling decisions might favor allowing
      intra-session requests over session-initiating requests.  In the
      absence of local policies or application specific requirements to
      the contrary, Individual session-initiating requests can be given
      equal treatment when making throttling decisions.

   Correlated session-initiating requests:

      A Request that results in a new binding, where the binding is used
      for routing of Service Attacks
           -- Existing text from section 8.2 --
     9.3. Non-Compliant Nodes
           -- Existing text from section 8.3 --
     9.4. End-to End-Security Issues
           -- Existing text from section 8.4 --
   10. Contributors
   11. References
     11.1. Normative References
     11.2. Informative References
   Appendix A. Issues left subsequent session-initiating requests to the same
      server, represents more work load than other requests.  As such,
      these requests might be throttled more frequently than other
      request types.

   Pseudo-session requests:

      Throttling decisions for future specifications
     A.1. Additional traffic abatement algorithms
     A.2. Agent Overload
     A.3. DIAMETER_TOO_BUSY clarifications
     A.4. Per reacting node reports
   Appendix B. Examples
     B.1. Mix pseudo-session requests can take into
      consideration where individual requests fit into the overall
      sequence of Destination-Realm routed requests within the pseudo session.  Requests that are
      earlier in the sequence might be throttled more aggressively than
      requests that occur later in the sequence.

   Intra-session requests:

      There are two types of intra-sessions requests, requests that
      terminate a session and the remainder of intra-session requests.
      Implementors and Destination-
           Host routed operators may choose to throttle session-
      terminating requests
   Authors' Addresses less aggressively in order to gracefully
      terminate sessions, allow clean-up of the related resources (e.g.
      session state) and avoid the need for additional intra-session
      requests.  Favoring session-termination requests may reduce the
      session management impact on the overloaded entity.  The default
      handling of other intra-session requests might be to treat them
      equally when making throttling decisions.  There might also be
      application level considerations whether some request types are
      favored over others.

Authors' Addresses
   Jouni Korhonen (editor)
   Broadcom
   Porkkalankatu 24
   Helsinki  FIN-00180
   Finland

   Email: jouni.nospam@gmail.com

   Steve Donovan (editor)
   Oracle
   7460 Warren Parkway
   Frisco, Texas  75034
   United States

   Email: srdonovan@usdonovans.com

   Ben Campbell
   Oracle
   7460 Warren Parkway
   Frisco, Texas  75034
   United States

   Email: ben@nostrum.com

   Lionel Morand
   Orange Labs
   38/40 rue du General Leclerc
   Issy-Les-Moulineaux Cedex 9  92794
   France

   Phone: +33145296257
   Email: lionel.morand@orange.com