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Versions: (draft-donovan-dime-drmp) 00 01 02 03 04 05 06 07 RFC 7944

Diameter Maintenance and Extensions (DIME)                    S. Donovan
Internet-Draft                                                    Oracle
Intended status: Standards Track                       November 11, 2015
Expires: May 14, 2016


                   Diameter Routing Message Priority
                      draft-ietf-dime-drmp-02.txt

Abstract

   When making routing and resource allocation decisions, Diameter nodes
   currently have no generic mechanism to determine the relative
   priority of Diameter messages.  This document addresses this by
   defining a mechanism to allow Diameter endpoints to indicate the
   relative priority of Diameter transactions.  With this information
   Diameter nodes can factor that priority into routing, resource
   allocation and overload abatement decisions.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 14, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Abbreviations . . . . . . . . . . . . . . . .   3
   3.  Conventions Used in This Document . . . . . . . . . . . . . .   4
   4.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  First Responder Related Signaling . . . . . . . . . . . .   5
     5.2.  Emergency Call Related Signaling  . . . . . . . . . . . .   5
     5.3.  Differentiated Services . . . . . . . . . . . . . . . . .   5
     5.4.  Application Specific Priorities . . . . . . . . . . . . .   6
   6.  Theory of Operation . . . . . . . . . . . . . . . . . . . . .   7
   7.  Extensibility . . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative Behavior  . . . . . . . . . . . . . . . . . . . . .   8
   9.  Attribute Value Pairs . . . . . . . . . . . . . . . . . . . .  11
     9.1.  DRMP AVP  . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.2.  Attribute Value Pair flag rules . . . . . . . . . . . . .  12
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  AVP codes  . . . . . . . . . . . . . . . . . . . . . . .  12
     10.2.  New registries . . . . . . . . . . . . . . . . . . . . .  12
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  13
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     13.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   The DOIC solution [RFC7683] for Diameter overload control introduces
   scenarios where Diameter routing decisions made by Diameter nodes can
   be influenced by the overload state of other Diameter nodes.  This
   includes the scenarios where Diameter endpoints and Diameter agents
   can throttle requests as a result of the target for the request being
   overloaded.

   With currently available mechanisms these Diameter nodes do not have
   a mechanism to differentiate request message priorities when making
   these throttling decisions.  As such, all requests are treated the
   same meaning that all requests have the same probability of being
   throttled.

   There are scenarios where treating all requests the same can cause
   issues.  For instance it might be considered important to reduce the
   probability of transactions involving first responders during a



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   period of heavy signaling resulting from a natural disaster being
   throttled during overload scenarios.

   This document defines a mechanism that allows Diameter nodes to
   indicate the relative priority of Diameter transactions.  With this
   information other Diameter nodes can factor the relative priority of
   requests into routing and throttling decisions.

2.  Terminology and Abbreviations

   Diversion

      As defined in [RFC7683].  An overload abatement treatment where
      the reacting node selects alternate destinations or paths for
      requests.

   DOIC

      Diameter Overload Indication Conveyance.

   DRMP

      Diameter Routing Message Priority.

   Overload Abatement

      As defined in [RFC7683].  Reaction to receipt of an overload
      report resulting in a reduction in traffic sent to the reporting
      node.  Abatement actions include diversion and throttling.

   Priority

      The relative importance of a Diameter message.  A lower priority
      value implies a higher relative importance of the message.

   Throttling

      As defined in [RFC7683].  An abatement treatment that limits the
      number of requests sent by the DIOC reacting node.  Throttling can
      include a Diameter Client choosing to not send requests, or a
      Diameter Agent or Server rejecting requests with appropriate error
      responses.  In both cases the result of the throttling is a
      permanent rejection of the transaction.








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3.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   RFC 2119 [RFC2119] interpretation does not apply for the above listed
   words when they are not used in all-caps format.

4.  Problem Statement

   With the introduction of overload control mechanisms, Diameter nodes
   will be required to make decisions regarding which Diameter request
   messages should be throttled as a result of overloaded Diameter
   nodes.

   There is currently no generic mechanism to indicate which request
   messages should be given preferential treatment when these throttling
   decisions are made.

   As a result, all messages are treated equally and, as such, have an
   equal probability of being throttled.

   There are a number of scenarios where it is appropriate for an
   application to mark a request as being of a higher priority than
   other application requests.  These are discussed in the next section.

   This document defines a mechanism for applications to indicate
   priority for individual transactions, reducing the probability of
   those transactions being throttled if there are other lower priority
   transactions that are eligible for throttling treatment.

   While the primary usage of DRMP defined priorities is for input to
   Diameter overload control related throttling decisions, it is also
   expected that the priority information could also be used for other
   routing related functionality.  This might include giving higher
   priority transactions preferential treatment when selecting routes.

   It is also envisioned that DRMP priority information could be used by
   Diameter endpoints to make resource allocation decisions.  For
   instance, a Diameter Server might choose to use the priority
   information to treat higher priority requests ahead of lower priority
   requests.

      Note: There are a number of application specific definitions
      indicating various views of application level priority for
      different requests.  Using these application specific priority
      AVPs as input to throttling and other Diameter routing decisions



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      would require Diameter agents to understand all applications and
      do application specific parsing of all messages in order to
      determine the priority of individual messages.  This is considered
      an unacceptable level of complexity to put on elements whose
      primary responsibility is to route Diameter messages.

5.  Use Cases

   This section discussed various scenarios where Diameter transactions
   can benefit from the use of priority information.

5.1.  First Responder Related Signaling

   Natural disasters can result in a considerable increase in usage of
   network resources.  This can be made worse if the disaster results in
   a loss of network capacity.

   The combination of added load and reduced capacity can lead to
   Diameter nodes becoming overloaded and, as a result, the use of DOIC
   mechanisms to request a reduction in traffic.  This in turn results
   in requests being throttled in an attempt to control the overload
   scenario and prevent the overloaded node from failing.

   There is the need for first responders and other individuals
   responsible for handling the after effects of the disaster to be
   assured that they can gain access to the network resources in order
   to communicate both between themselves and with other network
   resources.

   Signaling associated with first responders needs to be given a higher
   priority to help ensure they can most effectively do their job.

   The United States Wireless Priority Services (WPS) and Government
   Emergency Telecommunications Service (GETS) are examples of systems
   designed to address these first responder needs.

5.2.  Emergency Call Related Signaling

   Similar to the first responder scenario, there is also signaling
   associated with emergency calls.  Given the critical nature of these
   emergency calls, this signaling should also be given preferential
   treatment when possible.

5.3.  Differentiated Services

   Operators may desire to differentiate network-based services by
   providing a service level agreement that includes preferential




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   Diameter routing behavior.  This might, for example, be modeled as
   Platinum, Gold and Silver levels of service.

   In this scenario an operator might offer a Platinum SLA the includes
   ensuring that all signaling for a customer who purchases the Platinum
   service being marked as having a higher priority than signaling
   associated with Gold and Silver customers.

5.4.  Application Specific Priorities

   There are scenarios within Diameter applications where it might be
   appropriate to give a subset of the transactions for the application
   a higher priority than other transactions for that application.

   For instance, when there is a series of transactions required for a
   user to gain access to network services, it might be appropriate to
   mark transactions that occur later in the series at a higher priority
   than those that occur early in the series.  This would recognize that
   there was potentially significant work done by the network already
   that would be lost if those later transactions were throttled.

   There are also scenarios where an agent cannot easily differentiate a
   request that starts a session from requests that update or end
   sessions.  In these scenarios it might be appropriate to mark the
   requests that establish new sessions with a lower priority than
   updates and session ending requests.  This also recognizes that more
   work has already taken place for established sessions and, as a
   result, it might be more harmful if the session update and session
   ending requests were to be throttled.

   There are also scenarios where the priority of requests for
   individual command codes within an application depends on the context
   that exists when the request is sent.  There isn't always information
   in the message from which this context can be determined by Diameter
   nodes other than the node that originates the request.

   This is similar to the scenario where a series of requests are needed
   to access a network service.  It is different in that the series of
   requests involve different application command-codes.  In this
   scenario it is requests with the same command-code that have
   different implied priorities.

      One example of this is in the 3GPP application [S6a] where a ULR
      request resulting from an MME restoration procedure might be given
      a higher priority than a ULR resulting from an initial attach.






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6.  Theory of Operation

   This section outlines the envisioned usage of DRMP.

   The expected behavior depends on the role (request sender, agent or
   request handler) of the Diameter node handling the request.

   The following behavior is expected during the flow of a Diameter
   transaction.

   1.  Request sender - The sender of a request, be it a Diameter Client
       or a Diameter Server, determines the relative priority of the
       request and includes that priority information in the request.
       The method for determining the relative priority is application
       specific and is outside the scope of this specification.  The
       request sender also saves the priority information with the
       transaction state.  This will be used when handling the answer
       messages.

   2.  Agents handing the request - Agents use the priority information
       when making routing decisions.  This can include determining
       which requests to route first, which requests to throttle and
       where the request is routed.  For instance, requests with higher
       priority might have a lower probability of being throttled.  The
       mechanism for how the agent determines which requests are
       throttled is implementation dependent and is outside the scope of
       this document.  The agent also records the transaction priority
       in the transaction state.  This will be used when handling the
       associated answer message for the transaction.

   3.  Request handler - The handler of the request, be it a Diameter
       Server or a Diameter Client, can use the priority information to
       determine how to handle the request.  This could include
       determining the order in which requests are handled and resources
       that are applied to handling of the request.

   4.  Answer sender - The handler of the request is also the sender of
       the answer.  The answer sender uses the priority information
       received in the request message when sending the answer.  This
       implies that answers for higher priority transactions are given
       preferential treatment to lower priority transactions.  The
       answer sender also has the option of including priority
       information in the answer message.  This is done what the answer
       message needs to have a different priority than the priority
       carried in the request message.

   5.  Agent handling the answer - By default, agents handling answer
       messages use the priority information stored with the transaction



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       state to determine the priority of relaying the answer message.
       However, priority information included in the answer message,
       when present, is used in place of the stored priority
       information.  The use of priority information implies that
       answers for higher priority transactions are given preferential
       treatment to lower priority transactions.

   6.  Answer handler - The answer handler uses the same method as the
       agent to determine the priority of the answer message.  By
       default the handler of the answer message uses the priority of
       the transaction.  Priority information in the answer message is
       used when present.  The priority is used when allocating
       resources for processing that occurs after the receipt of the
       answer message.

7.  Extensibility

   This document does not define extensibility mechanisms that are
   specific to the DRMP mechanism.  As a result, any extension that
   requires new AVPs will be required to use existing Diameter
   extensibility mechanisms defined in [RFC6733]

8.  Normative Behavior

   This section contains the normative behavior associated with Diameter
   Resource Message Priority (DRMP).

   When routing priority information is available, Diameter nodes SHOULD
   include Diameter routing message priority in the DRMP AVP in all
   Diameter request messages.

      Note: The method of determining the priority value included in the
      request is application specific and is not in the scope of this
      specification.

   The priority marking scheme SHOULD NOT require the Diameter Agents to
   understand application specific AVPs.

   When available, Diameter nodes SHOULD use routing priority
   information included in the DRMP AVP when making Diameter overload
   throttling decisions.

   Diameter agents MAY use routing priority information included in the
   DRMP AVP when relaying request and answer messages.  This includes
   the selection of routes and the ordering of messages relayed.






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      The priority information included in the DRMP AVP in request
      messages applies to both the request message and, by default,
      answer message associated with the transaction.

   Diameter endpoints MAY use routing priority information included in
   the DRMP AVP when making resource allocation decisions for the
   transaction associated with the request message that contains the
   DRMP information.

   Diameter endpoints MAY use routing priority information included in
   the DRMP AVP when making resource allocation decisions for the
   transaction associated with the answer messages using the DRMP
   information associated with the transaction.

   Diameter endpoints MAY include the DRMP AVP in answer messages.  This
   is done when the priority for the answer message needs to have a
   different priority than the priority carried in the request message.

   When determining the priority to apply to answer messages, Diameter
   nodes MUST use the priority indicated in the DRMP AVP carried in the
   answer message, if it exists.  Otherwise, the Diameter node MUST use
   the priority indicated in the DRMP AVP of the associated request
   message.

   Diameter nodes MUST have a default priority to apply to transactions
   that do not have an explicit priority set in the DRMP AVP.

   Diameter nodes SHOULD use the PRIORITY_10 priority as this default
   value.

   Diameter nodes MUST support the ability for the default priority to
   be modified through local configuration interfaces.

      Note: There are scenarios where operators might want to specify a
      different default value for transactions that do not have an
      explicit priority.  In this case, the operator defined local
      policy would override the use of PRIORITY_10 as the default
      priority.

   When using DRMP priority information, Diameter nodes MUST use the
   default priority for transactions that do not have priority specified
   in a DRMP AVP.

      Note: This guidance on the handling of messages without a priority
      does not result in a Diameter agent inserting a DRMP AVP into the
      message.  Rather, it gives guidance on how that specific
      transaction should be treated when its priority is compared with




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      other requests.  When a Diameter agent relays the request it will
      not insert a DRMP AVP with a priority value of 10.

   When setting and using priorities, PRIORITY_0 MUST be treated as the
   highest priority.

   When setting and using priorities, PRIORITY_1 MUST be treated as a
   lower priority than PRIORITY_0 and a higher priority than PRIORITY_2.

   When setting and using priorities, PRIORITY_2 MUST be treated as a
   lower priority than PRIORITY_1 and a higher priority than PRIORITY_3.

   When setting and using priorities, PRIORITY_3 MUST be treated as a
   lower priority than PRIORITY_2 and a higher priority than PRIORITY_4.

   When setting and using priorities, PRIORITY_4 MUST be treated as a
   lower priority than PRIORITY_3 and a higher priority than PRIORITY_5.

   When setting and using priorities, PRIORITY_5 MUST be treated as a
   lower priority than PRIORITY_4 and a higher priority than PRIORITY_6.

   When setting and using priorities, PRIORITY_6 MUST be treated as a
   lower priority than PRIORITY_5 and a higher priority than PRIORITY_7.

   When setting and using priorities, PRIORITY_7 MUST be treated as a
   lower priority than PRIORITY_6 and a higher priority than PRIORITY_8.

   When setting and using priorities, PRIORITY_8 MUST be treated as a
   lower priority than PRIORITY_7 and a higher priority than PRIORITY_9.

   When setting and using priorities, PRIORITY_9 MUST be treated as a
   lower priority than PRIORITY_8 and a higher priority than
   PRIORITY_10.

   When setting and using priorities, PRIORITY_10 MUST be treated as a
   lower priority than PRIORITY_9 and a higher priority than
   PRIORITY_11.

   When setting and using priorities, PRIORITY_11 MUST be treated as a
   lower priority than PRIORITY_10 and a higher priority than
   PRIORITY_12.

   When setting and using priorities, PRIORITY_12 MUST be treated as a
   lower priority than PRIORITY_11 and a higher priority than
   PRIORITY_13.






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   When setting and using priorities, PRIORITY_13 MUST be treated as a
   lower priority than PRIORITY_12 and a higher priority than
   PRIORITY_14.

   When setting and using priorities, PRIORITY_14 MUST be treated as a
   lower priority than PRIORITY_13 and a higher priority than
   PRIORITY_15.

   When setting and using priorities, PRIORITY_15 MUST be the lowest
   priority.

9.  Attribute Value Pairs

   This section describes the encoding and semantics of the Diameter
   Overload Indication Attribute Value Pairs (AVPs) defined in this
   document.

9.1.  DRMP AVP

   The DRMP (AVP code TBD1) is of type Enumerated.  The value of the AVP
   indicates the routing message priority for the transaction.  The
   following values are initially defined:

   PRIORITY_15 15  PRIORITY_15 is the lowest priority.

   PRIORITY_14 14  PRIORITY_14 is a higher priority than PRIORITY_15 and
      a lower priority than PRIORITY_13.

   PRIORITY_13 13  PRIORITY_13 is a higher priority than PRIORITY_14 and
      a lower priority than PRIORITY_12.

   PRIORITY_12 12  PRIORITY_12 is a higher priority than PRIORITY_13 and
      a lower priority than PRIORITY_11.

   PRIORITY_11 11  PRIORITY_11 is a higher priority than PRIORITY_12 and
      a lower priority than PRIORITY_10.

   PRIORITY_10 10  PRIORITY_10 is a higher priority than PRIORITY_11 and
      a lower priority than PRIORITY_9.

   PRIORITY_9 9  PRIORITY_9 is a higher priority than PRIORITY_10 and a
      lower priority than PRIORITY_8.

   PRIORITY_8 8  PRIORITY_8 is a higher priority than PRIORITY_9 and a
      lower priority than PRIORITY_7.

   PRIORITY_7 7  PRIORITY_7 is a higher priority than PRIORITY_8 and a
      lower priority than PRIORITY_6.



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   PRIORITY_6 6  PRIORITY_6 is a higher priority than PRIORITY_7 and a
      lower priority than PRIORITY_5.

   PRIORITY_5 5  PRIORITY_5 is a higher priority than PRIORITY_6 and a
      lower priority than PRIORITY_4.

   PRIORITY_4 4  PRIORITY_4 is a higher priority than PRIORITY_5 and a
      lower priority than PRIORITY_3.

   PRIORITY_3 3  PRIORITY_3 is a higher priority than PRIORITY_4 and a
      lower priority than PRIORITY_2.

   PRIORITY_2 2  PRIORITY_2 is a higher priority than PRIORITY_3 and a
      lower priority than PRIORITY_1.

   PRIORITY_1 1  PRIORITY_1 is a higher priority than PRIORITY_2 and a
      lower priority than PRIORITY_0.

   PRIORITY_0 0  Priority 0 is the highest priority.

9.2.  Attribute Value Pair flag rules

                                                         +---------+
                                                         |AVP flag |
                                                         |rules    |
                                                         +----+----+
                              AVP   Section              |    |MUST|
       Attribute Name         Code  Defined  Value Type  |MUST| NOT|
      +--------------------------------------------------+----+----+
      |DRMP                   TBD1  x.x      Enumerated  |    | V  |
      +--------------------------------------------------+----+----+


10.  IANA Considerations

10.1.  AVP codes

   New AVPs defined by this specification are listed in Section 9.  All
   AVP codes are allocated from the 'Authentication, Authorization, and
   Accounting (AAA) Parameters' AVP Codes registry.

10.2.  New registries

   There are no new IANA registries introduced by this document.







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11.  Security Considerations

   The DRMP could be used to get better access to services.  This could
   result in one segment of a Diameter network gaining assess to
   services that would otherwise be given to other segments of the
   Diamter network.

12.  Contributors

   The following people contributed substantial ideas, feedback, and
   discussion to this document:

   o  Janet P.  Gunn

13.  References

13.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6733]  Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
              Ed., "Diameter Base Protocol", RFC 6733,
              DOI 10.17487/RFC6733, October 2012,
              <http://www.rfc-editor.org/info/rfc6733>.

13.2.  Informative References

   [RFC4412]  Schulzrinne, H. and J. Polk, "Communications Resource
              Priority for the Session Initiation Protocol (SIP)",
              RFC 4412, DOI 10.17487/RFC4412, February 2006,
              <http://www.rfc-editor.org/info/rfc4412>.

   [RFC7683]  Korhonen, J., Ed., Donovan, S., Ed., Campbell, B., and L.
              Morand, "Diameter Overload Indication Conveyance",
              RFC 7683, DOI 10.17487/RFC7683, October 2015,
              <http://www.rfc-editor.org/info/rfc7683>.







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   [S6a]      3GPP, "Evolved Packet System (EPS); Mobility Management
              Entity (MME) and Serving GPRS Support Node (SGSN) related
              interfaces based on Diameter protocol", 3GPP TS 29.272
              10.8.0, June 2013.

Author's Address

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

   Email: srdonovan@usdonovans.com





































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