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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 7767

Network Working Group                                      S. Vinapamula
Internet-Draft                                          Juniper Networks
Intended status: Informational                              S. Sivakumar
Expires: May 4, 2016                                       Cisco Systems
                                                            M. Boucadair
                                                                T. Reddy
                                                        November 1, 2015

  Application-Initiated Flow High Availability Awareness through Port
                         Control Protocol (PCP)


   This document specifies a mechanism for a host to signal via Port
   Control Protocol (PCP) which connections should be protected against
   network failures.  These connections will be elected to be subject to
   high availability mechanisms enabled at the network side.

   This approach assumes that applications/users have more visibility
   about sensitive connections rather than any heuristic that can be
   enabled at the network side to guess which connections should be

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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.

   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."

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   This Internet-Draft will expire on May 4, 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Note  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Issues with the Existing Implementations  . . . . . . . . . .   3
   3.  CHECKPOINT-REQUIRED PCP Option  . . . . . . . . . . . . . . .   4
     3.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Operation . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Sample Use cases  . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative references  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  Appendix . . . . . . . . . . . . . . . . . . . . . .  11
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The risk of Internet service disruption is critical in service
   providers and enterprise networking environments.  Such a risk is
   often mitigated with the introduction of active/backup systems.  Such
   designs not only contribute to minimize the risk of service
   disruption, but also facilitate maintenance operations (e.g., hitless
   H/W or S/W upgrades).

   In addition, the nature of some connections leads to the
   establishment and the maintenance of connection-specific states by
   some of the network functions invoked when the connection is
   established.  During active/backup failover in case of a network

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   failure, the said states need to be check-pointed by the backup
   system.  Additional issues are further discussed in Section 2.

   Heuristics based on the protocol, mapping lifetime, etc., are used in
   the network to elect which connections need to be check-pointed
   (e.g., by means of high availability techniques).  This document
   advocates for an application-initiated approach that would allow
   applications/users to signal to the network which of their
   connections are critical.

   This document specifies how PCP [RFC6887] can be extended to signal
   which connection should be check-pointed for high availability
   (Section 3).  A set of use cases are provided for illustration
   purposes in Section 4.  This document does not make any assumption on
   the PCP-controlled device that will process the PCP-formatted
   signaling information from PCP clients.  These devices are likely to
   be flow-aware.

   The approach in this document is aligned with the networking trends
   advocating for open network APIs to interact with applications/
   services (e.g., [RFC7149]).  Policy-decision making process at the
   network side will be enriched with information signaled by
   application using PCP for instance.

1.1.  Note

   The CHECKPOINT-REQUIRED PCP option (Section 3) is defined in the
   Specification Required range (see Section 6).  In order to be
   assigned a code point in that range, a permanent publication is
   required as per Section 4.1 of [RFC5226].  Publication of an RFC is
   an ideal means of achieving this requirement and also to ease

   Note, this work was presented to the Port Control Protocol (pcp) WG
   but there was no consensus to define this option in the "Standards
   Action" range despite positive feedback was received from the working
   group.  Technical comments that were received during pcp meetings and
   those received on the mailing list were addressed.

2.  Issues with the Existing Implementations

   Regardless of the selected technology or design like HA-based
   designs, reliably securing connections is expensive in terms of
   memory, CPU and other resources.  Also check-pointing may not be
   required for all connections as all connections may not be critical.
   But, this leaves a challenge to identify what connections to check-

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   Typically, long-lived connections are identified and, only the states
   of such connections are check-pointed.

   Typically, this is addressed by identifying long lived connections
   and check-pointing state of only those connections that lived long
   enough, to the backup for service continuity.

   However, check-pointing long lived connections raises the following

   1.  It is hard for a network to identify/guess which connection is
       (business) critical.  This characterization is often customer-
       specific: a flow can be sensitive for a User#1 while it is not
       for another User#2.  Furthermore, this characterization can vary
       over time: a flow can be sensitive during hour X, while it is not
       be during other times.

   2.  Heuristics are not deterministic.

   3.  A potentially long-lived connection may experience disruption
       upon failure of the active system, but before it is check-

   4.  A connection may not be long lived but critical Voice over IP
       (VoIP) conversations.

   5.  Likewise, not all long-lived connections are deemed critical: for
       example, connections that pertain to free Internet services are
       usually considered not critical compared to the equivalent
       connections for paid services.  Only the latter need to be check-


3.1.  Format

   The solution is based on the assumption that an application or user
   is the best judge to decide which of its connections are critical.

   An application or user may explicitly identify the connections that
   need to be check-pointed by means of a PCP client, using the
   CHECKPOINT_REQUIRED option as described in Figure 1.

   The entry to be backed up is indicated by the content of a MAP or
   PEER message.

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |Option Code=TBA|  Reserved     |        Option Length          |

            Option Name: CHECKPOINT_REQUIRED
            Number: <TBA>
            Purpose:  Indicate if an entry needs to be check-pointed.
            Valid for Opcodes: MAP, PEER
            Length: 0.
            May appear in: request, response.
            Maximum occurrences: 1.

                 Figure 1: CHECKPOINT_REQUIRED PCP Option

   The description of the fields is as follows:

   o  Option Code: To be assigned by IANA (see Section 6).

   o  Reserved: This field is initialized as specified in Section 7.3 of

   o  Option Length: 0.  This means no data is included in the option.

   An application or user can take advantage of this PCP option to
   explicitly indicate which of the connections need to be check-pointed
   and should not be disrupted.  The processing of this option by the
   PCP server will then yield the check-pointing of the corresponding
   states by the relevant devices or functions dynamically controlled by
   the PCP server.

   Communication between application/user and PCP client is

3.2.  Operation

   Support of the CHECKPOINT_REQUIRED option by PCP servers and PCP
   clients is optional.  This option (Code TBA; see Figure 1) may be
   included in a PCP MAP/PEER request to indicate a connection is to be
   protected against network failures.

   There is a risk that every PCP client may wish to check-point every
   connection, which can potentially load the system.  Administration
   SHOULD restrict the number of connections that can be elected to be
   backed up and the rate of check-pointing on per network attachment
   point (e.g., CPE, host).  To that aim, the PCP server should
   unambiguously identify the network attachment point a PCP client

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   belongs to.  For example, the PCP server may rely on the PCP identity
   [RFC7652], the assigned prefix to a CPE/host, the subscriber-mask
   [I-D.vinapamula-softwire-dslite-prefix-binding], or other
   identification means.

   The PCP client includes a CHECKPOINT_REQUIRED option in a MAP or PEER
   request to signal that the corresponding mapping is to be protected.

   If the PCP client does not receive a CHECKPOINT_REQUIRED option in
   response to a PCP request that enclosed the CHECKPOINT_REQUIRED
   option, this means that either the PCP server does not support the
   option, or the PCP server is configured to ignore the option or the
   PCP server cannot satisfy the request expressed in this option (e.g.,
   because of a lack of resources).

   If the CHECKPOINT_REQUIRED option is not included in the PCP client
   request, the PCP server MUST NOT include the CHECKPOINT_REQUIRED
   option in the associated response.

   When the PCP server receives a CHECKPOINT_REQUIRED option, the PCP
   server checks if it can honor this request depending on whether
   resources are available for check-pointing.  If there are no
   resources available for check-pointing, but there are resources
   available to honor the MAP/PEER request, a response is sent back to
   the PCP client without including the CHECKPOINT_REQUIRED option
   (i.e., the request is processed as any MAP/PEER request that does not
   convey a CHECKPOINT_REQUIRED option).  If check-pointing resources
   are still available and the quota for this PCP client is not reached,
   the PCP server tags the corresponding entry as eligible to HA
   mechanism and sends back the CHECKPOINT_REQUIRED option in the
   positive answer to the PCP client.

   To update the check-pointing behavior of a mapping maintained by the
   PCP server, the PCP client generates a PCP MAP/PEER renewal request
   that includes a CHECKPOINT_REQUIRED option to indicate this mapping
   has to be check-pointed or without including a CHECKPOINT_REQUIRED
   option to indicate this mapping does not need be check-pointed
   anymore.  Upon receipt of the PCP request, the PCP server proceeds
   with the same operations to validate a MAP/PEER request updating an
   existing mapping.  If validation checks are passed, the PCP server
   updates the check-point flag associated with that mapping accordingly
   (i.e., it is set if a CHECKPOINT_REQUIRED option was included in the
   update request or it is cleared if no CHECKPOINT_REQUIRED option was
   included) , and the PCP server returns the response to the PCP client

   What information to check-point and how to check-point is out of
   scope of this document, and is left for implementations.  Also,

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   interest to indicate check-pointing by users/applications in a PCP
   request, may be automatic, semi-automatic, or human intervened.  This
   behavior is also left for application implementations.  For managed
   CPEs, a service provider may influence what connections to be check-

   It is RECOMMENDED to check-point state on backup for honored requests
   before a response is sent to the PCP client.

4.  Sample Use cases

   Below are provided some examples for illustration purposes:

   Example 1:  Consider a streaming service such as live TV
      broadcasting, or any other media streaming, that supports check-
      pointing signalling functionality.  Suppose, this application is
      installed in three hosts A, B and C.  For A it is critical and
      doesn't want interruption while for B it is not.  While for C,
      only some programs are of interest.  At the time of installing
      this application's software, corresponding preferences can be
      provisioned.  When the application starts streaming:

      *  All the flows associated with the streaming application are
         critical for A.  Limiting the number of flows to be backed up
         will ensure that host doesn't exceed the user's limit.

      *  In case of B, none of these flows are critical for check-
         pointing.  CHECKPOINT_REQUIRED option is not included in the
         PCP requests.

      *  In case of C, the user is invited to interact with the
         application by the means of a configuration option that is
         provided to dynamically select which streaming to check-point,
         based on the user's interest.

   Example 2:  Consider a streaming service offered by a provider.
      Suppose, three levels of subscriptions are offered by that
      provider: e.g., gold, silver, bronze.  To guarantee a certain
      level of quality of service for each subscription, policies are
      configured such that:

      *  All flows associated with a gold subscription should be check-

      *  Only some flows associated with a silver subscription are

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      *  None of the flows associated with a bronze subscription are

      When a user invokes the streaming service, he/she may fall into
      one of those buckets, and according to the configured policy, his/
      her associated streaming flows are automatically check-pointed.
      Login credentials can be used as a trigger to determine the
      subscription level (and therefore the associated check-pointing

   Example 3:  Consider a VoIP application that is able to request its
      flows to be check-pointed.  No matter what is configured by the
      user, some calls such as emergency calls should be check-pointed.
      The application has to identify such calls.

   Example 4:  In the context of an enterprise network, applications are
      customized by the administrator.  Instructions whether a
      CHECKPOINT_REQUIRED option is to be included is determined by the
      administrator.  Only the subset of applications identified by the
      administrator will make use of this option in conformance with the
      enterprise network management policies.  Any mis-behavior can be
      considered as an abuse.

   In order to avoid that every application includes a
   CHECKPOINT_REQUIRED option in its PCP requests, the following items
   are assumed:

   o  Applications may be delivered with some default settings for
      check-pointing, and these settings should be programmable by end

   o  Exposing and enforcing these settings is application specific.

   o  End user may customize these settings on need basis based on his

5.  Security Considerations

   PCP-related security considerations are discussed in [RFC6887].

   CHECKPOINT_REQUIRED option can be used by an attacker to identify
   critical flows, which is sensitive from a privacy standpoint.  Also,
   an attacker can cause critical flows to not be check-pointed by
   stripping the CHECKPOINT_REQUIRED option or by consuming the quota by
   adding the option to other flows.

   These two issues can be mitigated if the network on which the PCP
   messages are to be sent is fully trusted.  Means to defend against

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   attackers who can intercept packets between the PCP server and the
   PCP client should be enabled.  In some deployments, access control
   lists (ACLs) can be installed on the PCP client, PCP server, and the
   network between them, so those ACLs allow only communications between
   trusted PCP elements.  If the networking environment between the PCP
   client and the PCP server is not secure, PCP authentication [RFC7652]
   MUST be enabled.

   A network device can always override the end-user signalling, i.e.,
   what is signaled by the PCP client, if the instructions are
   conflicting with the network policies.

6.  IANA Considerations

   The following PCP Option Code is to be allocated in the
   "Specification Required" range (192-223; optional to process range)
   (the registry is maintained in http://www.iana.org/ assignments/pcp-

      CHECKPOINT_REQUIRED set to TBA (see Section 3.1)

7.  References

7.1.  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,

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,

   [RFC7652]  Cullen, M., Hartman, S., Zhang, D., and T. Reddy, "Port
              Control Protocol (PCP) Authentication Mechanism",
              RFC 7652, DOI 10.17487/RFC7652, September 2015,

7.2.  Informative References

              Vinapamula, S. and M. Boucadair, "Recommendations for
              Prefix Binding in the Softwire DS-Lite Context", draft-
              vinapamula-softwire-dslite-prefix-binding-12 (work in
              progress), October 2015.

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   [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,

   [RFC7149]  Boucadair, M. and C. Jacquenet, "Software-Defined
              Networking: A Perspective from within a Service Provider
              Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,

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Appendix A.  Appendix

   It was tempting to include additional fields in the option but this
   would lead to a more complex design that is not justified, e.g.,:

   o  Define a dedicated field to indicate a priority level.  This
      priority is intended to be used by the PCP server as a hint when
      processing a request with a CHECKPOINT_REQUIRED option.
      Nevertheless, an applications may systematically choose to set the
      priority level to the highest value so that it increases its
      chance to be serviced!

   o  Return a more granular failure error code to the requesting PCP
      client.  Nevertheless this would require extra processing at both
      the PCP client and server sides for handling the various error
      codes without any guarantee for the PCP client to have its
      mappings check-pointed.


   Thanks to Reinaldo Penno, Stuart Cheshire, Dave Thaler, Prashanth
   Patil, and Christian Jacquenet for their comments.

Authors' Addresses

   Suresh Vinapamula
   Juniper Networks
   1194 North Mathilda Avenue
   Sunnyvale, CA  94089

   Phone: +1 408 936 5441
   EMail: sureshk@juniper.net

   Senthil Sivakumar
   Cisco Systems
   7100-8 Kit Creek Road
   Research Triangle Park, NC  27760

   Phone: +1 919 392 5158
   EMail: ssenthil@cisco.com

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   Mohamed Boucadair
   Rennes  35000

   EMail: mohamed.boucadair@orange.com

   Tirumaleswar Reddy
   Cisco Systems, Inc.
   Cessna Business Park, Varthur Hobli
   Sarjapur Marathalli Outer Ring Road
   Bangalore, Karnataka  560103

   EMail: tireddy@cisco.com

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