Application-Initiated Flow High Availability Awareness through PCP
draft-vinapamula-flow-ha-03

Network Working Group                                      S. Vinapamula
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                            S. Sivakumar
Expires: March 8, 2015                                     Cisco Systems
                                                            M. Boucadair
                                                          France Telecom
                                                       September 4, 2014

   Application-Initiated Flow High Availability Awareness through PCP
                      draft-vinapamula-flow-ha-03

Abstract

   This document specifies a mechanism for a host to signal via 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 aplications/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
   secured.

Requirements Language

   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.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on March 8, 2015.

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Copyright Notice

   Copyright (c) 2014 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
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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.  Issues with the existing implementations  . . . . . . . . . .   3
   3.  CHECKPOINT-REQUIRED PCP Option  . . . . . . . . . . . . . . .   4
     3.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Behavior  . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Typical Usage Examples  . . . . . . . . . . . . . . . . . . .   6
   5.  Signaling HA for other Network Functions  . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative references  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Internet service continuity is critical in Service Providers'
   environment.  To achieve this, most Service Providers deploy active-
   backup systems.  This not only helps them in service continuity
   during failover, but also help in service continuity hitless upgrade
   or minimal hit upgrades of both software or hardware and achieve
   desired level of service continuity compliance.

   For some of the network functions, a state would be maintained for
   every connection for processing subsequent packets of that
   connection.  For service continuity of those connections on backup
   when active fail, that corresponding state had to be check-pointed on
   the backup.  NAPT is one such network function, where a state is
   maintained for every connection.

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   Heuristic based on the protocol, mapping lifetime, etc are used in
   the network side to elect which connections are elected to High
   Availability (HA) means.  This document advocates for an application-
   initiated approach that would allow applications/user to signal to
   the network which of their connections are critical.

   PCP-initiated signalling is superior to heuristics deployed at the
   network side.

   This document specifies how PCP can be extended to signal which
   connection should be subject to HA mechanism.  This document does not
   make any assumption on the PCP-controlled device that will make use
   of the content of signals issued by PCP clients.  These devices are
   likely to be flow-aware.

   The proposed approach is aligned with the current networking trends
   advocating for open network APIs to interact with applications/
   services.  Policy-decision making process at the network side will be
   enriched with information signaled by application using PCP for
   instance.

2.  Issues with the existing implementations

   In a high availability (HA) deployment, it is expensive in terms of
   memory, CPU and other resources to checkpoint all connections state.
   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 checkpoint.

   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, following are the issues with that approach:

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

   2.  Heuristics are not deterministic.

   3.  A connection which could potentially be long-lived would face
       disruption in service on failure of active system, before it had
       not lived long enough for it to be check-pointed.

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

   5.  Similarly not every long lived connection need to be critical,
       say a free-service connection of a hosted service need not be
       check-pointed while a paid-service connection has to be check-
       pointed.

3.  CHECKPOINT-REQUIRED PCP Option

3.1.  Format

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

   An application/user may indicate the desire for checkpoint through
   PCP client, using the CHECKPOINT_REQUIRED option as described in
   Figure 1.

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

    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.

   o  Reserved: This field is initialized as specified in Section 7.3 of
      [RFC6887].

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

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   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.

   An application or user can use this option to indicate that one or
   more of its connections are critical and disruption is not desired.
   Doing so will trigger check-pointing of state to the backup.

   Communication between application/user and PCP client is
   implementation-specific.

3.2.  Behavior

   Support for 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.

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

   A PCP server MAY ignore the CHECKPOINT_REQUIRED option sent to it by
   a PCP client (e.g., if it does not support the option or if it is
   configured to ignore it).  To signal that it has not accepted the
   option, a PCP server simply does not include the CHECKPOINT_REQUIRED
   option in the response.  If the PCP client does not receive a
   CHECKPOINT_REQUIRED option in a response to a request enclosing a
   CHECKPOINT_REQUIRED option, this means the PCP server does not
   support the option or it is configured to ignore it.

   If the CHECKPOINT_REQUIRED option is not included in the PCP client
   request, the PCP server does not include the CHECKPOINT_REQUIRED
   option in the associated response.  This is mainly because there are
   not valid motivation that would justify a PCP server notify a PCP
   client about it reliability decision.

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   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 need not be check-pointed anymore.
   Upon receipt of the PCP request, the PCP server proceeds to the same
   operations to validate a MAP/PEER request refreshing an existing
   mapping.  If validation checks are successfully 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 refresh request or it is cleared if no
   CHECKPOINT_REQUIRED option was included) , and the PCP server returns
   the response to the PCP client accordingly.

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

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

4.  Typical Usage Examples

   Below are provided some examples for illustration purposes:

   1.  Disruption in a VoIP connection is not desired: Application that
       is initiating a VoIP connection can include CHECKPOINT_REQUIRED
       option in its associated MAP/PEER message(s) to indicate to the
       server that the corresponding entry must be protected against
       failure.

   2.  Similarly disruption in media streaming is not desired: A user
       hosting a media service, uses CHECKPOINT_REQUIRED option while

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       initiating a mapping request, and may mark connection associated
       with that mapping, depending on whether the connection is from a
       paid subscriber or from a free subscriber through a PEER request.
       So check-pointing mapping doesn't result in auto check-pointing
       of connections, as it gives flexibility to the end user to pick
       specific connections only to checkpoint.

5.  Signaling HA for other Network Functions

   In conjunction with NAT, other network functions that may maintain
   state for each connection such as stateful firewall may register to
   PCP server, and may be triggered for check-pointing respective state
   of that connection.

6.  Security Considerations

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

   CHECKPOINT_REQUIRED option can be used by an attacker to identify
   critical flows.  This issue is mitigated if the network on which the
   PCP messages are to be sent is fully trusted.  Means to defend
   against 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 PCP server is not secure, means to protect
   exposing the content of PCP messages (e.g., DTLS [RFC6347]) are
   recommended.

   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.

   There is a risk that every PCP client may wish to checkpoint every
   connection, which can potentially load the system.  Administration
   SHOULD restrict the number of connections that can be elected to be
   backuped and the rate of check-pointing on per PCP client.

7.  IANA Considerations

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

      CHECKPOINT_REQUIRED set to TBA (see Section 3.1)

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8.  Acknowledgements

   Thanks to Reinaldo Penno, Tirumaleswar Reddy, Stuart Shechire, and
   Dave Thaler for their comments.

9.  References

9.1.  Normative references

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

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

9.2.  Informative References

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

Authors' Addresses

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

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

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

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

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   Mohamed Boucadair
   France Telecom
   Rennes 35000
   France

   EMail: mohamed.boucadair@orange.com

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