Flow high availability through PCP
draft-vinapamula-flow-ha-00

Network Working Group                                      S. Vinapamula
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                            S. Sivakumar
Expires: April 17, 2014                                    Cisco Systems
                                                        October 14, 2013

                   Flow high availability through PCP
                      draft-vinapamula-flow-ha-00

Abstract

   This document describes a mechanism for a host signal Network Address
   Translator's (NAT) High Availability (HA) module to checkpoint
   interested connections.

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   This Internet-Draft will expire on April 17, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Issues with the existing implementations  . . . . . . . . . .   2
   4.  Proposed Solution . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Some Usage Examples . . . . . . . . . . . . . . . . . . . . .   4
   6.  Signaling HA for other services . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Normative references  . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Uninterrupted Internet service continuity is critical in service
   provider environment.  To achieve this lots of service providers have
   active-backup systems.

   For some of the services, a state would be created 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 checkpointed on the backup.

   NAT is one such service, where, when the mapping between a private IP
   address port and public IP address port is dynamically established
   and torn down on per connection basis.  In such a case, connection's
   state has to be checkpointed to the backup, for uninterrupted service
   continuity even in case active fails.

   This document describes some of the existing issues in the way
   checkpointing is done today, and tries to address them.

2.  Terminology

   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 [RFC2119].

3.  Issues with the existing implementations

   In a high availability (HA) deployment, it is expensive in terms of
   memory and CPU and other resources to checkpoint all of the
   connections state periodically.  Also checkpointing may not be
   required for all flows as all flows may not be critical.  But, this
   leaves a challenge to identify what connections' to checkpoint.

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

   However, following are the issues with that approach:

   1.  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 checkpointed.

   2.  Also a connection may not be long lived but critical like shorter
       phone conversations.

   3.  Similarly not every long lived connection need to be critical,
       say a free service connections need not be checkpointed while a
       paid service connection is checkpointed of a hosted service.

4.  Proposed Solution

   An application or user is the best judge to decide which connection
   is critical.

   An application or user MUST indicate that one or more of its
   connections is critical and disruption is not desired.  This will
   trigger checkpointing of state to the backup.

   An application/user may indicate the desire for checkpoint through
   PCP client, and PCP client MUST mark bit zero of "Reserved" bits in
   the PCP request header as below.  Here after in the document, this
   bit is referred as HA bit.

   All other bits in the "Reserved" field MUST be marked zero on
   transmissions and MUST be ignored on reception.

    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Version = 2  |R|   Opcode    |         Reserved             1|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                 Requested Lifetime (32 bits)                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |            PCP Client's IP Address (128 bits)                 |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    :                                                               :
    :             (optional) Opcode-specific information            :

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    :                                                               :
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    :                                                               :
    :             (optional) PCP Options                            :
    :                                                               :
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   PCP request header with HA bit being the zero bit in the "Reserved"
   field.

   PCP server MAY honor this request depending on whether resources are
   available for checkpointing.  If there are no resources available for
   checkpointing, but there are resources available to honor request say
   PCP MAP/PEER request, request is honored and there is no error
   returned.

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

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

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

5.  Some Usage Examples

   1.  Disruption in a phone connection is not desired.  Application
       that is initiating a phone connection MUST mark connection HA bit
       in the header, while initiating a PCP request for checkpointing.

   2.  Similarly disruption in media streaming is not desired.  A user
       hosting a media service, MUST mark HA bit in the header while
       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.

6.  Signaling HA for other services

   In conjunction with NAT, if there are any other services, that
   maintain state for any connection, they MAY register to PCP server,
   and MAY be triggered for checkpointing of that state.

7.  Security Considerations

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   A NAT device can always override the end user signalling if the
   administrator specified rules are not in policy with the end user
   signaling.

   There is a risk that every client may wish to checkpoint every
   connection, which can potentially load the system.  Admin may
   restrict number of connections and the rate of checkpointing on per
   PCP client.

8.  IANA Considerations

   This document does not require any action from IANA.

9.  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.

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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