An Overview of Reliable Server Pooling Protocols
RFC 5351

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Network Working Group                                             P. Lei
Request for Comments: 5351                           Cisco Systems, Inc.
Category: Informational                                           L. Ong
                                                       Ciena Corporation
                                                               M. Tuexen
                                      Muenster Univ. of Applied Sciences
                                                            T. Dreibholz
                                            University of Duisburg-Essen
                                                          September 2008

            An Overview of Reliable Server Pooling Protocols

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   The Reliable Server Pooling effort (abbreviated "RSerPool") provides
   an application-independent set of services and protocols for building
   fault-tolerant and highly available client/server applications.  This
   document provides an overview of the protocols and mechanisms in the
   Reliable Server Pooling suite.

Lei, et al.                  Informational                      [Page 1]
RFC 5351                   RSerPool Overview              September 2008

Table of Contents

   1. Introduction ....................................................3
   2. Aggregate Server Access Protocol (ASAP) Overview ................6
      2.1. Pool Initialization ........................................6
      2.2. Pool Entity Registration ...................................6
      2.3. Pool Entity Selection ......................................7
      2.4. Endpoint Keep-Alive ........................................7
      2.5. Failover Services ..........................................7
           2.5.1. Cookie Mechanism ....................................7
           2.5.2. Business Card Mechanism .............................8
   3. Endpoint Handlespace Redundancy Protocol (ENRP) Overview ........8
      3.1. Initialization .............................................8
      3.2. Server Discovery and Home Server Selection .................8
      3.3. Failure Detection, Handlespace Audit, and Synchronization ..9
      3.4. Server Takeover ............................................9
   4. Example Scenarios ...............................................9
      4.1. Example Scenario Using RSerPool Resolution Service .........9
      4.2. Example Scenario Using RSerPool Session Services ..........11
   5. Reference Implementation .......................................12
   6. Security Considerations ........................................12
   7. IANA Considerations ............................................12
   8. Acknowledgements ...............................................12
   9. References .....................................................13
      9.1. Normative References ......................................13
      9.2. Informative References ....................................13

Lei, et al.                  Informational                      [Page 2]
RFC 5351                   RSerPool Overview              September 2008

1.  Introduction

   The Reliable Server Pooling (RSerPool) protocol suite is designed to
   provide client applications ("pool users") with the ability to select
   a server (a "pool element") from among a group of servers providing
   equivalent service (a "pool").  The protocols are currently targeted
   for Experimental Track.

   The RSerPool architecture supports high availability and load
   balancing by enabling a pool user to identify the most appropriate
   server from the server pool at a given time.  The architecture is
   defined to support a set of basic goals:

   o  application-independent protocol mechanisms

   o  separation of server naming from IP addressing

   o  use of the end-to-end principle to avoid dependencies on
      intermediate equipment

   o  separation of session availability/failover functionality from the
      application itself

   o  facilitation of different server selection policies

   o  facilitation of a set of application-independent failover
      capabilities

   o  peer-to-peer structure

   The basic components of the RSerPool architecture are shown in
   Figure 1 below:

Lei, et al.                  Informational                      [Page 3]
RFC 5351                   RSerPool Overview              September 2008

                                           .......................
         ______          ______            .      +-------+      .
        / ENRP \        / ENRP \           .      |       |      .
        |Server| <----> |Server|<----------.----->|  PE 1 |      .
        \______/  ENRP  \______/  ASAP(1)  .      |       |      .