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Network Working Group                                       T. Dreibholz
Internet-Draft                                Simula Research Laboratory
Intended status: Informational                                 M. Tuexen
Expires: February 22, 2018              Muenster Univ. of Appl. Sciences
                                                                M. Shore
                                                    No Mountain Software
                                                                 N. Zong
                                                     Huawei Technologies
                                                         August 21, 2017


  The Applicability of Reliable Server Pooling (RSerPool) for Virtual
              Network Function Resource Pooling (VNFPOOL)
             draft-dreibholz-vnfpool-rserpool-applic-06.txt

Abstract

   This draft describes the application of Reliable Server
   Pooling (RSerPool) for Virtual Network Function Resource
   Pooling (VNFPOOL).

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on February 22, 2018.

Copyright Notice

   Copyright (c) 2017 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
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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.  Abbreviations . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Virtual Network Function Resource Pooling . . . . . . . . . .   3
   3.  Reliable Server Pooling . . . . . . . . . . . . . . . . . . .   3
     3.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Registrar Operations  . . . . . . . . . . . . . . . . . .   4
     3.3.  Pool Element Operations . . . . . . . . . . . . . . . . .   5
     3.4.  Takeover Procedure  . . . . . . . . . . . . . . . . . . .   5
     3.5.  Pool User Operations  . . . . . . . . . . . . . . . . . .   6
       3.5.1.  Handle Resolution and Response  . . . . . . . . . . .   6
       3.5.2.  Pool Member Selection Policies  . . . . . . . . . . .   6
       3.5.3.  Handle Resolution and Response  . . . . . . . . . . .   6
     3.6.  Automatic Configuration . . . . . . . . . . . . . . . . .   7
     3.7.  State Synchronisation . . . . . . . . . . . . . . . . . .   7
       3.7.1.  Cookies . . . . . . . . . . . . . . . . . . . . . . .   7
       3.7.2.  Businesss Cards . . . . . . . . . . . . . . . . . . .   8
     3.8.  Protocol Stack  . . . . . . . . . . . . . . . . . . . . .   8
     3.9.  Extensions  . . . . . . . . . . . . . . . . . . . . . . .   9
     3.10. Reference Implementation and Deployment . . . . . . . . .   9
   4.  Usage of Reliable Server Pooling  . . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Testbed Platform  . . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

1.1.  Abbreviations

   o  PE: Pool Element

   o  PR: Pool Registrar

   o  PU: Pool User

   o  RSerPool: Reliable Server Pooling




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   o  SCTP: Stream Control Transmission Protocol

   o  VNFPOOL: Virtual Network Function Resource Pooling

2.  Virtual Network Function Resource Pooling

   Virtualised Network Function (VNF) (e.g. vFW, vLB) -- as introduced
   in more detail in [12] -- provides the same function as the
   equivalent network function (e.g. FW, LB), but is deployed as
   software instances running on general purpose servers via
   virtualisation platform.  The main features of VNF include the
   following aspects:

   1.  A service consists of a sequence of topologically distributed VNF
       instances where the data connections are preferably directly
       established between the instances.

   2.  There are potentially more factors that cause VNF instance
       transition or even failure; VNF pool refers to a group of VNF
       instances providing same network function.

   Virtualisation technology allows network function virtualisation
   operators to build a reliable VNF by pooling the underlying
   resources, such as CPU, storage, networking, etc. to form a cluster
   of VNF instances.  VNF pool refers to a cluster or group of VNF
   instances providing same network function.  Each VNF pool has a Pool
   Manager (PM) to manage the VNF instance such as instance selection,
   monitoring, etc.  There will be a redundancy mechanism for a reliable
   PM to achieve reliable VNF.  More details on VNF pool can be found in
   [12].

3.  Reliable Server Pooling

3.1.  Introduction

















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                         +---------------+
                         |   Pool User   |
                         +---------------+
                                 ^
                                 | ASAP
                                 V
                         +---------------+   ENRP   +---------------+
                         |   Registrar   |<-------->|   Registrar   |
                         +---------------+          +---------------+
                                 ^
                                 | ASAP
                                 V
         +------------------------------------------------------------+
         | +--------------+ +--------------+         +--------------+ |
         | | Pool Element | | Pool Element | ... ... | Pool Element | |
         | +--------------+ +--------------+         +--------------+ |
         | Server Pool                                                |
         +------------------------------------------------------------+


                                 Figure 1

   An overview of the RSerPool framework -- which is defined as RFC in
   [2] -- is provided in Figure 1.  There are three types of components:

   o  Pool Element (PE) denotes a server in a pool.  PEs in the same
      pool provide the same service.

   o  Pool User (PU) denotes a client using the service of a pool.

   o  Pool Registrar (PR) is the management component for the pools.

   The set of all pools within an operation scope (for example: an
   organisation, a company or a department) is denoted as handlespace.
   Clearly, a single PR would be a single point of failure.  Therefore,
   PRs also have to be redundant.  Within the handlespace, each pool is
   identified by a unique pool handle (PH).

3.2.  Registrar Operations

   The PRs of an operation scope synchronise their view of the
   handlespace by using the Endpoint haNdlespace Redundancy
   Protocol (ENRP, defined as RFCs in [4], [5]).  In contrast to for
   instance the Domain Name System (DNS), an operation scope is
   restricted to a single administrative domain.  That is, all of its
   components are under the control of the same authority (for example:
   a company).  This property leads to small management overhead, which
   also allows for RSerPool usage on devices having only limited memory



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   and CPU resources (for example: telecommunications equipment).
   Nevertheless, PEs may be distributed globally to continue their
   service even in case of localised disasters (like for example an
   earthquake).  Each PR in the operation scope is identified by a PR
   ID, which is a randomly chosen 32-bit number.

3.3.  Pool Element Operations

   Within their operation scope, the PEs may choose an arbitrary PR to
   register into a pool by using the Aggregate Server Access
   Protocol (ASAP, defined as RFCs in [3], [5]).  The registration is
   performed by using an ASAP_REGISTRATION message.  Within its pool, a
   PE is characterised by its PE ID, which is a randomly chosen 32-bit
   number.  Upon registration at a PR, the chosen PR becomes the Home-
   PR (PR-H) of the newly registered PE.  A PR-H is responsible for
   monitoring the availability of its PEs by ASAP_ENDPOINT_KEEP_ALIVE
   messages (to be acknowledged by a PE via an
   ASAP_ENDPOINT_KEEP_ALIVE_ACK message within a configured timeout).
   The PR-H propagates the information about its PEs to the other PRs of
   the operation scope via ENRP_UPDATE messages.

   PEs re-register regularly in an interval denoted as registration
   lifetime and for information updates.  Similar to the registration, a
   re-registration is performed by using another ASAP_REGISTRATION
   message.  PEs may intentionally deregister from the pool by using an
   ASAP_DEREGISTRATION message.  Also like for the registration, the
   PR-H makes the deregistration known to the other PRs within the
   operation scope by using an ENRP_UPDATE message.

3.4.  Takeover Procedure

   As soon as a PE detects the failure of its PR-H (that is: its request
   is not answered within a given timeout), it simply tries another PR
   of the operation scope for its registration and deregistration
   requests.  However, as a double safeguard, the remaining PRs also
   negotiate a takeover of the PEs managed by a dead PR.  This ensures
   that each PE again gets a working PR-H as soon as possible.  The PRs
   of an operation scope monitor the availability of each other PR by
   using ENRP_PRESENCE messages, which are transmitted regularly.  If
   there is no ENRP_PRESENCE within a given timeout, the peer is assumed
   to be dead and a so-called takeover procedure (see also [21] for more
   details) is initiated for the PEs managed by the dead PR: from all
   PRs having started this takeover procedure, the PR with the highest
   PR ID takes over the ownership of these PEs.  The PEs are informed
   about being taken over by their new PR-H via an
   ASAP_ENDPOINT_KEEP_ALIVE with Home-flag set.  The PEs are requested
   to adopt the sender of this Home-flagged message as their new PR-H.




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3.5.  Pool User Operations

3.5.1.  Handle Resolution and Response

   In order to access the service of a pool given by its PH, a PU
   requests a PE selection from an arbitrary PR of the operation scope,
   again by using ASAP.  This selection procedure is denoted as handle
   resolution.  Upon reception of a so-called ASAP_HANDLE_RESOLUTION
   message the PR selects the requested list of PE identities and
   returns them in an ASAP_HANDLE_RESOLUTION_RESPONSE message.

3.5.2.  Pool Member Selection Policies

   The pool-specific selection rule is denoted as pool member selection
   policy or shortly as pool policy.  Two classes of load distribution
   policies are supported: non-adaptive and adaptive strategies (a
   detailed overview is provided by [16], [18], [23], [19]).  While
   adaptive strategies base their selections on the current PE state
   (which requires up-to-date information), non-adaptive algorithms do
   not need such data.  A basic set of adaptive and non-adaptive pool
   policies is defined as RFC in [7].

   Defined in [7] are the non-adaptive policies Round Robin (RR),
   Random (RAND) and Priority (PRIO) as well as the adaptive policies
   Least Used (LU) and Least Used with Degradation (LUD).  While RR/RAND
   select PEs in turn/randomly, PRIO selects one of the PEs having the
   highest priority.  PRIO can for example be used to realise a master/
   backup PE setup.  Only if there are no master PEs left, a backup PE
   is selected.  Round-robin selection is applied among PEs having the
   same priority.  LU selects the least-used PE, according to up-to-date
   application-specific load information.  Round robin selection is
   applied among multiple least-loaded PEs.  LUD, which is evaluated by
   [20], furthermore introduces a load decrement constant that is added
   to the actual load each time a PE is selected.  It is used to
   compensate inaccurate load states due to delayed updates.  An update
   resets the load to the actual load value.

3.5.3.  Handle Resolution and Response

   PE may fail, for example due to hardware or network failures.  Since
   there is a certain latency between the actual failure of a PE and the
   removal of its entry from the handlespace -- depending on the
   interval and timeout for the ASAP_ENDPOINT_KEEP_ALIVE monitoring --
   the PUs may report unreachable PEs to a PR by using an
   ASAP_ENDPOINT_UNREACHABLE message.  A PR locally counts these reports
   for each PE and when reaching the threshold MAX-BAD-PE-REPORT
   (default is 3, as defined in the RFC [3]), the PR may decide to
   remove the PE from the handlespace.  The counter of a PE is reset



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   upon its re-registration.  More details on this threshold and
   guidelines for its configuration can be found in [22].

3.6.  Automatic Configuration

   RSerPool components need to know the PRs of their operation scope.
   While it is of course possible to configure a list of PRs into each
   component, RSerPool also provides an auto-configuration feature: PRs
   may send so-called announces, that is, ASAP_ANNOUNCE and
   ENRP_PRESENCE messages which are regularly sent over UDP via IP
   multicast.  Unlike broadcasts, multicast messages can also be
   transported over routers (at least, this is easily possible within
   LANs).  The announces of the PRs can be heard by the other
   components, which can maintain a list of currently available PRs.
   That is, RSerPool components are usually just turned on and
   everything works automatically.

3.7.  State Synchronisation

   RSerPool has been explicitly designed to be application-independent.
   Therefore, RSerPool has not intended to define special state
   synchronisation mechanisms for RSerPool-based applications.  Such
   state synchronisation mechanisms are considered as tasks of the
   applications themselves.  However, RSerPool defines two mechanisms to
   at least support the implementation of more sophisticated strategies:
   Cookies and Businesss Cards.  Details on these mechanisms can also be
   found in Subsection 3.9.5 of [16].

3.7.1.  Cookies

   ASAP provides the mechanism of Client-Based State Sharing as
   introduced in [17].  Whenever useful, the PE may package its state in
   form of a state cookie and send it -- by an ASAP_COOKIE message -- to
   the PU.  The PU stores the latest state cookie received from the PE.
   Upon PE failure, this stored cookie is sent in an ASAP_COOKIE_ECHO to
   the newly chosen PE.  This PE may then restore the state.  A shared
   secret known by all PEs of a pool may be used to protect the state
   from being manipulated or read by the PU.

   While Client-Based State Sharing is very simple, it may be
   inefficient when the state changes too frequently, is too large (the
   size limit of an ASAP_COOKIE/ASAP_COOKIE_ECHO is 64 KiB) or if it
   must be prevented that a PU sends a state cookie to multiple PEs in
   order to duplicate its sessions.







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3.7.2.  Businesss Cards

   Depending on the application, there may be constraints restricting
   the set of PEs usable for failover.  The ASAP_BUSINESS_CARD message
   is used to inform peer components about such constraints.

   The first case to use a Business Card is if only a restricted set of
   PEs in the pool may be used for failover.  For example, in a large
   pool, each PE can share its complete set of session states with a few
   other PEs only.  This keeps the system scalable.  That is, a PE in a
   pool of n servers does not have to synchronise all session states
   with the other n-1 PEs.  In this case, a PE has to tell its PU the
   set of PE identities being candidates for a failover using an
   ASAP_BUSINESS_CARD message.  A PE may update the list of possible
   failover candidates at any time by sending another Business Card.
   The PU has to store the latest list of failover candidates.  Of
   course, if a failover becomes necessary, the PU has to select from
   this list using the appropriate pool policy -- instead of performing
   the regular PE selection by handle resolution at a PR.  Therefore,
   some literature also denotes the Business Card by the more expressive
   term "last will".

   In symmetric scenarios, where a PU is also a PE of another pool, the
   PU has to tell this fact to its PE.  This is realised by sending an
   ASAP_BUSINESS_CARD message to the PE, providing the PH of its pool.
   Optionally, also specific PE identities for failover may be provided.
   The format remains the same as explained in the previous paragraph.
   If the PE detects a failure of its PU, the PE may -- now in the role
   of a PU -- use the provided PH for a handle resolution to find a new
   PE or use the provided PE identities to select one.  After that, it
   can perform a failover to that PE.

3.8.  Protocol Stack

   The protocol stack of a PR provides ENRP and ASAP services to PRs and
   PEs/PUs respectively.  But between PU and PE, ASAP provides a Session
   Layer protocol in the OSI model.  From the perspective of the
   Application Layer, the PU side establishes a session with a pool.
   ASAP takes care of selecting a PE of the pool, initiating and
   maintaining the underlying transport connection and triggering a
   failover procedure when the PE becomes unavailable.

   The Transport Layer protocol is by default SCTP (as defined in [1])
   -- except for the UDP-based automatic configuration announces (see
   Section 3.6) -- over possibly multi-homed IPv4 and/or IPv6.  SCTP has
   been chosen due to its support of multi-homing and its reliability
   features (see also [26]).




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3.9.  Extensions

   A couple of extensions to RSerPool are existing: Handle Resolution
   Option defined in [9] improves the PE selection by letting the PU
   tell the PR its required number of PEs to be selected.  ENRP Takeover
   Suggestion introduced in [11] ensures load balancing among PRs. [10]
   defines a delay-sensitive pool policy. [8] defines an SNMP MIB for
   RSerPool.

3.10.  Reference Implementation and Deployment

   RSPLIB is the Open Source reference implementation of RSerPool.  It
   is currently -- as of February 2016 -- available for Linux, FreeBSD,
   MacOS and Solaris.  It is actively maintained.  Particularly, it is
   also included in Ubuntu Linux as well as in the FreeBSD ports
   collection.  RSPLIB can be downloaded from [14].  Further details on
   the implementation are available in [16], [24].

   RSerPool with RSPLIB is deployed in a couple of Open Source projects,
   including the SimProcTC Simulation Processing Tool-Chain for
   distributing simulation runs in a compute pool (see [25] as well as
   the simulation run distribution project explained in [26] for a
   practical example) as well as for service infrastructure management
   in the NorNet Core research testbed (see [27], [28]).

4.  Usage of Reliable Server Pooling

   **** TO BE DISCUSSED! ****

   The following features of RSerPool can be used for VNFPOOL:

   o  Pool management.

   o  PE seclection with pool policies.

   o  Session management with help of ASAP_BUSINESS_CARD.

   The following features have to be added to RSerPool itself:

   o  Support of TCP including MPTCP as additional/alternative transport
      protocols.

   o  Possibly add some special pool policies?

   o  See also [13] for ideas on a next generation of RSerPool.

   The following features have to be provided outside of RSerPool:




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   o  State synchronisation for VNFPOOL.

   o  Pool Manager functionality as an RSerPool-based service.

5.  Security Considerations

   Security considerations for RSerPool can be found in [6].
   Furthermore, [23] examines the robustness of RSerPool systems against
   attacks.

6.  IANA Considerations

   This document introduces no additional considerations for IANA.

7.  Testbed Platform

   A large-scale and realistic Internet testbed platform with support
   for Reliable Server Pooling and the underlying SCTP protocol is
   NorNet.  A description of and introduction to NorNet is provided in
   [28], [29], [30].  Further information can be found on the project
   website [15] at https://www.nntb.no.

8.  Acknowledgments

   The authors would like to thank Xing Zhou for the friendly support.

9.  References

9.1.  Normative References

   [1]        Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,
              <https://www.rfc-editor.org/info/rfc4960>.

   [2]        Lei, P., Ong, L., Tuexen, M., and T. Dreibholz, "An
              Overview of Reliable Server Pooling Protocols", RFC 5351,
              DOI 10.17487/RFC5351, September 2008, <https://www.rfc-
              editor.org/info/rfc5351>.

   [3]        Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,
              "Aggregate Server Access Protocol (ASAP)", RFC 5352,
              DOI 10.17487/RFC5352, September 2008, <https://www.rfc-
              editor.org/info/rfc5352>.

   [4]        Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and A.
              Silverton, "Endpoint Handlespace Redundancy Protocol
              (ENRP)", RFC 5353, DOI 10.17487/RFC5353, September 2008,
              <https://www.rfc-editor.org/info/rfc5353>.



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   [5]        Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,
              "Aggregate Server Access Protocol (ASAP) and Endpoint
              Handlespace Redundancy Protocol (ENRP) Parameters",
              RFC 5354, DOI 10.17487/RFC5354, September 2008,
              <https://www.rfc-editor.org/info/rfc5354>.

   [6]        Stillman, M., Ed., Gopal, R., Guttman, E., Sengodan, S.,
              and M. Holdrege, "Threats Introduced by Reliable Server
              Pooling (RSerPool) and Requirements for Security in
              Response to Threats", RFC 5355, DOI 10.17487/RFC5355,
              September 2008, <https://www.rfc-editor.org/info/rfc5355>.

   [7]        Dreibholz, T. and M. Tuexen, "Reliable Server Pooling
              Policies", RFC 5356, DOI 10.17487/RFC5356, September 2008,
              <https://www.rfc-editor.org/info/rfc5356>.

   [8]        Dreibholz, T. and J. Mulik, "Reliable Server Pooling MIB
              Module Definition", RFC 5525, DOI 10.17487/RFC5525, April
              2009, <https://www.rfc-editor.org/info/rfc5525>.

   [9]        Dreibholz, T., "Handle Resolution Option for ASAP", draft-
              dreibholz-rserpool-asap-hropt-21 (work in progress),
              August 2017.

   [10]       Dreibholz, T. and X. Zhou, "Definition of a Delay
              Measurement Infrastructure and Delay-Sensitive Least-Used
              Policy for Reliable Server Pooling", draft-dreibholz-
              rserpool-delay-20 (work in progress), August 2017.

   [11]       Dreibholz, T. and X. Zhou, "Takeover Suggestion Flag for
              the ENRP Handle Update Message", draft-dreibholz-rserpool-
              enrp-takeover-18 (work in progress), August 2017.

   [12]       Zong, N., Dunbar, L., Shore, M., Lopez, D., and G.
              Karagiannis, "Virtualized Network Function (VNF) Pool
              Problem Statement", draft-zong-vnfpool-problem-
              statement-06 (work in progress), July 2014.

   [13]       Dreibholz, T., "Ideas for a Next Generation of the
              Reliable Server Pooling Framework", draft-dreibholz-
              rserpool-nextgen-ideas-08 (work in progress), August 2017.

9.2.  Informative References

   [14]       Dreibholz, T., "Thomas Dreibholz's RSerPool Page",
              Online: https://www.uni-due.de/~be0001/rserpool/, 2017,
              <https://www.uni-due.de/~be0001/rserpool/>.




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   [15]       Dreibholz, T., "NorNet -- A Real-World, Large-Scale Multi-
              Homing Testbed", Online: https://www.nntb.no/, 2017,
              <https://www.nntb.no/>.

   [16]       Dreibholz, T., "Reliable Server Pooling - Evaluation,
              Optimization and Extension of a Novel IETF Architecture",
              March 2007, <http://duepublico.uni-duisburg-
              essen.de/servlets/DerivateServlet/Derivate-16326/
              Dre2006_final.pdf>.

   [17]       Dreibholz, T., "An Efficient Approach for State Sharing in
              Server Pools", Proceedings of the 27th IEEE Local Computer
              Networks Conference (LCN) Pages 348-349,
              ISBN 0-7695-1591-6, DOI 10.1109/LCN.2002.1181806, November
              2002, <https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/StateSharing-Paper-
              ShortVersion.pdf>.

   [18]       Dreibholz, T. and E. Rathgeb, "On the Performance of
              Reliable Server Pooling Systems", Proceedings of the IEEE
              Conference on Local Computer Networks (LCN) 30th
              Anniversary Pages 200-208, ISBN 0-7695-2421-4,
              DOI 10.1109/LCN.2005.98, November 2005,
              <https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/LCN2005.pdf>.

   [19]       Dreibholz, T. and E. Rathgeb, "An Evaluation of the Pool
              Maintenance Overhead in Reliable Server Pooling Systems",
              SERSC International Journal on Hybrid Information
              Technology (IJHIT) Number 2, Volume 1, Pages 17-32,
              ISSN 1738-9968, April 2008, <https://www.wiwi.uni-
              due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/IJHIT2008.pdf>.

   [20]       Zhou, X., Dreibholz, T., and E. Rathgeb, "A New Server
              Selection Strategy for Reliable Server Pooling in Widely
              Distributed Environments", Proceedings of the 2nd IEEE
              International Conference on Digital Society (ICDS) Pages
              171-177, ISBN 978-0-7695-3087-1, DOI 10.1109/ICDS.2008.12,
              February 2008, <https://www.wiwi.uni-
              due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/ICDS2008-LUD.pdf>.









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   [21]       Zhou, X., Dreibholz, T., Fa, F., Du, W., and E. Rathgeb,
              "Evaluation and Optimization of the Registrar Redundancy
              Handling in Reliable Server Pooling Systems", Proceedings
              of the IEEE 23rd International Conference on Advanced
              Information Networking and Applications (AINA) Pages
              256-262, ISBN 978-0-7695-3638-5, DOI 10.1109/AINA.2009.25,
              May 2009, <https://www.wiwi.uni-
              due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/AINA2009.pdf>.

   [22]       Dreibholz, T. and E. Rathgeb, "Overview and Evaluation of
              the Server Redundancy and Session Failover Mechanisms in
              the Reliable Server Pooling Framework", International
              Journal on Advances in Internet Technology (IJAIT) Number
              1, Volume 2, Pages 1-14, ISSN 1942-2652, June 2009,
              <https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/IJAIT2009.pdf>.

   [23]       Dreibholz, T., Zhou, X., Becke, M., Pulinthanath, J.,
              Rathgeb, E., and W. Du, "On the Security of Reliable
              Server Pooling Systems", International Journal on
              Intelligent Information and Database
              Systems (IJIIDS) Number 6, Volume 4, Pages 552-578,
              ISSN 1751-5858, DOI 10.1504/IJIIDS.2010.036894, December
              2010, <https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/IJIIDS2010.pdf>.

   [24]       Dreibholz, T. and M. Becke, "The RSPLIB Project - From
              Research to Application",  Demo Presentation at the IEEE
              Global Communications Conference (GLOBECOM), December
              2010, <https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/Globecom2010-Demo.pdf>.

   [25]       Dreibholz, T. and E. Rathgeb, "A Powerful Tool-Chain for
              Setup, Distributed Processing, Analysis and Debugging of
              OMNeT++ Simulations", Proceedings of the 1st ACM/ICST
              International Workshop on OMNeT++ ISBN 978-963-9799-20-2,
              DOI 10.4108/ICST.SIMUTOOLS2008.2990, March 2008,
              <https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
              TDR/ReliableServer/Publications/OMNeTWorkshop2008.pdf>.

   [26]       Dreibholz, T., "Evaluation and Optimisation of Multi-Path
              Transport using the Stream Control Transmission Protocol",
               Habilitation Treatise, March 2012,
              <https://duepublico.uni-duisburg-
              essen.de/servlets/DerivateServlet/Derivate-29737/
              Dre2012_final.pdf>.




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   [27]       Gran, E., Dreibholz, T., and A. Kvalbein, "NorNet Core - A
              Multi-Homed Research Testbed", Computer Networks, Special
              Issue on Future Internet Testbeds Volume 61, Pages 75-87,
              ISSN 1389-1286, DOI 10.1016/j.bjp.2013.12.035, March 2014,
              <https://www.simula.no/file/simulasimula2236pdf/download>.

   [28]       Dreibholz, T. and E. Gran, "Design and Implementation of
              the NorNet Core Research Testbed for Multi-Homed Systems",
              Proceedings of the 3nd International Workshop on Protocols
              and Applications with Multi-Homing Support (PAMS) Pages
              1094-1100, ISBN 978-0-7695-4952-1,
              DOI 10.1109/WAINA.2013.71, March 2013,
              <https://www.simula.no/file/
              threfereedinproceedingsreference2012-12-207643198512pdf/
              download>.

   [29]       Dreibholz, T., "NorNet at NICTA - An Introduction to the
              NorNet Testbed",  Invited Talk at National Information
              Communications Technology Australia (NICTA), January 2016,
              <https://www.simula.no/file/nicta2016-presentationpdf/
              download>.

   [30]       Dreibholz, T., "An Experiment Tutorial for the NorNet Core
              Testbed at the the Universidad de Castilla-La Mancha",
               Tutorial at the Universidad de Castilla-La Mancha,
              Instituto de Investigacion Informatica de Albacete,
              February 2017, <https://www.simula.no/file/uclm2017-
              nornet-tutorialpdf/download>.

Authors' Addresses

   Thomas Dreibholz
   Simula Research Laboratory, Network Systems Group
   Martin Linges vei 17
   1364 Fornebu, Akershus
   Norway

   Phone: +47-6782-8200
   Fax:   +47-6782-8201
   Email: dreibh@simula.no
   URI:   https://www.simula.no/people/dreibh










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   Michael Tuexen
   Muenster University of Applied Sciences
   Stegerwaldstrasse 39
   48565 Steinfurt, Nordrhein-Westfalen
   Germany

   Email: tuexen@fh-muenster.de
   URI:   https://www.fh-muenster.de/fb2/personen/professoren/tuexen/


   Melinda Shore
   No Mountain Software
   PO Box 16271
   Two Rivers, Alaska  99716
   U.S.A.

   Phone: +1-907-322-9522
   Email: melinda.shore@nomountain.net
   URI:   https://www.linkedin.com/pub/melinda-shore/9/667/236


   Ning Zong
   Huawei Technologies
   101 Software Avenue
   Nanjing, Jiangsu  210012
   China

   Email: zongning@huawei.com
   URI:   https://cn.linkedin.com/pub/ning-zong/15/737/490






















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