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EXPERIMENTAL
Network Working Group                                       T. DreibholzRequest for Comments: 5356                  University of Duisburg-EssenCategory: Experimental                                         M. Tuexen                                      Muenster Univ. of Applied Sciences                                                          September 2008Reliable Server Pooling PoliciesStatus of This Memo   This memo defines an Experimental Protocol for the Internet   community.  It does not specify an Internet standard of any kind.   Discussion and suggestions for improvement are requested.   Distribution of this memo is unlimited.Abstract   This document describes server pool policies for Reliable Server   Pooling (RSerPool) including considerations for implementing them at   Endpoint Handlespace Redundancy Protocol (ENRP) servers and pool   users.Table of Contents1. Introduction ....................................................32. Conventions .....................................................33. Terminology and Definitions .....................................33.1. Load .......................................................33.2. Weight .....................................................34. Non-Adaptive Policies ...........................................44.1. Round Robin Policy .........................................44.1.1. Description .........................................44.1.2. ENRP Server Considerations ..........................44.1.3. Pool User Considerations ............................44.1.4. Pool Member Selection Policy Parameter ..............44.2. Weighted Round Robin Policy ................................54.2.1. Description .........................................54.2.2. ENRP Server Considerations ..........................54.2.3. Pool User Considerations ............................54.2.4. Pool Member Selection Policy Parameter ..............54.3. Random Policy ..............................................54.3.1. Description .........................................54.3.2. ENRP Server Considerations ..........................64.3.3. Pool User Considerations ............................64.3.4. Pool Member Selection Policy Parameter ..............64.4. Weighted Random Policy .....................................64.4.1. Description .........................................6Dreibholz & Tuexen            Experimental                      [Page 1]

RFC 5356                   RSerPool Policies              September 20084.4.2. ENRP Server Considerations ..........................64.4.3. Pool User Considerations ............................64.4.4. Pool Member Selection Policy Parameter ..............74.5. Priority Policy ............................................74.5.1. Description .........................................74.5.2. ENRP Server Considerations ..........................74.5.3. Pool Element Considerations .........................74.5.4. Pool Member Selection Policy Parameter ..............75. Adaptive Policies ...............................................85.1. Least Used Policy ..........................................85.1.1. Description .........................................85.1.2. ENRP Server Considerations ..........................85.1.3. Pool User Considerations ............................85.1.4. Pool Member Selection Policy Parameter ..............85.2. Least Used with Degradation Policy .........................95.2.1. Description .........................................95.2.2. ENRP Server Considerations ..........................95.2.3. Pool User Considerations ............................95.2.4. Pool Member Selection Policy Parameter ..............95.3. Priority Least Used Policy ................................105.3.1. Description ........................................105.3.2. ENRP Server Considerations .........................105.3.3. Pool User Considerations ...........................105.3.4. Pool Member Selection Policy Parameter .............105.4. Randomized Least Used Policy ..............................115.4.1. Description ........................................115.4.2. ENRP Server Considerations .........................115.4.3. Pool User Considerations ...........................115.4.4. Pool Member Selection Policy Parameter .............116. Security Considerations ........................................117. IANA Considerations ............................................127.1. A New Table for RSerPool Policy Types .....................128. Reference Implementation .......................................139. References .....................................................139.1. Normative References ......................................139.2. Informative References ....................................14Dreibholz & Tuexen            Experimental                      [Page 2]

RFC 5356                   RSerPool Policies              September 20081.  Introduction   The protocols defined in [RFC5353], [RFC5352], and [RFC5354] support   a variety of server policies.  Some of the policies use dynamic load   information of the pool elements and others do not.  Therefore, we   classify them as adaptive and non-adaptive.  The selection of the   pool element is performed by two different entities, the ENRP server   and the pool user.  Some of the consequences for policies that are   not stateless are described in [ICN2005] and [LCN2005].   Therefore, this document describes not only packet formats but also   gives a detailed description of the procedures to be followed at the   ENRP servers and the pool users to implement each server policy.2.  Conventions   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.  Terminology and Definitions3.1.  Load   The term load is a value specifying how much a pool element's   resources are currently utilized. 0x00000000 states that the pool   element is not utilized (0%); 0xffffffff states that it is fully   utilized (100%).  Defining what utilization means is application-   dependent and out of the scope of RSerPool.  However, it is required   that all pool elements of the same pool using load information have   the same definition of load.   For example, load may define the current amount of users out of a   maximum on an FTP server, the CPU usage of a database server, or the   memory utilization of a compute service.3.2.  Weight   Weight defines a pool element's service capacity relative to other   pool elements of the same pool.  Theoretically, there is no upper   limit for weight values (although limited by datatype size).   Defining what value weights compare is application-dependent and out   of the scope of RSerPool.  However, it is required that all pool   elements of the same pool using weight information have the same   definition of weight.Dreibholz & Tuexen            Experimental                      [Page 3]

RFC 5356                   RSerPool Policies              September 2008   A weight of 0 denotes that the pool element is not capable of   providing any service; a higher weight denotes that the pool element   is capable of providing better service than a pool element having a   lower weight.   For example, weight may define a compute service's computation   capacity.  That is, a pool element of weight 100 will complete a work   package in half the time compared to a pool element of weight 50.4.  Non-Adaptive Policies4.1.  Round Robin Policy4.1.1.  Description   The Round Robin (RR) policy is a very simple and efficient policy   that requires state.  This policy is denoted as the default policy   and MUST be supported by all RSerPool components.4.1.2.  ENRP Server Considerations   The ENRP server SHOULD hold the pool elements of each server pool in   a circular list and SHOULD store a pointer to one of the elements,   called the head.  On reception of a handle resolution request, the   ENRP server SHOULD return the pool elements from the circular list,   starting with head.  Then the head SHOULD be advanced by one element.   Using this algorithm ensures that not all lists presented to the pool   users start with the same element.4.1.3.  Pool User Considerations   A pool user SHOULD use the list of pool elements returned by the ENRP   server in a round robin fashion, starting with the first.  If all   elements of the list have been used, it should start from the   beginning again until the information is out of date.4.1.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0x8          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x00000001                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Dreibholz & Tuexen            Experimental                      [Page 4]

RFC 5356                   RSerPool Policies              September 20084.2.  Weighted Round Robin Policy4.2.1.  Description   The Weighted Round Robin (WRR) policy is a generalization of the RR   policy.  If all weights are 1, then WRR is just RR.4.2.2.  ENRP Server Considerations   The ENRP server SHOULD follow the same rules as RR but initialize and   modify the circular list differently.  The ENRP server puts each pool   element, possibly, multiple times into the list such that:   o  The ratio of the number of occurrences of a pool element to the      list length is the same as the ratio of the weight of that pool      element to the sum of weights.   o  The multiple entries of each pool element should be as evenly      distributed as possible in the circular list.4.2.3.  Pool User Considerations   The pool user SHOULD follow the same rules as RR.4.2.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0xc          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x00000002                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                              Weight                           |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  Weight (32 bits, unsigned integer): Weight constant for the WRR      process.4.3.  Random Policy4.3.1.  Description   The Random (RAND) policy is a very simple stateless policy.Dreibholz & Tuexen            Experimental                      [Page 5]

RFC 5356                   RSerPool Policies              September 20084.3.2.  ENRP Server Considerations   The ENRP server selects, at most, the requested number of pool   elements from the list of pool elements.  Each element MUST NOT be   reported more than once to the pool user.4.3.3.  Pool User Considerations   Each time the pool user must select one pool element, it does this by   randomly selecting one element from the list of pool elements   received from the ENRP server.4.3.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0x8          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x00000003                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+4.4.  Weighted Random Policy4.4.1.  Description   The Weighted Random (WRAND) policy is a generalization of the RAND   policy, adding a weight for each pool element entry.  RAND is equal   to WRAND having all weights set to 1.4.4.2.  ENRP Server Considerations   The ENRP server SHOULD select, at most, the requested number of pool   elements randomly from the list of pool elements.  Each element MUST   NOT be reported more than once to the pool user.  The probability of   selecting a pool element should be the ratio of the weight of that   pool element to the sum of weights.4.4.3.  Pool User Considerations   Each time the pool user must select one pool element, it does this by   randomly selecting one element from the list of pool elements   received from the ENRP server.Dreibholz & Tuexen            Experimental                      [Page 6]

RFC 5356                   RSerPool Policies              September 20084.4.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0xc          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x00000004                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                              Weight                           |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  Weight (32 bits, unsigned integer): Weight constant for the WRAND      process.4.5.  Priority Policy4.5.1.  Description   The Priority (PRIO) policy can be used to select always a pool   element with the highest priority.4.5.2.  ENRP Server Considerations   The ENRP server MUST select the pool elements with the highest   priorities.  They MUST be reported in decreasing order.  If multiple   pool elements have the same priority, they may be listed in any   order.4.5.3.  Pool Element Considerations   The pool user MUST select the active pool element with the highest   priority.4.5.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0xc          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x00000005                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                            Priority                           |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Dreibholz & Tuexen            Experimental                      [Page 7]

RFC 5356                   RSerPool Policies              September 2008   o  Priority (32 bits, unsigned integer): Larger numbers mean higher      priorities.5.  Adaptive Policies5.1.  Least Used Policy5.1.1.  Description   The Least Used (LU) policy uses load information provided by the pool   elements to select the lowest-loaded pool elements within the pool.5.1.2.  ENRP Server Considerations   The ENRP server SHOULD select, at most, the requested number of pool   elements.  Their load values SHOULD be the lowest possible ones   within the pool.  Each element MUST NOT be reported more than once to   the pool user.  If there is a choice of equal-loaded pool elements,   round robin selection SHOULD be made among these elements.  The   returned list of pool elements MUST be sorted in ascending order by   load value.5.1.3.  Pool User Considerations   The pool user should try to use the pool elements returned from the   list in the order returned by the ENRP server.  A subsequent call for   handle resolution may result in the same list.  Therefore, it is   RECOMMENDED for a pool user to request multiple entries in order to   have a sufficient amount of feasible backup entries available.5.1.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0xc          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x40000001                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                              Load                             |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  Load (32 bits, unsigned integer): Current load of the pool      element.Dreibholz & Tuexen            Experimental                      [Page 8]

RFC 5356                   RSerPool Policies              September 20085.2.  Least Used with Degradation Policy5.2.1.  Description   The Least Used with Degradation (LUD) policy extends the LU policy by   a load degradation value describing the pool element's load increment   when a new service association is accepted.5.2.2.  ENRP Server Considerations   For every pool element entry, a degradation counter MUST be stored.   When a pool element entry is added or updated by registration or re-   registration, this counter MUST be set to 0.  When an entry is   selected for being returned to a pool user, the internal degradation   counter MUST be incremented by 1.  The selection of pool element   entries is handled like for LU, except that the selected pool element   entries SHOULD have the lowest possible sum of load value +   degradation counter * load degradation value.5.2.3.  Pool User Considerations   See LU policy.5.2.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0x10         |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x40000002                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                              Load                             |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                        Load Degradation                       |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  Load (32 bits, unsigned integer): Current load of the pool      element.   o  Load Degradation (32 bits, unsigned integer): Load Degradation      constant of the pool element.Dreibholz & Tuexen            Experimental                      [Page 9]

RFC 5356                   RSerPool Policies              September 20085.3.  Priority Least Used Policy5.3.1.  Description   The Priority Least Used (PLU) policy uses load information provided   by the pool elements to select the lowest-loaded pool elements within   the pool under the assumption that a new application request is   accepted by the pool elements.  Therefore, the pool elements also   have to specify load degradation information.   Example: Pool elements A and B are loaded by 50%, but the load of A   will increase due to a new application request only by 10% while B   will be fully loaded.  PLU allows the specification of this load   degradation in the policy information; the selection is made on the   lowest sum of load and degradation value.  That is, A will be   selected (50+10=60) instead of B (50+50=100).5.3.2.  ENRP Server Considerations   The ENRP server SHOULD select, at most, the requested number of pool   elements.  Their sums of load + degradation SHOULD be the lowest   possible ones within the pool.  Each element MUST NOT be reported   more than once to the pool user.  If there is a choice of equal-   valued pool element entries, round robin SHOULD be made among these   elements.  The returned list of pool elements MUST be sorted   ascending by the sum of load and degradation value.5.3.3.  Pool User Considerations   The pool user should try to use the pool elements returned from the   list in the order returned by the ENRP server.  A subsequent call for   handle resolution may result in the same list.  Therefore, it is   RECOMMENDED for a pool user to request multiple entries in order to   have a sufficient amount of feasible backup entries available.5.3.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0x10         |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x40000003                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                              Load                             |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                        Load Degradation                       |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Dreibholz & Tuexen            Experimental                     [Page 10]

RFC 5356                   RSerPool Policies              September 2008   o  Load (32 bits, unsigned integer): Current load of the pool      element.   o  Load Degradation (32 bits, unsigned integer): Load Degradation      constant of the pool element.5.4.  Randomized Least Used Policy5.4.1.  Description   The Randomized Least Used (RLU) policy combines LU and WRAND.  That   is, the pool element entries are selected randomly.  The probability   for a pool element entry A, utilized with load_A, to be selected is   (0xFFFFFFFF - load_A) / (sum(0xFFFFFFFF-load_x)), i.e., this PE's   unload part related to the whole pool unload rate.5.4.2.  ENRP Server Considerations   The ENRP server SHOULD behave like WRAND, having every PE's weight   set to (0xffffffff -- load value provided by the pool element).5.4.3.  Pool User Considerations   See WRAND policy.5.4.4.  Pool Member Selection Policy Parameter       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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |    Param Type = 0x8           |         Length = 0xc          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   Policy Type = 0x40000004                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                              Load                             |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  Load (32 bits, unsigned integer): Current load of the pool      element.6.  Security Considerations   The security threats regarding RSerPool have been analyzed in   RSerPool threats [RFC5355].  The server policy descriptions in this   document do not add any other threats.Dreibholz & Tuexen            Experimental                     [Page 11]

RFC 5356                   RSerPool Policies              September 20087.  IANA Considerations   This document (RFC 5356) is the reference for all registrations   described in this section.  All registrations have been listed on the   RSerPool Parameters page.7.1.  A New Table for RSerPool Policy Types   RSerPool policy types that are 4-byte values are maintained by IANA.   The format of the policy type value is defined as follows:         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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |X|A|                   Policy Number                           |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  X: If set to 1, the policy is user defined and not standardized.      All standards policies reserved by the IETF use X=0.   o  A: If set to 1, the policy is adaptive.  Otherwise, it is non-      adaptive.   o  Policy Number: The actual number of the policy.   Nine initial policy types have been assigned and are maintained in a   new table, "RSerPool Policy Types":Dreibholz & Tuexen            Experimental                     [Page 12]

RFC 5356                   RSerPool Policies              September 2008     Value           Policy                                  Reference     -----           ---------                               ---------     0x00000000      (reserved, invalid value)RFC 5356     0x00000001      Round RobinRFC 5356     0x00000002      Weighted Round RobinRFC 5356     0x00000003      RandomRFC 5356     0x00000004      Weighted RandomRFC 5356     0x00000005      PriorityRFC 5356     0x00000006      (reserved by IETF)RFC 5356     ...     0x3fffffff      (reserved by IETF)RFC 5356     0x40000000      (reserved, invalid value)RFC 5356     0x40000001      Least UsedRFC 5356     0x40000002      Least Used with DegradationRFC 5356     0x40000003      Priority Least UsedRFC 5356     0x40000004      Randomized Least UsedRFC 5356     0x40000005      (reserved by IETF)RFC 5356     ...     0x7fffffff      (reserved by IETF)RFC 5356     0x80000000      (private use, non-standard policy)RFC 5356     ...     0xffffffff      (private use, non-standard policy)RFC 5356   Requests to register an RSerPool policy type in this table should be   sent to IANA.  The number must be unique and use the appropriate   upper bits.  The "Specification Required" policy of [RFC5226] MUST be   applied.   The policy type space from 0x80000000 to 0xffffffff is designated for   private use.8.  Reference Implementation   A reference implementation of RSerPool and the policies described in   this document is available at [RSerPoolPage] and described in   [Dre2006].9.  References9.1.  Normative References   [RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate                   Requirement Levels",BCP 14,RFC 2119, March 1997.Dreibholz & Tuexen            Experimental                     [Page 13]

RFC 5356                   RSerPool Policies              September 2008   [RFC5226]       Narten, T. and H. Alvestrand, "Guidelines for Writing                   an IANA Considerations Section in RFCs",BCP 26,RFC 5226, May 2008.   [RFC5354]       Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,                   "Aggregate Server Access Protocol (ASAP) and Endpoint                   Handlespace Redundancy Protocol (ENRP) Parameters",RFC 5354, September 2008.   [RFC5352]       Stewart, R., Xie, Q., Stillman, M., and M. Tuexen,                   "Aggregate Server Access Protocol (ASAP)",RFC 5352,                   September 2008.   [RFC5353]       Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and                   A. Silverton, "Endpoint Handlespace Redundancy                   Protocol (ENRP)",RFC 5353, September 2008.   [RFC5355]       Stillman, M., Ed., Gopal, R., Guttman, E., Holdrege,                   M., and S. Sengodan, "Threats Introduced by Reliable                   Server Pooling (RSerPool) and Requirements for                   Security in Response to Threats",RFC 5355,                   September 2008.9.2.  Informative References   [RSerPoolPage]  Dreibholz, T., "Thomas Dreibholz's RSerPool Page",                   <http://tdrwww.iem.uni-due.de/dreibholz/rserpool/>.   [Dre2006]       Dreibholz, T., "Reliable Server Pooling --                   Evaluation, Optimization and Extension of a Novel                   IETF Architecture", Ph.D. Thesis University of                   Duisburg-Essen, Faculty of Economics, Institute for                   Computer Science and Business Information Systems,                   March 2007, <http://duepublico.uni-duisburg-essen.de/servlets/DerivateServlet/Derivate-16326/Dre2006-final.pdf>.   [LCN2005]       Dreibholz, T. and E. Rathgeb, "On the Performance of                   Reliable Server Pooling Systems", Proceedings of the                   30th IEEE Local Computer Networks Conference,                   November 2005.   [ICN2005]       Dreibholz, T., Rathgeb, E., and M. Tuexen, "Load                   Distribution Performance of the Reliable Server                   Pooling Framework", Proceedings of the 4th IEEE                   International Conference on Networking, April 2005.Dreibholz & Tuexen            Experimental                     [Page 14]

RFC 5356                   RSerPool Policies              September 2008Authors' Addresses   Thomas Dreibholz   University of Duisburg-Essen, Institute for Experimental Mathematics   Ellernstrasse 29   45326 Essen, Nordrhein-Westfalen   Germany   Phone: +49-201-1837637   Fax:   +49-201-1837673   EMail: dreibh@iem.uni-due.de   URI:http://www.iem.uni-due.de/~dreibh/   Michael Tuexen   Muenster University of Applied Sciences   Stegerwaldstrasse 39   48565 Steinfurt   Germany   Phone: +49-2551-962550   Fax:   +49-2551-962563   EMail: tuexen@fh-muenster.deDreibholz & Tuexen            Experimental                     [Page 15]

RFC 5356                   RSerPool Policies              September 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Dreibholz & Tuexen            Experimental                     [Page 16]

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