Internet Engineering Task Force                            E. Haleplidis
Internet-Draft                                            O. Koufopavlou
Intended status: Informational                                S. Denazis
Expires: July 14, 2011                              University of Patras
                                                        January 10, 2011


                 ForCES Implementation Experience Draft
          draft-haleplidis-forces-implementation-experience-02

Abstract

   The forwarding and Control Element Separation (ForCES) protocol
   defines a standard communication and control mechanism through which
   a Control Element (CE) can control the behavior of a Forwarding
   Element (FE).  This document captures the experience of implementing
   the ForCES protocol and model.  Its aim is to help others by
   providing examples and possible strategies for implementing the
   ForCES protocol.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 14, 2011.

Copyright Notice

   Copyright (c) 2011 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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   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.  Terminology and Conventions  . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Document Goal  . . . . . . . . . . . . . . . . . . . . . .  4
   3.  ForCES Architecture  . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Pre-association setup - Initial Configuration  . . . . . .  6
     3.2.  TML  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  Model  . . . . . . . . . . . . . . . . . . . . . . . . . .  7
       3.3.1.  Components . . . . . . . . . . . . . . . . . . . . . .  7
       3.3.2.  LFBs . . . . . . . . . . . . . . . . . . . . . . . . . 10
     3.4.  Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 11
       3.4.1.  TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 11
       3.4.2.  Message Deserialization  . . . . . . . . . . . . . . . 13
       3.4.3.  Message Serialization  . . . . . . . . . . . . . . . . 15
   4.  Developement Platforms . . . . . . . . . . . . . . . . . . . . 17
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 21
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22























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1.  Terminology and Conventions

   The terminology used in this document is the same as in the
   Forwarding and Control Element Separation Protocol [RFC5810] and is
   not copied in this document.














































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2.  Introduction

   Forwarding and Control Element Separation (ForCES) defines an
   architectural framework and associated protocols to standardize
   information exchange between the control plane and the forwarding
   plane in a ForCES Network Element (ForCES NE).  [RFC3654] has defined
   the ForCES requirements, and [RFC3746] has defined the ForCES
   framework.

   The ForCES protocol works in a master-slave mode in which FEs are
   slaves and CEs are masters.  The protocol includes commands for
   transport of Logical Functional Block (LFB) configuration
   information, association setup, status, and event notifications, etc.
   The reader is encouraged to read the Forwarding and Control Element
   Separation Protocol [RFC5810] for further information.

   [RFC5812] presents a formal way to define FE Logical Functional
   Blocks (LFBs) using XML.  LFB configuration components, capabilities,
   and associated events are defined when the LFB is formally created.
   The LFBs within the Forwarding Element (FE) are accordingly
   controlled in a standardized way by the ForCES protocol.

   The Transport Mapping Layer (TML) transports the protocol messages.
   The TML is where the issues of how to achieve transport level
   reliability, congestion control, multicast, ordering, etc. are
   handled.  It is expected that more than one TML will be standardized.
   The various possible TMLs could vary their implementations based on
   the capabilities of underlying media and transport.  However, since
   each TML is standardized, interoperability is guaranteed as long as
   both endpoints support the same TML.  All ForCES Protocol Layer
   implementations must be portable across all TMLs.  Although more than
   one TML may be standardized for the ForCES Protocol, all ForCES
   implementations must implement the SCTP TML [RFC5811].

   The Forwarding and Control Element Separation Applicability Statement
   [RFC6041] captures the applicable areas in which ForCES can be used.

2.1.  Document Goal

   This document captures the experience of implementing the ForCES
   protocol and model and its main goal is not to tell others how to
   implement, but to provide alternatives, ideas and proposals as how it
   can be implemented.

   Also, this document mentions possible problems and potential choices
   that can be made, in an attempt to help implementors develop their
   own products.




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   Additionally this document takes into account that the reader has
   become familiar with the three main ForCES RFCs, the Forwarding and
   Control Element Separation Protocol [RFC5810], the Forwarding and
   Control Element Separation Forwarding Element Model [RFC5812] and the
   SCTP-Based Transport Mapping Layer (TML) for the Forwarding and
   Control Element Separation Protocol [RFC5811].













































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3.  ForCES Architecture

   This section discusses the ForCES architecture, implementation
   challenges and how to overcome them.

3.1.  Pre-association setup - Initial Configuration

   The initial configuration of the FE and the Control Element (CE) is
   done respectively by the FE Manager and the CE Manager.  These
   entities have not as yet been standardized.

   The simplest solution, are static configuration files, which play the
   role of the Managers and are read by FEs and CEs.

   For more dynamic solutions however, it is expected that the Managers
   will be entities that will talk to each other and exchange details
   regarding the associations.  Any developer can create any Manager,
   but they should at least be able to exchange the following details:

   From the FE Manager side:

   1.  FE Identifiers (FEIDs)

   2.  FE IP addresses, if the FEs and CEs will be communicating via
       network.

   3.  TML.  The TML that will be used.  If this is omitted, then SCTP
       must be chosen as default.

   4.  TML Priority ports.  If this is omitted as well, then the CE must
       use the default values from the respective TML RFC.

   From the CE Manager side:

   1.  CE Identifiers (CEIDs)

   2.  CE IP addresses, if the FEs and CEs will be communicating via
       network.

   3.  TML.  The TML that will be used.  If this is omitted, then SCTP
       must be chosen as default.

   4.  TML Priority ports.  If this is omitted as well, then the FE must
       use the default values from the respective TML RFC.







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3.2.  TML

   All ForCES implementations must support the SCTP as TML.  Even if
   another TML will be chosen by the developer, SCTP is mandatory and
   must be supported.

   There are several issues that should concern a developer for the TML.

   1.  Security.  TML must be secure according to the respective RFC.
       For SCTP you have to use IPSec.

   2.  NAT issues.  ForCES can be deployed everywhere and can run over
       SCTP/IP.  In order for the FE and CE to work behind NATs you must
       ensure that the TML ports are forwarded and that the firewall
       allows SCTP through.  This problem was identified during the
       first ForCES interoperability test and documented in the
       Implementation Report for Forwarding and Control Element
       Separation [RFC6053].

3.3.  Model

   The model inherently is very dynamic.  Using the basic atomic values
   that are specified, new datatypes can be built using atomic (single
   valued) and/or compound (structures and arrays).

   The difficulty is to create something that is completely scalable so
   a develeper doesn't need to write the same code for new LFBs, or for
   new components etc.  Just create code for the defined atomic values
   and then new components can be built based on already written code.

   The model itself provides the key which is inheritance.

3.3.1.  Components

   First, a basic component needs to be created as the mother of all the
   components with the basic parameters of all the components:

   o  The ID of the component.

   o  The access rights of that component.

   o  If it is an optional component.

   o  If it is of variable size.

   o  Minimum data size.





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   o  Maximum data size.

   If the data size of the component is not variable, then the size is
   either the minimum or the maximum size, as both should have the same
   value.

   Next, some basic functions are in order:

   o  A common constructor.

   o  A common deconstructor.

   o  Retrieve Component ID.

   o  Retrieve access right property.

   o  Query if it is an optional component.

   o  Get Full Data.

   o  Set Full Data.

   o  Get Sparse Data.

   o  Set Sparse Data.

   o  Del Full Data.

   o  Del Sparse Data.

   o  Get Property

   o  Set Property

   o  Get Value.

   o  Set Value.

   o  Del Value.

   o  Get Data.

   o  Clone component.

   The Get/Set/Del Full/Sparse Data and Get/Set Property functions
   handle the respective ForCES commands and return the respective TLV,
   for example the Set Full Data should return a Result TLV.  The Get/
   Set/Del Value are called from the Get/Set/Del Full/Sparse Data



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   respectively and provide the interface to the actual values in the
   hardware, separating the forces handling logic from the interface to
   the actual values.

   The Get Data function should return the value of the data only, not
   in TLV format.

   The last function seems out of place.  That function must return a
   new component that has the exact same values and attributes.  This
   function is useful in array components as described further.

   The only requirement is to implement the base atomic data types.  Any
   new atomic datatype can be built as a child of a base data type which
   will inherit all the functions and if necessary override them.

   The struct component can then be built.  A struct component is a
   component by itself, but consists of a number of atomic components.
   These atomic components create a static array within the struct.  The
   ID of each atomic component is the array's index.  The Clone
   function, for a struct component, must create and return an exact
   copy of the struct component with the same static array.

   The most difficult component to be built is the array.  The
   difficulty lie in the actual benefit of the model.  You have absolute
   freedom over what you build.  An array is an array of components.  In
   all rows you have the exact same type of component either a single
   component or a struct.  The struct can have multiple single
   components, or a combination of single components, structs and arrays
   and so on.  So, the difficulty lies in how to create a new row, a new
   component by itself.  This is where the Clone function is very
   useful.  For the array a mother component that can spawn new
   components exactly like itself is needed.  Once a Set command is
   received, the mother component can spawn a new component, if the
   targeted row does not exists, and add it into the array, and with the
   Set Full Data the value is set in the recently spawned component, as
   the spawned component knows how the data is created.  In order to
   distinguish these spawned components from each other and their
   functionality, some kind of index is required that will also reflect
   on how the actual data of the specific component is stored on the
   hardware.

   Once the basic constructors of all possible components are created,
   then a developer only has to create his LFB components or datatypes
   as a child of one of the already created components and the only
   thing the developer really needs to add, is the three functions of
   Get/Set/Del value of each component which is platform dependent.  The
   rest stays the same.




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3.3.2.  LFBs

   The same architecture in the components can be used for the LFBs,
   allowing a developer to write LFB handling code only once.  The
   parent LFB has some basic attributes:

   o  The LFB Class ID.

   o  The LFB Instance ID.

   o  An Array of Components.

   o  An Array of Capabilities.

   o  An Array of Events.

   Then some common functions:

   o  Handle Configuration Command.

   o  Handle Query Command.

   o  Get Class ID.

   o  Get Instance ID.

   Once these are created each LFB can inherit all these from the parent
   and the only thing it has to do is to add the components that have
   already been created.

   An example can be seen in Figure 1.  The following code creates a
   part of FEProtocolLFB:

   //FEID
   cui = new Component_uInt(FEPO_FEID, ACCESS_READ_ONLY, FE_id);
   Components[cui->get_ComponentId()]=cui; //Add component to array list

   //Current FEHB Policy Value
   cub = new Component_uByte(FEPO_FEHBPolicy, ACCESS_READ_WRITE, 0);
   Components[cub->get_ComponentId()]=cub; //Add component to array list

   //FEIDs for BackupCEs Array
   cui = new Component_uInt(0, ACCESS_READ_WRITE, 0);
   ca = new Component_Array(FEPO_BackupCEs, ACCESS_READ_WRITE);
   ca->AddRow(cui, 1);
   ca->AddMotherComponent(cui);
   Components[ca->get_ComponentId()]=ca; //Add component to array list




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         Figure 1: Example code for creating part of FEProtocolLFB

   The same concept can be applied to handling LFBs as one FE.  An FE is
   a collection of LFBs.  Thus all LFBs can be stored in an array based
   on the LFB's class id, version and instance.  Then what is required
   is an LFBHandler that will handle the array of the LFBs.  A specific
   LFB, for example, can be addressed using the following scheme:

   LFBs[ClassID][Version][InstanceID].

   Note: While an array can be used in components, capabilities and
   events, a hash table or a similar concept is better suited for
   storing LFBs using the component ID as the hash key with linked lists
   for collision handling, as the created array can have large gaps if
   the values of LFB Class ID vary greatly.

3.4.  Protocol

3.4.1.  TLVs

   The goal, for protocol handling, is to create a general and scalable
   architecture that handles all protocol messages instead of something
   implementation specific.  There are certain difficulties that have to
   be overcome first.

   Since the model allows a developer to define any LFB required, the
   protocol has been thus created to give the user the freedom to
   configure and query any component whatever the underlying model.
   While this being a strong point for the protocol itself, one
   difficulty lies with the unkwown underlying model and the unlimited
   number of types of messages that can be created, making creating
   something generic a daunting task.

   Another difficulty also arises from the batching capabilities of the
   protocol.  You can have multiple Operations within a message, you can
   select more than one LFB to command, and more than one component to
   manipulate.

   A possible solution is again provided by inheritance.  There are two
   basic components in a protocol message.

   1.  The common header.

   2.  The rest of the message.

   The rest of the message is divided in Type-Length-Value (TLV) units,
   and in one case Index-Length-Value (ILV) units.




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   The TLV hierarchy can be seen in the Figure 2:

                         Common Header
                               |
                   +-----------+----------+-----------+
                   |           |          |           |
                Redirect   LFBSelect   ASResult   ASTreason
                  TLV         TLV        TLV         TLV
                               |
                               |
                           Operation
                              TLV
                               |
                               |            Optional
                            PathData  ---> KeyInfo TLV
                              TLV
                               |
                    +----------+---------+----------+
                    |          |         |          |
                SparseData   Result   FullData   PathData
                   TLV        TLV       TLV        TLV

                      Figure 2: ForCES TLV Hierrachy

   The above figure shows only the basic hierarchy level of TLVs and
   does not show batching.  Also this figure does not show the recursion
   that can occur at the last level of the hierarchy.  The figure shows
   one kind of recursion with PathData within PathData.  FullData can be
   within FullData and SparseData.  The possible combination of TLVs are
   described in detail in the Forwarding and Control Element Separation
   Protocol [RFC5810] as well as the data packing rules.

   A TLV's main attributes are:

   o  Type

   o  Length

   o  Data

   o  An array of TLVs.

   The array of TLVs is the next hierarchy level of TLVs nested in this
   TLV.

   A TLVs common function could be:





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   o  A basic constructor.

   o  A constructor using data from the wire.

   o  Add a new TLV for next level.

   o  Get the next TLV of next level.

   o  Get a specific TLV of next level.

   o  Replace a TLV of next level.

   o  Get the Data.

   o  Get the Length.

   o  Set the Data.

   o  Set the Length.

   o  Set the Type.

   o  Serialize the header.

   o  Serialize the TLV to be written on the wire.

   All TLVs inherit these functions and attributes and either override
   them or create new where it is required.

3.4.2.  Message Deserialization

   What follows is a the algorithm for deserializing any protocol
   message:

   1.  Get the message header.

   2.  Read the length.

   3.  Check the message type to understand what kind of message this
       is.

   4.  If the length is larger than the message header then there is
       data for this message.

   5.  A check can be made here regarding the message type and the
       length of the message

   If the message is a Query or Config type then for this level there



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   are LFBSelector TLVs:

   1.  Read the next 2 shorts(type-length).  If the type is an
       LFBSelector then the message is valid.

   2.  Read the necessary length for this LFBSelector and create the
       LFBSelector from the data of the wire.

   3.  Add this LFBSelector to the mainheader array of LFBSelectors

   4.  Do this until the rest of the message has finished.

   The next level of TLVs are Operation TLVs

   1.  Read the next 2 shorts(type-length).  If the type is an
       OperationTLV then the message is valid.

   2.  Read the necessary length for this OperationTLV and create the
       OperationTLV from the data of the wire.

   3.  Add this OperationTLV to the LFBSelector array of TLVs.

   4.  Do this until the rest of the LFBSelector TLV has finished.

   The next level of TLVs are PathData TLVs

   1.  Read the next 2 shorts(type-length).  If the type is a PathData
       then the message is valid.

   2.  Read the necessary length for this PathDataTLV and create the
       PathDataTLV from the data of the wire.

   3.  Add this PathData TLV to the Operation TLV's array of TLVs.

   4.  Do this until the rest of the Operation TLV is finished.

   Here it gets interesting, as the next level of PathDataTLVs can be
   either:

   o  PathData TLVs.

   o  FullData TLV.

   o  SparseData TLV.

   o  Result TLV.

   The solution to this difficulty is recursion.  If the next TLV is



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   PathDataTLV then the PathDataTLV that is created uses the same kind
   of deserialisation until it reaches a FullDataTLV or SparseDataTLV.
   There can be only one FullDataTLV or SparseData within a PathData.

   1.  Read the next 2 shorts(type-length).

   2.  If the Type is a PathDataTLV then do again the previous algorithm
       but add the PathDataTLV to this PathDataTLV's array of TLVs.

   3.  Do this until the rest of the PathData TVL is finished.

   4.  If the Type is a FullDataTLV then create the FullData TLV from
       the message and add this to the PathData's array of TLVs.

   5.  If the Type is a SparseDataTLV then create the SparseData TLV
       from the message and add this to the PathData's array of TLVs.

   6.  If the Type is a ResultTLV then create the Result TLV from the
       message and add this to the PathData's array of TLVs.

   If the message is a Query it must not have any kind of data inside
   the PathData.

   If the message is a Query Response then it must either have a
   ResultTLV or a FullData TLV.

   If the message is a Config it must have inside either a FullDataTLV
   or a SparseData TLV.

   If the message is a Config Reponse, it must have inside a ResultTLV.

   More details regarding message validation can be be read in Section 7
   of the Forwarding and Control Element Separation Protocol [RFC5810].

   Note: When deserializing, implementors must take care to ignore
   padding of TLVs as all must be 32-bit aligned.  The length value in
   TLVs includes the Type and Length (4 bytes) but does not include
   padding.

3.4.3.  Message Serialization

   The same concept can be applied in the message creation process.
   Having the TLVs ready, a developer can go bottom up.  All that is
   required is the serialization function that will transform the TLV
   into bytes ready to be transfered on the network.

   For example for the creation of a simple query from the CE to the FE,
   all the PathData are created.  Then they will be serialized and



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   inserted into an Operation TLV, which in turn will be serialized and
   inserted into an LFB Selector and in turn serialized and entered into
   the Common Header which will be passed to the TML to be transported
   to the FE.

   Having an array of TLVs inside a TLV that are next in the TLV
   hierarchy, allows the developer to insert any number of next level
   TLVs thus creating any kind of message.

   Note: When the TLV is serialized to be written on the wire,
   implementors must take care to include padding to TLVs as all must be
   32-bit aligned.







































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4.  Developement Platforms

   Any development platform that can support the SCTP TML and the TML of
   the developer's choosing is available for use.

   Figure 3 provides an initial survey of SCTP support for C/C++ and
   Java at present time.

         /-------------+-------------+-------------+-------------\
         |\ Platform   |             |             |             |
         | ----------\ |   Windows   |    Linux    |   Solaris   |
         |  Language  \|             |             |             |
         +-------------+-------------+-------------+-------------+
         |             |             |             |             |
         |    C/C++    |  Supported  |  Supported  |  Supported  |
         |             |             |             |             |
         +-------------+-------------+-------------+-------------+
         |             |   Limited   |             |             |
         |    Java     | Third Party |  Supported  |  Supported  |
         |             | Not from SUN|             |             |
         \-------------+-------------+-------------+-------------/

                Figure 3: SCTP Support on Operating Systems

   A developer should be aware of some limitations regarding Java
   implementations.

   Java inherently does not support unsigned types.  A workaround this
   can be found in the creation of classes that do the translation of
   unsigned to java types.  The problem is that the unsigned long cannot
   be used as is in the Java platform.  The proposed set of classes can
   be found in [Java Unsigned Types].



















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5.  Acknowledgements

   The authors would like to thank Adrian Farrel for sponsoring this
   document and Jamal Hadi Salim for discussions to make this document
   better.














































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6.  IANA Considerations

   This memo includes no request to IANA.
















































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7.  Security Considerations

   Developers of ForCES FEs and CEs should take the security
   considerations of the Forwarding and Control Element Separation
   Framework [RFC3746] and the Forwarding and Control Element Separation
   Protocol [RFC5810] into account.

   Also, as specified in the security considerations section of the
   SCTP-Based Transport Mapping Layer (TML) for the Forwarding and
   Control Element Separation Protocol [RFC5811] the transport-level
   security, has to be ensured by IPSec.








































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8.  References

8.1.  Normative References

   [RFC5810]  Doria, A., Hadi Salim, J., Haas, R., Khosravi, H., Wang,
              W., Dong, L., Gopal, R., and J. Halpern, "Forwarding and
              Control Element Separation (ForCES) Protocol
              Specification", RFC 5810, March 2010.

   [RFC5811]  Hadi Salim, J. and K. Ogawa, "SCTP-Based Transport Mapping
              Layer (TML) for the Forwarding and Control Element
              Separation (ForCES) Protocol", RFC 5811, March 2010.

   [RFC5812]  Halpern, J. and J. Hadi Salim, "Forwarding and Control
              Element Separation (ForCES) Forwarding Element Model",
              RFC 5812, March 2010.

   [RFC6041]  Crouch, A., Khosravi, H., Doria, A., Wang, X., and K.
              Ogawa, "Forwarding and Control Element Separation (ForCES)
              Applicability Statement", RFC 6041, October 2010.

   [RFC6053]  Haleplidis, E., Ogawa, K., Wang, W., and J. Hadi Salim,
              "Implementation Report for Forwarding and Control Element
              Separation (ForCES)", RFC 6053, November 2010.

8.2.  Informative References

   [Java Unsigned Types]
              "Classes that support unsigned primitive types for Java.
              All except the unsigned long",
              <http://darksleep.com/player/JavaAndUnsignedTypes.html>.

   [RFC3654]  Khosravi, H. and T. Anderson, "Requirements for Separation
              of IP Control and Forwarding", RFC 3654, November 2003.

   [RFC3746]  Yang, L., Dantu, R., Anderson, T., and R. Gopal,
              "Forwarding and Control Element Separation (ForCES)
              Framework", RFC 3746, April 2004.













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Internet-Draft   ForCES Implementation Experience Draft     January 2011


Authors' Addresses

   Evangelos Haleplidis
   University of Patras
   Patras,
   Greece

   Email: ehalep@ece.upatras.gr


   Odysseas Koufopavlou
   University of Patras
   Patras,
   Greece

   Email: odysseas@ece.upatras.gr


   Spyros Denazis
   University of Patras
   Patras,
   Greece

   Email: sdena@upatras.gr



























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