Internet Engineering Task Force E. Haleplidis
Internet-Draft University of Patras
Intended status: Informational October 1, 2012
Expires: April 4, 2013
ForCES Model Extension
draft-haleplidis-forces-model-extension-00
Abstract
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). RFC5812 has defined
the ForCES Model provides a formal way to represent the capabilities,
state, and configuration of forwarding elements within the context of
the ForCES protocol, so that control elements (CEs) can control the
FEs accordingly. More specifically, the model describes the logical
functions that are present in an FE, what capabilities these
functions support, and how these functions are or can be
interconnected.
RFC5812 has been around for two years and experience in its use has
shown room for extensions without a need to alter the protocol while
retaining backward compatibility with older xml libraries.
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 April 4, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
Haleplidis Expires April 4, 2013 [Page 1]
Internet-Draft ForCES Model Extension October 2012
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
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
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. ForCES Model Extension overview . . . . . . . . . . . . . . . 4
4. Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Complex Metadata . . . . . . . . . . . . . . . . . . . . . 5
4.2. DataType and Metadata Optional Default Value . . . . . . . 5
4.3. Optional Frame Produced . . . . . . . . . . . . . . . . . 5
4.4. Strengthen XML Validation . . . . . . . . . . . . . . . . 6
5. XML Extension Schema for LFB Class Library Documents . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19
Haleplidis Expires April 4, 2013 [Page 2]
Internet-Draft ForCES Model Extension October 2012
1. Terminology and Conventions
1.1. Requirements Language
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].
1.2. Definitions
This document follows the terminology defined by the ForCES Model in
[RFC5812]. The required definitions are repeated below for clarity.
FE Model - The FE model is designed to model the logical
processing functions of an FE. The FE model proposed in this
document includes three components; the LFB modeling of individual
Logical Functional Block (LFB model), the logical interconnection
between LFBs (LFB topology), and the FE-level attributes,
including FE capabilities. The FE model provides the basis to
define the information elements exchanged between the CE and the
FE in the ForCES protocol [RFC5810].
LFB (Logical Functional Block) Class (or type) - A template that
represents a fine-grained, logically separable aspect of FE
processing. Most LFBs relate to packet processing in the data
path. LFB classes are the basic building blocks of the FE model.
LFB Instance - As a packet flows through an FE along a data path,
it flows through one or multiple LFB instances, where each LFB is
an instance of a specific LFB class. Multiple instances of the
same LFB class can be present in an FE's data path. Note that we
often refer to LFBs without distinguishing between an LFB class
and LFB instance when we believe the implied reference is obvious
for the given context.
LFB Model - The LFB model describes the content and structures in
an LFB, plus the associated data definition. XML is used to
provide a formal definition of the necessary structures for the
modeling. Four types of information are defined in the LFB model.
The core part of the LFB model is the LFB class definitions; the
other three types of information define constructs associated with
and used by the class definition. These are reusable data types,
supported frame (packet) formats, and metadata.
Element - Element is generally used in this document in accordance
with the XML usage of the term. It refers to an XML tagged part
of an XML document. For a precise definition, please see the full
set of XML specifications from the W3C. This term is included in
Haleplidis Expires April 4, 2013 [Page 3]
Internet-Draft ForCES Model Extension October 2012
this list for completeness because the ForCES formal model uses
XML.
Attribute - Attribute is used in the ForCES formal modeling in
accordance with standard XML usage of the term, i.e., to provide
attribute information included in an XML tag.
LFB Metadata - Metadata is used to communicate per-packet state
from one LFB to another, but is not sent across the network. The
FE model defines how such metadata is identified, produced, and
consumed by the LFBs, but not how the per-packet state is
implemented within actual hardware. Metadata is sent between the
FE and the CE on redirect packets.
ForCES Component - A ForCES Component is a well-defined, uniquely
identifiable and addressable ForCES model building block. A
component has a 32-bit ID, name, type, and an optional synopsis
description. These are often referred to simply as components.
LFB Component - An LFB component is a ForCES component that
defines the Operational parameters of the LFBs that must be
visible to the CEs.
LFB Class Library - The LFB class library is a set of LFB classes
that has been identified as the most common functions found in
most FEs and hence should be defined first by the ForCES Working
Group.
2. Introduction
The ForCES Model [RFC5812] presents a formal way to define FEs
Logical Function Blocks (LFBs) using XML. [RFC5812] has been
published a litlte more than two years and current experience in its
use has shown some room for adding new and changing existing modeling
concepts.
This document extends the ForCES Model by changing and adding new
concepts. These extensions do not require any changes on the ForCES
protocol [RFC5810] as they are simply changes of the schema
definition. Additionally backward compatibility is ensured as xml
libraries produced with the earlier schema are still valid with the
new one.
3. ForCES Model Extension overview
The folowing extensions are considered:
Haleplidis Expires April 4, 2013 [Page 4]
Internet-Draft ForCES Model Extension October 2012
1. Allow complex metadata.
2. Allow optional default values for datatypes and metadata.
3. Change from mandatory to optional the frame produced in the
output port of LFBs.
4. Strengthen the XML validation.
4. Extensions
Some of these extensions were product of the work done on the
OpenFlow library [I-D.haleplidis-forces-openflow-lib] document.
4.1. Complex Metadata
Section 4.6. (Element for Metadata Definitions) in the ForCES Model
[RFC5812] limits the datatype use in metadata to only atomic types.
With this extension, complex data types are also allowed,
specifically structs and arrays as metadata. A simple use case can
be seen in the OpenFlow switch [OpenFlowSpec1.1] where exists the
Action Set metadata which is an array.
4.2. DataType and Metadata Optional Default Value
In the original schema, default values can be defined only in
datatypes defined inside LFB components. However when it's a complex
datatype or it's a refered datatype, using the default value field is
difficult to be used. Additionally there is no option in a complex
datatype to use the default value field for only one component in the
complex datatype.
This extension allows optionally to add default values to atomic and
typeref types, whether they are as simple or complex datatypes. A
simple use case would be to have a struct component where one of the
components is a counter which the default value would be zero. The
same applies to metadata.
4.3. Optional Frame Produced
In the original schema, frame expected in LFB inputs is optional, but
frame produced in LFB outputs is mandatory. There is a case in the
OpenFlow switch [OpenFlowSpec1.1] where the OpenFlow switch buffers
the packet and sends only part of it to the controller with a Buffer
ID as metadata. In this case the input port of the Redirect LFB will
not expect any packets but only metadata. The LFB that performs the
Haleplidis Expires April 4, 2013 [Page 5]
Internet-Draft ForCES Model Extension October 2012
buffering will only send metadata and not the packet.
4.4. Strengthen XML Validation
The following validation rules have been inserted in the original
schema in [RFC5812]:
1. Each metadata ID must be unique. This validation rule checks
only within the xml file.
2. LFB Class IDs must be unique. This validataion rule checks only
within the xml file.
3. Component ID, Capability ID and Event Base ID must be unique per
LFB.
4. Event IDs must be unique per LFB.
5. Special Values in Atomic datatypes must be unique per atomic
datatype.
5. XML Extension Schema for LFB Class Library Documents
Schema for Defining LFB Classes and associated types (frames,
data types for LFB attributes, and metadata).
Haleplidis Expires April 4, 2013 [Page 6]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 7]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 8]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 9]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 10]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 11]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 12]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 14]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 15]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 16]
Internet-Draft ForCES Model Extension October 2012
Haleplidis Expires April 4, 2013 [Page 17]
Internet-Draft ForCES Model Extension October 2012
OpenFlow XML Library
6. Acknowledgements
TBD
7. IANA Considerations
This memo includes no request to IANA.
8. Security Considerations
TBD
Haleplidis Expires April 4, 2013 [Page 18]
Internet-Draft ForCES Model Extension October 2012
9. References
9.1. Normative References
[I-D.haleplidis-forces-openflow-lib]
Haleplidis, E., Cherkaoui, O., Hares, S., and W. Wang,
"Forwarding and Control Element Separation (ForCES)
OpenFlow Model Library",
draft-haleplidis-forces-openflow-lib-01 (work in
progress), July 2012.
[OpenFlowSpec1.1]
http://www.OpenFlow.org/, "The OpenFlow 1.1
Specification.", .
[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.
[RFC5812] Halpern, J. and J. Hadi Salim, "Forwarding and Control
Element Separation (ForCES) Forwarding Element Model",
RFC 5812, March 2010.
9.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Evangelos Haleplidis
University of Patras
Department of Electrical and Computer Engineering
Patras, 26500
Greece
Email: ehalep@ece.upatras.gr
Haleplidis Expires April 4, 2013 [Page 19]