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Title : ForCES Forwarding Element Functional Model
Author(s) : L. Yang et al.
Filename : draft-yang-forces-model-00.txt
Pages : 12
Date : 24-Jun-02
This document defines a functional model for ForCES forwarding
elements (FEs). This model is used to describe the state of ForCES
forwarding elements within the context of the ForCES protocol, so
that ForCES control elements (CEs) can control the FEs accordingly.
The model is to specify what logical function instances are present
in the FEs and in what order these functions are performed. The
forwarding element model defined herein is intended to satisfy the
requirements specified in the ForCES requirements draft [FORCES-
REQ]. Using this model, predefined or vendor specific logical
functions can be expressed and configured. However, the definition
of these components are not described and defined in this document.
A set of terminology associated with the ForCES requirements is
defined in [FORCES-REQ] and is not copied here. The following list
of terminology is relevant to the FE model defined in this document.
Datapath -- A conceptual path taken by packets within the forwarding
plane, inside an FE. There might exist more than one datapath within
Forwarding Element (FE) Block -- An abstraction of the basic packet
processing functions in the datapath. It is the building block of FE
functionality. This concept abstracts away implementation details
from the parameters of interest for configuration, control and
management by CE. The general rule of thumb on the granularity of FE
blocks is that FE blocks should be coarse grained, stateful and
focus on a particular domain. For example, RFC1812 compliant IPv4
forwarder, classifiers, meters, etc..
Forwarding Element (FE) Stage -- Representation of a FE block
instance in a FE's datapath. As a packet flows through an FE along a
datapath, it flows through one or multiple distinct stages, with
each stage implementing an instance of a certain logical function.
There may be one or more combination of such instances in a FE's
datapath. Using NAT as
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