Forwarding and Control Element Separation
|The information below is for an older proposed charter
Forwarding and Control Element Separation WG
||Forwarding and Control Element Separation
||Charter Edit AD
||Send notices to
This working group focuses on the ForCES architecture.
The ForCES architecture constitutes:
* One or more Control Elements (CE) interacting with one or more Forwarding
Elements (FEs) to form a Network Element (NE). Any or all of these entities
could be physical or virtual.
* a data model to define the controlled or configured entity
* a protocol used to communicate between CEs and FEs which is agnostic to the
* one or more xml documents describing the controlled entity using the ForCES
data model. The protocol acts (in the direction of the controller to
datapath) on these definitions to achieve an end goal of control,
configuration, packet redirect and in the reverse direction for responses,
packet redirects and events.
This working group was originally started to address the desire to create a
standardized control-datapath architecture to control off-the shelf hardware
that implements IP forwarding plane capability. This could be commercial
chips, ASICs, FPGAs, Network Processors, or software based forwarding plane
As the work evolved, in order to avoid prejudicing implementation choices an
abstract data model for the forwarding elements and a protocol for manipulating
those forwarding elements was developed and standardized. Implementations and
interoperation were demonstrated.
With the emergence of SDN as an industry focus, there is renewed interest in
the control capabilities and data plane flexibility provided by the ForCES
architecture. Also, with this interest in SDN there has been a realization that
the same abstractions can be used for service manipulation for overall device
control or for configuration of the services.
The ForCES working group is now working on a set of additions to the model and
protocol and libraries based on the experience gained from developing the
standards and from many efforts using this architecture.
In addition to the specific work items described below, it is understood that
there are a number of external activities which may have interactions with the
ForCES work. Discussions of how to use ForCES to model topics of interest to
Network Function Virtualization, I2RS, or OpenFlow may be discussed and
reviewed, although primary responsibility for such documents is likely to live
in other working groups, individual contributions, or other standards bodies.
The following 5 work items are the chartered tasks of this working group:
o Model Extensions and protocol:
This work is to address a set of extensions to the base model and protocol
resulting in updates to RFCs 5810 and 5812.
This effort will produce 2 standards effort documents (one for the model and
another for the protocol).
The model extensions will:
1. Allow complex metadata.
2. Allow optional default values for datatypes
3. Allow optional access-type for datatypes inside complex components
4. Define new base type: Bitmap
5. Define new events to monitor states
The protocol extension will:
1. Table range query.
2. Table append
3. Additional return codes to reduce ambiguity
4. Define data packing rule for bitmap datatype
o Inter-FE Connectivity:
It has been found that ForCES processing often needs to be spread across
multiple FEs. The original framework identified this as the Fi interface.
Protocol and LFB mechanisms to carry metadata across this Fi interface are
now needed. This effort will produce a standards track doument defining the
protocol on the wire to address this need, and the LFBs used to represent the
Interfaces for sending and receiving such information.
While in theory an FE can implement an LFB chain with paralellization, the
current mechanism has no means to represent when synchronization is needed,
or to allow the CE to specify where it believes such paralllism is useful.
This work item will produce a single standards track document to improve the
handling of this case.
o Subsidiary Management:
Deployment experience has demonstrated usefulness of expressing the FEM
with the same semantics as any other LFB and thus be controlled by the CE.
This work item assumes the presence of an initially booted FE whose
configuration could then be updated at runtime via an FEM LFB for runtime
config purposes (eg adding a new CE and its associated IP address).
This work item can also be useful in addressing control of virtual FEs
where individual FEM Managers can be addressed to control the creation,
configuration, and resource assignment of such virtual FEs within a physical
FE. This work would result in a standards track LFB FEM library RFC.
Goals and Milestones
September 2013 Request for Publication of Standards Track documents
specifying model and protocol changes
February 2014 Request for publication of Subsidiary management LFB
March 2014 Request for publication of Inter-FE LFB and parallelization
LFBs April 2014 Shutdown?