Method for representing and controlling packet data flow through packet forwarding hardware

[0001] The present invention relates generally to packet processing performed by packet forwarding hardware. In particular, the present invention relates to a method for representing and controlling packet data flow through packet forwarding hardware.

[0002] Today, numerous independent hardware vendors (IHV) produce networking application specific integrated circuits (ASIC) to perform a myriad of packet processing tasks. The current interface to such ASICs are generally memory mapped registers that have corresponding bit level behavior and documentation. However, not all IHVs limit their products to register level descriptions. Some offer C level or other software interfaces to the hardware, but usually, these are merely a convenient reflection of the underlying registers and therefore differ from one IHV to another. These register level models represent a steep learning curve and tight coupling for an original equipment manufacturer (OEM) or an independent software vendor (ISV) that desires to use the ASICs or networking silicon in a product. At such a micro level description (i.e., the register bits), it is difficult to write code that is reusable across these various ASICs. It is also difficult to decipher the micro level functionality of the ASICs networking silicon.

[0003] A patent issued to Narid et al. (U.S. Pat. No. 6,157,955), entitled “Packet Processing System Including A Policy Engine Having A Classification Unit,” describes a general purpose, programmable packet processing platform for accelerating network infrastructure applications, which have been structured to separate the stages of classification and action. Narid et al. thus attempts to describe a software model for programming packet data flow. The application programming interface (API) described in Narid et al. defines action/classification engines (ACE) which form software objects that can be connected together to form a directed graph of data/packet flow. Packet flow, as described herein, refers to the path of a packet from its point of origination to its destination, including all intermediate nodes. However, ACEs have a high level of granularity due to the fact that each ACE contains a classification and action portion. Furthermore, the ACE directed graph is not an abstraction of data flow. Rather than providing an abstraction of underlying hardware which performs the packet processing, the ACE objects perform the packet processing at a software level. Unfortunately, performing packet processing at a software level sacrifices performance provided by performing packet processing at a hardware level.

[0004] A recent trend in the networking industry is the replacement of ASICs, which are relatively inflexible, with more programmable but still performance-oriented, network processors. Network processors are in their infancy stages and many do not have an abstract programming model, or do not have one expressive and flexible enough to grow with advances in the processor itself. In both cases, the lack of a state of the art programming model hinders both ISVs, who must write their own firmware to a moving API, and silicon vendors. ISVs and silicon vendors inevitably compete for inclusion in the designs of network devices of other network equipment companies.

[0005] Therefore, there remains a need to overcome one or more of the limitations in the above described existing art.

[0030] A method for representing and controlling packet data flow through packet forwarding hardware is described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description provides examples, and the accompanying drawings show various examples for the purposes of illustration. However, these examples should not be construed in a limiting sense as they are merely intended to provide examples of the present invention rather than to provide an exhaustive list of all possible implementations of the present invention. In other instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the details of the present invention.

[0031] In an embodiment, the steps of the present invention are embodied in machine-executable instructions. The instructions can be used to cause a general-purpose or special-purpose processor that is programmed with the instructions to perform the steps of the present invention. Alternatively, the steps of the present invention might be performed by specific hardware components that contain hardwired logic for performing the steps, or by any combination of programmed computer components and custom hardware components.

[0032] The present invention may be provided as a computer program product which may include a machine-readable medium having stored thereon instructions which may be used to program a computer (or other electronic devices) to perform a process according to the present invention. The machine-readable medium may include, but is not limited to, floppy diskettes, optical disks, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnet or optical cards, flash memory, or other type of media/machine-readable medium suitable for storing electronic instructions. Moreover, the present invention may also be downloaded as a computer program product, wherein the program may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals embodied in a carrier wave or other propagation medium via a communication link (e.g., a modem or network connection).

System Architecture

[0033] Referring now to FIG. 1, a block diagram of a conventional network 100 is illustrated. The conventional network 100 includes a first network switching/routing device 110. This first device 110 is, for example, a router configured as a firewall (firewall router 110). The firewall router 110 is coupled between a wide area network (Internet) 102 and a local area network (private network) 140. The conventional network 100 further includes a second network switching/routing device 130. This second device 130 is, for example, a router configured to perform intrusion detection services (IDS router 130). The IDS router 130 is coupled with the firewall router 110. Finally, the conventional network 100 includes a third network switching/routing device 120. The third device is, for example, a router configured as a virtual private network (VPN) router 120. The VPN router 120 is coupled between an input router 104 and the private network 140. The input router 104 is coupled to the Internet 102 and routes data packets 106 to either the firewall router 110 or the VPN router 120.

[0034] As such, the conventional network provides firewall capabilities, as known to those skilled in the art, and intrusion detection capabilities, as known to those skilled in the art, using the firewall router 110 and the IDS router 130. Additionally, the conventional network 100 is configured as a virtual private network utilizing the VPN router 120. The various network switching/routing devices 110-130 are essentially fixed function ASIC devices or fixed function forwarding elements.

[0035] Referring now to FIG. 2, a block diagram 150 of the internal control processing of a network switching/routing device 160, such as for example, the network switching/routing devices 110-130 as depicted in FIG. 1. The functionality provided by the switching/routing device 160 includes control plane processing 172 and forwarding plane processing 174 and 176. Control plane processing tasks include such tasks as routing protocols and admission controls. Forwarding plane processing includes data-path packet processing, such as classification, forwarding and manipulation. In essence, the forwarding plane provides a range of packet processing capabilities from hardware accelerated to software programmable. Packet processing includes layer 2 and layer 3 switching, packet redirection, packet filtering and packet manipulation. Unfortunately, in a fixed function switching/routing device 160, such as depicted in FIG. 2, the device is limited by tightly coupled proprietary forwarding plane hardware 176 and software 174 designed to suit a specific need. In addition, updating the hardware 176 requires an update of all of the software 174.

[0036] The present invention defines an object-oriented programming model appropriate for both ASIC-based networking silicon as well as network processors. This model obtains this range of expressiveness by identifying the fundamental units of packet processing performed by underlying hardware 176 (either ASIC or network processor). Software objects as described in further detail below, called Stages, are then created to encapsulate and represent these fundamental units of packet processing. At the first level of decomposition, specific types of stages including, for example, links, classifiers, editors, schedulers, queues, and monitors are formed. A link is a stage which represents a physical interface, including framing. A classifier stage represents a filtering or matching algorithm, while schedulers and queues can be combined to represent packet flow. On the other hand, monitor stages gather statistical information about packets and their data flows. The present invention also defines a meta stage or composition of stages such that the meta stage includes the same interface as the stage itself. This enables groups of stages to be treated as one large unit of packet processing.

[0037] Referring now to FIG. 3, a subset of a class hierarchy 200 of stages associated with the present invention is depicted. Each of the classes described above, such as scatterer 204 or gatherer 210, are types of stages. Although each stage type within the contemplation of the present invention is not illustrated in FIG. 3, this representation provides ample illustration of the various possible stage types encompassed by the present invention. Additional stage types illustrated by the present invention are described in further detail below under the application programming interface (API) description of the present invention. However, the listing of stage types in the API is not intended to provide an exhaustive list of all stage types within the contemplation of the present invention. FIG. 3 illustrates the number of inputs (to the left side of each stage type) and the number of outputs (to the right side of each stage type) for each Stage. The inputs and outputs of Stages are connected together to form a data flow topology as described in further detail below.

[0038] The API model described by the present invention provides an object-oriented abstraction of forwarding plane packet processing capabilities. These capabilities include packet classification, forwarding, queueing, and transmit scheduling which are abstracted into objects called Stages. Depending on the underlying hardware programmability, the API model can range from simply allowing a user to discover the static configuration of some Stages, to allowing arbitrary creation and interconnection of Stages. The API model provides a solution by abstracting the macro level functionality of network silicon ASICs. This enables firmware engineers to write re-useable code. More particularly, it provides a common understanding of the functionality of the silicon. In other words, the API model provides a framework in which IHVs need write only the lower layers of the API model to map from object-oriented abstractions (i.e., Stages) into their registers.

[0039] Stages have three main attributes: a set of numbered inputs, numbered outputs and named parameters. The API model enables the connection of the inputs and outputs of different Stages to form a data flow topology model of the underlying forwarding hardware. Each Stage has zero or more inputs and zero or more outputs as depicted in FIG. 3. The outputs (inputs) of one Stage are connected to inputs (outputs) of another Stage. These inputs and outputs represent both the packet data traversing the underlying forwarding engine hardware, as well as a tag. This tag is associated with the packet data and carries the interstage state. (Note, however, that the tag is not part of the packet data and is an addition to the packet data.) Some Stages pass the tag-through, some read the tag and others modify the outgoing tag. The parameters of a Stage, along with a few special (internal) synchronization objects affect the behavior of the Stage as described in further detail below. Also, the parameters of a Stage are not directly accessible, but indirectly via methods on the Stage, as synchronous modification of changes in the underlying hardware can be provided by parameters via a callback mechanism.

[0040] Referring now to FIG. 4, a block diagram of an interconnection of various Stages to form a data flow topology 250 of the underlying forwarding hardware is depicted. However, this data topology is provided as an example, such that those skilled in the art will appreciate that various interconnections of stage objects are within the contemplation of the present invention. The data flow topology 250 includes a link Stage as an input port 252. An output port 254 of the input port object 252 is coupled to a classifier Stage, or input classifier 256. The input classifier object 256 is coupled to a scatterer class or demux object 260. The output of the demux object is routed to either a monitor Stage 268 (RMON) or an editor Stage 270 (transcoder object). A gatherer object or gatherer Stage 276 is coupled to the demux object 260 and functions as a layerer object. Finally, a link Stage functions as an output port 280.

[0041] FIG. 4 shows the inputs and outputs of the Stages providing connections to form a data flow topology 250. Each box within the block diagram represents a Stage or functional operation performed on packet data traversing this Stage. Using such a topology provides an expressive way in describing both ordering and functionality of the underlying forwarding hardware. Note that if the above topology were abstracting an ASIC, the connections would be immutable by the programmer. Conversely, if the underlying forwarding hardware was a programmable network processor, the actual topology could be rearranged to form different types of packet processing. In either case, the above is merely a representation of how the packet processing is done by the underlying forwarding hardware. Packet data does not itself traverse the software objects in this invention. Rather, the packets still traverse the actual hardware, thus taking advantage of performance innovations in the ASICs or network processors.

[0042] Referring now to FIG. 5, a network 300 utilizing a switching/routing device 302 configured in accordance with the teachings of the present invention is depicted. This network 300 includes the routing device 302 coupled between a wide area network (Internet) 304 and a local area network (private network) 306. The network 300 depicted in FIG. 5 provides the same functionality achieved by the conventional network 100 depicted in FIG. 1. However, rather than using application-specific switching/routing devices, such as utilized in the conventional network 100, the network 300, in accordance with the present invention, utilizes a single switching/routing device to perform each of the packet processing tasks in a single box.

[0043] Referring now to FIG. 6, an internal representation of the switching/routing device 302, as depicted in FIG. 6, is illustrated. The routing device 302 includes a memory 310 containing control plane software 310, and forwarding plane software 320. The device 302 also includes forwarding plane hardware 360. The memory 310 of the router device 302 can be configured to include a compiled and linked, directed graph of packet processing Stages created using the API model object-oriented software for abstraction, as taught by the present invention. A classification/routing Stage 330 is programmed to perform input processing for the network 300. The directed graph further includes a Stage object 334 configured to perform firewall data path packet processing functionality. The directed graph 330 further includes a Stage object 336 programmed to perform intrusion detection services ID (IDS). Finally, the directed graph 330 includes a Stage object configured to perform virtual private network functionality 338.

[0044] As described above, each Stage, or software object, is designed to describe both ordering and functionality of the underlying forwarding hardware 360. The directed path 330 is merely a representation of how the packet processing is done by the forwarding hardware. The packet data does not, itself, traverse the software objects of the directed graph 330. Rather, the packets still traverse the actual hardware, thus taking advantage of the performance innovations in the ASICs, or network processors. Moreover, the various stage objects can be added or removed to add/remove functionality without affecting the underlying hardware. An API for describing directed graphs of software objects to perform data path packet processing functionality is now described.

Application Programming Interface

API Forwarding Hardware Engine Model Infrastructure

[0045] The following describes an application programming (API) interface for modeling underlying forwarding engine hardware using an object-oriented programming model that abstracts the fundamental units of packet processing performed by the hardware into software objects called stages. Those skilled in the art will appreciate that the following API merely represents one possible implementation for such an application programming interface. As a result, changes or modifications to the following API, including various additions or deletions of software object stages or various interconnections therewith to form data flow topologies are within the scope and the contemplation of the present invention. In other words, the following API description should not be construed in a limiting sense, as this API is merely intended to provide an example of the present invention, rather than to provide an exhaustive list of all possible API implementations of the inventive techniques taught by the present invention. In the following class descriptions, some C++-like code is used. This code has been intentionally simplified for clarity. It has not been compiled, nor does it have sufficient error checking to be considered final.

[0046] FIG. 7 shows the Stage-related classes 400 in the infrastructure of the API forwarding hardware engine model. The API describes a model of the underlying forwarding hardware since the API hardware engine model (engine model) provides a language for describing ordering and functionality of the underlying forwarding hardware. Packet data does not itself traverse the software objects of the present invention. There are two classes defined in FIG. 7: Stage 402, and Stage::Parameter 410. Of these, only Stage is dealt with directly by the Engine Model user. Stage::Parameter is internal to the API Model. Both are important to understanding and implementing the model.

[0047] In addition to these classes, FIG. 9 shows several classes needed for inter-stage information and operations. The main class in FIG. 9 is the EngineGraphManager, which provides an entry point for discovering the capabilities and Stages of the Engine Model. Each of these classes is described in further detail below.

[0048]

Stage Class
	Name:	Stage
	Specializes:	N/A
	Qualifiers:	Abstract

[0049] The Stage class is the central class in the Engine Model. It is the base class for virtually all other classes within this model. Its essential attributes are a set of numbered inputs, numbered outputs, and named parameters.

[0050] The inputs and outputs connect with other Stages' outputs and inputs respectively to form the topology (data flow) of the forwarding engine hardware. These inputs and outputs represent both a tag and the actual packet data. The tag represents inter-Stage state. The Engine Model programmer specifies the actual value of the tag (see Classifier, below).

[0051] Assuming the underlying forwarding hardware is not fixed function, the topology or data flow is dynamic, i.e., the Engine Model user can establish connectivity at runtime. This approach provides a more expressive, powerful model. If the underlying forwarding engine does not support such dynamic reconfiguration, the connect method can be implemented to unconditionally throw an exception.

[0052] The parameters, which are synchronized and double-buffered, provide a mechanism by which the internal behavior of a Stage is controlled. Synchronized and double-buffered is akin to a two-phase commit database transaction. See the Stage::Parameter class for more details. An external Engine Model user can register an asynchronous callback for each parameter of a Stage. Whenever the underlying forwarding engine changes the value of a parameter, the corresponding, registered callback is invoked.

Related Types:

• [0053] See also Stage::Parameter
• [0054] See Link (section 5.2.1), for other examples.
• [0055] typedef pair<Stage *, u_int16_t> StageConn;

[0056]

Attributes
		Quali-
Attribute	Type	fiers	Description
m_inputs	vector<StageConn>	Pri-	A container of numbered
		vate	inputs for this Stage. Each
			input holds a pointer to its
			neighboring Stage and the
			neighbor's output number.
			Each of these inputs
			represents a tag plus
			the data for one packet.
m_outputs	vector<StageConn>	Pri-	A container of numbered
		vate	outputs for this Stage.
			Each output holds a pointer
			to its neighboring Stage and
			the neighbor's input
			number. Each of these
			outputs represents a
			tag plus the data
			for one packet.
m_params	map<string,	Pri-	A container of named
	Parameter>	vate	parameters for this Stage.
			Each is of type Parameter.
m_syncEna	bool	Pri-	True if this Stage is
bled		vate	supposed to update the
			underlying hardware when
			Synchronize () is called.
			Note: This is no longer
			used now.
M_Monitor	Monitor	Pri-	A monitoring object
		vate

Methods
The following methods are defined.

[0057]

Methods	Services
Synchronize	Update Stage parameters.
GetInputNeighbor	For a given input number,
	get the neighboring Stage.
GetOutputNeighbor	For a given output number, get the neighboring
	Stage.
Connect	Connect another Stage and its input to the output
	of this Stage.
Ibegin	Get beginning enumerator for Stage inputs.
Iend	Get ending enumerator for Stage inputs.
Obegin	Get beginning enumerator for Stage outputs.
Oend	Get ending enumerator for Stage outputs.
Register	Register a callback function
	for a specified parameter.
DeRegister	Remove a registered callback function.
GetType	Returns a char* indicating type of Stage
GetOutputMatchStages	Returns the Stages matching the
	filter on a particular output
GetInputMatchStages	Returns the Stages matching the
	filter on a particular input
GetParm	Retrieve a parameter by name.
SetParm	Set the value of a named parameter.
GetMonitor	Get the monitoring object
	associated with this Stage
SetMonitor	Set the monitoring object.
Hw_UpdateInput	Updates the input connection
	in the forwarding engine
Hw_UpdateOutput	Updates the output connection
	in the forwarding engine
Hw_UpdateParameter	Updates the parameter in the forwarding engine
Hw_ValidateInput	Validates a new input connection
Hw_ValidateOutput	Validate a new output connection.

[0058]

Sychronize
Description:	virtual void Synchronize(pair<bool, bool>
	firstLast = pair<true, true>)
	throw (update_Stage_parameter_failed);
	Updates the Stage's parameters in the actual forwarding engine. This
	method calls Hw_UpdateParameter ( ) for each parameter that
	needs updating. (IsDirty( ) returns true). The parameter commit( ) is
	called only if all Hw_UpdateParameter ( ) calls return true.
	(Note: m_syncEnabled is no longer used since auto synchronization is
	no longer present, and there is no motivation for it now.)
Parameters:	IN:pair<bool, bool>	firstLast
		Indicates that this call to
		Synchronize is the first (last) in a
		series of related Synchronize calls.
		It provides a hint to the
		Stage about when to obtain write
		locks on shared data.
		The default value is (true, true).
Returns:	Nothing.
Exceptions:	For the first Hw_UpdateParameter ( ) that fails (i.e. returns false
	indicating that the hardware was not changed), an
	update_Stage_parameter_failed is thrown.
	Note: Changes may need to be backed in case of failure.
GetInputNeighbor
Description:	virtual const StageConn&
	GetInputNeighbor (u_int16_t num)
	throw (uint_out_of_range);
	Retrieves the neighboring Stage and its output number for a given
	input.
Parameters:	IN: u_int16_t num	The zero-based number of the input to
	retrieve.
Returns:	Neighboring Stage output number.
	The returned StageConn.first could be NULL, indicating that
	nothing is connected to the given input.
Exceptions:	If the given input number is not an input of the Stage, an
	exception is thrown.
GetOutputNeighbor
Description:	virtual const StageConn&
	GetOutputNeighbor(u_int16_t num)
	throw (uint_out_of_range);
	Retrieves the neighboring Stage and its input number for a given
	output.
Parameters:	IN: u_int16_t num	The zero-based number of the output to
	retrieve.
Returns:	Neighboring Stage input number.
	The returned StageConn.first could be NULL, indicating that
	nothing is connected to the given output.
Exceptions:	If the given input number is not an output of the Stage, an
	exception is thrown.
Connect
Description:	virtual void Connect(u_int16_t outNum,
	Stage *neigh, u_int16_t
	neighInNum)
	throw (uint_out_of_range,
	invalid_connection);
	Connects another Stage and its input to this Stage's output.
	Note that Connect is called only to establish the forward connection but
	connections are established in both directions so that a backward
	connection is established from the neighbor Stage to this Stage. The
	given Stage * could be NULL, indicating that the output is to be
	disconnected. This calls Hw_UpdateInput and Hw_UpdateOutput to
	update the connections in hardware.
Parameters:	IN: u_int16_t outNum	Number of the output to connect to
		the given neighbor.
	IN: Stage *neigh	Stage * that is to become the
		neighbor of the output.
	IN: u_int16_t neighInNum	Input number of neigh to which
		the output is connected.
Returns:	Nothing.
Exceptions:	If the given output number is not an output of this Stage, an
	exception is thrown.
	If the given input number is not an input of the neighbor, an
	exception is also thrown.
	If the Stages can't be connected, invalid_connection is thrown.
Ibegin
Description:	vector<StageConn>::const_iterator Ibegin ( )
	Enumerator for the inputs of the Stage.
Parameters:	None.
Returns:	Starting iterator for the inputs of the Stage.
Exceptions:	None.
Iend
Description:	vector<StageConn>::const_iterator Iend ( )
	Enumerator for inputs of the Stage.
Parameters:	None.
Returns:	Iterator pointing to the end of the inputs of the Stage
Exceptions:	None.
Obegin
Description:	vector<StageConn>::const_iterator Obegin ( )
	Enumerator for the outputs of the Stage.
Parameters:	None.
Returns:	Returns the starting iterator for the outputs of the Stage.
Exceptions:	None.
Oend
Description:	vector<StageConn>::const_iterator Oend ( )
	Enumerator for the outputs of the Stage.
Parameters:	None.
Returns:	Ending iterator for the outputs of the Stage.
Exceptions:	None.
Register
Description:	void Register (string name,
	CBFunctor<pair<string,  Stage*>>
	cbFunc)
	throw (item_not_found<string>);
	Registers a callback functor for changes to the named parameter. (See
	[CESAS])
	Whenever this parameter is modified, the named callback will be
	invoked.
Parameters:	IN:   string name	Name of a parameter.
	IN: CBFunctor cbFunc	Callback functor to be invoked when
		the named parameter is modified.
Returns:	Nothing.
Exceptions:	If the given name does not specify a valid parameter for the Stage,
	item_not_found<name> is raised.
DeRegister
Description:	void DeRegister(string name,
	CBFunctor<pair<string, Stage*>>
	cbFunc)
	throw (item_not_found<string>);
	Removes a callback previously registered by RegisterCB.
Parameters:	IN: string name	Name of a parameter.
	IN: CBFunctor cbFunc	Previously registered callback functor
		to be removed.
Returns:	Nothing.
Exceptions:	If the callback cannot be deregistered item_not_found<name> is raised.
GetType
Description:	virtual const uint8_t* GetType ( ) = 0;
	Returns the type of the Stage. Must be implemented by specific types of
	Stages to return a string of the form “Stage:Class . . . ” by appending to
	the results returned from the parent classes. eg, Ipv4Classifier returns
	“Stage:Classifier:IPv4Classifier”. RTTI typeid(obj).name instead
	returns only the class name without reference to the class hierarchy.
Parameters:	None
Returns:	Type of Stage in char* format
Exceptions:	None
GetOutputMatchStages
Description:	vector<Stage* > GetOutputMatchStages (uint16_t
	output,  const   StageType*  filter) throws
	(uint_out_of_range);
	Returns all the Stages that are of type filter reachable from the given
	output. As of now StageType just contalns a uint8_t* to denote the type
	of Stage. Note: RTTI could be used here with a template member
	function
	Eg. template<class Type>
	vector<Type*> GetOutputMatches(uint16_t output, Type u)
	which uses dynamic cast to check if a Stage is of type u, but this
	requires creating unnecessary dummy objects of type u to pass in as an
	argument. Also having a separate filter class is more flexible, since it
	allows selective filtering on certain attributes of a Stage.
Parameters:	IN: uintl6_t output	The output port on which you want to
		search for a given Stage
	IN: const StageType *filter	The type of Stage to match. If null it
		returns all the Stages
Returns:	vector of matching Stages that can be reached from the given output.
Exceptions:	uint_out_of_range if output not valid
GetInputMatchStages
Description:	vector<Stage* > GetInputMatchStages(uint16_t
	input, const StageType* filter)throws
	(uint_out_of_range);
	Retuns the Stages that are of type filter reachable on the given input
Parameters:	IN: uintl6_t input	The input port on which you want to search
		for a given Stage
	IN: const StageType *filter	The type of Stage to match. If null it
		returns all the Stages.
Returns:	vector of matching Stages that can be reached from the given input
Exceptions:	uint_out_of_range if input not valid
GetMonitor
Description:	Monitor* GetMonitor( )
	Get the monitor associated with the Stage
Parameters:	None.
Returns:	A pointer to a monitor object. This could be null to specify, no
	monitoring supported by this Stage. Also it could be dynamic cast to a
	specific type of monitor to take advantage of finer granularity/specific
	type of monitoring.
Exceptions:	None
SetMonitor
Description:	bool SetMonitor(const Monitor&)
	Sets the monitoring object for a Stage.
Parameters:	IN: Monitor& The monitor object to associate with the Stage.
Returns:	true if succeeds, false if not.
Exceptions:	None
GetParam
Description:	(protected) virtual const Parameter&
	GetParam(string name)
	throw (item_not_found<string>)
	Retrieves a parameter by name. This is used internally within the
	Stage. Parameters are held in a generic mechanism by the base class
	Stage. This enables all subclasses of Stage to have a consistent
	mechanism by which synchronization can be performed. In this context,
	a string names each parameter. These names are exclusively internal.
Parameters:	IN: string name	Name of the parameter to retrieve.
Returns:	Named parameter.
Exceptions:	item_not_found<string>
SetParam
Description:	(protected) virtual void SetParam(string name,
	void *value)
	throw (item_not_found<string>);
	Sets the value of a named parameter.
	Note: this method is specifically written to prevent Stage subclasses
	from adding new parameters by accidentally passing an invalid name.
	This relies on the same exception mechanism used by GetParam.
Parameters:	IN: string name	Name of the parameter to have its deferred
	value set to value.
	IN: void *value	Pointer to a new deferred value for the named
	parameter.
Returns:	Nothing.
Exceptions:	item_not_found<string>
Hw_UpdateParameter
Description:	(protected) virtual bool Hw_UpdateParameter
	(string name, Parameter& p) =
	0;
	Stage calls this routine to update a parameter in the forwarding engine
	(i.e. hardware). If the value could not be updated, this method should
	leave the hardware in the previous state and return false.
	This method will contain platform-specific code for each subclass of
	Stage.
	Note: Operations should be performed as follows:
	1. Read the deferred value of the given parameters.
	2. Transform new p into hardware-specific format.
	3. Perform an actual register poke, trap into the operating system, or
	driver call.
Parameters:	IN: string name	Name of the parameter.
	IN: Parameter& p	If a parameter is to be updated, p represents a
		parameter that isDirty and needs updating
		in the hardware.
	Returns: Returns true if the value was updated correctly; false if
	not.
Exceptions:	None.
Hw_UpdateInput Hw_UpdateOutput
Description:	(protected) virtual bool Hw_UpdateInput
	(u_int16_t num, StageConn conn) = 0;
	(protected) virtual bool Hw_UpdateOutput
	(u_int16_t num, StageConn conn) = 0;
	Stage calls this routine to update an input, or an output in the
	forwarding engine (i.e. hardware). If the value could not be updated,
	this method should leave the hardware in the previous state and return
	false.
	This method will contain platform-specific code for each subclass of
	Stage.
Parameters:	IN: u_intl6_t num	Number of the input or output.
	IN: StageConn conn	If an input (output) is to be updated,
	conn contains
		the neighboring Stage and its connecting
		output (input) number.
Returns:	Returns true if the value was updated correctly; false if not.
Exceptions:	None
Hw_ValidateInput
Description:	(protected) virtual bool
	Hw_ValidateInput(u_int16_t num,
	StageConn newConn) = 0;
	Called at the beginning of connect ( ) validate input connectivity. No
	hardware is updated during this call.
Parameters:	u_int16_t num	Number of the input being
	connected.
	StageConn newConn New connection to be validated.
Returns:	Returns true if the new connection is valid (i.e., supported by the
	hardware). If the new value is somehow incompatible with the
	hardware, false is returned
Exceptions:	None.
Hw_ValidateOutput
Description:	(protected) virtual bool
	Hw_ValidateOutput(u_int16_t num,
	StageConn newConn) =0;
	Called at the beginning of connect ( ) to validate output connectivity.
	No hardware is updated during this call.
Parameters:	u_int16_t num	Number of the output being
	connected.
	StageConn newConn	New connection to be validated.
Returns:	Returns true if the new connection is valid (i.e., supported by the
	hardware). If the new value is somehow incompatible with the
	hardware, false is returned.
Exceptions:	None

Example:
Refer to FIG. 4 to see the Stages used in this example:

[0059]

	// Connect the inputClassifer to the monitor, editor, and
	// gatherer
	inputClassifier->connect(0, dmux, 0);
	dmux->connect(0, rmon, 0);
	dmux->connect(1, layerer, 0);
	dmux->connect(2, transcoder, 0);
	transcoder->connect(0, layered, 1);
	// Explore the Outputs of the dmux.
	#define STAGE_OF(x) (x).first
	#define NUM_OF(x) (x).second
	vector<StageConn>::const_iterator i;
	for (i = dmux->obegin( ); i != dmux->oend( ); ++i)
	{
	// *i hold a pointer to the neighbor and its input number.
	Stage *neighbor = STAGE_OF(i);
	u_int16_t neighInputNum = NUM_OF(i);
	if (i == dmux->obegin( ))
	{
	assert(neighInputNum == 0); // RMON's input
	assert(neighbor == rmon);
	}
	}

Stage::Parameter Class

[0060]

	Name:	Stage::Parameter
	Specializes:	EventCallback<pair<string, Stage*>>
	Qualifiers:	protected

[0061] The Stage::Parameter class 410 represents a Stage's parameter. The motivation for this simple class is to encapsulate the notion of double buffering (or two-phase commit). As described with reference to FIG. 8, a Parameter 410 maintains a shadow of the value currently in hardware plus a deferred value that will be placed into the hardware during the owning Stage's synchronization.

[0062] Parameters can also conveniently capture the asynchronous changes in the underlying forwarding engine hardware. To enable this, every Parameter can be given a list of callbacks to invoke when the parameter changes. The actual registration mechanism is exposed through the Stage::Register and Stage::DeRegister methods.

Related Types:

See Stage

[0063]

Attributes
Name	Type	Qualifiers	Description
m_currentValue	Void	* Protected	The current value of this
			parameter (a shadow
			of the hardware).
m_deferredValue	Void	* Protected	The next, or new, value of the
			parameter that will be placed
			into hardware during the
			next Stage synchronization.

Methods
The following methods are defined.

[0064]

	Methods	Services
	Get	Get current value.
	GetDeferred	Get the deferred value.
	IsDirty	Test for value reset.
	Set	Set deferredValue.
	Commit	Copy deferredValue to
		currentValue.

[0065]

	Get
	Description:	const void *Get () const;
		Retrieves the current value (a shadow of
		the value currently in the hardware).
	Parameters:	None.
	Returns:	Current value.
	Exceptions:	None.
	GetDeferred
	Description:	const void *GetDeferred () const;
		Retrieves the future value, which could be NULL.
	Parameters:	None.
	Returns:	Deferred value.
	Exceptions:	None.
	IsDirty
	Description:	bool IsDirty () ;
		Discover if the deferred value has been
		set since the last Commit ().
	Parameters:	None.
	Returns:	True if deferred value has been set; false if not.
	Exceptions:	None.
	Set
	Description:	void Set (void *value) ;
		Sets the deferred (or new, or next) value of this parameter.
		After this method returns, IsDirty ()
		will be true until the next invocation of Commit ().
	Parameters:	IN: void *value	A void pointer which will become the
			deferred value of the parameter.
			The Parameter is not responsible for
			memory management of the pointer.
	Returns:	Nothing.
	Exceptions:	None.
Commit
Description:	void Commit () ;
	If the parameter IsDirty, commit copies the deferredValue to
	the currentValue and obsoletes the deferredValue. In addition,
	all registered callbacks are signaled to indicate a change to the underlying
	hardware.
	Because of this, all implementers of Stage subclasses must call
	Commit after they have updated a Paramater's value.
	Stage::Synchronize calls Commit after the
	parameter has been updated. After Commit is called,
	IsDirty is false until the next invocation of Set.
Parameters:	None.
Returns:	Nothing.
Exceptions:	None.
EngineGraphManager Class
Name:	EngineGraphManager
Specializes:	N/A
Qualifiers:	N/A

[0066] The EngineGraphManager 452, as depicted with reference to FIG. 9, is a singleton class. The one instance of this class is used to gather global information (such as available Stages, constraints on interconnecting Stages, and intra-Stage parameter updating). Currently the EngineGraphManager 452 provides a mechanism to retrieve all of the terminal Stages (i.e., Links 462) in the Engine Model. The Engine Model can then be traversed to find information on all the connected Stages.

[0067] The EngineGraphManager 452 exposes the possible interconnections of the Stages. Each Stage also holds an attribute optional which is true if the Stage can be bypassed. Intra-Stage parameter updating constraints are taken care of by providing read only attributes (i.e. only Get methods) for the corresponding parameters (e.g., in FIG. 4, if the classifier was optional, the output of the link could be directly connected to the scatterer). On the other hand, the editor being optional is implicit in the way we have a scatterer/gatherer, which by means of parameter setting can bypass the editor. We could make the parameter read-only if that wasn't desired. If the model was completely flexible and programmable then the topology could be connected in anyway without connect throwing an exception.

[0068] The other way, is to have an mutable attribute for any connection. This has the advantage that a meta-Stage (composite Stage) defined at runtime, can be installed and removed as desired. (This can be done using the isoptional attribute in Stage too, but then that meta-Stage has to be defined at compile-time). In this case to represent an optional Stage we would have to make the outconnection of previous Stage and inconnection of the following Stage as mutable

[0069] Note: The capabilities of an FE related to links are in the Link class, other capabilities such as the ability to do certain types of filtering etc, can in some sense be represented in the interconnection of Stages. In order to represent a specific type we will use that Stage eg. Five Tuple Classifier in the interconnected model whereas to represent a general type of classification we will use Classifier Stage in the model, and the FEAPI model user can then model that Stage to be the specific type of classifier it wants.
Related Types:
See also LinksContainer.

[0070]

Attributes
Name	Type	Qualifiers	Description
m_instance	EngineGraphManager	Static	The single instance
		private	of this class.
m_links	LinksContainer	Private	The list of input output
			Links within this
			instance of the
			Engine Model.

Methods
The following methods are defined.

[0071]

	Methods	Services
	GetInstance	Get the single instance of this class.
	GetLinks	Get set of Links that represent inputs/outputs to
		the engine model.

[0072]

GetInstance
Description:	static EngineGraphManager& GetInstance( );
	Gets the single instance of this class.
Parameters:	None.
Returns:	Returns the single instance of this class.
Exceptions:	None.
GetInputLinks
Description:	const LinksContainer& GetLinks( );
	Gets the set of links that represent inputs/outputs within
	this instance of the Engine Model.
Parameters:	None.
Returns:	Returns the Links.
Exceptions:	None.
Example:
// Get the single instance of the EngineGraphManager
// and find out how many input and output links there
// are in this instance of the model
// Assumption: 1. A link is both an input and output link
// 2. A link will always be either at beginning or end of
packet flow.
// If these assumptions do not hold true then we may need
sets of input
//and output links as before.
EngineGraphManager& egm = EngineGraphManager::GetInstance( );
const LinksContainer& links = egm.GetLinks( );
cout << “There are” << links.size( );
cout << “ports on this FE” << endl;
// Obviously each Link is a Stage, so you can also use
// the iterators to traverse the data flow network
void depthFirstTraversal (Stage *s)
{
	cout << “At Stage” << s << endl;
	vector<StageConn>::const_iterator i;
	u_int16_t outNum = 0;
	// For each output of the given Stage, traverse it
	for (i = s->Obegin( ); i != s->Oend( ); ++i, ++outNum)
	{
	// Find the neighbor and if it is not a link recurse
	Stage *neigh = STAGE_OF(i);
	if (!(neigh instanceof Link)) // dynamic cast in C++
	{
	// the same Stage could be encountered in multiple
paths
	// because of gatherer and scatteror, and hence
	// have a check to make sure this is enountered for
first time
	// can skip if not
	cout << “Output ”<< outNum;
	cout << “ is hooked to” << neigh <<
	cout << “ input << NUN_OF(i) << endl;
	depthFirstTraversal (neigh);
	}
	}
	cout << “Leaving Stage ” << s << endl;
}
// For each input link, walk through the data path
for (i = links.begin( ); i != links.end( ); ++i)
	depthFirstTraversal (&(*i));

[0073]

LinksContainer Class
	Name:		LinksContainer
	Specializes:	N/A
	Qualifiers:	N/A

[0074] This class holds a list of the Links (terminal Stages) in the data-flow topology. The class provides access to an immutable iterator over these Links.

Related Types:

See also EngineGraphManager.

[0075] Attributes

[0076]

Attributes
	Name	Type	Qualifiers	Description
	m_links	list<Link>	Protected	List of Links.

Methods
The following methods are defined.

[0077]

	Methods	Services
	begin	Get the beginning iterator for the list of
		Links.
	end	Get the ending iterator for the list of Links.
	size	Get the number of Links in the list.

[0078]

begin
Description:	list<Link>::const_iterator begin( );
Parameters:	None.
Returns:	Returns the beginning iterator for the list of Links.
Exceptions:	None.
end
Description:	list<Link>::const_iterator end( );
Parameters:	None.
Returns:	Returns the ending iterator for the list of Links.
Exceptions:	None.
size
Description:	int size( );
Parameters:	None.
Returns:	Returns the number of Links in the list.
Exceptions:	None.

Example:
See EngineGraphManager.
Stage Types

[0079] Specific types of Stages are defined in this section. These build off the infrastructure direct graph of packet flow 250 depicted in FIG. 4. For each new type of Stage the number of inputs and outputs is specified. The parameters (or adjustments) of the particular Stage are described in terms of operations on the Stage.

[0080] FIG. 10 shows the multiplexing and demultiplexing Stage types. FIG. 11 shows some of the remaining first layer of specific Stage types defined in the Engine Model. Each Stage type is a subclass of the Stage class. In the following sections, each of these Stage types is described along with its subclasses.

Multiplexing and Demultiplexing Types

Scatterer Class

[0081]

	Name:	Scatterer
	Specializes:	Stage
	Qualifiers:	N/A

[0082] A scatterer 534, as depicted in FIGS. 10 and 12, is a subclass of Stage 532 has one input 536, multiple outputs 538 (538-1, . . . , 538-N), and operates much like a demultiplexor. A Scatterer Stage 534 copies any data on its data input 536 to all of its enabled outputs 538. A mask-instance variable 539 controls which outputs 538 are considered enabled. There are two main uses of this class:

• • [0083] A Scatterer can represent a simple user-controlled N-way switch. Setting one bit in the mask to 1 achieves this functionality. This might be used to insert or remove a coprocessor from the data path of the forwarding engine hardware.
  • [0084] A Scatterer can also represent a bus or replicator. Setting multiple bits in the mask to 1 achieves this functionality. This might be used when data within the forwarding engine is sent in parallel to two or more Stages. The Scatterer in FIG. 4 illustrates this use.
    Note: As stated in the introduction, no data actually passes through the Scatterer object, which is merely a representation of the underlying hardware.
    Combinations of the above functionality are also possible. However, a Scatterer does not model per-packet demultiplexing. See SwitchFabric for such functionality.

[0085] This class is essential to representing many of the parallel operations of the underlying forwarding-engine hardware. For example, it would allow a coprocessor to be switched on and off, or a remote monitoring agent to gather statistics in parallel with standard forwarding Stages.

Related Types:

• [0086] See also Gatherer
• [0087] Stage Parameters

[0088]

	Parameter	Type	Description
	mask	bitmask	The mask controls where incoming
			packets are copied.

Methods
The following methods are defined.

[0089]

Methods	Services
GetMask	Get the current mask value.
SetMask	Set the deferred mask value.
GetMask
Description:	bitmask GetMask() const;
Parameters:	None.
Returns:	Current value of the mask.
Exceptions:	None.
SetMask
Description:	void SetMask (bitmask m);
	Sets the deferred value of the mask
Parameters:	IN: bitmask m	The new bitmask to use to determine what outputs
		are enabled.
		Takes effect after the next Synchronize().
Returns:	Nothing.
Exceptions:	None.

Example:

[0090]

	// The dmux object would be created as follows:
	Scatterer *dmux = new Scatterer(3); // 3 = # Outputs
	// The Scatterer would be connected to the other Stages
	// as in the example from the Stage class.
	inputClassifier->Connect(0, dmux, 0);
	dmux->Connect(0, rmon, 0);
	dmux->Connect(1, layerer, 0);
	dmux->Connect(2, transcoder, 0);
	transcoder->Connect(0, layerer, 1);
	// Model a simple two-way switch
	dmux->SetMask(0×1);
	dmux->Synchronize( );	// Data now flows from inputClassifier
		// through rmon
dmux->SetMask(0×4);
dmux->Synchronize( );	// Data now flows from inputClassifier
	// through the transcoder
// Model a replicator (duplicator)
// This would be the typical use of dmux in the example model
dmux->SetMask(0×7);
dmux->Synchronize( );	// Data now flows from inputClassifier
	// through rmon, transcoder and layerer
	// in parallel

[0091]

Gatherer Class
	Name:	Gatherer
	Specializes:	Stage
	Qualifiers:	N/A

[0092] A Gather class 540, as depicted in FIG. 13, is a subclass of Stage has one output 548 and N inputs 546 (546-1, . . . , 546-N). It operates much like a multiplexor. A Gatherer Stage 544 copies data on any of its enabled inputs 546 to its output 544. The mask-instance variable 549 controls which inputs are considered enabled. The Gatherer represents a simple user-controlled collection point. This might be used to merge a previously scattered data stream back into one steam.

[0093] As with Scatterer, no data actually passes through the Gatherer object, which is merely a representation of the underlying hardware.

Stage Parameters

[0094]

	Parameter	Type	Description
	mask	bitmask	The mask controls which incoming
			packets (on the input) are copied to the
			output.

Methods
The following methods are defined.

[0095]

	Methods	Services
	GetMask	Get the current mask value.
	SetMask	Set the deferred mask value.

[0096]

GetMask
Description:	bitmask GetMask() const;
Parameters:	None
Returns:	Current value of the mask.
Exceptions:	None.
SetMask
Description:	void SetMask(bitmask m);
	Sets the deferred value of the mask
Parameters:	IN: bitmask m	The new bitmask to use to determine what outputs
	are enabled.
		Takes effect after the next Synchronize().
Returns:	Nothing.

Example:

[0097]

	// The layerer object would be created as follows:
	Gatherer *layerer = new Gatherer(2); // 2 = # Inputs
	// The Gatherer would be connected to the other Stages
	// as follows.
	dmux->Connect(1, layerer, 0);
	transcoder->Connect(0, layerer, 1);
	layerer->Connect(0, outputPort, 0);
	// Set the mask to 0×3 to allow packets from either the
	// dmux or transcoder to pass through
	layerer->SetMask(0×3);
	layerer->Synchronize( );

Related Types:
See also Scatterer.

[0098]

SwitchFabric Class
	Name:	SwitchFabric
	Specializes:	Stage
	Qualifiers:	N/A

[0099] A SwitchFabric class 550, as depicted in FIG. 14, is a subclass of Stage 552 and represents a per-packet demultiplexor. A SwitchFabric 554 has one input 556 and N outputs 559 (559-1, . . . , 559-N). A SwitchFabric uses the incoming tag to decide on which outputs 558 (558-1, . . . , 558-N) to forward the packet. A SwitchFabric 554 has a parameter, tagMap 559 that defines the mapping from incoming tags to outputs 558.

Related Types:

See also Classifier

[0100]

Stage Parameters
Parameter	Type	Description
tagMap	map<u_int64_t,	Specifies the mapping from
	bitmask>	incoming tags to outputs. Each bit in the
		bitmask represents one output. If a bit
		in the bitmask is set, the incoming data
		is switched out the corresponding output.

Methods
The following methods are defined.

[0101]

Methods	Services
GetTagMap	Get the tag-to-output mapping table.
SetTagMap	Sets the deferred value of the mapping
	table.
AddTag	Add an entry to the mapping table.
RemoveTag	Remove and entry from the mapping
	table.

[0102]

GetTagMap
Description:	map<u_int64_t, bitmask> GetTagMap( );
	Gets the tag-to-output mapping table.
Parameters:	None.
Returns:	Returns mapping table.
Exceptions:	None.
SetTagMap
Description:	void SetTagMap(map<u_int64_t, bitmask> m);
	Sets the deferred value of the tag-to-output mapping table.
Parameters:	IN: m	The new mapping from incoming tags to bitmasks.
		The bitmasks indicate on which outputs to
	forward the
		incoming data.
Returns:	Nothing.
Exceptions:	None.
AddTag
Description:	void AddTag(pair<u_int64_t, bitmask> t);
	Adds a given entry into the tag-to-output mapping table.
Parameters:	IN: t	The new entry to add into the tagMap. If there is an
		existing entry with the same tag, the bitmask is
		replaced with this one
Returns:	Nothing
Exceptions:	None.
RemoveTag
Description:	void RemoveTag(u_int64t)
	throw(item_not_found<string>);
	Remove the designated entry from the tagMap.
Parameters:	IN: u_int64_t t	Tag of the entry to be deleted.
Returns:	Nothing.
Exceptions:	If the entry does not exist, item_not_found<string> is raised.
Example:
See Ipv4Classifier.

Other Stage Types

[0103]

Link Type
	Name:	Link
	Specializes:	Stage
	Qualifiers:	N/A

[0104] Additional Stage classes 560, are depicted in FIG. 15. A link class 570, as depicted in FIG. 16, represents a physical link. A Link object 572 is intended to be the terminating (beginning or end) Stage 562 of a data-flow topology defined in accordance with the Engine Model. The parameters of a Link are likely candidates for event registration.

[0105]

Stage Attributes
	Attribute	Type	Description
	m_number	uint16_t	Number of the link
	m_name	string	Name of the interface eg. eth0

[0106]

Stage Parameters
Parameter	Type	Description
status	enum	Values could be Up, Down, or AdminDown
speed	Integer	Kbits/s
L2Address	string	The L2 address of the link. A link can
		have multiple L2address? May
		need to make this a vector too.
L3Address	Vector<L	The set of L3Addresses for this link.
	3Address>	For description of L3Address see Appendix.
type	Enum	The type of the Link (e.g., Ethernet, ATM, Frame
		Relay, etc.)
		This enum should be consistent with a known
		standard or at least within ON project.

Methods
The following Methods are defined.

[0107]

	Methods	Services
	GetStatus	Test if Link is operating.
	SetStatus	Set operating state of Link to
		UP or AdminDown
	GetType	Get Link type (e.g., Ethernet,
		ATM, Frame Relay, etc.)
	GetL2Address	Get the L2 address of the Link.
	BeginL3Address	Get the beginning iterator to
		set of L3 addresses of the Link.
	EndL3Address	Get the ending iterator to set
		of L3 addresses of the link
	GetSpeed	Get the speed of the Link.
	GetNumL3Address	Get the number of L3 addresses
		of the link
	AddL3Address	Adds an L3 address to the Link
	RemoveL3Address	Removes an L3 address from the
		link
	GetName	Get the name of the link
	GetNumber	Get the number of this link
	SendPacket	Send the specified packet on
		this link

[0108]

GetStatus
Description:	enum GetStatus( ) const;
	Tests if Link is operational.
Parameters:	None.
Returns:	Returns Up if Link is operating; Down or AdminDown if not.
Exceptions:	None.
SetStatus
Description:	void SetStatus(bool en);
	Sets the operating state of the Link.
Parameters:	IN: bool en	Set to true if the Link is to be brought up;
		false if the Link is to be taken down.
		Only the link class will set the up attribute
		directly to Down if the link goes down.
Returns:	Nothing.
Exceptions:	None.
GetType
Description:	string GetType( ) const;
	Gets the Link type (e.g., Ethernet, ATM, Frame Relay, etc.).
Parameter:	None.
Returns:	Type of the physical Link.
Exceptions:	None.
GetL2Address
Description:	string GetL2Address( ) const;
	Gets the L2 address of the physical Link.
Parameters:	None.
Returns:	L2 address (string) of the Link.
Exceptions:	None.
BeginL3Address
Description:	vector<L3ADDRESS>::const_iterator BeginL3Address( )
	const;
	Gets the beginning iterator to the set of L3 address of the Link.
Parameters:	None.
Returns:	beginning iterator to the set of L3 address of the Link.
Exceptions:	None.
EndL3Address
Description:	vector<L3ADDRESS>::const_iterator EndL3Address( )
	const;
	Gets the ending iterator to the set of L3 address of the Link.
Parameters:	None.
Returns:	ending iterator to the set of L3 address of the Link.
Exceptions:	None
GetSpeed
Description:	u_int32_t GetSpeed( ) const;
	Get the Link speed in Kbits/s
Parameters:	None.
Returns:	Link speed.
Exceptions:	None.
GetNumL3Address
Description:	u_int16_t GetNumL3Address( ) const;
	Get the Number of L3 addresses on this link.
Parameters:	None.
Returns:	Um of L3 addresses
Exceptions:	None
AddL3Address
Description:	void AddL3Address(L3Address L3Addr) throw
	(cant_add_L3);
	Add the given L3Address to the link
Parameters:	IN: L3Address L3Addr   L3Address to add
Returns:	None
Exceptions:	cant_add_L3_exception
RemoveL3Address
Description:	void RemoveL3Address(L3Address L3Addr) throw
	(item_not_found<string>;
	Remove the given L3Address to the link
Parameters:	IN: L3Address L3Addr   L3Address to remove
Returns:	None
Exceptions:	item_not_found<string>
GetName
Description:	string GetName( ) const;
	Get the Name of this link eg. eth0.
Parameters:	None.
Returns:	Name of link.
Exceptions:	None
GetNumber
Description:	string GetNumber( ) const;
	Get the Number of this link.
Parameters:	None.
Returns:	Number of the link.
Exceptions:	None
SendPacket
Description:	virtual uint32_t SendPacket(uint16_t protocol, const
	uint8_t* data, const ulnt32_t len )= 0;
	This is a virtual function which will be defined in the specific link type
	for a particular Hw/OS and will send the packet out on that link.
Parameters:	IN: uint16_t protocol	L3 protocol of the packet to send
	IN: uint8_t *data	Pointer to packet data to send
	IN: uint32_t Len	length of the data packet
Returns:	uint32_t
Exceptions:	None
Note: To redirect a packet to CE or APP server, we will probably have special links for the purpose.
Note: When a packet is received from a link, the tag will be set to a value identifying the link it arrived on.

Example:

[0109]

	// Register a callback to be notified of changes to the
	// operational status of a Link.
	void callback(string name, Stage *s)
	{
	cout << “The Link's ” <<name << “Parameter has ”;
	cout << “changed state to” << s->GetStatus() << endl;
	}
	CBFunctor<string> cbFunc(NULL, &callback);
	EngineGraphManager& egm = EngineGraphManager::getInstance( ) ;
	Link 1 = egm.GetLinks( ).begin( );
	l.RegisterCB(“up”, &cbFunc);
	// Now any changes to the link state will invoke callback( )
	l.SetStatus(false);
	l.Synchronize( ); // callback( ) invoked!
	Note: For link statistics you can now query the monitor object associated with the link.

Link Types
The Link will be further specialized into Ethernet, ATM link etc

[0110]

Queue Type
	Name:	Queue
	Specializes:	Stage
	Qualifiers:	None.

[0111] The Queue class type 556, as depicted in FIG. 15, represents a first-in-first-out store within the forwarding engine hardware. The motivation for having Queues 556 in the Engine Model is to provide a representation of any internal buffering. Right now the capacity is just in bytes.

[0112]

Stage Attributes
Attribute	Type	Description
M_numbytes	U_int32_t	Number of bytes the queue holds
m_packets	u_int32_t	Number of packets the queue holds

[0113]

Stage Parameters
	Parameter	Type	Description
	m_depth	u_int32_t	Number of bytes the queue can hold.

Methods
The following methods are defined.

[0114]

	Methods	Services
	GetDepth	Get the number of bytes the queue can
		hold.
	Set Depth	Set the number of bytes the queue can
		hold.
	GetNumBytes	Get the number of bytes the queue
		presently holds
	GetNumPackets	Get the number of packets the queue
		holds.

[0115]

GetDepth
Description:	u_int32_t GetDepth () const;
	Gets the number of bytes the queue
	can hold.
Parameters:	None.
Returns:	Depth of queue.
Exceptions:	None.
SetDepth
Description:	bool SetDepth (u_int32_t d);
	Sets the depth of the queue.
Parameters	IN: u_int32_t d	New depth of the
		queue.
Returns:	True if dept set successfully else
	false.
Exceptions:	None.
GetNumBytes
Description:	void GetNumBytes ();
	Gets the number of bytes in the
	queue.
Parameters	None
Returns:	Number of bytes in the queue
Exceptions:	None
GetNumPackets
Description:	void GetNumPackets ();
	Gets the number of packets in the
	queue.
Parameters	None
Returns:	Number of packets in the queue
Exceptions:	None
Example:
See Scheduler.
Note:
Now since the monitoring is part of a Stage, the queue could monitor how many packets were received, dropped and transmitted etc.

[0116]

Classifier Type
	Name:	Classifier
	Specializes:	SingleIOStage
	Qualifiers:	Abstract

[0117] A Classifier class 580, as depicted in FIGS. 15 and 17, is a Stage with one input 586 and outputs 588 (588-1, . . . , 588-N). A Classifier object 584 represents a Stage that matches packets against a set of patterns (or filters) and then forwards the packet with a specified output tag on a specified output. When a packet, including a tag, arrives on the input 586, a Classifier 584 attempts to match the packet against an ordered list of patterns (the patternTable parameter 589). Once a match is found, the packet is forwarded out the proper output 588 with a modified tag.

[0118] The following are characteristics of the Classifier interface:

• • [0119] Inputs and outputs in the Engine Model consist of a tag plus the packet; Classifiers can modify tags.
  • [0120] While patterns are specific to the sub-types of Classifier, patterns contain the input tag. This input tag can be, but does not have to be, used in addition to the pattern for matching purposes. Therefore, one Classifier can use the result of a previous Classifier. See the addEntry method for details.
  • [0121] The output tag from a classifier can be either a combination of the input tag with certain bits modified, or can be completely independent of the input tag. This is determined solely at the discretion of the Engine Model programmer. The implicit requirement is that the output tag has meaning to any downstream Stage that consumes it.

[0122] The following pseudo-code illustrates how a Classifier 602 should work, as depicted with reference to FIG. 18:

• [0123] if ((incoming packet matches pattern) && (incoming tag & inTag.mask)==inTag.value))
  then
  • [0124] outputTag=(incoming tag & ˜outTag.mask)|outTag.value;

[0125] In this example, the pattern 616, inTag 618, and outTag 619 are specified by each entry in the patternTable 604.

[0126] Finally, the abstract Classifier class 602 overrides the UpdateHardware method of the Stage class. This is done so that each specific Classifier implementation does not have to implement UpdateHardware. Rather, Classifier takes over this responsibility and calls three methods: Hw_DeleteEntry( ), Hw_AddEntry( ), and Hw_ModifyEntry( ). Classifier::UpdateHardware( ) calls hw_xxxEntry( ) methods for only those entries in the action table that have changed. This can potentially reduce hardware updates.

[0127]

	Related Types:
	typedef u_int64_t bitmask;
	typedef pair<bitmask, u_int64_t> MaskValue;
	typedef pair<T, MaskValue> ClsInput;
	typedef pair<MaskValue, u_int16_t> ClsOutput;

[0128]

Stage Parameters
Parameter	Type	Description
m_patternTable	map<ClsInput,	An ordered set of patterns with
	ClsOutput>	corresponding output tag modifica-
	with ordering	tions. Each entry in this table con-
		tains the sub-class specific pattern,
		the incoming tag pattern, the out-
		going tag pattern and the output con-
		nection to send the packet for a
		graphical representation of this data
		structure.

Methods
The following methods are defined.

[0129]

	Methods	Services
	GetTable	Get the complete pattern table.
	SetTable	Set (replace) the complete pattern table.
	AddEntry	Add a new entry to the pattern table.
	RemoveEntry	Delete an entry from the pattern table.
	UpdateHardware	Selectively update hardware as required.
	Hw_DeleteEntry	Delete an entry from the hardware.
	Hw_AddEntry	Add an entry to the hardware.
	Hw_ModifyEntry	Replace an existing pattern with a new value.

[0130]

GetTable
Description:	map<ClsInput, ClsOutput> GetTable () const;
	Gets the complete pattern table.
	See the description of the patternTable parameter for the format of
	this table. The type T (which is part of ClsInput) in the table is
	specified by the concrete subclasses of Classifier.
Parameters:	None.
Returns:	Complete pattern table.
Exceptions:	None.
SetTable
Description:	void SetTable(map<clsInput, ClsOutput> t);
	Sets (replaces) the pattern table.
Parameters:	IN: map t	New pattern table.
Returns:	Nothing.
Exceptions:	None.
AddEntry
Description:	void AddEntry (ClsInput in, MaskValue outTag,
	u_int16_t outConn);
	Add a new entry into the pattern table.
Parameters:	IN: ClsInput in	The key of the new pattern-table
	entry. This
		key contains both a subclass-specific
		pattern and an input tag pattern. The
		input tag pattern is a mask-value pair.
		See the description of this class for
		how the input tag pattern is used.
	IN:MaskValue outTag	This combined with the outConn is
		the value of the new pattern-table
		entry. This is a mask-value pair that is
		applied to the input tag to produce an
		output tag. See the description of this
		class for how this value is used.
	IN: u_int16_t outConn	The output connection on which to output the
		packet with the modified tag. This together
		with the outTag forms the new value in the
		pattern table for key in.
Returns:	Nothing.
Exceptions:	None.
RemoveEntry
Description:	void RemoveEntry (ClsInput in)
	throw(item_not_found<string>);
	Delete an entry from the pattern table.
Parameters:	IN: ClsInput in	Key of the entry to delete.
Returns:	Nothing.
Exceptions:	Throws item_not_found<string> if entry does not exist.
UpdateHardware
Description:	(private) virtual bool
	UpdateHardware (string name,
	Parameter& p);
	This method is overridden from class Stage and is used to make the
	implementation of specific Classifier types easier. The only value
	of p for Classifiers is the patternTable.
	1. Compares the current value of the patternTable to the deferred
	value.
	2. Calls Hw_DeleteEntry () for each entry found in the current
	value but not in the deferredValue.
	3. Calls Hw_AddEntry () for each entry found in the deferred value
	and not in the current value.
	4. Calls Hw_ModifyEntry for any keys common to both the current
	and deferred value, but with different values.
Parameters:	IN: string name	Name of the Parameter to update.
		This should always be “patternTable.”
	IN: Parameter& p	Parameter (patternTable) to be updated.
		Contains the current value of the hardware
		(shadow) as well as the deferred (new) value.
		This method uses these two values to
		compare the existing table to the new table
		and calls Hw_XxxEntry () only for
		differences between the current and deferred
		tables.
Returns:	False if any of the Hw_XxxEntry () calls return false; otherwise
	true.
Exceptions:	None.
Hw_DeleteEntry
Description:	(protected) bool Hw_DeleteEntry (ClsInput in) = 0;
	Delete the given entry from the hardware.
Parameters:	IN: ClsInput in	Entry to delete.
Returns:	True if successful, false if not.
Exceptions:	None.
Hw_AddEntry
Description:	(protected) bool Hw_AddEntry(ClsInput in,
	MaskValue out, u_int16_t outConn);
	Adds the given entry into the hardware.
Parameters:	IN:	ClsInput in	The key of the pattern table to
	add.
	IN:	MaskValue out	The mask/value pair specifying how
	to
			modify the input tag to produce the
			output tag.
	IN: u_int16_t	The output connection on which to output the
		packet with the modified tag.
Returns:	True if successful; false if not.
Exceptions:	None.
Hw_ModifyEntry
Description:	(protected) bool Hw_ModifyEntry (ClsInput in,
	MaskValue out, u_int16_t outConn);
	Replaces the existing pattern with the new value.
Parameters:	IN: ClsInput in	The existing entry in the pattern table. The
	value
		of this entry should be replaced with out.
	IN:	MaskValue out	The new mask-value
	pair to replace the existing entry.
	IN: u_int16_t	The output connection on which to output the
		packet with the modified tag
Returns:	True if successful, false if not.
Exceptions:	None.

Example:

[0131]

	// Since a Classifier outputs a tag and Editors look at tags
	// as input, they will typically be coupled together
	Classifier *cls = new Classifier (); // by default a single
	I/O classifier
	Editor *ed = new Editor ();
	// Hook the classifier to the Editor. This would be
	// useful for firewalling, NAT, etc.
	cls.Connect (0, ed, 0);
	// See the subclasses of Classifier for concrete examples

IPFiveTupleClassifier

[0132]

	Name:	IPFiveTupleClassifier
	Specializes:	Classifier<FiveTuple>

Qualifiers: None.
An IPFiveTupleClassifier is a specific type of Classifier whose patterns are standard IP five-tuples.
Example:

[0133]

	// A 5-tuple classifier could be used for a myriad of
	// purposes depending upon the editor or switch fabric it is
	// coupled with.
	IPFiveTupleClassifier *cls = new IPFiveTupleClassifier ();
	// Create a simple pattern table that contains
	// two patterns: one to pass HTTP packets, the other
	// drop anything
	#define PATTERN (x) (x) .first.first
	#define IN_TAG_MASK (x) (x) .first.second.first
	#define IN_TAG_VALUE (x) (x).first.second.second
	#define OUT_TAG_MASK (x) (x).second.first.first
	#define OUT_TAG_VALUE (x) (x) .second.first.second
	#define OUT_PORT (x) (x).second.second
	pair<ClsInput, Output> http, any;
	// just a representation
	PATTERN (http) = new FiveTuple (“*”, “*”, “*”, 0, 80);
	IN_TAG_MASK (http) = 0x0;
	IN_TAG_VALUE (http) = 0x0; // Says to ignore the input tag
	OUT_TAG_MASK (http) = 0xffffffffffffffff;
	OUT_TAG_VALUE (http) = ACCEPT_TAG; // output tag value
	OUT_PORT (http) = 0;
	PATTERN (any) = new FiveTuple (“*”, “*”, “*”, 0, 0);
	IN_TAG_MASK (any) = 0x0;
	IN_TAG_VALUE (any) = 0x0; // Say to ignore the input tag
	OUT_TAG_MASK (http) = 0x0;
	OUT_TAG_VALUE (http) = 0x0; // output tag = input tag
	OUT_PORT (http) = 0;
	cls.AddEntry (http.first, http.second.first,
	http.second.second);
	cls.AddEntry (any.first, any.second.first, any.second.second);

IPv4Classifier

[0134]

	Name:	IPv4Classifier
	Specializes:	Classifier<RouteEntry>
	Qualifiers:	None.

The IPv4Classifier is a specific type of Classifier whose filters are routing entries. Such a Classifier is used to perform the lookup phase of IP routing.
Example:

[0135]

	// A IPv4 classifier would be used for routing
	// 1 input, 4 outputs
	IPv4Classifier *rtr = new IPv4Classifier (4);
	// Install a route
	pair<ClsInput, ClsOutput> e;
	PATTERN (e) = new RouteEntry (“1.1.0.0”, 0xffff0000,
	“2.2.2.251”, “eth3”, 10);
	OUT_TAG_MASK (e) = 0xffffffffffffffff;
	OUT_TAG_VALUE (e) = 4;
	OUT_PORT (e) = 4; // 4 = connected to link eth3
	rtr.AddEntry (e.first. e.second.first, e.second.second);

Editor Type

[0136]

	Name:	Editor
	Specializes:	Stage
	Qualifiers:	Abstract

[0137] An Editor class 620, as depicted in FIGS. 15 and 19, is a Stage 622 that modifies or alters packets passing through it. Editor 624 maintains an action table that is keyed by the tags that come from an upstream Classifer. The Engine Model does not specify the actual value of the tag. The only requirement is that there must be a contract between the upstream Classifier that creates the tags and the downstream Editor Stage. This contract means that the tags sent out by the Classifier are the same as the keys in the Editor's actionTable. For Linux, an editor will always be preceded by a Classifier.

[0138] The value in the Editor's action table that corresponds to an incoming tag specifies how to modify the current packet for that tag and on which connection to output. Editors do not modify the outgoing tag. The concrete subclasses of Editor define the format of the action table.

[0139] Finally, like Classifier, the abstract Editor class overrides the updateHardware method of the Stage class. This is done for the same reason, and with the same mechanism, as Classifier. See Classifier, Section 0, for details.

Related Types:

• [0140] typdef pair<T, u_int16_t>=OutputAction//u_{—l int—}16 is the output port on which to output the packet.

[0141]

Stage Parameters
Parameter	Type	Description
ActionTable	map<MaskValue,	A collection of key, value pairs. The
	OutputAction>	keys are of the same type as the in-
		coming tags. The values specify how to
		edit the packet. The actions are specific
		to the concrete subclasses of Editor.

Methods
The following methods are defined.

[0142]

	Methods	Services
	GetTable	Get complete pattern table.
	SetTable	Set (replace) pattern table.
	AddEntry	Add an entry to the pattern table.
	RemoveEntry	Remove an entry from the pattern table.
	UpdateHardware	Selectively update hardware as required.
	Hw_DeleteEntry	Delete a specified entry from the hardware.
	Hw_AddEntry	Add an entry to the hardware.
	Hw_ModifyEntry	Update the entry for a specified tag.

[0143]

GetTable
Description:	map<MaskValue, OutputAction> GetTable () const;
	Get the complete pattern table. The format of each entry (T) is specified
	by the concrete subclasses of Classifier.
Parameters:	None.
Returns:	Complete pattern table.
Exceptions:	None.
SetTable
Description:	void SetTable (map<Maskvalue, OutputAction> t);
	Set (replace) the pattern table.
Parameters:	IN: map t	New pattern table.
Returns:	Nothing.
Exceptions:	None.
AddEntry
Description:	void AddEntry (pair<MaskValue, OutputAction> e);
	Adds a new entry into the pattern table.
Parameters:	IN: pair e	Entry to add into the pattern table.
Returns:	Nothing.
Exceptions:	None.
RemoveEntry
Description:	void RemoveEntry (pair<Maskvalue, OutputAction> e)
	throw (item_not_found<string>);
	Delete an entry from the pattern table.
Parameters:	IN: pair e	Entry to delete from pattern table.
Returns:	Nothing.
Exceptions:	Throws item_not_found<string> if entry does not exist.
UpdateHardware
Description:	(private) virtual
	bool UpdateHardware (string name, Parameter& p);
	This method is overridden from class Stage and is used to make the
	implementation of specific Editor types easier. The only value of p
	for an Editor is the actionTable.
	1. Compare the current value of the actionTable to the deferred
	value.
	2. Call Hw_DeleteEntry () for each entry found in the current value
	but not in the deferred value.
	3. Call Hw_AddEntry () for each entry found in the deferred value but
	not in the current value.
	4. Calls Hw_ModifyEntry () for any keys common to both the
	current and deferred values, but with different action values.
Parameters:	IN: string name	The string representing the name of the
		Parameter to update. Should always be
		“actionTable”
	IN:	Parameter& p	The parameter (actionTable) to be
			updated.
			This parameter contains the current value of
			the hardware (shadow) as well as the deferred
			(new) value. This method uses these two
			values to compare the existing table to the
			new table and only calls hw_xxxEntry ()
			for differences between the current and
			deferred tables.
Returns:	False if any of the Hw_XxxEntry calls return false; otherwise true.
Exceptions:	None.
Hw_DeleteEntry
Description:	(protected) bool Hw_DeleteEntry (pair<MaskValue,
	OutputAction> e) = 0;
	Delete the given entry from the hardware.
Parameters:	IN:	:pair<MaskValue, OutputAction>	Entry to
	delete.
Returns:	Returns true if successful, false if not.
Exceptions:	None.
Hw_AddEntry
Description:	(protected) bool Hw_AddEntry (pair<MaskValue,
	OutputAction> e);
	Add the given entry into the hardware.
Parameters:	IN: :pair<MaskValue, OutputAction> Entry to add.
Returns:	True if successful, false if not.
Exceptions:	None.
Hw_ModifyEntry
Description:	(protected) bool Hw_ModifyEntry (pair<MaskValue,
	OutputAction> e);
	Update the value (OutputAction) for the given tag (MaskValue) in
	the hardware.
Parameters:	IN: pair<MaskValue, OutputAction>	Entry to
	modify.
Returns:	True if successful, false if not.
Exceptions:	None.
Note:
Some examples of specific editors include ones used for redirecting traffic to CE or App server.

Example:
See Classifier.

[0144]

Scheduler
	Name:	Scheduler
	Specializes:	Stage
	Qualifiers:	Abstract

[0145] A Scheduler class 630, as depicted in FIGS. 15 and 20, represents a Stage 632 that services (dequeues) packets from several input queues 636 (636-1, . . . , 636-N) and copies them to one output 638. The concrete sub-classes of Scheduler (640, 642) specify additional parameters to control the policy behind this scheduling.

Example:

[0146]

	// A Scheduler would typically be used at either input
	// or output. In this case, we build a Scheduler
	// to provide two traffic classes on an output link
	Link& 1 = *(LinksContainer: :begin () );
	Scheduler *sch = new Scheduler (2);	// two input queues
	Queue	*q1 = new Queue (200),	// packet depth
		*q2 = new Queue (500);
	q1.Connect (0, sch, 0);
	q2.Connect (0, sch, 1);
	sch.Connect (0, 1, 0);
	// Now add a classifier to place packets
	// into the queues
	// here it is abstract for demonstration purpose, have a
	spcific instance //here
	Classifier *cls = new Classifier (2); // 2 outputs
	cls.Connect (0, q1, 0);
	cls.Connect (1, q2, 0);
	// Now depending upon the classifier (which is not
	// specified in this example) and the scheduling policy
	// of the Scheduler (also not shown), the output link
	// will output packets based on the two queues.

[0147]

Logger Stage
	Name:	Logger
	Specializes:	None
	Qualifiers:	None

[0148] This is a concrete Stage that is empty, essentially a null Stage. It only holds on to a monitoring object, so can be used as a logging Stage. A logger can have either 0 or 1 outputs. If it has 0 outputs it passively monitors the packets in parallel with possibly other operations. If it has one output, it outputs the packet without modification on that output.

[0149]

Monitoring Types
	Monitor
	Name:	Monitor
	Specializes:	None
	Qualifiers:	None.

[0150] The monitor class 650, as depicted in FIG. 21, allows a user to gather statistics (e.g., packet counts) for each input and output of the Stage that's owns it. There may be sub-types like RMON 654 and ClassifierMonitor 656.

[0151]

Attributes
Attribute	Type	Description
m_owner	Stage&	A reference to the Stage that holds this monitor

Methods
The following methods are defined.

[0152]

Methods	Services
GetInputBytes	Gets the number of bytes arriving on the
	given input.
GetInputPackets	Gets the number of packets arriving on the
	given input
GetOutputBytes	Gets the number of bytes leaving the given
	output
GetOutputPackets	Get the number of packets leaving the given
	output
GetTotalInputPackets	Total packets arriving in the Stage
GetTotalInputBytes	Total bytes arriving in the Stage
GetTotalOutputPackets	Total packets leaving the Stage
GetTotalOutputBytes	Total bytes leaving the Stage

[0153]

GetInputBytes/GetInputPackets
Description:	uint32_t GetInputBytes (uint16_t input) const;
	Uint32_t GetInputPackets (uint16_t input) const;
	Gets the bytes(packets) arriving on a particular input of the owner Stage.
Parameters:	IN: uint16_t	Input for which number of bytes(packets)
	required.
Returns:	Number of bytes(packets) on the given input of owner Stage.
Exceptions:	None.
GetOutputBytes/GetOutputpackets
Description:	uint32_t GetOutputBytes (uint16_t output) const;
	Uint32_t GetOutputpackets (uint16_t output) const;
	Gets the bytes(packets) leaving on a particular output of the owner
	Stage.
Parameters:	IN: uint16_t	output for which number of bytes(packets)
	required.
Returns:	Number of bytes(packets) on the given output of owner Stage.
Exceptions:	None.
GetTotalInputBytes/GetTotalInputPackets
Description:	uint32_t GetTotalInputBytes () const;
	Uint32_t GetTotalInputpackets () const;
	Gets the total bytes(packets) arriving at the owner Stage.
Parameters:	None.
Returns:	Number of bytes(packets) arriving at the owner Stage.
Exceptions:	None.
GetTotalOutputBytes/GetTotalOutputPackets
Description:	uint32_t GetTotalOutputBytes () const;
	Uint32_t GetTotalOutputPackets () const;
	Gets the total bytes(packets) leaving the owner Stage.
Parameters:	None.
Returns:	Number of bytes(packets) leaving the owner Stage.
Exceptions:	None

Examples:
A monitor held by a link can be queried for packets/bytes received and transmitted.
A monitor held by a Queue can be used to query packets received, as well as packets pulled from the queue, and this can be used to calculate the number of packets dropped.

[0154]

ClassifierMonitor
	Name:	ClassifierMonitor
	Specializes:	Monitor
	Qualifiers:	Abstract.

[0155] A ClassifierMonitor class 656, as depicted in FIG. 21, is an abstract class in a sense similar to the Classifier Stage. Specific types such as FiveTupleClassifierMonitor will specify the pattern, and hence the ClsInput for which the statistics is required.

[0156] (Or since the map in classifier is ordered, we could have just a patternid/position as input, and get statistics for it; this would be more generic, but with less intuition about what the pattern actually is.)

[0157]

Related Types:
typedef pair<bitmask, uint64_t> Mask Value
typedef pair<T, MaskValue> ClsInput // T is specified by specific types of
classifiermonitors.

Attributes
Methods
The following methods are defined.

[0158]

Methods	Services
GetNumBytes	Gets the number of bytes matching a given pattern.
GetNumPackets	Gets the number of packets matching a given pattern

[0159]

GetNumBytes/GetNumPackets
Description:	uint32_t GetNumBytes (clsInput pattern) const;
	Uint32_t GetNumPackets (ClsInput pattern) const;
	Gets the bytes(packets) matching the pattern in owner Stage.
Parameters:	IN: ClsInput	Pattern for which number of bytes(packets)
	required.
Returns:	Number of bytes(packets) matching the given pattern of owner Stage.
Exceptions:	no_such_pattern

Composition of Stages

[0160] Individual Stages can be combined to form more complex Stages, as depicted in FIGS. 22 and 23, and be treated as a single entity at compile time by defining new classes. At the same time meta-Stages can be formed at run time that behave as a single unit (in terms of being there as a whole or not being there at all) by using the mutable property of the connections.

Classifier with a Switchfabric

[0161] A classifier 676 with a switch fabric 680 is described with reference to FIG. 22. A classifier outputs packets 678 on one of the outputs. However at times we may need the packet to take multiple paths based on the classification (ie. multicast Ipv4Classifier). This can be easily accomplished by a MultiClassifier 670 formed by combining a Classifier 676 (with one output) with a switchfabric 680 (and optionally a monitor in between). The classifier outputs the packet 678 with the tag on its output and the switchfabric 680 sends the packet on one or more of its output 682 (682-1, . . . , 682-N) based on the tag output by the classifier.

MultiClassifier

[0162] A multiclassifier 690, as described with reference to FIG. 23, can be defined at runtime as follows.

Link Aggregation

[0163] We can use composition of Stages to represent link aggregation too. Thus an output aggregate link 704 (704-1, . . . , 704-n) can be represented as depicted in FIG. 23. The other approach for link aggregation would be to use the composite design pattern. This would allow us to present the same interface for single as well as aggregate links. This would mean adding methods in Link class for adding/deleting links. Users then would always access links through the Link Interface, which could contain single or multiple Ethernet (or possibly other) links. It would internally contain the scheduler if it had more than one physical link.

[0164] It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiment of the invention, this disclosure is illustrative only. Changes may be made in detail, especially matters of class structure and management of objects to form directed graphs of data/packet flow within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular API forwarding engine and underlying forwarding engine hardware may vary depending on the particular application for the novel object abstraction and identical API model while maintaining substantially the same functionality without departing from the scope and spirit of the present invention.

[0165] In addition, although an embodiment described herein is directed to a Forwarding Engine API, it will be appreciated by those skilled in the art that the teaching of the present invention can be applied to other systems. In fact, systems for network processing including ASICs as well as network process programmed using an API model as described herein are within the teachings of the present invention, without departing from the scope and spirit of the present invention.

[0166] The present invention provides many advantages over known techniques. The present invention provides a unified software programming model that is expressive enough to represent both fixed-function hardware as well as programmable network processors. This invention is a large step up from the register-level programming models offered by current ASICs because it is a state-of-the-art object-oriented programming model. This invention is a unifying technology for current network processors that are typically in their infancy in terms of programming model. A key advantage of this approach for network processors is that it does not sacrifice performance by actually executing the packet-processing in software, rather it abstracts the capabilities of the network processor but does not emulate them. In either case, this invention benefits both ISVs by providing a high-level programming model that does not sacrifice performance and the silicon vendors themselves, by providing an API that can grow with the evolution of their hardware while not alienating their ISV partners.

[0167] Having disclosed exemplary embodiments, modifications and variations may be made to the disclosed embodiments while remaining within the scope of the invention as defined by the following claims.