Class Note for ECE 596A at UA
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Date Created: 02/06/15
ECE 596C Network Simulation OPNET Communication Mechanisms Packets Packets can be Formatted U nformatted Value vectors Specify eld sizes bitsbytes and a base size Memory allocation is not the same as packet size ECE 596C Network Simulation Packet processing Getting ownership of a packet oppkcreate oppkcreatefmt oppkcreatevvecO Copying a packet oppkco py Decapsulating a packet oppknfdget oppkfdget Receiving a packet oppkgeto Packet stream obtains ownership of a packet through oppksend oppksenddeayed oppksendquietO oppksendforcedO ECE 596C Network Simulation Packet strea ms Physical connections that support transfer of packets between modules De ned between output port of a source module to input port ofa destination module Queuing atinput stream Associated with destination module s input stream No limit on the numberof packets that the stream can hold Waits until the destination module picks up the packet using opipkigetO Queuing is FIFO Delays associated wnh packer iianslei must elapse aevme packer emels mpm sueam queue uesmamn Each mpul sueam queues El Wing packers and ieleases mem m we desmanun m n F0 order when opjmeu is called ECE 5967C Network Simulation Sending a packet oppksend Schedules a stream event at the destination Time ofthe event is the current time quotdelay attribute ofthe packet stream Destination may receive the packet using oppkget may also choose to ignore Even if an interrupt cannot be generated at the destination packet is still queued oppkdelayed Uses event scheduling framework Generates an interrupt for an appropriate process in the destination module Supports delaying the packet by a prespeci ed time Generates an interrupt at current time speci ed time delay attribute time Note delay is set on an a perpacket basis so can be used for nonFIFO delivery ECE 596C Network Simulation Sending a packet oppksendforced Suspends the sending process Ignores the quotdelay attribute of the packet stream Schedules an interrupt for the destination module Sending process resumes execution ONLY AFTER the destination process blocks oppksendquiet No interrupt is generated at the destination module Just queues the packet in the packet stream You can use the quiet way for reducing the number of interrupts Send many packets using quiet send the last one using regular means Destination can checkthe stream using opstrmempty or opstrmpksize ECE 596C Network Simulation Packet delivery Transmitting packets from one node to another Irrespective of physical connection Allows packet transfer from one processorqueue module to another Irrespective of location Functions oppkdeliver oppkdeliverdelayed oppkdeliverforced oppkdeliverquiet Need to specify destination module s object ID Objectle are identi ed using ID and TOPO packages of the simulation kernel Any number of sources can send packet to an input stream A packet may be sent to any number of input streams ECE 596C Network Simulation Communication links Wired links 7 Pointtopoint links Bus Wireless links aka radio links Pointtopoint links Simplex and duplex Must be attached to transmitter and receiver modules four modules ifduplex Think of linkas a bundle of channels channels may be viewed aswavelengths inWDM net mm sneam n uipui sneam n mm a mpui sireaml 9 mm sneaml channel l mpu leamg WW urpuisneamZ mm s ream cha ng 3 uipul sheam 3 ECE 5967C Network Simulation More on pointtopoint links Builtin queuing of transmitter channels slreami 0 one hanneli slrezm 7 V 0 channel slnam k 7 channel k The packer arihe head m each queue is me one cm remiy imdeigumg n ansmissiun Each channei meunems e 52pm are queue Pipeline stages ofa link Series of userde nable models Decides time of reception bit error rates etc ECE 5967C Network Simuiztion Bus links Shared bus such as ethernet USB bus etc Used with bus transmitters and bus receivers at a node quotTapquotthe bus fortransmitter receiver or both Unused n ansmnrow Receiveroniy Duplex Transmission travels on both sides of the bus Delay attribute denotestime for signal to propagate one meter Packet transmission will result in quotstaggeredquotarriva at nodes Bus can also have multiple channels similar to pointtopoint links ECE 5967C Network Simulation 10 Bus links Each node receives a distinct copy of the packet allglnal llalsm med ackel A packer will also be sem in me same nudemm n ansmmed me original packer n we bus rap isdupiex Collisions When two packet receptions overlap the receiver is in a collided state Collisions are at the receiver Collisions are considered to be destructive to the packet default behavior Behaviorof collisions can be changed through pipeline stages BusTransceiver Pipeline ECE 5967C Network Simulation 11 Consistency of physical links Not all links between nodes are valid Unlike nodes links do not have an underlying objects All properties ofa linkarequotattributes M AM inmwww Link interface attributes Link model interfaces Keywords Comments Supported linktypes Link model derivation Baum ammuies or me mm abject have been sex in applupllaie values and maaen The usel can no lungel change mese Ammmes haveaeen renamed and sex in veasanaale Hmlal values ECE 5967C Network Simulation 12 Interface control information ICI List of userde ned data that can be associated with an event Communication mechanisms between modules in same or different nodes ICI provides a payload Payload is transferred from the module that sets the interrupt to the one that receives Event types self opintrptscheduleself Provides only an integer value to denote the event name remote process multicast Similar to self only integer code is provided access no information is provided statistic one oating point value may be conveyed with this type of interrupt For our application it may be used for interlayer communication ECE 596C Network Simulation 13 ICI content ICI creation Function call opiiciicreateO ICI format speci cation Structure attributes contain address Memory must be deallocated by user Allocate a structure of type quotCommandquot to pass within an ICI commandptr Command oppr gmemalloc sizeoF CorrmandD Setup the command structure c0mmandptr 7gttype COMMANDJYPLA c0mmandptr 7gtpr ior ity COMMANDPRIORITYLOW c0mmandptr 7gtr equest SETCOMPRESSEDMODE Install the structure in quotcommandquot attribute of a new ICI iciptr 0picicr eate quotlinLcontr olquot 0piciattr set iciptr quotcommandquot commamLptr Getting amp setting attributes opiciattrget opiciattrset ECE 5967C Network Simulation 14 ICI mechanics ICI installation At most one ICI installed per process Function call opiciinstall How to schedule events with ICI Create an ICI and set the attributes Install the ICI Schedule the event Uninstall the ICI you may leave this installed ifyou want to schedule multiple events To uninstall call function opiciinstall function with parameter OPCNL ICI is only useful if the destination of the event knows about it ICI is not like packets no ownership Any process that has the address can modify delete the ICI ECE 596C Network Simulation 15 Communicating with event states Event states are similar in functionality to lCls except that they are faster Accessing the attributes is made easier with event states You can create an arbitrary data structure Access it using standard CC way ECE 596C Network Simulation l6 Communication with statistics Ouput and input statistics The source ofthe statisticquotoutputs the statistics The destination ofthe statistic takes quotinputquot Any module can be the source of a statistic Only processor or queue module may be the destination of a statistic Statistic wire input ports are indexed by integers uuipui iesuiis mpm vesuiis ianoul ECE 5967C Network Simuiztion 17 More on statistic wires Input statistics are capable of accepting multiple statistic wires Writing to a wire opstatwrite by specifying the index ofthe output statistic A oating point value is transfered Two possible behaviors based on value assigned to quotintrpt method FORCED change occurs at the destination immediately SCHEDULED arrival time at the destination s input statistic is determined by wire delay SCHEDULED is the default behavior Statistic wires provide active noti cation of changes Generate an event if some conditions on the input statistics are met OPNET provides different kinds of triggers Rising edge Falling edge Repeated value Zero crossing LowHigh threshold trigger ECE 596C Network Simulation 18 Application of statistic wires Dynamic monitoring Dynamically monitor the state of other modules within the node Performance is better than polling strategy Improved accuracy as the process may be noti ed immediately FORCED interrupt By using triggers you can alert a module ONLY when it is appropriate Semaphores To implement lowlevel signaling mechanisms between modules One implementation is lock value is O or 1 Statistics in modules other than processors or queues Monitors only the activity provides past and present metrics to predict future Using triggers you can generate alarms ECE 596C Network Simulation 19
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