PARSEC/Glomosim Tutorial

1. PARSEC/Glomosim Tutorial Vlasios Tsiatsis EE206 UCLA, 5/1/02

2. PARSEC Entities • Discrete-event simulation language • Basically C with extensions • parallel executing ENTITIES entity Sort (int n, int a[20]) { sorting(); finalize{ } } //entity declaration, creation ename s1; ... sl = new Sort(20, a[20]); ... useful for statistics collection entity body entity handle Vlasios Tsiatsis

3. PARSEC Messages • Entities communicate via message passing • Each entity has one built-in message queue • time-stamped, typed, MESSAGES like C structs messageRequest { int units; ename id; }; /* declaration - initialization*/ messageRequest myrequest; myrequest.units =20; myrequest.id = self; handle of current entity Vlasios Tsiatsis

4. Entity Communication • Entities exchange messages using the send and receive primitives • send – send a typed message to an entity messageRequest myrequest; sendRequest{10, self} to E2; send oldrequest to E2; send oldrequest to E2 after 5; This modifier changes the message timestamp Vlasios Tsiatsis

5. Entity Communication (cont’d) • receive – process message from the internal queue (blocking call) /* complex receive */ receive (Request r) { req = r; } orreceive (Release r) { units = r.units; } ortimeoutin (5) { ... } messageRequest req; int units; /* simple receive */ receive (Request r) { req = r; } • Two semantics: • in – timeout has highest priority • after – receive has highest priority Vlasios Tsiatsis

6. Timing considerations • PARSEC keeps track of the simulation time by using an internal discretesimulation clock • Only a few statements can advance this clock: • send M1 to E1 after T with T>0 • timeoutwith non-zero timeovalue • hold(T) with T>0 (like a delay function) • …so if you don’t have any of these statements in your code the simulation time is going to be zero! • send statements deposit the message asynchronously in the receiving entity queue time-stamping it with the current or modified time Vlasios Tsiatsis

7. Timing considerations (cont’d) • receive statements take the earliest message from queue (according to timestamps) and if there are multiple messages with the same timestamp the order is NOT deterministic! • The user can get the value of simulation clock by the simclock()function • The user can set the maximum value of simulation clock by the setmaxclock()function Vlasios Tsiatsis

8. Development Cycle • Your equivalent main()function is the entity driver() • Use this entity to create all the other entities and setup the simulation environment • Also use this entity to collect all the statistics from all other entities by sending them request messages • If you need to connect entities together use messages with the entity reference (self) in the message • If an entity A needs some information from another entity B create a dummy request message: send DummyReq to B; // no delay receive(DummyRep rep){ needed_info = rep.info } Vlasios Tsiatsis

9. Example • How would we simulate a wireless sensor network under PARSEC ? • First thought- one entity per physical node • What about node communication ? How do you model the wireless channel? • The solution follows a layered approach • 1 entity type for the channel • 1 entity type for the physical layer • 1 entity type for link layer • and so on… Vlasios Tsiatsis

10. Example – NESL Code Organization* • To keep things simple we only have 3 types of “networking” entity types: • Channel • Radio (physical and MAC layer) • Node (network and application layer) • And one entity responsible for setting up the simulation environment (driver entity) and gathering the simulation results * The author of the first version of this code is Curt Schurgers Vlasios Tsiatsis

11. Architecture MAIN Node 1 Node N Radio 1 Radio N Channel One physical sensor node Statistics messages Network messages Each building block corresponds to 4 files • <entity_name>.pc – Implementation • <entity_name>.h – Declarations • <entity_name>_functions.h – Functions • <entity_name>_parameters.h – Parameters Vlasios Tsiatsis

12. PARSEC Implementation main.pc code entity driver(int argc,char** argv) { ... // Topology (xcoord, ycoord) creation ... channel = (ename*)malloc(sizeof(ename)); channel = new Channel(self,num_nodes,BER); ... for (i=0;i<num_nodes;i++) { node[i]=new SensorNode(i,xcoord[i],ycoord[i],TX_RANGE, self, channel, num_nodes); } ... while(TRUE){ receive (StatisticsMessage){ ... } ... } MAIN SensorNodes Vlasios Tsiatsis

13. Main entity • Read the command line arguments • Create the topology • Create the Channel • Create the individual Nodes and pass a reference to the Channel • Wait for statistics collection messages from nodes (when nodes finish they send all the desired statistics to the main entity) Vlasios Tsiatsis

14. PARSEC Implementation node.pc code entity SensorNode(int node_ID,float xcoord,float ycoord, floatTxrange, ename top,ename channel, intnum_nodes) { ... // inform the channel about the node location ... radio= new Radio(node_ID,self,channel,top,num_nodes,1); // connect the channel with the radio by sending a // message to the channel channelmsg.radio = radio; send channelmsg to channel; ... while(1){ receive(NMsg_1) {...} or receive (NMsg_2) {...} ... or receive (NMsg_N) {...} } MAIN Node 1 Radio Vlasios Tsiatsis

15. PARSEC Implementation radio.pc code entity Radio(int id, ename node, ename channel, ename top, int num_nodes, int radio_mode) { ... while(1){ receive(RMsg_1) {...} or receive (RMsg_2) {...} ... or receive (RMsg_N) {...} }} Node MAIN Radio 1 Channel channel.pc code entity Channel(ename top,int num_nodes,float ber) {... while(1){ receive(CMsg_1) { //topology maintenance here } or receive (CMsg_2) {...} ... or receive (CMsg_N) {...} }} Radio Channel Vlasios Tsiatsis

16. Radio/Channel Entity • The Radio entity has 3 modes: • Ideal Radio – No collisions • Collisions, no channel sensing, no TX buffer • Collision Detection, radio buffers • Radio entity sends a message to the node entity every time a packet transmission ends because the TX time is not deterministic due to buffering and backoff delays (mode 3) • Channel entity maintains a neighborhood matrix updated whenever a new node entity is created • Channel entity routes packets from one node to it radio neighbors Vlasios Tsiatsis

17. GlomoSim Model • GlomoSim uses PARSEC • All nodes are aggregated into PARSEC aggregation entities for: • Scalability • ease of neighborhood calculations (remember this model was created for mobile ad-hoc networks) • Current release supports only 1 partition • Node state is maintained in a global data structure BUT simulation code for one node does not access other nodes’ state GLOMOPartition Vlasios Tsiatsis

18. Application Transport Network Link(MAC) Physical GlomoSim Model (cont’d) • Follows a layered approach for a network protocol architecture • Uses one entity for all the communication layers for ease of inter-layer communication • Neighboring layers exchange messages by fixed APIs Vlasios Tsiatsis

19. Protocol Layer Functions Each layer has 3 major functions: • Initialization Function void NetworkLar1Init(GlomoNode *node, GlomoNetworkLar1** lar1, const GlomoNodeInput *nodeInput); • Finalization Function – statistics void NetworkLar1Finalize(GlomoNode *node); • Message Dispatcher Function void NetworkLar1HandleProtocolPacket( GlomoNode* node, Message* msg); • Data structures: • GlomoNode – State of a node (handle of a node) • Message – Message or packet • GlomoNetworkLar1 – Protocol Specific information (e.g. statistics variables) • GlomoNodeInput –configuration options from command line Vlasios Tsiatsis

20. If everything else fails… • Read the manuals (they are relatively small!): • PARSEC http://pcl.cs.ucla.edu/projects/parsec/ • GlomoSim http://pcl.cs.ucla.edu/projects/glomosim/ • Read the source code: • You may need to modify it • You may need to watch the flow of packets from one layer to another Vlasios Tsiatsis