1、1,第9講 路由與組播,Routing modules in ns-2,2,講課內(nèi)容,單播及仿真方法 組播協(xié)議 仿真元件 組播仿真示例,3,1.1 Static Dijkstras SPF,Simulator instproc run $self check-node-num $self rtmodel-configure;# 4 dynamic schemes $self get-routelogic configure $self instvar scheduler_ Node_ link_ started_ set started_ 1 return $scheduler_ run ,S

2、imulator instproc get-routelogic $self instvar routingTable_ if !info exists routingTable_ set routingTable_ new RouteLogic return $routingTable_ ,ns-route.tcl,ns-lib.tcl,4,1.1 Static Dijkstras SPF,Simulator instproc run $self check-node-num $self rtmodel-configure;# 4 dynamic schemes $self get-rout

3、elogic configure return $scheduler_ run ,RouteLogic instproc configure $self instvar rtprotos_ if info exists rtprotos_ foreach proto array names rtprotos_ eval Agent/rtProto/$proto init-all $rtprotos_($proto) else Agent/rtProto/Static init-all ,route-proto.tcl,ns-lib.tcl,$ns rtproto Static $ns rtpr

4、oto Session $ns rtproto DV . $ns rtproto LS .,Simulator proc compute-routes,Simulator proc compute-flat-routes,A pure OTcl class,5,1.1 Static Dijkstras SPF,Simulator instproc compute-flat-routes set r $self get-routelogic $self cmd get-routelogic $r ;# propagate rl in C+ foreach ln array names link_

5、 set L split $ln : set srcID lindex $L 0 set dstID lindex $L 1 if $link_($ln) up? = up $r insert $srcID $dstID $link_($ln) cost? else $r reset $srcID $dstID $r compute set n Node set nn_ $self populate-flat-classifiers $n ,ns-route.tcl,4 each nodes chassifiers,Dijkstra algo. Impl.ed in C+ class,6,1.

6、2 Multipath routing,/tcl/test/test-suite-linkstate.tcl,7,Codes brief,. Node set multiPath_ 1 . $ns link $n2 $n4 cost 2 $ns link $n4 $n2 cost 2 . $ns rtmodel Deterministic .35 .25 $n2 $n4 . $ns rtproto LS .,Default: cost =1,0.5,0.35,0.25,VT,Link State routing,8,2. Properties of multicasting,The most

7、complex service, vs uni-casting and broad-casting Underlined recipients can be over one million,9,Group management,IGMP,IGMP,IGMP,Mcast routing protocols,10,2.1 Internet Group Management Protocol (IGMP),It lets all the systems on a physical network know which hosts currently belong to which multicas

8、t groups. Format of datagram is similar to ICMP with constant length, IP header + IGMP message (8 bytes). Support joining, querying and reporting functions.,11,An example (v1. RFC 1112),The router is asking each host to identify each group on that interface.,Multicast Router,Host,IGMP query, TTL=1 I

9、GMP group addr =0 Dest IP addr = 224.0.0.1(all-hosts group) Src IP addr = routers IP addr,IGMP report, TTL=1 IGMP group addr = group addr Dest IP addr = group addr Src IP addr = hosts IP addr,12,2.2 Flood and Prune Protocols,known as reverse-path multicast algorithm. DVMRP (Distance Vector Multicast

10、 Routing Protocol) and Dense-mode PIM (Protocol Independent Multicast).,prune,prune,Routers not on the delivery tree need to store prune state.,13,2.3 Center-based Trees,To map the multicast group address to a particular unicast address of a router, and build explicit distribution trees centered aro

11、und this particular router. Core-Based Trees (CBT), Sparse-mode PIM (SM-PIM) and the Border Gateway Multicast Protocol (BGMP).,14,Formation of a CBT bidirectional shared tree,CBT never properly solved the problem of how to map a group address to the address of a core. Good core placement is a hard p

12、roblem. So, ,15,Sparse-Mode PIM,Rendezvous Point (RP), is the equivalent of a CBT Core and largely serves the same purpose,16,Summary of multicast routing,Dense mode DVMRT, MOSFP, PIM-DM Sparse mode CBT, PIM-SM Scalable and reliable multicast (SRM) S.Floyd etal 95, by ns-2,17,2.4 SRM, motivation,ACK

13、,NACK,NACK-storm,18,SRM scheme,Randomize NACKs (request repairs) All traffic including request repairs and repairs are multicast A repair can be sent by any node that heard the request A node suppresses its request repair if another node has just sent a request repair for the same data item A node s

14、uppresses a repair if another node has just sent the repair,19,2.4 SRM, an illustration,NACK,repair,R1,R2,R3,R4,R5,20,3.1 Enable mcast in Nodes,set ns new Simulator multicast on #creating nodes $ns mrtproto .,Node instproc mk-default-classifier Node instvar module_list_ # At minimum we should enable

15、 base module foreach modname Node set module_list_ $self register-module new RtModule/$modname ,Node,module_list_,init,RtModule/Base,RtModule/Mcast,RtModule/Hier,RtModule/Manul,init multicast Node:enable-module Mcast,21,3.2 CtrMcast, a pure OTcl class,set ns new Simulator multicast on #creating node

16、s $ns mrtproto .,Onle 3 protocols supported: CtrMcast (PIM-SM) DM: Dense Mode ST: Shared Tree (CBT?),McastProtocol,CtrMcast,BST,DM,ST,CtrMcastComp,CtrRPComp,ctrrpcomp,Glist_, Mlist_,Node,mrtObject_,agent_,22,Routing computations,set ns new Simulator multicast on #creating nodes $ns mrtproto . $node join-group $recv $group ,McastProtocol,CtrMcast,BST,DM,ST,CtrMcastComp,ctrrpcomp,Glist_, Mlist_,Node,mrtObject_,agent_,compute-branch,23,CtrMcactComp:compute-branch,S,R,RP,In SPT: dest = S