Explaining Multicast参考.ppt

Explaining Multicast Unicast Traffic Unicast Traffic (cont.) Unicast Traffic (cont.) Broadcast Traffic Multicast Traffic IP Multicast Characteristics Group Membership Multicast IP Address Structure Layer 2 Multicast Addressing IP Multicast to MAC Multicast Mapping IP Multicast Basic Addressing IP group addresses: Class D address (high-order three bits are set) Range from 224.0.0.0 through 239.255.255.255 Well-known addresses assigned by IANA Reserved use: 224.0.0.0 through 224.0.0.255 224.0.0.1 (all multicast systems on subnet) 224.0.0.2 (all routers on subnet) 224.0.0.4 (all DVMRP routers) 224.0.0.13 (all PIMv2 routers) 224.0.0.5, 224.0.0.6, 224.0.0.9, and 224.0.0.10 used by unicast routing protocols IP Multicast Basic Addressing (Cont.) Transient addresses, assigned and reclaimed dynamically (within applications): Global range: 224.0.1.0-238.255.255.255 224.2.X.X usually used in MBONE applications Limited (local) scope: 239.0.0.0/8 for private IP multicast addresses (RFC-2365) Site-local scope: 239.255.0.0/16 Organization-local scope: 239.192.0.0 to 239.251.255.255 Part of a global scope recently used for new protocols and temporary usage IP Multicast Addresses END Explaining Multicast Routing Protocols Multicast Protocol Basics Types of multicast distribution trees Source-rooted; also called shortest path trees (SPTs) Rooted at a meeting point in the network; shared trees Rendezvous point (RP) Core Types of multicast protocols Dense mode protocols Sparse mode protocols Multicast Distribution Trees Shortest-Path Trees (Cont.) Shared Distribution Trees Shared Distribution Trees (Cont.) Multicast Distribution Trees Identification (S,G) entries For this particular source sending to this particular group Traffic forwarded via the shortest path from the source (*,G) entries For any (*) source sending to this group Traffic forwarded via a meeting point(RP) for this group Multicast Forwarding Multicast routing operation is the opposite of unicast routing. Unicast rou