数据与计算机通信第19章.ppt

William StallingsData and Computer Communications7th Edition Chapter 19 Internetwork Protocols 内容 19.1 Multicasting 19.2 Routing Protocols 19.3 Integrated Services Architecture 19.4 Differentiated Services 19.1 Multicasting Addresses that refer to group of hosts on one or more networks Application Multimedia “broadcast” Teleconferencing Database Distributed computing Real time workgroups Example Config Suppose that multicast server on the network N1 is transmitting packets to a multicast address that repesents the workstations indicated on networks N3,N5,N6. See P617 倒数第二段中间 Broadcast and Multiple Unicast Broadcast a copy of packet to each network Requires 13 copies of packet Multiple Unicast Send packet only to networks that have hosts in group 11 packets True Multicast Determine least cost path to each network that has host in group Gives spanning tree configuration containing networks with group members Transmit single packet along spanning tree Routers replicate packets at branch points of spanning tree 8 packets required Multicast Example Requirements for Multicasting (1) Router may have to forward more than one copy of packet Convention needed to identify multicast addresses IPv4 - Class D - start 1110 IPv6 - 8 bit prefix, all 1, 4 bit flags field, 4 bit scope field, 112 bit group identifier Nodes must translate between IP multicast addresses and list of networks containing group members Router must translate between IP multicast address and network multicast address Requirements for Multicasting (2) Mechanism required for hosts to join and leave multicast group Routers must exchange info Which networks include members of given group Sufficient info to work out shortest path to each network Routing algorithm to work out shortest path Routers must determine routing paths based on source and destination addresses Spanning Tree from Router C to Multicast Group Internet Group Management Protocol (IGMP) RFC 3376 Host and router exchange of multicast group i