H3C S9500 Series Operation Manual

Also see for S9500 Series: Operation manual Operation manual Operation manual Operation manual Operating manual

Contents

Operation Manual – Multicast ProtocolH3C S9500 Series Routing Switches Chapter 1 IP Multicast Overview1-4z Occasional communication for training and cooperationz Data storage and finance (stock) operationz Point-to-multipoint data distributionWith the increasing popularity of multimedia services over IP network, multicast isgaining its marketplace. In addition, the multicast service becomes popular andprevalent gradually.1.2 Implementation of IP Multicast1.2.1 IP Multicast AddressesIn multicast mode, there are questions about where to send the information, how tolocate the destination or know the receiver. All these questions can be narrowed downto multicast addressing. To guarantee the communication between a multicast sourceand a multicast group (that is, a group of receivers), the network layer multicast address(namely the IP multicast address) is required, along with the technique to correlate itwith the link layer MAC multicast address. Following is the introduction to these twokinds of addresses.I. IP Multicast AddressesAccording to the definition in Internet Assigned Number Authority (IANA), IP addressesfall into four types: Class A, Class B, Class C and Class D. Unicast packets use IPaddresses of Class A, Class B or Class C, depending on specific packet scales.Multicast packets use IP addresses of Class D as their destination addresses, butClass D IP addresses cannot be contained in the source IP field of IP packets.During unicast data transmission, a packet is transmitted "hop-by-hop" from the sourceaddress to the destination address. However, in IP multicast environment, a packet hasmore than one destination address, or a group of addresses. All the informationreceivers are added to a group. Once a receiver joins the group, the data for this groupaddress starts flowing to this receiver. All members in the group can receive the packets.This group is a multicast group.Membership here is dynamic, and a host can join or leave the group at any time. Amulticast group can be permanent or temporary. Some multicast group addresses areallocated by IANA, and the multicast group is called permanent multicast group. The IPaddresses of a permanent multicast group are unchangeable, but its membership ischangeable, and the number of members is arbitrary. It is quite possible for apermanent group to not a single member. Those not reserved for permanent multicastgroups can be used by temporary multicast groups. Class D multicast addresses rangefrom 224.0.0.0 to 239.255.255.255. More information is listed in Table 1-1 Ranges andmeanings of Class D addresses.