http://blog.csdn.net/bloghome/article/details/4682984
Multicast Overview: Multimedia applications integrate sound, graphics, animation, text, and video, and this application is more and more in the current network environment.
Multimedia TrafficThere are three main modes of communication in the network: 1, Unicast (unicast) 2, broadcast (broadcast) 3, multicast (multicast) each transmission mode has different influence on the network bandwidth. Unicast will send a copy of the traffic to each client individually, and if the destination client is large, unicast has to
Send multiple, and if this happens on a shared link, the bandwidth footprint is huge. Broadcast only send a copy, but all clients must stop in the hands of the work, to check whether this traffic is sent to their own, occupy the CPU processing time of the client, if only the general broadcast traffic, because the traffic is relatively small, But the broadcast of multimedia traffic consumes up to 7Mbps or even higher bandwidth, which consumes almost all of the bandwidth. This approach is obviously inappropriate if the number of clients is small.
Multicast is the best way to send a copy of a packet to a group of users in a multimedia network environment. Multicast features 1, multicast is the unified data sent to a host group
(host group)2, the use of "connectionless" transmission mode, that is, UDP, also known as "best Effort" 3, members can always join the exit, that is, dynamic member management, members can join multiple host group (host groups) 4, members are not limited by the number and location of the limit 5, support multiple host Group (host group) 6, multicast delivery, that is, the source side does not need to join the host group (host groups) 7, multicast group members do not need to send data and several points, compared to unicast, multicast because only send a copy of the data, almost at the same time to reach each client,
The unicast has to send copies of the data in sequential order, so that the data arrives at the destination with a delay. Again, multicast group members can remain anonymous, multicast because of the use of UDP mechanism, which requires at the receiving end of the need for a fault-scheduling mechanism. Third, the multicast address multicast address is Class D address, namely 224.0.0.0-239.255.255.255. Unlike a, B, and C IP addresses, Class D addresses are not layered and unstructured. The multicast address can be dynamically assigned or statically specified. Statically specified addresses are mostly well-known addresses, and the IANA is responsible for assigning these addresses, which are permanent host group (host groups) and are similar to the well-known port numbers in TCP and UDP. For example, 224.0.0.5 and 224.0.0.6 are OSPF used to exchange data between DR/BDR and Drother, 224.0.0.10 allocated ripv2,224.0.0.9 is dedicated to EIGRP.
| Description |
Range |
| Reserved Link Local Address |
224.0.0.0 to
224.0.0.255 |
| Globally scoped Address |
224.0.1.0 to
238.255.255.255 |
| Source Specific Multicast |
232.0.0.0 to
232.255.255.255 |
| Glop Address |
233.0.0.0 to
233.255.255.255 |
| Limited Scope Address |
239.0.0.0 to
239.255.255.255 |
Reserved link local Address:iana is assigned to the network protocol of the LAN segment, the routing device does not forward the packets, this is done by setting the TTL value in the header. 224.0.0.1 specifies all hosts, 224.0.0.2 specifies all routers. Globally scoped address: These addresses can be delivered on the Internet source specific multicast: For SSM glop adress: Use limited scope with as bindings addres S: used locally as or in domain, routers should filter these addresses, usually within the company, or within the university.
Four, multicast trees (multicast tree) 1, source Distribution tree (sources distribution trees) 2, shared distribution tree (shared distribution trees) Source Distribution tree is represented as: (S,G), for example (192.168.2.2,224.1.1.1) The shared distribution tree is represented as: (*,G), for example (*,224.2.2.2) comparison: 1, the benefit of the source tree is: There is the most optimized path choice, the stronghold is when in a network with many sources and host group, will have a huge impact on the source router, resulting in the exhaustion of resources. 2, the advantage of the shared tree is to save resources, but the path from source to destination is not necessarily the best Five, PIM PIM is IP routing protocol-independent, independent of the routing protocol, but still need to have a routing table exists, This is a requirement to prevent loops. PIM is divided into sparse mode and dense mode six, IGMP and cGMP IGMP v1: Include group member query package, team members reply package. 3 60 seconds to cancel this member IGMP v2: New leave report, version 2 Member query message, can be free from multicast group IGMP v3: New version 3 of the team member query and reply message IGMP V3lite: Cisco private agreement, does not have a broad meaning cGMP is used to advertise the multicast group membership MAC address to the switch, used on router, suitable for use with low-end switches, Cisco Private protocol IGMP snooping is the IETF standard protocol, used on switch, to listen for multicast group member MAC address, the resource is very large, High-end switches can be applied. VII. Configuration multicast 1, IP multicast-routing IP PIM sparse-mode | Dense-mode | Sparse-dense-mode 2, configuration AUTO-RP, Cisco Private Protocol, PIM version 1 IP PIM send-rp-announce type number scope TTL group-list access- list-number //Definition RP IP PIM send-rp-discovery scope TTL//definition RP Agent 3, configure PIM version 2 IP PIM version 1 | 2 IP PIM BSR-border IP PIM bsr-candidate interface Hash-mask-length [priority]//proxy IP PIM rp-candidate type number TTL group-list AC Cess-list-number//RP Eight, monitoring IP multicast show ip mroute show ip mroute summary show ip mroute Active show IP mroute count show ip PIM interface show IP interface
