Multicast address planning

The following is reproduced from: http://www.enet.com.cn/article/2011/0705/A20110705880890.shtml

I. Introduction to the topology structure of the network

The structure of the network consists of three layers: the core layer, the aggregation layer and the access layer.

The core layer consists of 5 core nodes (each core node is configured with a routing switch CiscoCatalyst6509), which is interconnected via gigabit fiber to an incomplete mesh structure.

The aggregation layer consists of 53 nodes (one routing switch CiscoCatalyst4006 per node), which, depending on the geographic location, is connected in star mode with 5 core nodes, respectively, via gigabit fiber.

Access layer According to the number of specific units and business requirements, respectively, using CiscoCatalyst3524, 3548, such as the hundred trillion or gigabit fiber connected to the aggregation layer.

Second, the planning of the multicast address

Ipmulticast address is Class D address, address range 224.0.0.0-239.255.255.255, and Class D address is divided into local link multicast address, reserved multicast address, administrative rights multicast address

Local link Address: 224.0.0.0~224.0.0.255, for LAN, routers do not forward IP packets belonging to this range, the local link address is assigned as follows:

224.0.0.1– all systems on the local subnet
224.0.0.2– all routers on the local subnet
224.0.0.5–OSPF Router
224.0.0.6–OSPF specifying routers
224.0.0.9–ripv2 Router
224.0.0.10–IGRP Router
224.0.0.13–PIMV2 Router
224.0.0.22–igmpv3

Reserved multicast address: 224.0.1.0~238.255.255.255, for Global or network protocols, the Network range address (224.0.1.0–224.0.1.255) is assigned as follows:

224.0.1.39–cisco-rp-announce (AUTO-RP)
224.0.1.40–cisco-rp-discovery (AUTO-RP)

Administrative rights Address: 239.0.0.0~239.255.255.255, internal use of the organization, used to limit the multicast range;

The multicast address in this project uses the administrative authority address, within the administrative authority address, defines the organization (organization-local) and the site (site-local) multicast address.

Address range of the organization: 239.8.0.0–239.8.126.255– Global Application

Address range for this site: 239.8.128.0–239.8.255.255– local Application

Third, the choice of multicast routing

Multicast routing we chose protocol-Independent Multicast (PROTOCOLINDEPENDENTMULTICAST:PIM), as the name implies, PIM does not depend on a particular unicast routing protocol, It can take advantage of the unicast routing tables established by various unicast routing protocols to complete the reverse path forwarding RPF (reversepathforwarding) Check function instead of maintaining a separate multicast routing table for multicast forwarding. Because PIM does not have to send and receive multicast routing updates, PIM overhead is much lower than other multicast protocols. The PIM design is designed to support the shortest path tree SPT and the shared tree at the same time in the Internet, and to enable a flexible conversion between the two, thus centralizing their advantages and improving the multicast efficiency. PIM defines two modes: dense mode (dense-mode) and sparse mode (Sparse-mode)

1. Dense mode (Dense-mode)

PIM-DM dense mode protocol, using the "diffusion/pruning" mechanism. At the same time, assuming that the bandwidth is unrestricted, each router wants to receive multicast packets. PIM-DM uses reverse path forwarding RPF to dynamically establish the shortest path tree SPT.

This model is suitable for the following situations: the smaller high-speed network, the multicast source and receiver are closer, the sender is less, the receiver is more, and the multicast data stream is relatively large and stable.

2. Sparse mode (Sparse-mode)

The fundamental difference between PIM-SM and the "diffusion/pruning" model is that PIM-SM is based on an explicit join model, where the receiver sends a join message to the collection point RP, and the router forwards the packet only on a multicast group output interface that has been joined to that multicast group.

PIM-SM Multicast packet forwarding using a shared tree. Each group has a collection point (RENDEZVOUSPOINT:RP), the multicast source sends data to the RP along the shortest path, and the RP sends the data to each receiving end along the shortest path. One of the main advantages of PIM-SM is that it is not limited to receiving multicast information through a shared tree, but also provides a mechanism for converting from a shared tree to SPT.

Because of the large scale of the project network and many video sources, PIM-SM sparse mode is chosen.

Four, the choice of the RP of the rendezvous point

Since the video source is mostly concentrated in the core layer, so the RP chooses on the core routing device, from the network reliability, usability and other aspects of comprehensive consideration, choose 5 core equipment for RP, through CISCOANYCASTRP technology can achieve load balance and redundancy, multicast Source Discovery Protocol (MSDP) is the key protocol for implementing Anycast RP, and MSDP allows the RP to share activity source information.

In the ANYCASTRP environment, two or more RP configurations have the same IP address on the loopback interface. The Anycastrploopback address should be the host address of the 32-bit mask. IP routing will automatically select the best rp.anycast RP to provide ipmulticast fast switching (within seconds) and load balancing.

Switch CiscoCatalyst4006 for all aggregation tiers are configured with 10.6.2.1 as their RP address. The configuration is as follows:

Router (config) #ippimrp-address10.6.2.1

Multicast design in a five or two-tier environment (IGMP-SNOOPINGANDCGMP)

The igmp-snooping runs on a layer two switch, and igmp-snooping requires the LAN switch to check for some three layers of information (igmpjoin/leave information). When the switch sees the IGMP host report join a group, the switch increases the host's port number to the appropriate multicast table entry. When the switch sees the IGMP host report leaving a group, the switch removes the host's port number to the appropriate multicast.