Multicasting Unicast

Unicast is not scalable Multicasting Unicast is not scalable

Multicasting Broadcast Wastes Bandwidth and Increases Processing Load on CPU

TCP/IP Protocols

Multicasting The six basic requirements for supporting multicast across a routed network are as follows: A designated range of Layer 3 addresses that can only be used by multicast applications must exist. A network administrator needs to install a multicast application on a multicast server using a Layer 3 multicast address from the designated range

Multicasting A multicast address must be used only as a destination IP address, and specifically not as a source IP address. Unlike a unicast IP packet, a destination IP address in a multicast packet does not specify a recipient’s address, but rather signifies that the packet is carrying multicast traffic for a specific multicast application

Multicasting The multicast application must be installed on all the hosts in the network that need to receive the multicast traffic for the application. The application must be installed using the same Layer 3 multicast address that was used on the multicast server. This is referred to as launching an application or joining a group

Multicasting All hosts that are connected to a LAN must use a standard method to calculate a Layer 2 multicast address from the Layer 3 multicast address and assign it to their network interface cards (NICs) There must be a mechanism by which a host can dynamically indicate to the connected router whether it would like to receive the traffic for the installed multicast application The Internet Group Management Protocol (IGMP) provides communication between hosts and a router IGMP snooping helps switches learn which hosts have requested to receive the traffic for a specific multicast application and to which switch ports these hosts are connected

Multicasting There must be a multicast routing protocol that allows routers to forward multicast traffic from multicast servers to hosts without overtaxing network resources. Some of the multicast routing protocols are Distance Vector Multicast Routing Protocol (DVMRP), Multicast Open Shortest Path First (MOSPF), and Protocol Independent Multicast dense mode (PIM-DM) and sparse mode (PIM-SM)

Multicasting How Multicast Delivers Traffic to Selected Users

Multicasting Multicasting Is Scalable

Multicast IP Address Ranges 224.0.0.0 to 239.255.255.255 This range represents the entire IPv4 multicast address space. It is reserved for multicast applications 224.0.0.0 to 224.0.0.255 This range is part of the permanent groups. Addresses from this range are assigned by IANA for network protocols on a local segment. Routers do not forward packets with destination addresses used from this range. 224.0.1.0 to 224.0.1.255 This range is also part of the permanent groups. Addresses from this range are assigned by IANA for the network protocols that are forwarded in the entire network. Routers forward packets with destination addresses used from this range. 239.0.0.0 to 239.255.255.255 This range is used for private multicast domains. These addresses are called administratively scoped addresses

Multicast IP Address Ranges Some well known reserved multicast addresses 224.0.0.1 All multicast hosts 224.0.0.2 All multicast routers 224.0.0.4 DVMRP routers 224.0.0.5 All OSPF routers 224.0.0.6 OSPF designated routers 224.0.0.13 PIM routers 224.0.0.22 IGMPv3

Mapping IP Multicast Addresses to MAC Addresses

Traditional Routing and MPLS

Limitations of Traditional Routing Routing table is consulted every time a packet is received Hard to obtain optimal traffic flows Traffic always takes the low cost route No provision of having private networks within shared infrastructure Requirement of running Border Gateway Protocol (BGP) on every router of provider core

Multi-Protocol Label Switching (MPLS)

The Label

MPLS Applications

Benefits of MPLS The use of one unified network infrastructure Better IP over ATM integration Border Gateway Protocol (BGP)-free core The peer-to-peer model for MPLS VPN Optimal traffic flow Traffic engineering