Multicast

what are the multicast routing protocols?

- DVMRP (Distance Vector Multicast Routing Protocol) - MOSPF (Multicast Open Shortest Path First) - PIM (Protocol Independent Multicast)

What are the different protocols that are required to make multicast work?

- IGMP so hosts can tell routers they want to receive multicast traffic. - IGMP snooping so the switch knows where to forward multicast traffic. - Multicast routing: we need a protocol like PIM that can route multicast traffic.

convert 239.192.0.1 to multicast MAC address.

- care about last 23 bits of the iP. - change last 23 bits into hexadecimal. -concat 01-00-5e and would become 10-00-01

what is IGMP?

IGMP (Internet Group Management Protocol). Hosts that want to receive multicast traffic will use the IGMP protocol to tell the router which multicast traffic they want to receive. the switch figure out where to forward multicast traffic, we can use IGMP snooping. The switch will "listen" to IGMP messages between the host(s) and router to figure out where it should forward multicast traffic to.

Multicast IP Address to MAC address mapping.

Multicast IP address live in the 224.0.0.0 - 239.255.255.255 range on layer 3. In the first octet of a 48 bit MAC,bit 0 of the first octet reserved for broadcast or multicast traffic.For unicast traffic its 0 for broadcast or multicast traffic this bit will be set to 1.

Multicast components.

Multicast is efficient but it doesn't work "out of the box". - class D range for this: 224.0.0.0 to 239.255.255.255. These addresses are only used as destination addresses, not as source addresses. - Require applications that support multicast.Ex- VLC mediaplayer.

what is the disadvantage of using multicast?

Multicast requires some additional protocols to make it work. Also, multicast only supports UDP traffic so we can't use the advantages of TCP like windowing and acknowledgments.

What about internet?

Since multicast is so much more efficient than unicast, large companies like Netflix and Youtube must be using this to stream videos right? Unfortunately multicast on the Internet has never really been implemented. These large video companies use LOTS of unicast traffic to deliver videos to their customers. The only place where you might see multicast on the Internet is your local ISP. They typically use multicast for IPTV to deliver video to their own customers.

What is the reserved prefix for layer-2.

The 24-bit MAC address prefix 01-00-5E (first three octet) is reserved for layer 2 multicast.Unfortunately only half of the MAC addresses in this 24-bit prefix can be used for multicast, this means we only have 23 bits of MAC address space to use for multicast.

Whats the problem with unicast?

The main problem with unicast traffic is that it is not scalable.

Unicast VS multicast?

When using unicast, each additional host will increase the load and traffic rate. With multicast it will remain the same.

Each multicast IP address has 28 unique bits because the first 4 bits are always the same (1110) 224.0.0.0 - 239.255.255.255.

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What is the difference between unicast and multicast IP addresses?

unicast IP addresses represent a single network device while multicast IP addresses represent a group of receives.