Question

Describe how multicast groups are managed and how a protocol such as IGMP is used. Describe some more multicast routing protocols in addition to IGMP? what is PIM-SSM?

what are the reserved multicast addresses that start with 224.x.x.x used for? Give some examples? What are some messages used by IGMP?

Answer 1

1. Multicast Groups Management: Multicast groups are groups of the devices basically routers which are listen to and receive traffic addressed to a specific, shared multicast IP address.Multicast uses special addresses to send data from a single sender to multiple recipients, even though the recipient only sends one copy. Hosts or routers can join multicast groups via IGMP(Internet Group Management Protocol) to tell other routers that they are interested.Now IGMP works in manner that There is one multicast router for each group that distributes multicast packet to members of that group. It means the network will have two multicast routers, if there are two multicast groups.
2. Protocols other than IGMP:

• Core-Based Trees Multicast Routing Protocol (CBT): CBT is primarily intended as an inter-domain multicast routing protocol.It is quite similer to other protocols.it also uses the IP address the only difference is messages could also be protected using IP security provided that appropriate key management facilities existed.

• PIM-SM: this is most importan multicasting protocol now a days in it has an independent nature thats why it is ideal to use.

3. PIM-SSM: PIM(protocol independent multicast) is the protocol for multicast routing protocols.PIM does not include its own topology discovery mechanism, but instead uses routing information supplied by other routing protocols. PIM uses the unicast routing table for reverse path forwarding.PIM Source-Specific Multicast (PIM-SSM) is one of the varient of PIM.it builds trees which are rooted in just one source.offering a more secure and scalable model for a limited number of applications that is most of the time broadcasting of contentIn SSM, an IP datagram is transmitted by a source S to an SSM destination address G, and receivers can receive this datagram by subscribing to channel (S,G).this is basics at which PIM-SSM protocol Works.

4.Extensions required of a host implementation of the Internet Protocol (IP) to support multicasting.The range between  224.0.0.0 and 224.0.0.255 used for routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting.Following are the Uses.

224.0.0.0 (Base Address (Reserved) )
224.0.0.1 (All Systems on this Subnet )
224.0.0.2 (All Routers on this Subnet )
224.0.0.3( Unassigned )
224.0.0.4( DVMRP Routers)
224.0.0.5 (OSPFIGP OSPFIGP All Routers)
224.0.0.6 (OSPFIGP OSPFIGP Designated Routers )
224.0.0.7 (ST Routers )
224.0.0.8 (ST Hosts )
224.0.0.9 (RIP2 Routers )
224.0.0.10 (IGRP Routers )
224.0.0.11 (Mobile-Agents )
224.0.0.12 (DHCP Server / Relay Agent)
224.0.0.12 - 224.0.0.255( Unassigned )

224.0.1.23( XINGTV)

224.0.2.1 ("rwho" Group (BSD) (unofficial))
224.0.2.2 (SUN RPC PMAPPROC_CALLIT)

224.0.3.000-224.0.3.255 (RFE Generic Service )
224.0.4.000-224.0.4.255 (RFE Individual Conferences )
224.0.5.000-224.0.5.127( CDPD Group)
224.0.5.128-224.0.5.255 ( Unassigned )
224.0.6.000-224.0.6.127 ( Cornell ISIS Project)
224.0.6.128-224.0.6.255 ( Unassigned)
224.0.7.000-224.0.7.255 ( Where-Are-You )
224.0.8.000-224.0.8.255 (INTV )
224.0.9.000-224.0.9.255 (Internet Railroad)

224.1.0.0-224.1.255.255 (ST Multicast Groups )
224.2.0.0-224.2.255.255 ( Multimedia Conference Calls )

224.252.0.0-224.255.255.255 ( DIS transient groups)

5.There are basically 4 types of massages in IGMP:

Membership Query: Used by IGMPv1 and IGMPv2 multicast routers to locate the multicast groups in use by hosts on the local network.

V1 Membership Report: Identifies this message as an IGMPv1 Membership Report.

V2 Membership Report: Identifies this message as an IGMPv2 Membership Report.

V2 Level Report: Used by IGMPv2 hosts to announce that they are leaving a multicast group.