IP Multicast:

IP datagrams three transmission modes:

Unicast:
unicast data packets sent to a single destination, and each send a unicast packet uses a unicast IP address
as the destination address. Is a point to point transmission mode.

broadcast:

Broadcasting refers to the transmission data packet to a data transmission or the same broadcast domain to all devices within the subnet,
is a point to multipoint transmission mode.

Multicast (multicast):
When the network require some user specific data, multicast data sender to send data only once, by
the establishment of a multicast distribution tree for the multicast packets multicast routing protocol, data is passed to reach from the end user to make
node may close after the start of reproduction and distribution, it is a point-to- multipoint transmission.

IP multicast addresses:
IP multicast address allows the source device to send a packet to a group of devices. Equipment belonging to the multicast group will be assigned a multicast group IP address ( a group of co-hosts of the same identification requirements ).
Multicast address range 224.0.0.0 ~ 239.255.255.255 (class D address), - - a class D address represents a multicast group. It can only be used as a packet destination address . The source address is always a unicast address .
1. multicast datagrams is "best effort" does not provide reliable delivery, used UDP.
2. multicast packets do not generate ICMP error messages.
3. Not all Class D addresses can be used as a multicast address.
Hardware Multicast:

With unicast address, the multicast IP addresses requires a corresponding multicast MAC address of the frame is actually transmitted on the local network. Multicast MAC address hexadecimal value 01-00-5E starts, the remaining six bits is a hexadecimal address of the IP multicast group of the last 23 converted to.

Multicast packets received host data, but also filtered using software in the IP layer, not according to the host to receive data packets discarded.
IP address into a multicast MAC address, [01005E] Fixed front, behind the copy, and then convert binary hexadecimal can!

IGMP protocol multicast routing protocols:

IGMP protocol:

IGMP protocol allows the router to know if there is (process) host on this LAN to participate or withdraw from the multicast group.

IGMP two phases of work:]

ROUND 1:
When a host wants to join a multicast group, the host sends a multicast address to the multicast group - one IGMP packet, declared himself to be called a member of the group.
After the local multicast router receives IGMP packets, to make use of multicast routing protocols this group membership is available to other multicast routers on the Internet.
ROUND 2:
local multicast router periodically polling hosts on the local network, in order to know whether the members of these hosts or multicast group.
As long as there is a host to a group response, the multicast router will think this group is active; if after a few polling does not have a host response
should be, that there is no multicast router this multicast group hosts on the local network , there is no longer a member of this group of relations distributed to other multicast routers.
Membership multicast router knows only the presence or absence of a multicast group members of the LAN connection.

Multicast routing protocols:

Multicast routing protocols aimed at identifying the source host to the root of the multicast forwarding tree.
Tree can be configured to avoid circles between routers .
For different multicast groups corresponding to different multicast forwarding tree; the same multicast group, the different sources will have different points of multicast forwarding tree.

Three algorithms multicast routing protocol commonly used:
the route selection based on link state
based on the distance - vector routing
multicast protocol independent (sparse / dense)

Mobile IP:

Related Terms:

Mobile IP mobile node (computer / server, etc.) to a fixed network IP address , to achieve across different segments of the roaming function, and ensure that the
network authority any IP network does not change based on roaming.
Mobile node: a mobile device having a permanent IP address.
Home Agent (local agent) : a mobile node has on the "home" called home network, mobility management entity to perform functions on behalf of the mobile node is called a home agent in the home network.
Foreign Agent (FA): helping the mobile node to complete mobility management functions in an external network entity called a foreign agent.
Permanent address (home address / primary address): a mobile station in the home network address of the original.
Care-of address (secondary address): a temporary address the mobile station used in the external network.