Digi X2 - Manual (Page 231)

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Internet Group Management Protocol (IGMP)
Internet Group Management Protocol (IGMP) provides a way for an Internet computer
to report its multicast group membership to adjacent routers. Multicasting allows one
computer on the Internet to send content to multiple other computers that have
identified themselves as interested in receiving the originating computer's content.
Multicasting can be used for such applications as updating the address books of mobile
computer users in the field, sending out company newsletters to a distribution list, and
“broadcasting” high-bandwidth programs of streaming media to an audience that has
“tuned in” by setting up a multicast group membership.
IP filtering
A network configuration that can be enabled to establish rules allowing devices to
permit or deny specific IP addresses, networks, or devices from connection access. Also
known as access control list.
IPsec (Internet Protocol Security)
A framework for a set of protocols for security at the network or packet processing layer
of network communication. Earlier security approaches have inserted security at the
application layer of the communications model. IPsec is said to be especially useful for
implementing virtual private networks and for remote user access through dial-up
connection to private networks. An advantage of IPsec is that security arrangements can
be handled without requiring changes to individual user computers.
IPsec provides two choices of security service: Authentication Header (AH), which
essentially allows authentication of the sender of data, and Encapsulating Security
Payload (ESP), which supports both authentication of the sender and encryption of data
as well. The specific information associated with each of these services is inserted into
the packet in a header that follows the IP packet header. Separate key protocols can be
selected, such as the ISAKMP/Oakley protocol.