TCP/IP Tutorial and Technical Overview - IBM Redbooks

► Default Forwarder Function Group (DFFG): In the absence of direct
client-to-client connectivity, the DFFG provides default forwarding for traffic
destined either within or outside the IASG.
– Provides internetwork layer multicast forwarding in an IASG; that is, the
DFFG acts as the multicast server (MCS) in an MPOA-based MARS
implementation.
– Provides proxy LAN emulation function for AHFGs (that is, for AHFGs that
do not have a LANE client) to enable AHFGs to send/receive traffic with
earlier enterprise-attached systems.
► Route Server Functional Group (RSFG): RSFG performs internetworking
level functions in an MPOA network. This includes:
– Running conventional internetworking routing protocols (for example,
OSPF, RIP, and BGP)
– Providing address resolution between IASGs, handling requests, and
building responses
► Remote Forwarder Functional Group (RFFG): RFFG is the group of functions
performed in association with forwarding traffic from a source to a destination,
where these can be either an IASG or an MPOA client. An RFFG is
synonymous with the default router function of a typical IPv4 subnet.
2.11.4 MPOA operation
Note: One or more of these functional groups can co-reside in the same
physical entity. MPOA allows arbitrary physical locations of these groups.
The MPOA system operates as a set of functional groups that exchange
information in order to exhibit the desired behavior. To provide an overview of the
MPOA system, the behavior of the components is described in a sequence order
by significant events:
Configuration Ensures that all functional groups have the
appropriate set of administrative information.
Registration and discovery Includes the functional groups informing each
other of their existence and of the identities of
attached devices and EDFGs informing the
ICFG of earlier devices.
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