TCP/IP Tutorial and Technical Overview - IBM Redbooks

2.11.3 MPOA functional components
The mapping between the logical and physical components are split between the
following layers:
► MPOA functional group layer
► LAN emulation layer
► Physical layer
The MPOA solution will be implemented into various functional groups that
include:
► Internetwork Address Sub-Group (IASG): A range of internetwork layer
addresses (for example, an IPv4 subnet). Therefore, if a host operates two
internetwork-layer protocols, it will be a member of, at least, two IASGs.
► Edge Device Functional Group (EDFG): EDFG is the group of functions
performed by a device that provides internetworking level connections
between a traditional subnetwork and ATM.
– An EDFG implements layer 3 packet forwarding, but does not execute any
routing protocols (executed in the RSFG).
– Two types of EDFG are allowed, simple and smart:
Smart EDFGs request resolution of internetwork addresses (that is, it
will send a query ARP type frame if it does not have an entry for the
destination).
62 TCP/IP Tutorial and Technical Overview
Simple EDFGs will send a frame via a default class to a default
destination if no entry exists.
– A coresident proxy LEC function is required.
► ATM-Attached Host Functional Group (AHFG): AHFG is the group of
functions performed by an ATM-attached host that is participating in the
MPOA network.
A coresident proxy LEC function is optional.
Within an IASG, LAN emulation is used as a transport mechanism to either
traditional devices or LAN emulation devices, in which case access to a LEC
is required. If the AHFG will not be communicating with LANE or other
devices, a co-resident LEC is not required.
► IASG Coordination Functional Group (ICFG): ICFG is the group of functions
used to coordinate the distribution of a single IASG across multiple traditional
LAN ports on one or more EDFG or ATM device, or both. The ICFG tracks the
location of the functional components so that it is able to respond to queries
for layer 3 addresses.