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MPOA
4.3.3
MPOA Components
MPOA requires LANE services for both ELAN traffic handling and MPOA configuration.
LANE/MPOA Client (LEC/MPC)
The LEC/MPC can wear two different “hats.” When
wearing its LEC “hat,” it simply communicates with
other ELAN components (the LES and BUS) to
resolve MAC addresses into ATM addresses. When it
puts on its MPC “hat,” the additional function of the
LEC/MPC in an MPOA-aware network is to source
and sink internetwork shortcut circuits. A LEC/MPC
that is the source of a shortcut is known as an ingress
LEC/MPC. A LEC/MPC that is the sink of a shortcut
is known as an egress LEC/MPC. The LEC/MPC
includes an NHRP Client (NHC).
An ingress LEC/MPC monitors traffic flow that is
being forwarded over an ELAN to a router that
contains an MPS. When the ingress LEC/MPC
recognizes a flow rate (configurable) that could
benefit from a shortcut (and thus bypass the routed
path), it requests a shortcut to the destination. If a
shortcut is available, the ingress LEC/MPC sets up a
shortcut VCC, and forwards traffic for the
destination over the shortcut.
An egress LEC/MPC receives internetwork traffic
from other LEC/MPCs to be forwarded to its local
interfaces/users. For traffic received over a shortcut,
the egress LEC/MPC adds the appropriate
encapsulation and forwards them via a LAN
interface (that may be a bridge port, an internal host
stack, etc.).
MPOA Server (MPS)
An MPS includes an NHRP Server (NHS) and is the
logical component of a router that provides
internetwork layer forwarding information to
LEC/MPCs. The MPS answers MPOA queries from
ingress LEC/MPCs and provides encapsulation
information to egress LEC/MPCs.
The MPS also converts between MPOA requests and
replies, and NHRP requests and replies on behalf of
LEC/MPCs.
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ForeRunner ATM Switch Network Configuration Manual