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MPOA in an ATM Network
893-01006-C
3-5
Egress MPC Functionality
An egress MPC receives internetwork data frames from other MPCs to be
forwarded to its local users. When an egress MPC receives a frame over a
shortcut, it adds the appropriate DLL encapsulation and sends it on the bridge
ports or internal host stack. The MPC receives the DLL encapsulation information
from the egress MPS. DLL encapsulation information is stored in the egress cache
of the MPC.
The egress MPC sends a cache imposition reply to the egress MPS for each cache
imposition request it receives. The egress MPC must first determine if it has
enough resources to maintain the cache entry and receive a new VCC. If resources
are not available, error status information is inserted into the reply.
MPOA Servers
The MPOA server provides internetwork layer forwarding information to MPCs.
One or more MPSs exist on a router, such as an ATM router engine or a Centillion
Multiprotocol Engine. The MPS uses NHRP to get routing information, to answer
MPOA resolution requests from ingress MPCs, and to provide DLL encapsulation
information to egress MPCs.
Figure 3-1
illustrates how the MPS interacts with the Next Hop Server (NHS), the
associated LECs, and MPOA clients.
Figure 3-1. MPOA Server and Components
8854EA
Convergence
functions
LEC(s)
MPOA Server
Router
Next Hop
Server
Other NRHP
components
MPOA Clients
LANE