Route Determination; Bridging - SMC Networks Barricade SMC7401BRA User Manual

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ETWORKING ONCEPTS
Data flows are broken up into fixed length cells, each of which contains a
Virtual Path Identifier (VPI) that identifies the path between two nodes,
and a Virtual Circuit Identifier (VCI) that identifies the data channel within
that virtual path. Each virtual circuit maintains a constant flow of cells
between the two end points. When there is no data to transmit, empty cells
are sent; when data needs to be transmitted, it is immediately inserted into
the cell flow.

Route Determination

Depending on the ATM transport protocol used, this router can handle
traffic as a Layer-2 bridge, using only the physical address stored in the
packet's source and destination address fields. Or it can forward traffic as a
fully functional Layer-3 router, using a specific route (that is, next hop) for
each IP host or subnet that is statically configured or learned through
dynamic routing protocols.

Bridging

If ATM Protocol Encapsulation is set for Ethernet/ATM (RFC 1483), the
router behaves like a wire directly connecting your local network to the
ISP. The router acts as a transparent bridge between a local PC or LAN
attached to the Ethernet port and a remote site across the ADSL link.
Bridging can be used to make two separate networks appear as if they were
part of the same physical network. Bear in mind that compared to routing,
bridging generates a lot more traffic and can significantly slow down the
router.
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