3Com 3C63400-3AC-C - PathBuilder S700 Switch, Справочное руководство

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Supported Applications 85
The traffic shapers work as follows:
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The packet is segmented using a dual leaky buffer algorithm, whereby the cells
are transmitted from each connection in the shaper at an average rate until the
bucket of tokens fills up (a token is given to the connection at an average rate
if it has no cells to transmit at that moment).
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The shaper then turns the burst mode on and transmits at the peak rate for a
burst length. Note that the shaper serves every connection independently.
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PCR, SCR, and MBS settings are available.
Supported
Applications
This section describes the following applications supported by the
PathBuilder S700:
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Virtual circuits
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Bridging
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Spanning Tree
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CBR application
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Ethernet and voice application
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Frame application
See the following subsections for details about how the PathBuilder S700
implements these applications.
Bridging The bridge function is an integral part of the Ethernet module. The PathBuilder
S700 supports ATM permanent virtual circuits (PVCs) for access to the ATM
network. These PVCs connect an PathBuilder S700 Ethernet port through the ATM
network to another PathBuilder S700 Ethernet port. All the PVCs configured for a
port will form a virtual Bridged Ethernet network to all other ports at the other
end of the PVC.
The bridge operation is equivalent to a multiport bridge. The two Ethernet ports
on the module are treated separately unless they are connected through the ATM
network via PVCs. The ATM Layer operates transparently under the datalink layer
to allow higher level protocols to run without changes.
The CPU examines each packet's headers while they are in memory and performs
the bridging operations. A bridge is configured and maintained for each slot and
port in the PathBuilder S700. The bridge maintains the following:
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A forwarding table in its memory that lists the source and destination addresses
contained in each packet that passes through the PathBuilder S700
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An aging timer that removes addresses from the forwarding table if an address
is not used for a configured time
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A configured list of protocols, source addresses, and destination addresses that
will be rejected by the bridge. For information on configuring bridging filters,
see “Configuring the Bridge”” in Chapter 5.
The bridge learns and builds forwarding tables for every PVC that is tied to that
port. When a packet is received on the port or any PVC tied to that port, the
Source MAC address is learned and kept in the forwarding table until the aging