Sr-Tb Bridging; Spanning Tree Algorithm; Flexible Network Bus (Fnb) - Cabletron Systems SmartSwitch 9000 User Manual

Operation

SR-TB Bridging

SR-TB Bridging is only between the front panel Token Ring and the backplane
FNB. Source Routing (SR) packets from the front panel Token Ring must be
converted to Transparent Bridging (TB) type packets before it is sent over the
FNB. The RIF is stripped off the packet and placed in a RIF cache.
The SR-TB bridge is a learning type bridge. It learns what nodes are present by
listening to incoming packets and saving their MAC addresses to a database
table. If the packet is source routed, it also updates the RIF cache.
If the destination is unknown or is a broadcast address, the bridge sends either a
STE or ARE packet for the Token Ring interface, or a TP packet for the FDDI
interface, to carry the data to the end station. This is user configurable.

Spanning Tree Algorithm

The 9T125-08 promotes maximum network use in multiple bridge environments.
A bridge learns the bridge topology of its network from bridge protocol data that
it receives from other bridges within the network. The bridges then apply the
Spanning Tree Algorithm (STA) to select a root bridge, and then determine
primary data paths within potential data loop configurations.
Spanning Tree Algorithm is a hierarchy (or tree) of priorities that bridges establish
between themselves. This hierarchy guarantees that primary and redundant data
paths are clearly defined at all times, so that the network is continuously available
to users.
In a multiple bridge environment, one bridge in the network establishes itself as
the root bridge. As the root, this bridge has priority over all other bridges. In a
Spanning Tree, all of the bridges must determine which bridge is the root, and
then determine their own relative priority within the network.

Flexible Network Bus (FNB)

The FNB consists of two dual FDDI networks, the FNB-1 and FNB-2, providing
up to 400 Mbps of data bandwidth. These FDDI networks are 100% ANSI
FDDI-compliant supporting SMT (version 7.3), MAC, PHY, and PMD standards.
This allows the FNB to traverse multiple SmartSwitch 9000 hubs, or connect to
any ANSI FDDI-compliant device, through standard A/B port connections, using
the FDDI repeater module.
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