User`s guide

1-14
Introduction
as the originating packet, the ATX immediately forwards the
packet to the segment associated with the destination address.
Local traffic, data packets whose source and destination address is
on the same segment, is automatically discarded.
The ATX forwards data packets to network segments based on the
IEEE 802.1D spanning tree algorithm, which converts multiple
LANs into a “spanning tree” of networks. This standard defines a
logical (not physical) network configuration consisting of one
extended LAN without active duplicate paths between ATXs. The
ATX and other spanning tree compliant bridges in the network
dynamically configure the network topology into a single
spanning tree by exchanging bridge protocol data units (BPDUs).
In a parallel configuration of bridges packets are forwarded to
LANs by only one ATX (or other spanning tree compliant bridge).
When there are multiple ATXs between two LANs, only one of the
ATXs forwards any individual packet. The spanning tree
algorithm determines which ATX should forward each packet.
Packets originating from one device and destined for a remote
device are forwarded in the same order in which they are received.
Each port of the ATX can be configured for transparent (802.1d)
bridging, IBM source routing bridging, or source routing
transparent bridging (802.5M). Depending on network topology, it
may be desirable to include a mix of these methods within a single
ATX.
The choice of bridging methods is determined both by end station
requirements and by other internetworking equipment.
Source routing end stations may use any of the ATX three bridging
methods. Transparent end stations must use either transparent or
SRT bridging. When in doubt, transparent bridging is the easiest to
configure and use.
If redundant links are employed along with IBM source routing
bridges, then the attached ATX port should be configured for
source routing. This will enable the mesh of bridges to derive a
spanning tree suitable for spanning tree explorer frames and for