Sun Microsystems SunLink SNA 9.1 PU2.1, Руководство по настройке

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IBM Token Ring Concepts D-9
D
Configuration issues that determine whether to transmit to the second ring
include internal bridge congestion, matching ring and bridge numbers, and
largest frame passable by the bridge.
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All-routes broadcast - Used when the path to the destination ring station is
not known. A bridge receiving an all-routes broadcast frame appends
segment field information depending on whether or not that exact segment
already occurs in the route. Therefore, multiple copies of the original frame,
each with different source routing information, may arrive at the destination
ring station and may also occur more than once on the same ring. The
originating station must be prepared to receive multiple responses (usually
nonbroadcast) and then select the optimum route, depending on such
parameters as frame sizes allowable by bridges, total number of bridges that
must be crossed (number of hops), and response time.
•
Single-route broadcast - Used when the path to the destination ring station
is not known. Single-route broadcast packets are forwarded only by
specially configured bridges that have single-route broadcast active. Bridges
not configured with the single-route broadcast feature do not forward the
frame.
Single-route broadcast bridges communicate with one another and make use
of the spanning tree protocol to represent and continuously update the
topology of the network. The result is that the transmitted frame only occurs
once for each ring and the destination ring station only receives one copy of
the frame. The destination can respond to the originating station by using a
nonbroadcast frame containing the routing information of the frame that it
just received, or it can choose an all-routes broadcast to respond.
All of the bridges discard a frame when the hop count is exceeded. This
prevents prolonged packet forwarding and reduces the total number of
packets generated in an all-routes broadcast scenario.
Sun's IBM Token Ring network connectivity products use all-routes broadcasts
in source routing for route discovery. This increases the probability of
contacting the destination ring station if no intermediate bridge with single
route feature is active on the network. In addition, route selection is based on
response time, hop count, and maximum allowable frame size of intermediate
bridges. Sun products use sharable, cached source-routing tables so that
multiple products do not have to engage in redundant route discovery
attempts. Before the search for a ring station is sent to multiple rings, Sun
products check the local ring. This reduces the amount of network traffic and
provides compatibility with those ring stations that do not support source