Transmission Priority Queues; Clearsession Support - Cabletron Systems SmartSTACK STS16-20RM Installation And User Manual

Transmission Priority Queues

To address the needs of delay-sensitive data, such as multimedia, the Token Ring
ports of the switch have two transmit queues, a high-priority queue and a low-
priority queue.
The queue for a frame is determined by the value of the priority field in the frame
control (FC) byte. If FC priority is above a configurable level (default 3), the frame
is put into the high-priority queue. If an output port becomes congested, you can
dynamically configure the port to transmit all frames at high priority regardless of
the FC byte contents.

ClearSession Support

The STS16-20RM series switches support ClearSession high availability and
network redundancy features.
ClearSession is a framework for mission critical networks. It prevents session loss by
providing a network failure recovery time of, typically, less than three seconds.
ClearSession consists of a several product features. Some of these, ClearServer,
CrossLinks and Dynamic Source Route Recovery, are supported by the STS16-
20RM series switches. These features provide the following functionality:
ClearServer. Token-Ring ClearServer for LAN, allow multiple adapters to be
treated as one virtual adapter in the server, thus allowing multiple connections
between a server and the backbone switch or switches. During normal operation the
traffic is distributed on the links. The STS16-20RM series switches support
ClearServer for LAN to be used on servers connected to the switch.
CrossLinks. Any Token-Ring link or dedicated Token-Ring link between STS16-
20RM series switches may be expanded to a CrossLink. A CrossLink is an
aggregation of two to eight identical parallel links, working as one link of the
aggregate capacity, providing protection from physical link failure. Should one of
the links fail, the traffic is redistributed among the remaining operational links.
Dynamic Source Route Recovery. DSRR is a feature that enables two or more
STS16-20RM series switches, performing source route bridging between a shared-
media access ring and a common backbone ring, to function as backup for each
other. Should one of the switches fail or lose connectivity to one of the access rings,
the other switch immediately takes over and bridges source-routed traffic marked
with the failed path. DSRR protects source-routed traffic to and from shared access
segments, such as user rings, with redundant connections to two Token-Ring
switches. Traffic to and from such rings that is non-source-routed relies on the
spanning tree.
Switch Overview SmartStack STS16-20RM/STS16-20FRM Token Ring Switches, P/N: 9032957-01
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