Cabletron Systems STS16-20R - Manual (Page 46)

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SmartStack STS16-20D/STS16-20R Token Ring Switches Installation and User Guide Switch Overview
Dynamic Source Route Recovery
Dynamic Source Route Recovery (DSRR) is a proprietary protocol that enables a
group of switches to handle a link or switch failure without session loss.
A basic redundant setup must have a minimum of two switches performing source
route bridging between a legacy Token-Ring and an emulated Token-Ring (or
another legacy ring) as illustrated in Figure 8.
Figure 8. Example of Dynamic Source Route Recovery, Base Configuration
This configuration already has redundant paths between the two rings, but since
moving traffic from one path to the other involves changing source route, this
would involve session loss.
When DSRR is enabled, an extra path is automatically created between the two
rings for each switch, as shown in Figure 9. During normal operation, these extra
paths do not forward any traffic.
A
T
M
A
T
M
BRF
Bridge No. B1
CRF
CRF
CRF
CRF
BRF
Bridge No. B2