Source Route Switching (Srs); Source Route Bridging (Srb) - Cabletron Systems SmartSTACK STS16-20RM Installation And User Manual

The CRF communicates via a logical, virtual port with the bridge relay function,
which functions as a multiport (virtual) bridge between the logical rings. The
switch can support up to 63 logical rings.
There are two levels of relay functions supported by the switch. The first level is
the CRF to which the ports are assigned. The second level is the BRF. This is the
parent relay function to which CRFs are assigned. The switch maintains certain
configuration information and management statistics on a per BRF/CRF basis.
Therefore, when you access VLAN specific switch configuration or management
screens (such as the Current Spanning Tree Information screen), you will be
prompted to specify the desired BRF or CRF.

Source Route Switching (SRS)

This mode is used between ports comprising a logical ring.
SRS switching combines the normal transparent bridge function with the ability to
forward frames based on source route information to locally attached source-route
bridges. The switch does not otherwise act as a source route bridge. For non source-
routed packets, the switch decision is based upon destination MAC Addresses. For
source-routed packets, it is based on the source-route information combined with
the destination MAC address.
The switch learns MAC addresses and source-routing route descriptors of Source
Route Bridges attached to local switch ports.
Parallel paths are eliminated via the IEEE 802.1D Spanning Tree Protocol.

Source Route Bridging (SRB)

The BRF acts as a multiport source route bridge between CRFs with the following
characteristics:
•
Each logical ring has a different ring number
•
Source-routed frames are forwarded between the logical rings by the bridge
relay function based on the route information field
•
Non-source-routed frames are not forwarded between logical rings
•
The bridge relay function has a single bridge number and multiple ring
numbers (one per logical ring)
SRS is used between the ports of each logical ring. The bridge relay function runs
the IBM Spanning Tree Protocol to eliminate parallel paths with other source-route
bridges. The IEEE 802.1D Spanning Tree Protocol is still used with each logical
ring. Duplicate MAC addresses are allowed only if they are on different logical
rings.
Switch Overview SmartStack STS16-20RM/STS16-20FRM Token Ring Switches, P/N: 9032957-01
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