Source Route Bridging - Cabletron Systems SmartSwitch 9000 User Manual

The second filtering process, the Cabletron Systems Special Filtering Database,
provides an additional step in the filter/forward decision. Through Remote
Management, you can define up to 10 additional filtering parameters for
incoming network traffic.
These parameters include (but are not limited to) the:
• Destination address
• Source address
• Type field (protocol)
• 64 bytes of the data field (using a data offset)
For example, using this process, you can ensure that the 9T125-08 always filters or
forwards packets with a specific protocol or address.

Source Route Bridging

Source Route Bridging is only provided between front panel rings. It operates by
transmitting frames over a designated route. Unlike Transparent Bridging, all
devices in a Source Route Bridged (SRB) network "know" the locations of other
stations within the network. Using a portion of the MAC frame header known as
the RIF (Routing Information Field), the source device determines the route for
the frames it sends.
In order for source routing to work, the source station must determine the proper
route to reach the desired destination. To accomplish this:
1. The source station sends out frames called All Route Explorer (ARE) or Single
Route Explorer (SRE) frames onto the network. All Source Route Bridges
recognize these frames and forwards them to their outbound ports.
2. The receiving bridges append their own route information to the Route
Information Field (RIF) in the MAC frame header and transmit the frame
again.
3. Eventually, the original source device receives all of the ARE replies from the
other end stations on the network.
4. From this information, the source device can determine a desired route for
each frame it transmits.
Operation
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