Spirent SmartBits System, Reference Manual

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Chapter 13: Token Ring Cards
Ring Protocols Used by the TR-8405
SmartBits System Reference 185
TR-8405 operation in TXI mode is identical to that in normal Token Passing modes. The
statistics will reflect the disconnection between the transmitter and the receiver since the
receiver will no longer see transmitted frames.
Ring Protocols Used by the TR-8405
This section describes the parts of the Token Ring protocols implemented by the TR-8405.
Normal (Token Passing) Operation
The TR-8405 will generate these MAC frames (assuming a BIA is set):
• Standby Monitor.
• Report SUA Change.
• Initialize Ring Station.
This is the minimum set to allow this unit to coexist with other stations on a ring. The card
will not participate in claim sequences.
The Initialize Ring Station frame has no subvectors (they are all listed as optional ). The
card responds to some initialization requests to prevent adapters from failing to open due
to an initialization error - it will respond if no other card does.
DTR (TXI) Operation
The TR-8405 will participate in a connection sequence based on the 802.5r draft standard.
The unit has to have a BIA set to enable this mode of operation. The card will generate:
• Registration Request (when a station).
• Registration Response (when an adapter).
• Lobe Test (when a station).
• Insertion Request (when a station).
• Insertion Response (when an adapter).
• Station Heartbeat (when a station).
• Port Heartbeat (when an adapter).
The unit is set up to initiate connections when a station. It will output Registration Request
frames at one second intervals. (The requests will indicate TXI protocols, Phantom to be
raised just before registration and an IAC of zero.) Upon a favorable response the station
will output some Lobe Test frames, raise the Phantom and issue an Insertion Request. On
Receiving a favorable reply the unit will start transmitting Hearbeat frames at regular
intervals.
The TR-8405 only implements a subset of the protocols and FSMs, enough to get and
maintain a connection to a typical unit. Errors or denial responses are dealt with by
timeouts.