Claim Token Process
FDDI operation needs a token passing the ring. Token-ring (IEEE 802.5) networks ensure ring operation by a designated active monitor; FDDI doesn't because all FDDI adapters check ring performance.
The first FDDI station inserted into ring initializes the ring and transmits a token frame.
If a FDDI adapter misses a token within the token rotation time (no token received within token rotation time) it will transmit a claim token frame.
Each claim token frame contains a request for the current valid TTRT (target token rotation time) value.
Each station joining the claim token process checks the claim token frame's source address as well as the conveyed TTRT value.
If the claim token frame's TTRT value is less than the local TTRT value (the receiving station's TTRT value), the receiving station won't transmit any more claim token frames. All received claim token frames are repeated.
If the claim token frame's TTRT value is higher than the local TTRT value, all received claim token frames are replaced by claim token frames sent by the receiving station.
If a ring station receives only its own claim token frames it is the last station joining the claim token process. It will reinitiate the ring.