FDDI PCI
ANSI X3T9.5 - Fiber Distributed Data Interface
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The FDDI protocol is similar to the token-ring protocol. But in detail, they are different: Some changes had been necessary in order to support transmission speed of 100 Mbps and ring length of 100 km.
FDDI is standardized by ANSI ASC X3T9.5 and ISO 9314.
The most important changes (compared to token-ring) are as follows:
1. Token-ring stations will set the token bit to T=1 if they start frame transmission; FDDI stations will discard the token.
2. Token-ring stations may (or may not) support early token release; FDDI stations always use early token release.
3. FDDI allows a ring length of 100 km.
The following frame types are used by FDDI:
1. LLC Frames / User Data
Data of upper layer protocols (LLC first) / user data.
2. MAC Frames / SMT (Station Management)
ECF - Echo Frame
ESF - Extended Service Frame
NIF - Neighbor Information Frame
PMF - Parameter Management Frame
RAF - Resource Allocation Frame
RDF - Request Denied Frame
SIF - Status Information Frame
SRF - Status Report Frame
The FDDI SMT controls all FDDI functions:
FDDI media access control (MAC):
Literature/Sources: