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Fiber Distributed Data Interface
Order Number:
EK-DFDDI-CG-001
Fiber Distributed
Data Interface
Network Configuration
Guidelines Fiber Distributed
Data Interface
Network Configuration
Guidelines
November 1991
This manual describes the guidelines
for connecting devices to an FDDI net-
work. It also includes network configu-
ration examples.
Supersession/Update Information:
This is a new manual.
Order Number: EK-DFDDI-CG-001 EKDFDDICG001
November 1991
The information in this document is subject to change without
notice and should not be construed as a commitment by Digi-
tal Equipment Corporation. Digital Equipment Corporation
assumes no responsibility for any errors that may appear in
this document.
Copyright
©

1991 by Digital Equipment Corporation
All Rights Reserved.
Printed in U.S.A.
The following are trademarks of Digital Equipment Corpora-
tion:
DEBET
DECnet
TURBOchannel
DEC
DECstation
ULTRIX
DEC FDDIcontroller
DECsystem
UNIBUS
DECbridge
DECUS
VAX
DECconcentrator
DECwindows
VAXcluster
DECconnect
LAN Traffic Monitor
VAXstation
DECelms
PDP
VMS
the Digital logo
ThinWire
This manual was produced by Telecommunications
and Networks Publications. iii
Contents
Preface
1
FDDI Network Connection Rules
1.1
PHY Port Connection Rules
1
. . . . . . . . . . . . .
1.2
FDDI Station Connection Guidelines
4
. . . . . .
1.3
Optical Bypass Relay
6
. . . . . . . . . . . . . . . . . . .
2
FDDI Network Configurations
2.1
Standalone Configurations Using
Concentrators
9
. . . . . . . . . . . . . . . . . . . . . . . . .
2.2
Tree Configurations Using Concentrators
and Bridges
10
. . . . . . . . . . . . . . . . . . . . . . . . .
2.3
Dual Ring Configuration
13
. . . . . . . . . . . . . . . .
2.4
FDDI Dual Homing
14
. . . . . . . . . . . . . . . . . . . .
2.5
Single-Mode Fiber Configurations
15
. . . . . . .
3
FDDI Specifications
3.1
FDDI and Cable Specifications
17
. . . . . . . . . .
3.2
Optical Bypass Link Loss
22
. . . . . . . . . . . . . . .
A
Related Documents
Index
Figures
11
PHY-Port Types
2
. . . . . . . . . . . . . . . . . . . . . .
12
FDDI Connection Rules Matrix
2
. . . . . . . . .
13
Installed Optical Bypass Relay
6
. . . . . . . . .
14
Optical Bypass Connector Signals
7
. . . . . .
21
Standalone Workgroup Installation
9
. . . . . .
22
Dedicated Network in a Dual Ring
Installation
10
. . . . . . . . . . . . . . . . . . . . . . . . . .
23
Tree of Concentrators in a Campus
11
. . . .
24
Tree of Concentrators in a Building
12
. . . . .
25
Dual Ring of Concentrators Installed in a
Building
13
. . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
26
Concentrators Installed for Dual Homing 14
27
DAS Bridge Installed for Dual Homing
14
. .
28
Connecting to the Dual Ring Through a
Single-Mode Link
15
. . . . . . . . . . . . . . . . . . . .
29
Dual Ring with Mixed Link Lengths
15
. . . . .
Tables
31
FDDI General Specifications
17
. . . . . . . . . .
32
Optical System General Specifications
18
.
33
Multimode Fiber Optic Cable
Specifications
19
. . . . . . . . . . . . . . . . . . . . . . .
34
Single-Mode Fiber Optic Cable
Specifications
19
. . . . . . . . . . . . . . . . . . . . . . .
35
FDDI 100/140-
µ
m Multimode Fiber Optic
Cable Specifications
20
. . . . . . . . . . . . . . . . .
36
FDDI 50/125-
µ
m Multimode Fiber Optic
Cable Specifications
21
. . . . . . . . . . . . . . . . .
37
ThinWire and Shielded Twisted-Pair
Cable Specifications
22
. . . . . . . . . . . . . . . . .
38
Calculating Allowable Link-Loss Budget 23
. v
Preface
This manual provides the rules for connecting Fiber Dis-
tributed Data Interface (FDDI) devices to the network. This
manual also contains examples of FDDI network configu-
rations built on Digitals implementation of the EIA/TIA 568
wiring standard for commercial buildings.
Intended Audience
This manual is for network system managers, network
planners, installers, and others who set up, manage, and
troubleshoot FDDI networks and network devices.
Document Structure
This manual contains three chapters and an appendix:
Chapter 1
Provides rules for connecting FDDI devices
to the network.
Chapter 2
Provides FDDI network configuration exam-
ples.
Chapter 3
Lists FDDI and cable specifications.
Appendix A
Lists related documents.
The postage-paid Readers Comments card in this docu-
ment requests your critical evaluation to help us prepare
future documentation. 1
1
FDDI Network Connection Rules
The FDDI standards specify four physical port (PHY port)
types: A, B, M, and S.
1.1 PHY Port Connection Rules
Figure 11, a simplified diagram of a concentrator, shows
the various PHY ports. FDDI defines the PHY ports as
follows: PHY A Connects to the incoming primary ring and
the outgoing secondary ring of the FDDI dual ring.
This port is part of a dual attachment station (DAS) or
a dual attachment concentrator (DAC). This port also
connects to PHY M of a concentrator as the backup
path in a dual homing topology. PHY B Connects to the outgoing primary ring and
the incoming secondary ring of the FDDI dual ring.
This port is part of a DAS or a DAC. This port also
connects to PHY M of a concentrator as the primary
path in a dual homing topology. PHY M Connects a concentrator to a single attach-
ment station (SAS), DAS, or another concentrator.
This port is implemented only in the concentrator. PHY S Connects a SAS to a PHY M of a concentra-
tor. PHY S also connects to a DAS or another SAS,
but these configurations are not always recom-
mended. 2
FDDI Network Configuration Guidelines
Figure 11:
PHY-Port Types
Concentrator
PHY M
Primary
ring
Secondary
ring
PHY A
PHY B
PHY M
PHY M
PHY B
PHY S
DAS or DAC
SAS or SAC
LKG-5579-91I
The FDDI standards specify connection rules to prevent
illegal topologies. Connections between stations have the
status of in use or not in use. When a cable is connected,
the system decides whether to use the cable in the token
path. Figure 12 shows the ring-connection rules for Digi-
tal devices. This Node is the reference point for all con-
nection decisions.
Figure 12:
FDDI Connection Rules Matrix
LKG-5580-91I
PHY port
A
B
M
S
A
B
M
S
No
Rule 1
Yes
Yes
Rule 2
No
Yes
Yes
Rule 3
Yes
No
Yes
Note 1
Yes
Yes
Yes
Yes
This Node
Other
Node
Yes = Accepts this connection.
No = Does not accept this connection.
Note 3 FDDI Network Connection Rules
3
Rule 1:
PHY B of T<b>his Node accepts connection to
PHY A of Other Node if: PHY A of This Node is not connected, or PHY A of This Node is connected to PHY
B or PHY S of another node.
Rule 2:
PHY A of This Node accepts connection to
PHY B of Other Node if: PHY B of This Node is not connected, or PHY B of This Node is connected to
PHY A or PHY S of another node.
See also Note 2.
Rule 3
:
PHY A of This Node accepts the connection to
PHY M of Other Node if: PHY B of This Node is not connected, or PHY B of This Node is connected to PHY A
or PHY S of another node.
See also Note 2.
Note 1:
The following conditions apply for a backup tree
connection (dual homing).
The connection of PHY B of This Node to PHY M of Oth-
er Node always supersedes the connection of PHY A of
This Node to PHY M of another node.
Any connection between PHY A of This Node and a PHY
M or PHY B of another node is disconnected when PHY B
of T<b>his Node connects to PHY M of Other Node.
If the connection breaks between PHY B of T<b>his Node
and PHY M of Other Node, the system reestablishes the
connection between PHY A of This Node and PHY M of
another node.
Note 2:
Tree connections come before dual ring con-
nections when only one of two connections may be ac-
cepted.
The connection of PHY A or B of This Node to PHY M of
Other Node always supersedes the connection of the
remaining PHY (A or B) of T<b>his Node to PHY A or PHY B
of another node. 4
FDDI Network Configuration Guidelines
The system disconnects the connection between the re-
maining PHY (A or B) of This Node and PHY A or PHY B
of another node when PHY A or PHY B of This Node con-
nects to PHY M of Other Node.
Note 3:
The shielded twisted-pair and ThinWire PMD
specifications support only connections from PHY M to
PHY S. The specifications do not support connections
from PHY S to PHY S.
1.2 FDDI Station Connection Guidelines
Use the following guidelines when connecting a SAS or
DAS concentrator, bridge, bridge/router or adapter into an
FDDI network.
Distance requirements: Maximum distance between FDDI stations must not
exceed: 2 km (1.2 mi) for ANSI multimode 1 km (0.62 mi) for low-power multimode 40 km (24.8 mi) for single-mode 100 m (330 ft) for single segment point-to-point
ThinWire and shielded tw