Ref: 03250407
Title: DEC Ethernet Configuration Rules
Date: 6/9/87

Copyright 3Com Corporation, 1991.  All rights reserved.

We have put together the following list of "rules" from DEC
literature on Ethernet networks.

ThinWire Rules:

1) Maximum segment length = 185m
2) Stations attach using DESTA and 'T' connector
3) Minimum distance between 'T' connectors = 0.5m
4) Maximum stations on segment regularly = 30
5) Maximum stations on segment with DEMPR = 29
6) Maximum stations on segment with SER and faceplate = 28


Standard Ethernet Cable rules:

1) Stations attach using transceiver
2) Maximum segment length regularly = 500m
3) Maximum segment length with DELNI/DEMPR combination = 300m
4) Maximum transceivers on segment = 100
5) Connect DELNI to segment using transceiver, no heartbeat
6) Connect DEMPR to segment using transceiver, <45m of
   transceiver cable
7) Minimum distance between transceivers = 2.5m


DELNI rules:

1) DELNI allows 8 devices to share transceiver
2) Stand-alone cascading DELNI network interconnects 8 DELNIs and 64 stations
   using transceiver cable
3) Connect DELNI to standard Ethernet cable using transceiver
4) DEMPR connects to DELNI using < 45m of transceiver cable
5) Main DELNI in stand-alone cascading DELNI network must be in 'global' mode
6) Non-Main DELNIs in stand-alone cascading DELNI network must be in 'local'
   mode
7) A DELNI is not a network addressable unit


DEMPR rules:

1) Connect DEMPR to DELNI using <45m of transceiver cable
2) Connect DEMPR to standard Ethernet cable using transceiver
3) Segments attached to DEMPRs can have 29 stations
4) Main DEMPR in stand-alone cascading DEMPR network uses ThinWire
5) Only one segment attached to main DEMPR in stand-alone cascading
   DEMPR network can have DEMPRs on it
6) The cascading segment in the stand-alone cascading DEMPR network
   can have up to 29 DEMPRs on it
7) DEMPRs on cascading segment of a stand-alone cascading DEMPR network
   are attached using DESTAs
8) A DEMPR grounds an Ethernet segment
9) A DEMPR provides a termination end to a segment
10) A DEMPR is not a network addressable unit


General Ethernet Network Rules:

1) Maximum cable length between stations = 2800m (all media)
2) All segments must be grounded
3) All segments must be terminated on each of the two ends
4) Maximum stations on a single Ethernet network = 1024
5) A station = network addressable unit
6) Maximum stations on an extended network = 8000
7) Maximum length of low loss transceiver cable = 50m
8) Maximum length of high loss transceiver cable = 12.5m
9) Stand-alone networks cannot be attached to Ethernet networks


Repeater Rules

1) Local repeaters join segments < 100m apart
2) Remote repeaters join segments <1000m apart
3) No more than 2 repeaters between any two stations (Ver. 1)
4) A DEREP cannot be connected to a DELNI


Bridge Rules

1) No more than 7 bridges between any 2 stations
2) Local bridges are connected using <100m of transceiver cable
3) Remote bridges are connected using <2000m of fiber cable
4) Each remote bridge half counts as a bridge for the "7 bridge" rule
