Star: LAN Technology Report

105 Pages·1991·3.859 MB·English

by  Architecture Technology Corp. (Auth.)

STARLAN TECHNOLOGY
REPORT
FOURTH EDITION
SEPTEMBER 1991
JE (cid:29) ARCHITECTURE DISTRIBUTED OUTSIDE THE USA/CANADA BY:
ELSEVIER ADVANCED TECHNOLOGY
J f! •[ TECHNOLOGY
MAYFIELD HOUSE
CORPORATION 256 BANBURY ROAD
^•Bl SPECIALISTS IN COMPUTER ARCHITECTURE ELSEVIER OXFORD 0X2 7DH
UNITED KINGDOM
ADVANCED
P.O. BOX 24344 · MINNEAPOLIS, MINNESOTA 55424 · [phone]
TECHNOLOGY
© Copyright 1991 Architecture Technology Corporation. All rights reserved. No part of this publication may be reproduced, photocopied, stored on a
retrieval system, or transmitted without the express prior written consent of the publisher.
STARLAN TECHNOLOGY
REPORT
FOURTH EDITION
SEPTEMBER 1991
JE (cid:29) ARCHITECTURE DISTRIBUTED OUTSIDE THE USA/CANADA BY:
ELSEVIER ADVANCED TECHNOLOGY
J f! •[ TECHNOLOGY
MAYFIELD HOUSE
CORPORATION 256 BANBURY ROAD
^•Bl SPECIALISTS IN COMPUTER ARCHITECTURE ELSEVIER OXFORD 0X2 7DH
UNITED KINGDOM
ADVANCED
P.O. BOX 24344 · MINNEAPOLIS, MINNESOTA 55424 · [phone]
TECHNOLOGY
© Copyright 1991 Architecture Technology Corporation. All rights reserved. No part of this publication may be reproduced, photocopied, stored on a
retrieval system, or transmitted without the express prior written consent of the publisher.
DISCLAIMER
Architecture Technology Corporation makes no representations or warranties with respect to the contents
hereof and specifically disclaims any implied warranties of merchantability of fitness for any particular
purpose.
Further, reasonable care has been taken to ensure the accuracy of this report, but errors and omissions
could have occurred. Architecture Technology assumes no responsibility for any incidental or consequen-
tial damages caused thereby.
Further, Architecture Technology Corporation reserves the right to revise this guide and to make changes
from time to time in the content thereof without obligation to notify any person or organization of such
revision or changes.
This disclaimer applies to all parts of this document.
FOREWORD
Originally promoted by AT&T as the answer as a low-cost, twisted pair local area networking solution for
workstations, StarLAN has received wide spread recognition by becoming a standard in the IEEE 802.3
local area network (LAN) specification for 1BASE5. StarLAN has since been enhanced to a 10 Mbps
over twisted-pair draft standard.
The purpose of this report is to provide insight into the technology and operation of StarLAN 1 and 10
Mbps and to detail various vendor offerings of StarLAN products.
By becoming a standard, numerous vendors are designing products that conform to this standard and we
are beginning to see StarLAN develop into a highly competitive market just as Ethernet did. The 10
Mbps version of StarLAN for unshielded twisted-pair, is rekindling interest in the StarLAN technology
and products. StarLAN is fast becoming the standard for CSMA/CD operation over twisted-pair.
The StarLAN Technology Report
List off Figures
Figure 1: Daisy Chain Configuration 5
Figure 2: Room Star Configuration 6
Figure 3: Typical Closet Star Configuration 7
Figure 4: Multiple-Closet Star 8
Figure 5: An Example Manchester Encoding 9
Figure 6: Collision Presence 9
Figure 7: Example 3-Stack Hub 11
Figure 8: StarLAN Topology 13
Figure 9: Maximum Transmission Path with 3 Coax Segments 17
Figure 10: Example of Maximum Transmission Path 18
Figure 11: Example of Maximum Transmission Path 18
Figure 12: 10BASE-T Relationship to OSI and CSMA/CD LAN 19
Figure 13: Twisted-Pair Link 21
Figure 14: MAU MDI Connector 25
Figure 15: Twisted-Pair Link Segment Connector 25
Figure 16: Crossover Function 26
Figure 17: Basic Node 30
Figure 18: Hierarchical Structure 30
Figure 19: Node Detail 33
Figure 20: 82C550A Block Diagram . 42
Figure 21: 82C551A Hub Block Diagram 44
Figure 22: Example 10-NET 47
Figure 23: OfficeShare Network 60
Figure 24: StarLAN 10 Hub 64
Figure 25: Twisted-Pair MAU 66
Figure 26: NetWare TCP/IP Gateway 76
Figure 27: IEEE 802.3-Compatible StarLAN/Ethernet/Cheapernet LAN Chipset 80
Figure 28: DP8390 NIC Configuration 82
Figure 29: NIC Buffer Reception 83
Figure 30: StarLAN Daughter Card Installation for DP839EB 84
Figure 31: LattisNet Network Management Overview 90
Figure 32: A Typical LattisNet Active Hierarchical Star Configuration 93
Figure 33: LattisNet Workgroup Concentrators 93
Figure 34: Western Digital StarLAN Configurations 102
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The StarlAN Technology Report
1. Introduction
The extensive use of personal computers as business tools has placed a PC on almost everyone's desk.
Working in a stand-alone PC environment, however, soon generates a need for linking personal computers
for very basic reasons, such as file sharing, diskless operation, and electronic mail.
Local area networks (LANs) are the ideal solution for enhancing the productivity of multiple PC
workstations in a business environment. In fact, industry analysts forecast that by 1990, nearly 20 million
PCs will be interconnected through LANs. To what extent this holds true depends on several factors:
achieving low-cost networking, ease of design, ease of installation, and achievement of industry standards
to allow inter-connectability of equipment from different vendors.
So-called "traditional" local area networks such as Ethernet and Cheapernet (also called Thin Ethernet)
have gained acceptance by both large and small companies as high-speed LANs. However, because of
cable requirements, they can be relatively expensive to implement. A number of "non-traditional," less
expensive networks are available, but lack a significant market share, for want of major company backing
and backing from standards organizations such as the IEEE, CCITT, or ISO.
The StarLAN network offers many advantages, such as its low equipment cost and ease of installation.
The key advantage of StarLAN is that it can use existing office phone wiring, which means installation is
simple and cost is reduced. It offers the same type of multiple access and data collision avoidance
methods used in more expensive systems, such as Ethernet, and it provides data transfer rates up to ten
million bits per second, using baseband communications techniques.
The StarLAN Network was originally planned as a low-cost alternative to the Ethernet standard. The
network's evolution began as AT&T, Intel, and NCR proposed to the IEEE 802.3 working group to study
a network in the 1- to 2-Mbps range. By spring of 1984, the group agreed to concentrate on star-
configured networks operating at 1 Mbps. In early 1985, AT&T announced its StarLAN network and
demonstrated some of its working hardware. StarLAN became a standard in 1987 as the IEEE 802.3
1BASE5 standard. 10BASE-T is a 10Mbps StarLAN-Type network that became a standard September 28,
1990.
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2.1 Mbps StarLAN
2.1 Definition
The original StarLAN Network is a 1-Mbps local area network for linking workstations, terminals, and
computers. Users can exchange information, transfer files and programs, access databases, and share
system resources such as printers and data storage devices. Vendor support for StarLAN allows MS-DOS
workstations and UNIX System V workstations to communicate and share resources. The system can
effectively link up to 1,200 workstations, but depending on the application, it operates effectively with up
to 20 to 200 active workstations. The distribution medium for the network is standard telephone wiring.
StarLAN conforms to the IEEE 802.3 standard for Carrier Sense Multiple Access with Collision Detection
(CSMA/CD), 1-Mbps local area networking 12BASE5. This draft standard has industry-wide support by
major equipment manufacturers.
The name StarLAN is derived from "star-configured LAN," the network's wiring topology - that is, an
intelligent node in the center with lines radiating outward. User stations on the network contend for the
center node, which in StarLAN terms is called a hub.
The network is expanded by taking one of the radial arms emanating from one hub and connecting it to
another hub. The distance between one hub and another or one station and a hub is 250 meters
(approximately 800 feet). With special links the distance could be extended to 4 kilometers (approximately
13,000 feet or 2.5 miles).
Connection to the StarLAN Network is provided by a Network Access Unit (NAU - all of the "generic"
abbreviations here are actually from AT&T), which connects into an expansion slot of the supported
workstation.
The StarLAN Network provides for different workstation configurations depending on user needs. The
basic configurations are a daisy chain arrangement, the star arrangement, or a combination of the two.
Daisy chain configurations are constructed by interconnecting workstations with modular cords. These
configurations are generally confined to a room or office; ten workstations may be configured within a
span of 400 feet.
A Network Expansion Unit (NEU) allows users to interconnect up to 11 (with the AT&T version) links of
separately daisy-chained and/or individually connected workstations creating a star configuration. With the
use of the NEU, daisy-chained and/or individually connected workstations can be located up to 800 feet
from the NEU. Typically the links are connected to the NEU through a standard telephone wall jack that
connects into the NEU. In addition to this, up to 11 NEUs can be linked together within a telephone
closet.
StarLAN also provides connectivity to offerings such as AT&T's Information System Network (ISN),
through the StarLAN Interface Module. This interface allows the workstations to access host computers,
terminals, other networks, and shared resource networking services such as AT&T's System 75/85. This
module also allows ISN to act as a backbone for multiple AT&T StarLAN Networks.
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2.2 Configurations
A StarLAN Network can be configured for virtually any office layout, as well as rearranged and expanded.
The four StarLAN configurations described in this section are:
1) Daisy Chain
2) Room Star
3) Closet Star
4) Multiple-Closet Star
2.2.1 Daisy Chain
In a daisy chain configuration, a Network Access Unit is installed in each terminal. The OUT jack of one
NAU is linked to the IN jack of another with a modular cord. The OUT jack of the first and the IN jack
of the NAU are left empty.
The daisy chain is considered to be the least expensive configuration because it requires minimal network
hardware. Installation is not difficult, and users can configure the daisy chain themselves. Active daisy
chain workstations can exchange data even when other workstations in the chain are turned off. However,
adding or removing a node disrupts communication until all nodes in the daisy chain are connected.
A daisy chain configuration can support up to ten nodes linked by cords totalling a maximum of 400 feet.
If users are in adjoining rooms, and if building codes permit, the modular cords can be routed through
drop ceilings (plenum ceilings require plenum cords) or through holes drilled in the walls.
The nodes in a daisy chain cannot be connected to each other through a building's phone wiring.
Figure 1 illustrates an example of a daisy chain configuration.
2.2.2 Room Star
In a room star configuration, nodes in a single room are connected to a Network Extension Unit (NEU).
The NEU mounts wherever it's most convenient for routing modular cords, and near an electric outlet to
power the NEU.
Adding a terminal only requires the installation of a Network Access Unit (NAU) into the workstation,
and plugging one end of a modular cord into the OUT jack of the NAU and the other end into an IN jack
on NEU. To add an RS-232-C NAU, one end of a modular cord is plugged into its OUT jack, and the
other into an IN jack on the NEU. To remove the terminal or RS-232-C NAU, either end of the cord is
unplugged. A room star can thus be expanded and rearranged without disrupting the network.
When a room star uses multiple NEUs, one is designated the Master NEU. Multiple NEUs are arranged
hierarchically in two levels: the Master NEU is level 1; the other NEUs are at level 2, and are called
Secondary NEUs. The OUT jack of each Secondary NEU is connected by a modular cord to an IN jack of
the Master NEU. Efficient network operation demands that no more than four NEUs be linked in a room
star. The maximum length of the cords connecting a workstation or server to an NEU is 800 feet.
A room star configuration is suitable for nodes located in a single large office space, and allows for
somewhat easier rearrangement and expansion than a daisy chain. The configuration supports a typical
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The StarLAN Technology Report
4-Pair
Modular Cords
Network
Access-
Unit
Maximum Allowable Cord Length
Is 400 ft. (122 m).
Figure 1: Daisy Chain Configuration
department equipped with 50 to 100 personal computers, approximately 25% of which use the network at
any given time. A room star can support up to 200 terminals using light applications such as printer
sharing and electronic mail.
Up to ten nodes can be linked in a daisy chain to each IN jack on an NEU. The maximum cord length of
such a daisy chain varies from 400 to 800 feet, depending on the number of nodes in the daisy chain.
Figure 2 illustrates an example of a room star configuration.
2.2.3 Closet Star
A closet star connects nodes through the unused pairs in a building's telephone wiring. A single-line
analog telephone can share the wall jack with a Network Access Unit (NAU). This eliminates in offices
uncluttered by extra cords and cables. Each node requires two pairs of wire unused by telephones or other
devices.
A NAU is connected with modular cord to an office phone outlet. At the outlet, the device is wired
through the unused pairs to a Network Extension Unit (NEU) mounted in the wiring closet. More than
one NEU can be used, if needed.
A single-line analog phone displaced from the phone outlet can access the phone pairs through the phone
jack on the NAU. A digital phone or a hybrid analog-and-digital phone displaced from the phone outlet
requires an additional outlet. When a daisy chain is connected to a closet star, only the phone jack on the
first node in the chain (the one plugged into the phone outlet) can be used.
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The StarLAN Technology Report
Figure 2: Room Star Configuration
Installing a closet star first requires first identifying the building's wiring environment, then selecting or
installing at each office wall outlet the adapter or connecting block that accesses the two unused pairs.
Next, the modular cords that connect the nodes to the wall outlets must be selected. Finally, the
appropriate connections must be made in the wiring closet.
A closet star configuration is suitable when users are located in non-adjoining rooms. It also provides
greater security, because the wiring closets can be locked to prevent unauthorized individuals from
unplugging cords from the NEUs.
As an alternative to a daisy chain, NEUs may be installed in rooms, then connected to the wiring closet.
This configuration minimizes the wire pairs utilized in the building wire to connect the nodes from the
room to the wiring closet.
A closet star supports a typical department equipped with 50 to 100 personal computers, approximately
25% of which use the network at any given time. A closet star can support up to 200 computers using
light applications such as printer sharing and electronic mail.
Figure 3 illustrates a typical closet star configuration.
2.2.4 Multiple-Closet Star
In a multiple-closet star, individual closet stars are connected to each other through a building's phone
wiring. A Network Repeater Unit (NRU) installed in a wiring closet amplifies and retimes the signals
coming from the Network Extension Units (NEUs), allowing the signals to travel an additional 800 feet in
cable length between closets.
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