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Document:	Fibre Channel Arbitrated Loop Hub User's Guide
Order Number:	EK-DHGGA-UG
Revision:	A01
Pages:	26
Original Filename:

OCR Text

Fibre Channel Arbitrated Loop Hub
(DS-DHGGA-CA)
User’s Guide
EK-DHGGA-UG. A01

Digital Equipment Corporation
Maynard, Massachusetts

First Edition, October 1997
The disclosure of this information does not grant to the user a license under any patents,
pending patents, trademarks, or copyrights or other rights of Digital Equipment
Corporation, or of any third party.
This software is proprietary to and embodies the confidential technology of Digital
Equipment Corporation. Possession, use or copying of the software described in this
publication is authorized only pursuant to a valid written license from Digital
Equipment Corporation or an authorized sublicensor.
Digital Equipment Corporation makes no representation that the use of its products in
the manner described in this publication will not infringe on existing or future patent
rights, nor do the descriptions contained in this publication imply the granting of
licenses to make, use, or sell equipment or software in accordance with the description.

The following are trademarks of Digital Equipment Corporation:
DEC
DIGITAL
StorageWorks
DIGITAL UNIX
and the DIGITAL logo.
UNIX is a registered trademark in the United Sates and other countries, licensed
exclusively through X/Opin company, Ltd.
The following are third party trademarks: Windows 95 and Windows NT are registered
trademarks of Microsoft Corporation. Intel is a registered trademark of Intel
Corporation. PostScript and Acrobat Reader are registered trademarks of the Adobe
Corporation.
© Digital Equipment Corporation 1997
Printed in U. S. A

Contents
Revision Record ............................................................................................. vii
About This Guide ........................................................................................... ix
1

Introduction
1.1

Functional Description
2.1
2.2
2.3
2.4
2.5
2.6

General Description.......................................................................................... 2–1
Operation ......................................................................................................... 2–1
Hub Port Functionality ..................................................................................... 2–2
Data Detection Tests ........................................................................................ 2–2
Time_In and Time_Out Periods........................................................................ 2–3
Fault Indicators ................................................................................................ 2–4

Configuration
3.1

Fibre Channel Technology................................................................................ 1–1

Port Order ........................................................................................................ 3–1

Installation and Cabling
4.1
4.2
4.3
4.4
4.5

Mounting ......................................................................................................... 4–1
Cabling ............................................................................................................ 4–1
Connector Definition........................................................................................ 4–1
Twinax Cables.................................................................................................. 4–1
Power............................................................................................................... 4–2

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User’s Guide – Fibre Channel Hub (EK–DHGGA–CA)

Appendix A
A.1
A.2
A.3
A.4

FCC Statement .................................................................................................A–1
Industry Canada Compliance Statement ...........................................................A–1
Safety Information ...........................................................................................A–2
CE Mark ..........................................................................................................A–2

Appendix B
B.1
B.2
B.3
B.4
B.5

Notices

Specifications

Mechanical.......................................................................................................B–1
Electrical..........................................................................................................B–2
Power...............................................................................................................B–3
Environmental..................................................................................................B–4
Agency Approvals............................................................................................B–5

Figures
3–1
B–1

Fibre Channel Arbitrated Loop Hub Internal Port Order ................................... 3–1
Mechanical Dimensions ...................................................................................B–2

EK–DHGGA–UG. A01

Revision Record
This Revision Record provides a concise publication history of this manual. It lists the
manual revision levels, release dates, and reasons for the revisions. It also describes
how the changes to affected pages are marked in the manual.

The following revision history lists all revisions of this publication and their
effective dates. The publication part number is included in the Revision Level
column, with the last entry denoting the latest revision.

Revision Level

Date

Summary of Changes

EK–DHGGA–UG. A01

October 1997

Original release.

EK–DHGGA–UG. A01

About This Guide
This section identifies the audience of this guide and describes the contents (chapter by
chapter) and structure. In addition, this section includes a list of associated documents
and the conventions used in this guide.

Visit our Web Site for the Latest Information
Check out the Web for the latest drivers, technical tips, and documentation.
We can be found in the technical area of our web page,
http://www.storage.digital.com/
This guide provides the following:
•
•
•
•

An overview of fibre channel technology
A functional description of fibre channel technology
Configuration information
Installation and cabling information

Intended Audience
This guide is intended for administrators of StorageWorks fibre channel
technology. It requires an overall understanding of fibre channel concepts.

Document Structure
This guide contains the following major sections:

Chapter 1: Introduction
This chapter contains information on fibre channel technology.

Chapter 2: Functional Description
This chapter describes the functionality of the Fibre Channel Arbitrated Loop
hub.

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vii

Fibre Channel Arbitrated Loop Hub User’s Guide

Chapter 3: Configuration
This chapter describes how to configure the Fibre Channel Arbitrated Loop
hub.

Chapter 4: Installation and Cabling
This chapter contains instructions for installing and cabling the Fibre Channel
Arbitrated Loop hub.

Appendix A: Notices
This appendix contains notices that are pertinent to the operation of the Fibre
Channel Arbitrated Loop hub.

Appendix B: Specifications
This appendix provides hardware specifications for the hub.

Associated Documents
For further information on the fibre channel technology, please refer to the
documents you received at the initial purchase of your system.

Conventions
This guide uses the following documentation conventions:

Table 2 Style Conventions

viii

Style

Meaning

boldface monospace type

To be input by the user.

italic type

For emphasis, manual titles, utilities, menus,
screens, filenames, variable values,
placeholders, and function argument
names.

plain monospace type

Screen text.

Represents the DIGITAL UNIX system
superuser prompt.

{name}

Braces represent items that are required.

EK–DHGGA–UG. A01

About This Guide

Support and Services
Who to contact in the Americas
Information and Product Questions:

Local Sales Office / StorageWorks Hotline
1-800-786-7967

Installation Support:

Contact the DIGITAL Distributor where the
Storage Solution was Purchased / Local
Digital Sales Office.

DIGITAL Multivendor Customer Service (MCS)
Installation

Contact the DIGITAL Customer Support
Center (CSC).

Warranty

Contact the DIGITAL Customer Support
Center (CSC) for warranty service after
solution is installed and operating.

Remedial

Contact the DIGITAL Customer Support
Center (CSC)
Note: A Service Contract is recommended
when the equipment is out of warranty.
Contact the local DIGITAL Sales Office.

Customer Support Center (CSC)

1 800-354-9000

Who to contact in Europe
Information and Product Questions,
Installation Support, and Installation:

Contact the DIGITAL Distributor or reseller
from whom the Storage Solution was
purchased.

For Warranty Service

See the Warranty Card packaged with the
product.

For Remedial Service

Contact the DIGITAL Distributor or reseller
from whom the Storage Solution was
purchased.
Note: A Service Contract is recommended
when the equipment is out of warranty.

Who to contact in Asia Pacific
For all services, contact the DIGITAL Distributor or reseller from whom the
equipment was purchased.

EK–DHGGA–UG. A01

1
Introduction
This chapter contains descriptive information on fibre channel technology.

1.1

Fibre Channel Technology
Fibre Channel is a serial, medium-to-high performance external interface that is
unaware of the content or meaning of transferred information. Fibre Channel
increases both the potential connectivity of devices and the usable distance
between devices.
The Fibre Channel Arbitrated Loop hub operates by collapsing the physical loop
into a logical star. Intelligent port by-pass functions manage movement of nodes
on and off the fibre channel arbitrated loop. Data availability is then preserved
by preventing the downtime associated with node failures, cable disconnections,
and network reconfigurations.
The Fibre Channel hub operates within an area address of 126 devices which
handle initialization, discovery, and addressing. Its gigabit infrastructure,
coupled with native storage (SCSI) attachment, makes the fibre channel
arbitrated loop hub the ideal solution for data intensive applications.

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1–1

2
Functional Description
This chapter describes the functionality of the Fibre Channel Arbitrated Loop active hub.

2.1

General Description
The Fibre Channel Arbitrated Loop is an active hub. It has intelligent, per-port
data detection check capabilities for automatic port bypass control. The hub is
configured to have nine default copper ports, each of which is supplied with
power to support the Fibre Channel Media Interface Adapters (MIA) for
electrical to optical conversion.

2.2

Operation
The hub operates without any user intervention. It continually monitors the serial
data and automatically configures a fibre channel arbitrated loop (FC-AL) based
on its intelligent bypass control logic. To operate in plug-and-play mode, valid
FC-AL nodes with ANSI-compliant cables are added.
The hub is transparent to the protocol. It does not consume any fibre channel
arbitrated loop addresses and so is not addressable by a FC-AL port. Because of
the intelligent signal detection tests, only valid fibre channel devices can be
connected to a loop when using the hub. If a fibre channel arbitrated node
transmits invalid fibre channel data, the node is taken off the loop. Examples of
node behaviors, which result in a bypass state are invalid characters, absence of
frames, and invalid signal amplitude.

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Fibre Channel Arbitrated Loop Hub (DS–DHGGA–CA) User’s Guide

2.3

Hub Port Functionality
2.3.1 Active Repeaters
The hub is "active" in that it re-drives the input signal to full amplitude and retimes the input signal with its recovered clock to attenuate jitter. Every port
implements active repeaters at each incoming node. Re-timed serial data
simplifies physical cabling management by allowing users to use any kind of
fibre channel compliant cables. Without re-driving and re-timing, the serial data
is degraded by the cable. For copper cables, the principal cause of signal
degradation is attenuation and intersymbol interference.
For fiber optic cables, the electrical-to-optical and optical-to-electrical
conversion induces jitter as well as model noise of the optical cable itself.
Without repeaters, users must keep track of total end-to-end cable distances. As
an active hub, it contains repeater PLLs (Phase Lock Loops) at every hub port.
These PLLs work only at the 1.0625 Gbit/sec fibre channel data rate. The fibre
channel arbitrated loop does not operate with multiple data speeds. Only active
ports re-time the serial data. Unused ports are not re-timed. Only in cascading
hubs would there be more than one repeater between two NL_Ports.

2.4

Data Detection Tests
The hub employs intelligent data detection checks to provide high availability for
an operating FC-AL loop. These checks minimize loop disruption due to
catastrophic node failures, node expansion, and incorrect node insertion.
The hub deploys look-aside data detection check circuits. The look-aside scheme
minimizes data latency through the hub. Three different data detection checks
(DDC) are used as listed below:

2–2

•

DDC 1: Checks for the absence of valid characters

•

DDC 2: Checks for the presence of oscillation.

•

DDC 3: Checks for crosstalk

EK–DHGGA–UG. A01

Chapter 2. Functional Description

DDC1 tests for the presence of invalid 8B/10B characters. 8B/10B code’s run
length is limited to no more than five consecutive runs of “1’s” or “0’s.” Any
data that exceeds the 8B/10B maximum run length of five is considered to be an
invalid 8B/10B character. This test will prevent the insertion of test sequences,
invalid bit rates (quarter or half speed), or any other non-fibre channel data
sequences onto an operating loop.
DDC2 checks for the presence of oscillation above 100 MHZ. Oscillation at such
a frequency can often cause an invalid DDC1 because 8B/10B is the only valid
data at this level. High frequency devices can often break into oscillation when
not properly driven. This can occur on open cables or when the host transmitter’s
outputs are shut off. DDC2 also ensures the reception of valid fibre channel
frames as it is checking for the presence of control characters that must occur
within a valid time window.
DDC3 checks for crosstalk in order not to falsely insert an unconnected node.
Fibre channel receivers use sensitive input receivers to provide design margins
resulting in low bit error rates even in the presence of large eye closure. High
sensitivity receivers can mistake crosstalk for valid fibre channel data. DDC3
tests for a valid input level to ensure proper bit error rate link performance. The
crosstalk test is a look-aside test, so it does not actually degrade input receiver
sensitivity. The link bit error rate is not affected.
All three data detection checks are performed continuously and simultaneously.
From field testing, it is found that only the simultaneous performance of all three
data detection tests can reliably prevent false loop operation.

2.5

Time_In and Time_Out Periods
One of the key design parameters for a hub design is in setting the hub’s “port
bypass sensitivity.” Port bypass sensitivity is the amount of time that passes
before a hub port removes a failed port or adds a new port. High port bypass
sensitivity results in bouncy performance and too low port bypass sensitivity
causes loop re-initialization.
The hub implements asymmetric port bypass sensitivity. It uses different
Time_In periods from its Time_Out periods. The Time_Out period is the period
of time used by the hub to decide whether a node is non-operational. The
Time_In period is the amount of time used by the hub to decide whether to add a
node onto a loop.
The goal for setting the test periods is to make it easier for a port to be taken off
the loop than for a port to be allowed onto a loop. This built-in hysteresis
prevents any peculiar modes that can cause fault propagation.

EK–DHGGA–UG. A01

2–3

Fibre Channel Arbitrated Loop Hub (DS–DHGGA–CA) User’s Guide

The hub must sense an error in four consecutive 50msec periods prior to
bypassing a port. Requiring four consecutive errors in 50msec periods ensures
that a port is not bypassed due merely to normal link noise. Maximum loop
frame disruption is 200msec.
The Time_In period is 100msec. This means that the hub must sense error-free
transmission for 100msec prior to allowing a port onto an operating loop. During
this interval, the hub PLL repeater locks onto the new port and then onto
incoming serial data within 2msec. This provides for overall error-free operation.

2.6

Fault Indicators
All LED indicators are on the front panel.
Amber LED’s per port are provided for link status indicators. If the amber LED
is off, the port is active and participating on an active fibre channel loop. If the
amber LED indicator is on, the port is bypassed and not participating on a fibre
channel loop.
A single green LED indicator is provided to indicate that the power is on.

2–4

EK–DHGGA–UG. A01

3
Configuration
This Chapter describes how to configure the fibre channel arbitrated loop hub.

3.1

Port Order
A hub collapses the physical loop within itself. In the hub, the loop operates from
left to right. Figure 3-1 shows the internal port order of a fibre channel arbitrated
loop hub.
Figure 3-1: DS-DHGGA-CA Internal Port Order

EK–DHGGA–UG. A01

3–1

4
Installation and Cabling
This chapter contains instructions for installing and cabling the fibre channel arbitrated
loop hub.

4.1

Mounting
The hub is designed for desktop usage.

4.2

Cabling
The hub accepts cabling options for distances up to 10 m.
NOTE
For further cabling and routing information, refer to
your solution-specific Getting Started manual.

4.3

Connector Definition
The hub uses the ANSI FC-PH standard DB-9 pinout connector with an
additional power pin to support an external module for electrical to optical
conversion. The DS-DHGGA-CA uses female DB-9 receptacles with Pin 4
keyed to prevent misplugging. The DB-9 type connector is the same as the
standard RS232 serial port connector on a computer.

4.4

Twinax Cables
Twinax cables are shielded twisted-pair cables that are electrically enhanced for
optimal gigabit data transmission. Electrical enhancement refers to the low skew
control required by ANSI on the differential pair conductors to minimize eye
closure and RFI emissions. The cables are ANSI-compliant and include four (4)
conductor cable assemblies. These assemblies are terminated with DB-9 male
plugs to provide for differential, duplex-data communication.
NOTE
For further cabling and routing information, refer to
your solution-specific Getting Started manual.

EK–DHGGA–UG. A01

4–1

Fibre Channel Arbitrated Loop Hub (DS–DHGGA–CA) User’s Guide

4.5

Power
The power cord must be connected to a nearby electrical outlet that is easily
accessible. Ensure that the appropriate power plug is available for the
installation area. The hub has an IEC 320 power connector on the back. A power
cable with the IEC 320 plug on one end and a suitable local power plug on the
other end must be used. If the power cable has the wrong connection for your
area, contact your sales or service representative.
There is no power switch on the hub. The hub should be the first operating
component in bringing up a fibre channel arbitrated loop system. Once the hub
is up and indicates it is ready (i.e., the green power LED is on), users can power
up the FC-AL nodes on the loop.

4–2

EK–DHGGA–UG. A01

A
Notices
This appendix contains notices that are pertinent to operation of the fibre channel
arbitrated loop hub.

A.1 FCC STATEMENT
NOTE: This equipment has been tested and found to comply with the limits for a
Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are
designed to provide reasonable protection against harmful interference in a
residential installation. This equipment generates, uses, and radiates radio
frequency energy and, if not installed and used in accordance with the
instructions, may cause harmful interference to radio communications. However,
there is no guarantee that interference will not occur in a particular installation.
If this equipment does cause harmful interference to radio or television reception,
(which can be determined by turning the equipment off and on), the user is
encouraged to try to correct the interference by implementing one or more of the
following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment into an outlet on a circuit different from that
• to which the receiver is connected.
• Consult the dealer or an experienced radio TV technician for help. Shielded
cables must be used with this unit to ensure compliance with the Class A FCC
limits.

A.2 INDUSTRY CANADA COMPLIANCE STATEMENT
This digital apparatus does not exceed the Class A limits for radio noise
emissions from digital apparatus set out in the Radio Interference Regulations of
the Canadian Department of Communications.
Le présent appareil numérique n’emet pas de bruits radioéléctriques dépassant
les limites applicables aux appareils numériques de la class A préscrites dans le
Règlement sur le brouillage radioéléctrique édicté par le ministère des
Communications du Canada.

EK–DHGGA–UG

A–1

Fibre Channel Arbitrated Loop Hub (DS–DHGGA–CA) User’s Guide

A.3 SAFETY INFORMATION
For PLUGGABLE EQUIPMENT, the socket-outlet shall be installed near the
equipment and shall be easily accessible. There are no field serviceable
components to this product. All service must be performed by the factory.
Opening the product voids the warranty.

A.4 CE MARK
This product was tested and found to be in compliance with the applicable
requirements of the following standards, enabling attachment of the CE mark to
the product label:

A–2

•

EN60950: Product Safety

•

EN50082-1:1992, Immunity Testing

•

EN55022:1994 (Class A), Emissions Testing

DS–DHGGA–CA

B
Specifications
This appendix provides hardware specifications for the fibre channel arbitrated loop hub.

B.1

Mechanical
Chassis Height .................... 43 mm (1.7 in)
Chassis Width ..................... 221 mm (8.7 in)
Chassis Depth ..................... 145 mm (5.7 in)
Chassis Weight.................... 3 lbs Net 93.3 lbs Shipping0
Figure B–1 Mechanical Dimensions

EK–DHGGA–UG. A01

B–1

Fibre Channel Arbitrated Loop Hub (DS–DHGGA–CA) User’s Guide

B.2

Electrical
Bit rate ............................... 1.0625 Gigabit per second
Standards/Profiles .............. ANSI X3T11 PH
Connector .......................... DB-9
Port LED............................. 1 Amber LED per port
Power LED ........................ 1 Green LED
Bypass Control ................... Automatic, Intelligent

B.3

Power
AC Voltage......................... 100 - 240 VAC autosensing
Power ................................. 2A, 50 - 60Hz
Power Consumption ........... 100VA

B.4

Environmental
Operating Temperature ....... 0 o C to +40 o C
Storage Temperature ........... -40 o C to +70 o C
Operating Humidity ............ 95% max relative humidity

B.5

Agency Approvals
EMI ................................... FCC Part 15 Class A (EN55022B), (EN50082-1)
Safety ................................. UL 1950, CSA 950, EN60950 (IEC950), CE Mark

B–2

EK–DHGGA–UG. A01

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