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AE-HO76A-TM

May 1978

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Document:	23.02.00 7809 DECnet-20 V1
Order Number:	AE-HO76A-TM
Revision:
Pages:	4
Original Filename:	http://bitsavers.org/pdf/dec/spd/23.02.00_7809_DECnet-20_V1.pdf

OCR Text

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Software Product Description
PRODUCT NAME: DECnet-20, Version 1.0
DESCRIPTION:
DECnet-20 Version 1.0 allows a suitably configured
DECSYSTEM-20 to participate as a Phase II DEC net
system in point-to-point computer networks. DECnet20 offers task-to-task communications using the
DIGITAL Network Architecture (DNA) protocols. DECnet-20 communicates with adjacent systems over synchronous communications lines. Access to DECnet-20
is made via MACRO-20 system calls.
DECnet-20 is a Phase II network product and is for
use only with Phase II DECnet products supplied by
DIGITAL.
The functionality available to a TOPS-20 user depends, in part, on the configuration of the rest of the
network. Each DECnet product offers its own level of
functionality and its own set of features to the user.
Networks consisting entirely of DECnet-20 systems
have the full functionality described in this SPO. Networks that mix DECnet-20 systems with other DECnet
products may limit the functions available to the DECnet user because some DECnet features are not supported by all DEC net products.
The Phase II products and functions available to
users on mixed networks can be determined by comparison of the SPDs for the component products. An
overview of DECnet and the common functionality
available with mixed networks can be obtained from
the General Phase II OECnet SPD(10.7B).

Task-to- Task Communication
Using DECnet-20, a TOPS-20 user program can exchange messages with other user programs using
Phase II DECnet DNA protocols. The two user programs can be on the same or adjacent DECnet systems. (Adjacent systems control opposite ends of a
point-to-point communication line. The DECSYSTEM2040/2050/2060 with its required communications
front-end processor, is defined as a DECnet system.)
If adjacent systems, the second system can be any
Phase II DEC net system that supports synchronous
communication lines. However, DECnet networks that
include systems other than DECSYSTEM2040/2050/2060, can also include only one DECSYSTEM-2040/2050/2060; e.g., two DECSYSTEM-2050s
may be connected via DECnet; but a DECnet network
containing a DECSYSTEM-2020 or DECnet-11 M, for
example, can also include only one DECSYSTEM2040/2050/2060.

September 1978

SPD 23.2.0
The DECnet messages sent and received by the two
user programs can be in any data format.

Network Control Program
The network control program (NETCON) supports the
logging and displaying of statistics, and loading and
dumping the DN20 communications front-end (applicable on 2040/2050/2060 systems only).
Using the DECnet-20 NETCON utility, an operator can
display DEC net activity at the local node. The user
can display statistics related to communication lines,
including data on traffic and errors. Output can be
directed to the terminal or to a report file.
Other utilities provide controlled local loopback test
arrangements. This enables the user to perform a
logical series of tests that will ~id in isolating communication problems.

Communications
DECnet-20 Version 1.0 supports the DIGITAL Data
Communications Message Protocol (DDCMP) for fullduplex transmission in pOint-to-point operation using
serial synchronous facilities. DDCMP provides error
detection/correction and physical link management
facilities.
DECnet-20 Version 1.0 implemented on a DECSYSTEM-2040/2050/2060 supports one point-to-point
synchronous link. On a DECSYSTEM-2020, two pointto-point synchronous links may be supported with the
proper hardware configuration as noted below. Only
one physical link may connect any pair of nodes.
The synchronous line units interface to Bell System
20BA modems for operation at speeds up to 4.BKB, to
ICC COMLINK II modems for speeds up to 19.2KB,
and to Bell 303 modems (using a C.C.I.T.T V.35
converter), for speeds in excess of 19.2KB. Equivalent
modems may also be used. Note that it is the customer's responsibility to demonstrate the equivalency.

DECnet-20 Operation
DECnet-20 is implemented as an ancillary process
under TOPS-20 with DIGITAL-supplied monitor-level
components and user-level utilities. DECnet-20 is implemented in two forms: For the DECSYSTEM2040/2050/2060, DECnet-20 resides in part in the
central processor and in part in a dedicated communication front-end, the ON20; for the DECSYSTEM2020, DECnet-20 resides entirely in the central processor.

AE-H076A-TM

DECnel-20, Version 1.0

SPD 23.2.0
-2-

DECnet-20 Configuration
The process of configuring a DECnet-20 system is
based primarily on tradeoffs of cost, performance,
and functionality, within the realm of satisfying the
user's application requirements. It can be readily expected that network applications will run the full
gamut from low-speed, low-cost situations to those of
relatively high performance and functionality. The
performance of a given DECnet system is a function
not only of the expected network traffic and resultant
processing ("global" conditions), but also of the
amount of concurrent processing expected on that
system ("local" conditions). Thus, system performance depends on many factors, including:
• CPU power or power of the communications frontend processor
• number of device interrupts per unit time
• communication line characteristics
• number and size of buffers
• message size and frequency
• "local" applications

It is important to note that the rate at which user data
can be transmitted ("throughput") over a communications line may sometimes approach, but will never
equal or exceed, the actual line speed; the same may
be said for multiple lines as well. The reason, simply
stated, is that the actual throughput is a function of
many factors, including the user application(s), network topology, protocol overhead, and the factors cited at the beginning of this section.
There are basically three groups of communications
interfaces presented in the tables below. They differ
in many respects, particularly in their effect upon
CPU utilization. The following tables show'the various
communications devices by category, and maximum
line speed of each.
• With character interrupt devices such as the
DUP11, CPU cycles are required not only for the
DDCMP processing but also for each character
sent and received.
• Devices such as the KMC11 (DUP11) are DMA devices. Since DDCMP is in the system software, CPU
cycles are required for DDCMP line protocol processing. This feature is employed on the DECnet-20
implementation for the DECSYSTEM-2020.
• The DMC11 is a direct memory access (DMA) device. Also the DDCMP line protocol is executed in
microcode by the DMC11 communication controller, off-loading the DN-20 front-end processor.
Thus, the only DEC net load the processor sees is
completed incoming and outgoing messages.
DECNET-20

DEVICE GROUPS
Device Group
Character
Interrupt
DUPll

Maximum Line Speed/Ki1obi ts/Sec
DECSYSTEM 2040/2050/2060

(DN20)

DECSYSTEM 2020

9.6

N/A

19.2

56.0

N/A

DMA
KMCll

(DUPll)

DMCll
DMCll-AL,

-MD

The tables below describe the physical hardware configurations supported by DECnet-20 in terms of CPU
class and communication interface device group.
NOTE
In the tables given below, the rated bandwidth is stated for a single device type. The maximum bandwidth
for an intermix of device types cannot be calculated
from these tables.
DECNET-20
MAXIMUM LINE CONFIGURATIONS ON DECSYSTEM 2040/2050/2060

Device Group
Character
Interrupt

Comm.
Option

Maximum
Device
Bandwidth
(Kilobi ts/Sec)

Mode

DUPll
DMC11-AL, MD

DN20-BA

9.6

FDX

DN21-BA

56.0

FDX

Max. No.
of Lines

DECNET-20
MAXIMUM LINE CONFIGURATIONS ON DECSYSTEM 2020

Device
Group

Comm.
Option

KMCll (DUPll)

DN20-BA
DN20-BB

Max. No.
of Lines

Maximum
Device
Bandwidth
(Kilobi ts/Sec)

Mode

19.2

FDX

In order to achieve a viable configuration, the user
and/or a DIGITAL software specialist must perform a
level of application analysis which addresses the factors above. In the preceding tables, the columns have
the following meanings:
Maximum Number Of Lines
The largest number of physical lines which can be
attached and driven by the DECnet-20 system.
Maximum Device Bandwidth
The maximum total number of bits per second which
can be handled by a system when all communication
devices of a single given type, such as character interrupt, are added together. For example, DECnet-20
on a DECSYSTEM-2020 can accommodate one full
duplex KMC11 (DUP11) operating at 19.2KB or two
lines similarly configured, operating at 9.6KB each.
Maximum device bandwidth should be calculated for
all lines known to operate concurrently.
Maximum Line Speed
The fastest clock rate at which the device can be driven under DECnet-20. This means that even if specific devices have the ability to operate at a maximum
rate, they must be configured subject to the
"maximum device bandwidth" restriction above.
Mode
This indicates whether the line is operating in either
half-duplex (a single-bit stream) or full-duplex (two
concurrent bit streams) mode.

SPD 23.2.0

DECnet-20, Version 1.0

-3-

MINIMUM HARDWARE REQUIRED:
Any valid DECSYSTEM-20 configuration with:
DECS YS TE M-20401205012060
• One DN20-C communications front-end processor
with one of the following:
1. One DN20-BA low speed sychronous interface
2. One DN21-BA high speed synchronous interface
DECSYS TEM-2020
• One DN20-BA low speed synchronous interface

OPTIONAL HARDWARE:
In order to support the optional second line capability
on a DECSYSTEM-2020, one DN20-88 is required.
PREREQUISITE SOFTWARE:
TOPS-20 operating system, Release 3A.
OPTIONAL SOFTWARE:
None
TRAINING CREDITS:
None
SUPPORT CATEGORY:
A - Software Support will be provided as stated in
the Software Support Categories Addendum to this
SPD.
Installation under Category A support will convert the
DECSYSTEM-20 system into a node with connection
potential to a DECnet Phase II network. Network installation is available as Level I Consulting Services.

CUSTOMER RESPONSIBILITIES:
Before installation of the software, the customer must:
1. Install or have installed all hardware, includi'ng
terminals, to be used on the system.
2. Make available to DIGITAL personnel all hardware, including terminals, to be used during installation for a reasonable period of time each
day, as mutually agreed upon by DIGITAL and
the Customer, until installation is complete.
Delays caused by any failure to meet these responsibilities will be charged at the then prevailing rate for
time and materials.

PREREQUISITE SUPPORT:
A Network Profile and DECnet Customer Support
Plan covering all intended network nodes and their
support must be prepared jOintly by DIGITAL and the
customer.
UPDATE POLICY:
Software Updates, if any, released by DIGITAL during
the one (1) year period following installation, will be
provided to the customer without additional charge
(includes no installation). After the first year, updates,
if any, will be made available according to then prevailing DIGITAL policies.

ORDERING INFORMATION:
All binary licensed software, including any subsequent updates, is furnished under the licensing provisions of DIGITAL's Standard Terms and Conditions of
Sale, which provide in part that the software and any
part thereof may be used on only the single CPU on
which the software is first installed, and may be copied, in whole or in part (with the proper inclusion of
the DIGITAL copyright notice and any DIGITAL
proprietary notices on the software) only for use on
such CPU. All source licensed software is furnished
only under the terms and conditions of a separate
Software Program Sources Agreement between Purchaser and DIGITAL.
DECnet-20 is available on 1600 bpi 9-track magnetic
tape only.
Standard Options
For DECSYSTEM 20401205012060
OTD01 AM Single-use license, binaries, documentation, support services
For DECSYSTEM 2020
OTD20 AM Single-use license, binaries, documentation, support services

ADDITIONAL SERVICES:
OJ 680 SZ
DECnet Level I Services. Level II services are also available. Consult the
DECnet Phase II Products SPD (10.78)
for a description of Level I and Level "
services.

SPO 23.2.0

DECnet-20, Version 1.0
-4-

ADDENDUM
SOFTWARE SUPPORT CATEGORIES
Each software product (hereinafter 'SOFTWARE') with a designated Support Category A or B in the applicable Software Product
Description (SPD) existing at the time of order will be the current release at the time of delivery and will conform to the SPD.
DIGITAL's sole obligation shall be to correct defects (nonconformance of the SOFTWARE to the SPD) as described below. Any
SOFTWARE with a designated Support Category C will be furnished on an 'as is' basis.
For SOFTWARE with a designated Support Category A or B, DIGITAL will provide the services set forth below without additional
charge.
CATEGORY A
1. Upon notification by customer to the nearest DIGITAL office that the computer system, including all required prerequisite
hardware and software, is ready for the installation of the SOFTWARE, DIGITAL will install such SOFTWARE in any location
within the contiguous forty-eight (48) United States, the District of Columbia, or a country in which DIGITAL or a subsidiary
of DIGITAL has a software service facility. The notification must be received by DIGITAL and the system must be ready for
installation within thirty (30) days after the delivery of the SOFTWARE to customer or DIGITAL will have no obligation to
install. Installation will consist of: (1) verification that all components of the SOFTWARE have been received by customer, (2)
loading the" SOFTWARE, and (3) executing a DIGITAL sample procedure.
2. During the ni"nety (90) day period after installation, if the customer encounters a problem with the current unaltered release
of the SOFTWARE which DIGITAL determines to be a defect in the SOFTWARE, DIGITAL will provide the following remedial
service (on site where necessary): (1) if the SOFTWARE is inoperable, apply a temporary correction (TC) or make a
reasonable attempt to develop an emergency by-pass, and (2) assist the customer to prepare a Software Performance
Report (SPR) and submit it to DIGITAL.
3. During the one -(1) year period following installation, if the customer encounters a problem with the SOFTWARE which his
diagnosis indicates is caused by a SOFTWARE defect, the customer may submit an SPR to DIGITAL. DIGITAL will respond
to problems reported in SPRs which are caused by defects in the current unaltered release of the SOFTWARE via the
Maintenance Periodical for the SOFTWARE, which reports SPRs received, code corrections, temporary corrections, generally
useful emergency by-passes and/or notice of the-availability of corrected code. Software Updates, if any, released by
DIGITAL during the one (1) year period, will be provided to the customer on DIGITAL's standard distribution media as
specified in the applicable SPD. The customer will be charged only for the media on which such updates are provided,
unless otherwise stated in the applicable SPD, at DIGITAL's then current media prices.
CATEGORY B
During the one (1) year period following delivery, the services provided to the customer will be the same as set forth in 3 above.
CATEGORY C
SOFTWARE is provided on an 'as is' basis. Any software services, if available, will be provided at the then current charges.
DIGITAL shall have the right to make additional charges for any additional effort required to provide services resulting from
customer use of other than current unaltered release of the SOFTWARE operated in accordance with the SPD.