Digital Equipment
Corporation (DEC) developed the DECnet protocol to allow high-speed
communication between DEC minicomputers across local and wide area
networks. The DECnet suite includes the following protocols:
- RP - Routing
Protocol.
- MOP - Maintenance
Operation Protocol.
- NSP - Network
Service Protocol.
- SCP - Session
Control Protocol.
- DAP - Data Access
Protocol.
- CTERM - Command
Terminal.
- LAT - Local Area
Transport.
- STP - Spanning Tree
Protocol.
- LAVC - Local Area
VAX Cluster.
The following diagram
illustrates the DECnet protocol suite in relation to the OSI
model:
DECnet
protocol suite in relation to the OSI model
RP
The
Routing Protocol (RP) distributes routing information among DECnet
hosts. It defines routing classes into two levels: level 1, which
handles routing within a single DECnet routing area; and level 2,
which handles routing between areas.
Frames
RP frames can be one of
the following types:
| [Level 1 hello]
|
Routing update
from a level 1 router. |
| [Level 2 hello]
|
Routing update
from a level 2 router. |
| [Endnode hello]
|
Routing update
from an endnode. |
| [L1 router msg]
|
Routing status for
a local area. |
| [L2 router msg]
|
Routing status for
other areas. |
| [routed data]
|
Segment of user
data. |
Frame
Parameter
All RP frames have the
following parameter:
Node
address
Node address. The
DECnet area and node given in the decimal dot form: Area.Node (where
Area can extend from 1-63 and Node can extend from
1-1023).
Hello
Parameters
Hello frames have the
following parameters:
Routing
priority
Routing priority on a
scale of 100 (not used for [endnode hello] frames).
Hello
period
Period between routing
update hello messages.
Version
The version in use.
Multicast
status
Y indicates that this
protocol supports multicast traffic on the link; N indicates it does
not support multicast traffic.
Maximum
Maximum frame size supported on the link (1500 for
Ethernet).
Router
Parameters
RP router frames have
the following parameters:
Source
node
The ID of the sending
node.
Number of
IDs
Number of IDs contained in
the routing table for this level 1 routing message.
Number of
areas
Number of areas
contained in the routing table for this level 2
message.
Data
Parameters
RP [routed data] frames
have the following parameters:
Request
return
When set to 1, sender
is requesting that the other party return the frame. When set to 0,
sender is suggesting that the other party discard the frame.
Return
path
When set to 1, frame is
on return path; when set to 0, frame is on outbound path.
Intra-Ethernet
When set to 1, frame is from a directly connected
Ethernet segment; when set to 0, the system forwarded the frame from
another segment.
Version
Must be 0.
MOP
The Maintenance
Operation Protocol (MOP) is used for utility services such as
uploading and downloading system software, remote testing and
problem diagnosis.
Frames
MOP frames can be one
of the following commands:
| [memory load data]
|
Contains memory
load data. |
| [mem load request]
|
Request fort
memory load segment. |
| [mem load w/addr]
|
Memory load with
transfer address. |
| [par load w/addr]
|
Parameter load
with transfer address. |
| [dump service req]
|
Request for
assistance with dump operation. |
| [mem dump request]
|
Request for next
memory dump segment. |
| [memory dump data]
|
Contains memory
dump data. |
| [dump completed]
|
Acknowledgment of
dump completion. |
| [volunteer assist]
|
Offer of
dump/load/loop assistance. |
| [request program]
|
Request for system
or loader program. |
| [rem boot request]
|
Request for boot
program. |
| [remote ID reqst]
|
Request for remote
console identification. |
| [remote system ID]
|
Remote console
identification information. |
| [counters request]
|
Request for
communication information counters. |
| [counters reply]
|
Communication
information counters. |
| [reserve console]
|
Remote console in
reserved state. |
| [release console]
|
Release of remote
console from reserved state. |
| [rem console poll]
|
Poll of remote
console for status. |
| [rem console rply]
|
Response to remote
console poll. |
| [loopback request]
|
Request to
loopback enclosed data. |
| [loopback reply]
|
Response to
loopback request with data. |
Memory Dump and Memory
Load Frames
MOP memory dump and
memory load frames use the following parameters:
Load
number
Data segment sequence
number of the current memory data segment.
Load
address
Memory load address
for storage of the memory data.
Transfer
address
Starting memory
address of the current segment.
Memory
address
Starting physical
memory address for the dump.
Count
Number of memory locations to dump.
Version
Protocol format version, currently 1.
Memory
size
Size of physical machine
memory.
Bits
Generally set to 2 for compatibility reasons.
Buffer
size
Local buffer size in
bytes.
Communication
device
Device type of the
requesting system. The following device codes can be
used:
| Code
|
Device
|
| DP |
DP11-DA
|
| UNA |
DEUNA
|
| DU |
DU11-DA
|
| CNA |
DECNA
|
| DL |
DL11-C/E/WA
|
| QNA |
DEQNA
|
| DQ |
DQ11-DA
|
| CI |
Comp. Intercon.
|
| DA |
DA11-B/AL
|
| PCL |
PCL11-B
|
| DUP |
DUP11-DA
|
| DMC |
DMC11-DA/FA/MA/MD
|
| DN |
DN11-BA/AA
|
| DLV |
DLV11-E/F/J
|
| DMP |
DMP11
|
| DTE |
DTE20 (PDP11-KL10)
|
| DV |
DV11-AA/BA
|
| DZ |
DZ11-A/B/C/D
|
| KDP |
KMC11/DUP11-DA
|
| KDZ |
KMC11/DZ11-A/B/C/D
|
| KL |
KL8-J
|
| DMV |
DMV11
|
| DPV |
DPV11
|
| DMF |
DMF-32
|
| DMR |
DMR11-AA/AB/AC/AE
|
| KMY |
KMS11-PX (X.25)
|
| KMX |
KMS11-BD/BE (X.25)
|
Parameter Load
Frames
MOP parameter load
frames have the following fields:
Load
number
The data segment
sequence number of the current data segment.
Target
name
ASCII system name for
target system.
Target
address
Hex address of target
system.
Host system
name
ASCII system name of
host.
Host system
address
Hex address of host
system.
Host system
time
Current time for host
system.
Request Program
Frames
MOP [request program]
frames have the following fields:
Communication
device
Refer to the values
given for dump/load frames above.
Version
Version currently in use.
Type
Type of program that the system requested:
| Secondary |
A secondary loader
program. |
| Tertiary |
A tertiary loader
program. |
| System |
An operating
system program. |
Software
ID
Software type that the
system requested:
| Standard O/S
|
Standard operating
system software |
| Maint
system |
Maintenance system
software. |
Processor
System
processor type:
| PDP-11 |
PDP-11
system. |
| Comm Srv |
Communications
server. |
| Profess |
Professional. |
Boot Request
Frames
Boot request frames have the following
fields:
Verification
number
A verification code that must match before
this protocol can honor a boot request.
Boot server
Boot
system device type:
| Req |
Requesting
system. |
| Def |
Default boot
server. |
| <device>
|
Specified
device. |
Software ID
The software type as
given for the [request program] frame above.
Remote Console Frames
MOP remote
console frames have the following fields:
Receipt
number
Used to identify a particular
request.
Command
status
Console command data status
given as OK if received, or Lost if not received.
NSP
The Network Services
Protocol (NSP) provides reliable virtual connection services with
flow control to the network layer Routing Protocol (RP).
Frames
NSP frames can be one
of the following commands:
| [data segment]
|
Carries higher
level data. |
| [interrupt]
|
Carries urgent
data. |
| [data request]
|
Carries data flow
control information. |
| [interrupt rq]
|
Carries interrupt
flow control information. |
| [data ackn]
|
Acknowledges
receipt of data. |
| [control ackn]
|
Acknowledges
receipt of interrupt messages. |
| [connect ackn]
|
Acknowledges a
[connect init] frame. |
| [connect init]
|
Requests a logical
link connection. |
| [connect ackn]
|
Acknowledges a
link connection. |
| [discnct init]
|
Requests
disconnection of a link. |
| [discnct ackn]
|
Acknowledges
disconnection of a link. |
| [no operation]
|
No operation
performed. |
Parameters
NSP frames can contain
the following fields:
Destination link
address
Destination port of
the link.
Source link
address
Source port of the
logical link.
Acknowledge
number
The segment number of
the last message received successfully or, if followed by {NAK}, the
segment number of the message for which the system requests a
retransmission.
Acknowledge
other
Same as acknowledge
number, but used to acknowledge other data.
Segment
number
Number of the current
data frame.
Flow
control
Can indicate the
following services:
| Seg_reqst |
Data segment
request count. |
| SCP_reqst |
Session control
protocol request count. |
Flow control
information
The data segment messages can
include flow control messages ({send} or {stop}) to indicate the
desired action of the receiving system.
BOM/EOM
Beginning of message/end of
message. Indicates the start or end of a data segment message.
SCP
The Session Control
Protocol (SCP) manages logical links for DECnet
connections.
Frames
SCP frames can be one
of the following commands:
| [connect data]
|
Transfers
connection parameters. |
| [disconnect]
|
Supplies
disconnect status information. |
| [reject data]
|
Supplies reject
status information. |
Connect Data
Parameters
SCP [connect data]
frames contain the destination name (Dest) and source name (Src)
parameters that can consist of the following fields:
Object
type
One of the following
object types:
| Type
|
Description |
| (User Process)
|
General task or
end user process. |
| (Files-DAP 1)
|
File access
through DAP version 1. |
| (Unit Record)
|
Unit record
service. |
| (App. TrmSrv)
|
Application
terminal services. |
| (Cmd. TrmSrv)
|
Command terminal
services. |
| (RSX-11M TC1)
|
RSX-11M task
control, version 1. |
| (Op Services)
|
Operator services
interface. |
| (Node Manage)
|
Node resource
manager. |
| (3270-BSC GW)
|
IBM 3270 BSC
gateway. |
| (2780-BSC GW)
|
IBM 2780 BSC
gateway. |
| (3790-SDLC)
|
IBM 3790 SDLC
gateway. |
| (TPS Applic.)
|
TPS application.
|
| (RT-11 DIBOL)
|
RT-11 DIBOL
application. |
| (TOPS-20 T H)
|
TOPS-20 terminal
handler. |
| (TOPS-20 R S)
|
TOPS-20 remote
spooler. |
| (RSX-11M TC2)
|
RSX-11X task
control, version 2. |
| (TLK Utility)
|
TLK utility.
|
| (Files-DAP4+)
|
File access
through DAP, version 4+. |
| (RSX-11S RTL)
|
RSX-11S remote
task Loader. |
| (NICE Proc.)
|
NICE processor.
|
| (RSTS/E MTP)
|
RSTS/E media
transfer program. |
| (RSTS/E HCTH)
|
RSTS/E homogeneous
command terminal handler. |
| (Mail Listen)
|
Mail listener.
|
| (Host TrmHnd)
|
Host terminal
handler. |
| (Con. TrmHnd)
|
Concentrator
terminal handler. |
| (Loop Mirror)
|
Loopback mirror
service. |
| (Event Rcvr)
|
Event receiver.
|
| (VAX/VMS PMU)
|
VAX/VMS personal
message utility. |
| (FTS Service)
|
FTS service.
|
Group
Group code identifier.
User
User code identifier.
Descriptor
A user-defined string of data.
Version
The SCP version, as in {SCP 1.0}.
Requestor
ID
User name for access
verification.
Password
Password for user verification.
Account
Link or service account data.
User data
End user connect
data.
Disconnect/Reject
Parameters
The decoding for SCP
[disconnect] and [reject data] frames lists the reason for
disconnection, as follows:
| {No error}
|
Normal disconnect
with no error. |
| {Shutting down}
|
Source node is
deactivating. |
| {Unknown user}
|
Destination end
user is unknown. |
| {Invalid username}
|
Destination end
user invalid. |
| {Dest. overloaded}
|
Destination out of
link resources. |
| {Unknown error}
|
Unspecified error.
|
| {Link aborted}
|
Link aborted by
third party. |
| {User aborted}
|
Link aborted by
end user. |
| {Host overloaded}
|
Source is out of
link resources. |
| {Bad ID/password}
|
Invalid ID or
password. |
| {Bad account info}
|
Invalid account
data. |
| {Data too long}
|
Connect data
parameters too long. |
DAP
The
Data Access Protocol (DAP) provides remote file access to systems
supporting the DECnet architecture.
Frames
DAP frames can be one
of the following commands:
| [configuration]
|
Exchanges
information about file systems and supported protocols.
|
| [file attribs]
|
Provides file
attributes. |
| [open file]
|
Opens the
specified file. |
| [create file]
|
Creates the
specified file. |
| [rename file]
|
Renames the
specified file. |
| [delete file]
|
Deletes the
specified file. |
| [list dir]
|
Lists the
specified directory. |
| [submit file]
|
Submits the
specified batch file. |
| [execute file]
|
Executes the
specified command file. |
| [control info]
|
Provides control
information about the file system. |
| [continue]
|
Continues I/O
operation after error. |
| [acknowledge]
|
Acknowledges open
file and control information commands. |
| [close file]
|
Closes file or
ends data stream. |
| [data message]
|
Carries file I/O
data. |
| [status]
|
Returns status and
error information. |
| [file index]
|
Specifies keys for
file indexing. |
| [allocate]
|
Creates or extends
a file. |
| [summary info]
|
Returns summary
information about a file. |
| [timestamp]
|
Specifies time for
time-stamped fields. |
| [protect mode]
|
Specifies file
protection mode. |
| [file name]
|
Renames files or
lists directories. |
| [access rights]
|
Specifies file
access rights. |
Frame
Parameters
DAP commands can
contain the following parameters:
Allocation
size
The number of blocks
allocated to a file.
Attribute
File attribute represented as follows:
| Seqnt |
Sequential access
supported. |
| Relatv |
Relative access
supported. |
| Index |
Indexed access
supported. |
| Hashed |
Hashed format.
|
Bit
count
Indicates the number of
unused bits in the last byte of the data message.
Bits per
byte
Number of bits in each
byte.
Block
size
Physical media block size
in bytes.
Bucket
size
Bucket size used to
access relative, hashed and indexed files.
Checksum
The 16-bit file checksum.
Data
type
Type of file
data:
| ASCII |
Standard 7-bit
ASCII characters. |
| Image |
Binary data.
|
| EBCDIC |
EBCDIC encoded
data. |
| Compr |
Compressed data
format. |
| Exec |
Executable code.
|
| Privil |
Privileged code.
|
| Senstv |
Sensitive data,
purge after delete. |
Device
type
Code which indicates the
type of device that DAP associates with the file.
File access
mode
The open mode for file
access which is specified as one of the following:
| Put |
Put (write) access
allowed. |
| Get |
Get (read) access
allowed. |
| Del |
Delete access
allowed. |
| Upd |
Update access
allowed. |
| Trn |
Truncate access
allowed. |
| BIO |
Block I/O access
allowed. |
| BRO |
Block and Record
I/O switching allowed. |
| FAO |
File Access
Options. The file access options code.
|
FilSys
File system, represented as one of the
following:
RMS-11
FCS-11
TOPS-20 |
RMS-20
RT-11
TOPS-10 |
RMS-32
None
OS-8 |
Maximum buffer
size
The maximum buffer size
the sending system can receive.
Operating system
type
Operating system type can
be of the following:
RT-11
RSX-11M
VAX/VMS
RTS-8
COPOS/11
|
RSTS/E
RSX-11D
TOPS-20
OS-8 |
RSX-11S
IAS
TOPS-10
RSX-11M+
|
Password
Password required for file access.
Record
attributes
Record attributes
code.
Record
format
Represented as
follows:
| Undef |
Undefined record
format. |
| FixLen |
Fixed-length
records. |
| VarLen |
Variable-length
records. |
| Var/FC |
Variable-length
records with fixed control format. |
| ASCII |
ASCII stream
format. |
Record
size
File record size in
bytes.
Record
number
The record used when
accessing file data.
Shared access
mode
The open mode for sharing
file access, specified as follows:
| Put |
Put (write) access
allowed. |
| Get |
Get (read) access
allowed. |
| Del |
Delete access
allowed. |
| Upd |
Update access
allowed. |
| MSE |
Multi-stream
access enabled. |
| UPI |
User-provided
interlocking allowed. |
| Nil |
No shared use
allowed. |
Stream
ID
The ID code used to
multiplex data streams on one file.
System
capabilities
System
capabilities code.
System specific
information
Information
specific to homogeneous systems.
Ver
Version. The DAP version number, the DAP software version
number, followed by the user modification number in
parenthesis.
Continue
Parameters
DAP [continue] frames
indicate the recovery action as one of the
following:
| {try again}
|
Repeat the
attempted operation. |
| {skip it}
|
Skip the attempted
operation and continue. |
| {abort transfer}
|
Abort the I/O
transfer. |
| {resume}
|
Restart the data
stream if suspended. |
Status
Parameters
DAP [status] frames can
report the following status information:
| {pending}
|
Operation in
progress. |
| {OK} |
Operation
successful. |
| {bad request}
|
Specified
operation unsupported. |
| {open error}
|
Error occurred
while opening file. |
| {I/O error}
|
Error occurred
while transferring data. |
| {I/O warning}
|
Non-fatal I/O
error occurred. |
| {close error}
|
Error occurred
while closing file. |
| {bad format}
|
Message format
invalid. |
| {sync error}
|
Message received
out of synchronization. |
CTERM
The Command Terminal
(CTERM) protocol is the terminal emulation protocol of the Digital
Network Architecture. CTERM uses DECnet to provide a command
terminal connection between DEC terminals and DEC operating systems
such as VMS and RSTS/E.
Frames
CTERM frames can be one
of the following commands:
| [initiate]
|
Initiates the
command terminal connection. |
| [start read]
|
Requests a read
from the terminal server. |
| [read data]
|
Transfers terminal
data to the host. |
| [out-of-band]
|
Conveys an
out-of-band character received by the server. |
| [abort read]
|
Requests that the
current terminal data read be aborted. |
| [clear input]
|
Requests that the
input and type-ahead buffers be cleared. |
| [write data]
|
Transfers terminal
write data and control information. |
| [write status]
|
Transfers terminal
write status. |
| [discard stat]
|
Signals whether to
discard terminal output. |
| [read config]
|
Requests the
current terminal characteristics. |
| [config data]
|
Transfers terminal
configuration data. |
| [check input]
|
Requests the
current input character count. |
| [input count]
|
Indicates the
number of input characters to be read. |
| [input state]
|
Indicates the
presence of new input characters.
|
CTERM
Parameters
The following are
possible CTERM parameters:
Buffer
size
Size of the terminal
character input buffer.
Character
count
Number of characters in
the input buffer.
End
Ending character position. Current position of the last
character displayed.
EOP
End of prompt. Character position of the first character
after the prompt.
Horizontal
position
Current horizontal
position of the displayed output.
Horizontal position
change
Horizontal position
change. Horizontal position change since the last read.
Low water
mark
Position of the last
character not modified.
Maximum receive
size
Length of the input
character buffer.
Maximum
transmit
Maximum transmit
buffer size.
Character
Out-of-band character. The out-of-band character
received.
Postfix
Postfix new line count. New line postfix count for the
current write.
Prefix
Prefix new line count. New line prefix count for the
current write.
Software
revision
Software revision
currently in use.
Start of
display
Position of the first
character to display.
Termination
Termination set bitmask. The 256-bit termination set for
the read.
Time
out
Amount time in seconds
before a read request aborts.
Version
Protocol version currently in use.
Vertical
position
Current vertical
position of the displayed output.
Vertical position
change
Change in vertical
position since the last read.
Messages
For certain CTERM
frames various messages can be displayed as detailed
below:
[input state] frames
display the current input status as
{more characters} or {no
more characters}.
[write status] frames
can display the write status as
{some output lost} or {no output
lost}.
[discard stat] frames
can display the discard status as
{discard} or {no discard}.
[abort read] frames
display the abort request as
{unconditional} or {if no more
input}.
[out-of-band] frames
can contain the disposition of the data as [discard].
LAT
The Local Area
Transport (LAT) protocol is designed to handle multiplexed terminal
traffic to/from timesharing hosts.
STP
The Spanning Tree
Protocol (STP) prevents the formation of logical looping in the
network. It is implemented by the 802.1d MAC Bridge Management
Protocol, to provide information on bridge topology.
LAVC
The Local Area VAX
Cluster (LAVC) protocol communicates between DEC VAX computers in a
cluster.
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