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name
Simple name assigned to the station when it is created.
address filters
All individual MAC addresses currently enabled by any of the ports on the station.communication port
DECnet-Plus device name for the station.hardware address
Individual medium access control (MAC) address that was assigned during manufacture of the communications hardware that is associated with the station.mac address
Current MAC address (if any) of the station. For more information about the MAC address, refer to the enable command.receive mode
Current receive mode for the station. Some stations may not support all modes.
normal The station receives only those frames (individual and multicast) that meet the normal format, protocol, and access control requirements. all multicast The station receives all individual-addressed frames that meet the normal format, protocol, and address requirements, and all multicast-addressed frames regardless of their format, protocol, and address types. This function is only supported on OpenVMS. promiscuous The station receives all frames (individual and multicast) regardless of format, Ethernet protocol type, SNAP identifier, LLC SAP address, or MAC address. This function is only supported on OpenVMS. state
Operational state of the station.
failed Either an attempt to enable the station failed during the self-test or the station was on and the data link determined that the station would now fail the self-test. initializing The station is currently being initialized and tested by the data link. off The station is disabled. on The station is enabled and available for use. For more information on station states, refer to the appropriate network management guide.
uid
Entity's unique identifier, which is generated when the station is created.
alignment error
This event is generated whenever an incoming frame does not contain an integral number of octets. This error can be caused by several conditions, such as electromagnetic interference, late collisions, or improperly set hardware parameters (for example, receiver squelch).carrier check failure
This event is generated on a transmission that failed, either because the data link did not sense the receive carrier signal that must accompany transmission of a frame, or because the data link did not detect an error. This error indicates a failure in either the transmitting or receiving hardware, such as the transceiver or transceiver cable.data overrun
This event is generated whenever an incoming frame is lost because of a hardware resource failure such as insufficient hardware buffers or insufficient CPU time.excessive collision
This event is generated whenever a transmission fails because the medium access algorithm reached the maximum number of allowable retransmission attempts resulting from collisions. This error can occur when too many systems are trying to transmit at the same time or when there are cable problems.frame check error
This event is generated whenever an incoming frame fails the frame check sequence (FCS) test. This error can be caused by several conditions, such as electromagnetic interference, late collisions, or improperly set hardware parameters (for example, receiver squelch).frame too long
This event is generated whenever a remote system sends a frame that exceeds the CSMA-CD MAC maximum length.late collision
This event is generated whenever a transmission fails because a collision was detected after the allowed window for collisions had elapsed. This error indicates either a problem with another system's carrier sense or a weak local transmitter.receive data length error
This event is generated whenever a remote system sends an 802.3 frame having a length field value that is not valid for the number of octets actually received by the MAC.unavailable station buffer
This event is generated whenever an incoming frame is discarded because there is no station buffer available to receive it. This error indicates a lack of local station buffers; that is, a lack of buffers between the cable and the user buffers.unavailable user buffer
This event is generated whenever an incoming frame is discarded because there is no user buffer queued to the appropriate port to receive it. This error indicates a lack of buffers in the user process; that is, the buffers supplied by the user for the Receive function.unrecognized individual destination pdu
This event is generated whenever an incoming frame that matches an enabled individual MAC address is discarded because the frame does not satisfy the filter criteria of any port. This error indicates that a remote system is using a protocol that is locally unsupported or that the local system has not enabled a protocol type, protocol identifier, or LLC SAP address that it should have.unrecognized multicast destination pdu
This event is generated whenever an incoming frame that matches an enabled multicast MAC address is discarded because the frame does not satisfy the filter criteria of any port. This error indicates that the local system has not enabled an Ethernet protocol type, SNAP identifier, or LLC SAP address that it should have, or that a remote system is sending traffic that is invalid for the combination of multicast and the currently specified protocol type, SNAP identifier, or LLC SAP.
For create:
already exists
A csma-cd station entity already exists.communication port in use
Failure to create the csma-cd station entity because the communications port is already reserved by another entity.invalid communications port
Failure to create the csma-cd station entity because you cannot run CSMA-CD data link on this communications port.For delete:
station in use (Digital UNIX)
Attempt to delete the csma-cd station entity failed because there is at least one active port still associated with this station. You must wait until the ports go away to delete this station.wrong state
Failure to delete the csma-cd station because the station must be disabled before deletion.
This chapter describes all the commands you can use to manage the entities that constitute the Digital Data Communications Message Protocol (DDCMP) module. The DDCMP module is a data link control procedure that ensures a reliable data communication path between communication devices connected by data links. DDCMP has been designed to operate over full- and half-duplex synchronous and asynchronous channels in both point-to-point and multipoint modes. It can be used in a variety of applications such as distributed computer networking, host/front-end processing, remote terminal concentration, and remote job entry-exit system operation.
Figure 5-1 shows the hierarchical relationship of the entities that constitute the DDCMP module.
Figure 5-1 Hierarchy of DDCMP Module Entities
The ddcmp entity is the top-level entity in the hierarchy of
entities belonging to the DDCMP module.
create [node node-id] ddcmp
delete [node node-id] ddcmp
show [node node-id] ddcmp [all [attributes] |
all characteristics]
dna version
Version number of the DDCMP architecture specification to which the implementation conforms. You cannot modify this characteristic.
For create:
already exists
A DDCMP entity already exists.
protocol protocol-type
Protocol mode used by the local station.
point The local station is one end of a point-to-point link. This is the default and only supported value. tributary The local station acts as a tributary of a multipoint link.
dead timer
Specifies the delay, in milliseconds, between polls of one of the set of dead tributaries. This attribute is supported only if the characteristic protocol is set to control.
Default: 10000 Value: 1--65535 delay timer
Specifies the minimum delay, in milliseconds, between polls. You can use this timer to limit the effect of a fast control station on slower tributaries. A value of 0 means that no delay is added. This attribute is supported only if the characteristic protocol is set to control.
Default: 0 Value: 0--65535 physical line
Name of the Physical layer entity over which the link operates. A value for this characteristic must be set before the link entity is enabled. You can modify this characteristic only when the entity is disabled.
Default: No name Value: Local-entity-name protocol
Protocol mode used by the local station. You cannot modify this characteristic.
Default: Point Value: See description The value of this characteristic is a copy of the protocol argument specified when the ddcmp link entity is created. The default value is point and is the only permissible value.
receive buffers
Number of receive buffers reserved for the link. You can modify this characteristic only when the entity is disabled. Also, you can only increase the characteristic value.
Default: 4 Value: 1--255 retransmit timer
Maximum time, in milliseconds, to wait between sending a message and receiving a valid response. If this time expires, the local station takes error recovery action. On full-duplex point-to-point links, the timer is started immediately when a message is sent.
Default: 3000 Value: 1--65535 scheduling timer
Time, in milliseconds, between the recalculation of tributary polling priorities. This attribute is supported only if the characteristic protocol is set to control.
Default: 200 Value: 50--65535 stream timer
Time, in milliseconds, for which a tributary or the remote station (on a half-duplex, point-to-point link) can hold the line. This characteristic is not supported if the characteristic protocol is set to tributary.
Default: 6000 Value: 0--65535
creation time
Time at which this entity was created.naks received indicating message header format error
Number of NAK messages received that report errors in message headers sent from the local station.naks received indicating receive overrun
Number of NAK messages received that report a receive overrun at the remote station.pdus received with message header format error
Number of times the local station detected an error in a message header.receive overruns
Number of times the local station detected a receive overrun.selection address errors
Number of times the controller of a multipoint link received a message with an address other than that of the currently selected station. This counter is supported only if the characteristic protocol is set to control.streaming tributaries
Number of times the remote station (or a tributary station) exceeded the maximum transmission interval without releasing the line, or failed to release the line after sending a message with the select flag set. This counter is present only on half-duplex, point-to-point links, or when the local station is a controller of a multipoint link. This counter is not supported if the protocol characteristic is set to tributary.transmit underruns
Number of times the local station detected a transmit underrun.
name
Simple name assigned to the link when it is created.
physical port
Name of the port entity in the Physical layer returned when the port is opened. If this is null, the port is not open.state
State of the DDCMP link. The value of this attribute is determined by the enable and disable commands.
off The entity is disabled. on The entity is enabled. In addition, the link is disabled and its state is set to off if the Physical layer port that the link uses is deleted.
uid
Entity's unique identifier, which is generated when the entity is created.
pdu received with header format error
Generated each time the local station detects invalid fields in a received message, even though the message's CRC was correct. The errors that can generate this event are:
- Invalid select flag
- Invalid addr value
- fill fields not zero
- Invalid control type or subtype fields
Arguments:
address Address of the remote station that caused the event. message header Message header that contains the error. selection address error
Generated each time the controller of a multipoint link receives a message that contains an address other than that of the currently selected tributary. This event is supported only on half-duplex, point-to-point links, or if the protocol characteristic is set to tributary.Arguments:
current address Address of the currently selected tributary station. previous address Address of the previously selected tributary station. received address Address contained in the received message. streaming tributary
Records potential jamming of a line by a remote station. It is generated:
- When a remote station exceeds a maximum transmission interval without releasing the channel.
- When a remote station fails to release a channel after sending a message with the select flag set.
- When the jamming condition is cleared.
Arguments:
previous address Address of the previously selected tributary station. received address Address contained in the message received after transmission should have ended. This argument is not present if no message is received. type Type of jamming that the local station detected, or indicates that jamming has now cleared. continued transmission after deselection The remote station continued to send information after it sent a message with the select flag set. continued transmission after timeout The remote station continued to send information after exceeding the maximum transmission interval. streaming cleared A previous streaming tributary error has been cleared. streaming tributary The remote station continued to send valid control messages or headers to data message after exceeding the maximum transmission interval.
For create:
already exists
A ddcmp link entity already exists.For delete:
cannot delete while subentities exist
Cannot delete while subentities exist.wrong state
Failure to delete the ddcmp link entity because the link must be disabled before deletion.For enable:
device constraint
The value of an attribute is not supported by the type of device used on the communications line. Modify the attribute to a suitable value, and retry the operation.open physical port failed
The opening of the port in the Physical layer failed. The exception includes an argument that gives more information about the failure.
active base
Base priority to which an active tributary is reset after it has been polled.
Default: 255 Value: 0--255 This characteristic is supported only if the characteristic protocol of the owning ddcmp link entity is set to control.
active increment
Value to be added to the active tributary priority each time the scheduling timer expires.
Default: 0 Value: 0--255 This characteristic is supported only if the characteristic protocol of the owning ddcmp link entity is set to control.
address
Data link address of the remote station or tributary. You can modify this characteristic only when the entity is disabled.
Default: 1 Value: 1--255 babble timer
Time, in milliseconds, for which a selected tributary or remote station is allowed to transmit. This characteristic is not used on full-duplex links.
Default: 6000 Value: 1--65535 This characteristic is not supported if the characteristic protocol of the owning ddcmp link entity is set to tributary.
buffer source
Source of the receive buffers.
Default: Implementation-specific Value: See description
client supplied Buffers are provided by the client entity. common pool Buffers are assigned from the common buffer pool. This characteristic is supported only if the characteristic protocol of the owning ddcmp link entity is set to control. You can modify this characteristic only when the entity is disabled.
dead threshold
Number of times an active, inactive, or dying tributary is polled before its status attribute polling substate is changed to dead because of receive timeouts.
Default: 8 Value: 0--255 This characteristic is supported only if the characteristic protocol of the owning ddcmp link entity is set to control.
dying base
Base priority to which a dying tributary is reset after being polled.
Default: 0 Value: 0--255 This characteristic is supported only if the characteristic protocol of the owning ddcmp link entity is set to control.
dying increment
Value to be added to a dying tributary's priority each time the scheduling timer expires.
Default: 16 Value: 0--255
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NCL_PROFILE_004.HTML OSSG Documentation 2-DEC-1996 12:47:41.99Copyright © Digital Equipment Corporation 1996. All Rights Reserved.