Document revision date: 28 June 1999
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DECnet-Plus
Network Control Language Reference


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4.3 csma-cd station

A csma-cd station entity manages a CSMA-CD controller. Wherever Phase IV DECnet manages a line, DECnet-Plus manages a station. Each station corresponds to a particular logical link control (LLC), medium access control (MAC), and physical attachment. The station-name refers to the station managed by this command.
create [node node-id] csma-cd station station-name communication port port-id
delete [node node-id] csma-cd station station-name
disable [node node-id] csma-cd station station-name
enable [node node-id] csma-cd station station-name mac address address
set [node node-id] csma-cd station station-name station buffers integer (OpenVMS)
show [node node-id] csma-cd station station-name [all [attributes] | all characteristics | all counters | all identifiers | all status]

4.3.1 Arguments

communication port

The system device name assigned to this station.

The name must be in the format ddn, where dd is the DIGITAL UNIX device name prefix and n is the device number.<>

The name must be in the format ddc, where dd is the OpenVMS device name prefix and c is the controller letter.<>
Device Type DIGITAL UNIX OpenVMS
DEBNA   et
DEBNI   et
DELQA   xq
DELUA   xe
DEMNA xna ex
DESVA   es
DEUNA   xe
DE422 ln er
KFE-32   ef
LANCE ln  
PMAD ln ec
SGEC   ez
TGEC te  
TULIP   ew

mac address

Individual medium access control (MAC) address for the station. If you do not specify a MAC address, the network uses the address specified in the first EnableMacAddress user interface call directed to this station.

4.3.2 Characteristic Attributes

station buffers

Default: 4 Value: 1--64
Number of receive buffers reserved for the station. You cannot modify this characteristic.

4.3.3 Counter Attributes

Unless stated otherwise, counts include both normal and multicast traffic and all protocol types, service access points (SAPs), and protocol identifiers.

alignment errors

Number of times a received frame did not contain an integral number of octets.

carrier check failures

Number of times the data link did not sense the receive carrier signal or detected an error in the receive carrier signal during transmission of a frame.

collision detect check failures

Number of times the collision detect test signal was not sensed after a transmission. If this count approximates the number of frames sent, either the collision detect circuitry is not working correctly or the test signal is not implemented.

creation time

Time at which the station was created.

data overruns

Number of times the hardware lost one or more consecutive, partially complete, incoming frames because it could not keep up with the incoming frame rate. Used in conjunction with pdus received, this count provides a measure of hardware resource and bandwidth failures.

excessive collisions

Number of times a transmission failed because the maximum allowable number of retransmission attempts all culminated in collisions.

frame check errors

Number of times a received frame containing an integral number of octets failed the frame check sequence (FCS).

frame size errors

Number of times the user requested transmission of a frame outside the range of valid frame sizes.

frames too long

Number of times a received frame exceeded the maximum length allowed by CSMA-CD medium access control.

initially deferred pdus sent

Number of times a PDU was deferred by the station access algorithm on the first attempt at transmission, but was then transmitted successfully without collision. Used in conjunction with pdus sent, this count measures the rate of CSMA-CD contention with no collisions.

late collisions

Number of times a collision was detected after the allotted time for collisions had expired.

multicast octets received

Number of multicast data octets that were received successfully. The count is the number of octets in the CSMA-CD user data field and does not include MAC headers. Comparing this count to the octets received count yields the gross percentage of bandwidth that was consumed (over time) by multicast frames received by the local system.

multicast octets sent

Number of multicast data octets that were sent successfully. The count is the number of octets in the MAC user data field, including any padding or length fields; it does not include MAC headers. Comparing this count to the octets sent count yields the gross percentage of bandwidth that was consumed (over time) by multicast frames transmitted by the local system.

multicast pdus received

Number of multicast PDUs that were received successfully. Comparing this count to the pdus received count yields a gross percentage of CSMA-CD usage for multicast PDUs received by this system.

multicast pdus sent

Number of multicast PDUs that were sent successfully. Comparing this count to the pdus sent count yields a gross percentage of CSMA-CD usage for multicast PDUs sent by this system.

multiple collisions pdus sent

Number of times a PDU was transmitted successfully on the third or later attempt by the station access algorithm after normal collisions on previous attempts. Used in conjunction with pdus sent, this count provides a measure of CSMA-CD media contention at a level where there are collisions and the backoff algorithm no longer works efficiently.

octets received

Total number of MAC user data octets that were received successfully from frames that passed address and protocol filtering for both individual and multicast MAC addresses. The count is the number of octets in the CSMA-CD user data field plus any padding, Ethernet length fields, or LLC header fields; it does not include MAC headers. Adding the octets received count to the protocol overhead calculated from the pdus received count yields the amount of CSMA-CD bandwidth consumed by frames received by the local system.

octets sent

Total number of user data octets that were sent successfully. The count is the number of octets in the MAC user data field including any padding or length fields; it does not include MAC headers. Adding the octets sent count to the protocol overhead calculated from the pdus sent count yields the amount of CSMA-CD bandwidth consumed (over time) by frames sent by the local system.

pdus received

Total number of PDUs that passed address and protocol filtering and were received without errors. The count provides a gross measurement of incoming CSMA-CD usage by the local system; this information can be used with other counters to approximate the average receive frame size or to determine the ratio of errors to successful receives.

pdus sent

Total number of PDUs successfully sent. The count provides a gross measurement of outgoing CSMA-CD usage by the local system; this information can be used with other counters to approximate the average transmit frame size or to determine the ratio of errors to successful transmissions.

receive data length errors

Number of times a frame was received with a length field value that was invalid for the number of octets actually received by medium access control.

send data length errors

Number of times the user requested transmission of an 802.3 frame with a length field value that was not valid for the number of octets actually passed.

single collision pdus sent

Number of times a PDU was successfully transmitted on the second attempt by the station access algorithm after a normal collision occurred on the first attempt. Used in conjunction with pdus sent, this count provides a measure of CSMA-CD media contention at a level where there are collisions, but the backoff algorithm still works efficiently.

station failures

Number of times the station self-testing procedures reported failure.

unavailable station buffers

Number of times a complete, fully received PDU was discarded because no station buffer was available. Used with pdus received, this count provides a measure of receive problems related to the station buffer.

unavailable user buffers

Number of times no user buffer was available for an incoming frame that passed all filtering for the port. Used with the pdus received count, this counter can indicate the rate of user buffer receive problems.

unrecognized individual destination pdus

Number of times a received PDU with an individual destination MAC address was discarded because there was no port with the correct Ethernet protocol type, SNAP protocol identifier, or link logical control SAP address enabled.

unrecognized multicast destination pdus

Number of times a received PDU with a multicast destination MAC address was discarded because there was no port with the correct Ethernet protocol type, SNAP protocol identifier, or link logical control SAP address enabled.

4.3.4 Identifier Attributes

name

Simple name assigned to the station when it is created.

4.3.5 Status Attributes

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.

4.3.6 Event Messages

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.

4.3.7 Exception Messages

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.


Chapter 5
DDCMP Module (OpenVMS)

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


5.1 ddcmp

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]

5.1.1 Characteristic Attributes

dna version

Version number of the DDCMP architecture specification to which the implementation conforms. You cannot modify this characteristic.

5.1.2 Exception Messages

For create:

already exists

A DDCMP entity already exists.

5.2 ddcmp link

The ddcmp link entity defines the attributes of a link to a communications port that uses DDCMP. The link-name refers to the link managed by this command.
create [node node-id] ddcmp link link-name protocol protocol-type
delete [node node-id] ddcmp link link-name
disable [node node-id] ddcmp link link-name
enable [node node-id] ddcmp link link-name
set [node node-id] ddcmp link link-name {dead timer integer | delay timer integer | physical line local-entity-name | receive buffers integer | retransmit timer integer | scheduling timer integer | stream timer integer}
show [node node-id] ddcmp link link-name [all [attributes] | all characteristics | all counters | all identifiers | all status]

5.2.1 Arguments

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.

5.2.2 Characteristic Attributes

dead timer

Default: 10000 Value: 1--65535
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.

delay timer

Default: 0 Value: 0--65535
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.

physical line

Default: No name Value: Local-entity-name
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.

protocol

Default: Point Value: See description
Protocol mode used by the local station. You cannot modify this characteristic.

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

Default: 4 Value: 1--255
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.

retransmit timer

Default: 3000 Value: 1--65535
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.

scheduling timer

Default: 200 Value: 50--65535
Time, in milliseconds, between the recalculation of tributary polling priorities. This attribute is supported only if the characteristic protocol is set to control.

stream timer

Default: 6000 Value: 0--65535
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.


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