Request for Comments: 1369
Implementation Notes and Experience for
The Internet Ethernet MIB
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited.
Table of Contents
1. Introduction ................................................ 1 2. Observations ................................................ 2 3. Conclusions ................................................. 3 4. Final Action ................................................ 4 5. Implementation Data ......................................... 5 6. Security Considerations ..................................... 7 7. Author's Address ............................................ 7
The Ethernet MIB Working group has been tasked with the following two work items:
- Develop a document explaining the rationale for assigning MANDATORY status to MIB variables which are optional in the relevant IEEE 802.3 specification (the technical basis for the Internet Ethernet MIB). This shall not be a standards-track document.
(2) Develop an implementation report on the Ethernet MIB.
This report shall cover MIB variables which are implemented in both Ethernet interface chips, and in software (i.e., drivers), and discuss the issues pertaining to both. This report shall also summarize field experience with the MIB variables, especially concentrating on those variables which are in dispute. This document shall not be a standards-track document. While the Ethernet MIB is progressing through the standardization process, this document shall be periodically updated to reflect the latest implementation and operational experience.
This document reflects the currently known status of 11 different implementations of the MIB by 7 different vendors on 7 different Ethernet interface chips.
There are some interesting points to be noted from this information:
- Only 4 variables are actually implemented in all implementations: AlignmentErrors, FCSErrors, ExcessiveCollisions and InternalMacTransmitErrors.
- There were another five variables implemented in all but one of the reported implementations, SingleCollisionFrames, MultipleCollisionFrames, LateCollisions, FrameTooLongs, and CarrierSenseErrors.
Three of these variables exist in implementations that use the same chip as the implementation that does not contain the variable. Specifically:
A) SingleCollisionFrames is not implemented in implementation number 3, which uses the AMD LANCE. However, other AMD LANCE implementations (7, 8, and 10) do implement the variable, implying that it is available on the LANCE. B) MultipleCollisionFrames is not implemented in implementation number 3, which uses the AMD LANCE. However, other AMD LANCE implementations (7, 8, and 10) do implement the variable, implying that it is available on the LANCE. C) LateCollisions is not implemented in implementation number 1, which uses the Intel 82586. However, another Intel 82586 based implementation (11) does implement the variable, implying that it is available on the Intel 82586. D) CarrierSenseErrors is not implemented on implementation number 2, which is based on the Fujitsu 86950 chip. However, there is only one implementation based on this chip and I have not been able to locate a data sheet on this part so no conclusion can be drawn at this time. E) FrameTooLongs is not implemented on implementation number 5, which is based on the National NIC 8390 chip. However, there is only one implementation based on this
chip and I have not been able to locate a data sheet on this part. It should also be noted that this variable is easily maintained by software as a "driver-level" function.
(3) Of the 22 variables in the MIB, 11, or 1/2 of the
variables, were implemented in about 1/2 or less of the implementations.
4) The number of variables implemented per implementation ranges from a low of 11 to a high of 16. The average number of variables truly implemented is 12.8. 5) The IEEE 802.3 encapsulation-specific variables (InRangeLengthErrors, and OutOfRangeLengthFields) are in 2 and 0 implementations respectively.
From this, the author concludes that:
The control variables (IntializeMAC, etc.) are not widely implemented, but this may be due to an aversion to implementing writable variables until security is in place.
One vendor has stated that the reason that these variables were not implemented was that the vendor did not believe the variables to be useful, and that they were hard to implement. Furthermore, this vendor has recommended dropping the variables entirely.
The two IEEE 802.3 encapsulation variables (InRangeLengthErrors and OutOfRangeLengthFields) are barely implemented. In Santa Fe, the Working group discussed moving them to an optional, 802.3 specific, group. The author believes that this is justified by this implementation data.
The collision histogram variables are also barely implemented. They should be in their own optional group -- and they are.
Of the remaining 13 statistical variables, 9 of them are in 10 or 11 implementations. This is good.
Two of them (SQETestErrors and ExcessiveDeferrals) are in 3 and 1 implementations, respectively. This is bad.
The remaining variables (DeferredTransmissions and InternalMacReceiveErrors) are in 8 or 9 implementations.
It should be noted that one of the two systems that do not implement DeferredTransmissions is based on the AMD LANCE, and other AMD LANCE based systems do implement this counter, leading to the conclusion that DeferredTransmissions could easily be on all but one of the implementations.
The other such variable, InternalMacReceiveErrors, is a general catchall for all other errors. If no other errors are detected by the hardware or software then returning 0 for the counter is perfectly acceptable.
This all seems to imply either:
- Splitting the statistics group into two groups, one of which is optional and contains SQETestErrors and ExcessiveDeferrals, or
- Eliminating SQETestErrors and ExcessiveDeferrals) from the MIB.
The variables with 8 or 9 implementations are a bit more problematic. They are implemented in more than 2/3s of the implementations, but it may not be appropriate to call this widespread implementation. However, it seems to be safe to conclude that the non-implementations of these variables is due to local implementation considerations rather than a fundamental lack of support for the variable.
4. Final Action
After consideration at the San Diego IETF Meeting on 17 March 1992, the Ethernet MIB Working Group made the following recommendations:
- The dot3TestTdrValue object will be deprecated from the standard mib. There are effectively no implementations of this object, and some chips were reported to return an incorrect value for the TDR count.
- The dot3StatsInRangeLengthErrors object and the dot3StatsOutOfRangeLengthFields object will be deprecated from the MIB. These objects were not widely implemented and their utility in diagnosing network problems was strongly questioned.
- The dot3InitializeMac object, the dot3MacSubLayerStatus object, the dot3MulticastReceiveStatus object, and the dot3TxEnabled object will be deprecated from the MIB. These objects were not widely implemented and their utility in diagnosing network problems was strongly questioned.
- The dot3StatsExcessiveDeferrals object will be deprecated from the MIB. Only one system implemented this object. Furthermore, its exact definition was called into question.
- The dot3StatsSQETestErrors object received few implementations. However, the working group strongly supported its retention in the MIB on the basis that certain forms of transceiver and cable errors that are not uncommon can only be detected with this counter.
- The collision histogram table (dot3CollTable) will be kept as an optional group, even though the objects are not widely implemented nor is there hardware support on all reported chips.
5. Implementation Data
The following raw data has been provided by vendors, each developing an implementation of the Ethernet MIB. Each reported implementation has a separate column in the following table. For each implementation/MIB Variable, a single character code has been entered indicating the rough implementation status of the variable. These codes are:
Y Fully implemented, reports a truthful count, or indication of state. All values may be written to the variable with the expected action occurring. N Not implemented at all. Would return a noSuchName error if accessed. C Implemented but returns a constant value for gets and returns a badValue error for any set attempt to set the variable to a value other than this constant (writable variables only). MIB Implementation Variable 1 2 3 4 5 6 7 8 9 10 11 Yesses InitializeMac C C Y Y Y Y Y C7 C7 N Y 6 MacSubLayerStatus C C Y Y Y Y Y C7 C7 N C 5 MulticastReceiveStatus C C Y C3 Y C C C7 C7 N C 2 TxEnabled C C Y Y Y Y Y C7 C7 N C 5 TestTdrValue C 1 C C4 C C C C4 C4 N C 1 AlignmentErrors Y Y Y Y Y Y Y Y Y Y Y 11 FCSErrors Y Y Y Y Y Y Y Y Y Y Y 11 SingleCollisionFrames Y Y Y N Y Y Y Y Y Y Y 10 MultipleCollisionFrames Y Y Y N Y Y Y Y Y Y Y 10 SQETestErrors Y C C C Y C C C C Y C 3 DeferredTransmissions Y C Y N Y Y Y Y Y Y Y 9 LateCollisions C Y Y Y Y Y Y Y Y Y Y 10 ExcessiveCollisions Y Y Y Y Y Y Y Y Y Y Y 11 InternalMacTransmitErrors Y Y Y Y Y Y Y Y Y Y Y 11 CarrierSenseErrors Y C Y Y Y Y Y Y Y Y Y 10 ExcessiveDeferrals C C Y C C C C C C N C 1 FrameTooLongs Y Y2 Y Y C Y Y Y Y Y Y 10 InRangeLengthErrors C C C N5 C Y Y C C N C 2 OutOfRangeLengthFields C C C C6 C C C C C N C 0 InternalMacReceiveErrors Y Y Y Y Y C C Y Y Y C 8 CollCount Y Y C N N N N C C N Y 3 CollFrequencies Y Y C N N N N C C N Y 3 Yesses 13 11 16 11 15 14 14 11 11 12 13
1 does not implement TDR test, but reports TDR from last collision! 2 Not supported by the chip, detected solely in software. 3 But set to disabled(2) -> badValue 4 Underlying TDR function not implemented on this chip. 5 Only counts frames too short though. 6 Due to Ethernet encapsulation 7 Implementation does not support set operations but reports the correct value for these.
The implementations are:
Implementation Vendor Chip 1 1 Intel 82586 2 1 Fujitsu 86950 3 2 Sonic 4 3 AMD Lance 5 4 National NIC 8390C 6 4 Intel 82596 7 4 AMD Lance 8 5 AMD Lance 9 5 AMD ILACC 10 6 AMD Lance 11 7 Intel 82586
6. Security Considerations
Security issues are not discussed in this memo.
7. Author's Address
Frank J. Kastenholz
2 High Street
North Andover Mass 01845
Phone: 508-685-4000 EMail: email@example.com