Shadow MIB Implementations

This appendix describes the implementation guidelines for monitoring FDDI, WAN, and ATM traffic.

SwitchProbe devices are designed to interoperate with network management applications. Although there is no RMON standard for FDDI, WAN and ATM, Cisco Systems has extended the standard for these topologies, making these extensions usable and exercisable by many third-party applications.

Implementing the FDDI Shadow MIB

Table A-1 describes implementation guidelines for monitoring FDDI traffic using RMON RFC 1757. The SwitchProbe agent uses the Ethernet MIB without modification, except for UnderSize, Oversize, Collisions, Fragments, and Jabbers, which are modified slightly for FDDI-specific conditions.

Table A-1: Ethernet and FDDI MIB Comparison

Ethernet MIB Variable	FDDI MIB Variable	Explanation
Undersize	<64	Packets less than 64 bytes in length
Oversize	>1518	Packets greater than 1518 bytes in length
Collisions	TokenPkts	Number of Token Ring packets
Fragments	SMTPkts	Number of SMT packets
Jabbers	—	Reserved

Unlike Ethernet, FDDI is based on a ring topology similar to Token Ring. To implement the FDDI Ring Monitor application, Token Ring RMON MIB (RFC 1513) groups are used as follows:

The Token Ring Station group is used with some modifications, as shown in Table A-2. Some MIB variables are not used, as indicated in Table A-3. The remaining MIB variables are used without modification.
The Token Ring Station Order group is used without modification.
The remaining groups in the Token Ring MIB extensions are not used.

Table A-2: Ring Station Group—Modified Variables

Token Ring MIB Variable Name	FDDI MIB Variable Name	Modification
ringStationDuplicateAddresses	Node Class	Indicates FDDI node type: 0—Station 1—Concentrator
ringStationInLineErrors	MAC Count	Counts MACs within the node.
ringStationOutLineErrors	Non-Master Count	Indicates number of Non-Master ports in a concentrator- type FDDI node. Valid only if Node Class is 1 (Concentrator).
ringStationInBurstErrors	StationState	Bit-encoded variable to indicate state of FDDI node. The following bits are used: Bit 0=1—Station state is Wrap. Bit 1=1—Station state is Attached- Concentrator. Valid only if Node Class is 1. Bit 2=1—Station state is Twisted-ring AA. Bit 3=1—Station state is Twisted-ring BB. Bit 4=1—Station state is Rooted-Station. Note Bit 0 is the least-significant bit.
ringStationInternalErrors	Master Count	Indicates number of Master ports in a concentrator-type FDDI node. Valid only if Node Class is 1 (Concentrator).
ringStationOutBurstErrors	DuplicateAddressTest	Status of Duplicate Address test the FDDI node SMT performs. 0—Node passed the Duplicate Address test. 1 or 2—Node failed the Duplicate Address test.

Table A-3: Ring Station Group—Unused Variables

MIB Variable Name	Change
ringStationACEErrors	Unused
ringStationLostFrameErrors	Unused
ringStationCongestionErrors	Unused
ringStationFrameCopiedErrors	Unused
ringStationFrequencyErrors	Unused
ringStationTokenErrors	Unused
ringStationInBeaconErrors	Unused
ringStationTokenOutBeaconErrors	Unused

Implementing the WAN Shadow MIB

Table A-4 describes implementation guidelines for monitoring WAN traffic using RMON RFC 1757. The SwitchProbe agent uses the Ethernet MIB with some modifications to account for WAN-specific conditions.

Table A-4: Ethernet and WAN MIB Comparison

Ethernet MIB Variable	WAN MIB Variable	Explanation
CRCAlignErrors	CRCErrors	Name change only.
UnderSize	LessThan64	Name change only.
OverSize	GreaterThan1518	Name change only.
Jabbers	Aborts	Sent by DTE or DCE; the number of abort sequences seen.
Fragments	Discards	Number of frames sent to the Frame Relay switch with the discard eligibility (DE) bit set.
Collisions	Congestions	Number of Frame Relay frames that have FECN or BECN bits set. Always 0 for other WAN connections.

The agent converts all WAN traffic to Ethernet traffic before processing, and supports multiple WAN encapsulation techniques, including those of the most often-used routers.

The conversion process works the following way:

1. The WAN header and trailer are removed.

2. When the MAC header is missing, it is rebuilt using the DTE address of 0x7ee1000000 and DCE address of 0x7ee2000000 (pseudo-MAC header).

3. The inOctets counter and the Utilization calculations use actual frame size, including the WAN header and trailer.

: The following formula calculates utilization, given the octets and link_speed in bits per second:

utilization = ((octets*8 per second)/link_speed)*100

4. In Protocol Decode displays, the adjusted frame size is displayed. This is the size of the Ethernet frame, formed after the WAN header and trailer are removed.

: In the Protocol Decode summary mode, a right arrow (->) indicates a packet transmitted from DTE to DCE. A left arrow (<-) indicates a packet transmitted from DCE to DTE.

Implementing the ATM Shadow MIB

The ATM SwitchProbe device assembles ATM cells into AAL5 protocol data units (PDUs). The device converts these PDUs into Ethernet-format frames to allow implementation of existing Remote Monitoring (RMON and RMON2) functionality. ATM-specific physical layer statistics (such as Cells, CallAttempts, and Calls) are mapped to certain etherStats objects in the Ethernet Statistics Group of the Ethernet RMON MIB (Table A-5). The resulting MIB is a "shadow" of the Ethernet RMON MIB.

Table A-5: ATM Statistics Information Mapped to Ethernet RMON MIB

ATM MIB Variable	Explanation	Mapped to (etherStats Object of Ethernet Statistics Group in Ethernet RMON MIB)
Cells	Total number of error-free cells detected.	etherStatusUndersizePkts
CallAttempts	Number of call attempts detected on all signaled ATM connections.	etherStatsJabbers
Calls	Number of successfully established calls detected on all signaled ATM connections.	etherStatsFragments
F5OAMCells	Number of F5OAM (operations and maintenance) cells.	etherStatsOversizePkts
CRCErrors	Cyclic redundancy check errors. The sum of AAL5 PDUs detected with CRC32 errors plus non-AAL5 cells detected with CRC10 errors.	etherStatsCRCAlignErrors
CLPCount	Number of AAL5 PDUs detected with CLP¹ bit set to 1.	etherStatsCollisions

¹CLP = Cell loss priority.

Table of Contents

Shadow MIB Implementations

Implementing the FDDI Shadow MIB

Implementing the WAN Shadow MIB

Implementing the ATM Shadow MIB