Table 28-1 on page 783 illustrates the basic format of a MAD. The first six dwords (24 bytes) are referred to as the base-MAD header and is the same for all MADs. The fields of the base MAD header are defined in Table 28-2 on page 783.
Only used in directed-route SMP (see Table 28-6 on page 789)
2
Transaction ID
3
4
AttributeID
Reserved
5
AttributeModifier
6–63
Data field. Contents is defined by the type of MAD.
Table 28-2. Definition of Base MAD Header Fields
Field
Length (in bits)
Description
Base Version
8
Version of base MAD format. Must be one (01h).
Management Class
8
Indicates the management class of the message. Possible values are listed in Table 28-3 on page 785.
Class Version
8
Version of MAD class-specific format. Must be 01h (except for Vendor class which may be 01h or greater).
R
1
Response bit. It's only set in the response packet returned in response to a request packet.
Method
7
Indicates the action to be performed on the indicated attribute. The Methods that are common to most (but not necessarily all) classes are listed in Table 28-4 on page 786.
Status
16
The Status field has no meaning in a request MAD. In a response MAD, it indicates the completion status of a previously issued request MAD. The status values common to all classes are listed in Table 27-2 on page 776.
Class-Specific
16
This field is only used in a directed-route SMP (where it contains the Hop Count and Hop Pointer variables). For more information, see “Discovery” on page 871.
TransactionID
64
The contents of the TransactionID (TID) field are implementation-dependent. When initiating a new management operation, TransactionID is set to a value that in combination with the packet's SGID (if it's a global GMP), and the MgmtClass is different from that of any other currently executing management operation.
Repeated Trap(Notice) messages issued by a device's SMA or GSA for the same event may or may not contain the same TransactionID.
The recipient of a MAD uses the combination of TID, SGID (if it's a global GMP), and MgmtClass to uniquely associate MADs or multi-MAD sequences.
When a management entity sends a multi-MAD request, the TransactionID in each MAD must be identical.
In a response MAD, the TransactionID must be identical to the TransactionID in the corresponding request.
When a multi-MAD response is transmitted, the TransactionID in each of the response MADs must be identical and must be the same as the TransactionID in the original request MAD.
When sending a series of MADs to accomplish one action (e.g., an SNMP PDU—Protocol Data Unit— being tunneled through IBA in a series of two or more request MADs), the TransactionID in each MAD that is part of the sequence must be set to an identical value.
AttributeID
16
Identifies the attribute affected by the method.
Attribute Modifier
32
When requesting certain method/attribute combinations, an attribute modifier is also necessary. As an example, a request to perform or a SubnGet(PortInfo) or SubnSet(PortInfo) sent to a switch's SMA must also supply a modifier specifying the port whose PortInfo attribute is to be accessed.
Table 28-3. Management Class Values
Management Class
Value
Description
Support Requirement
Subnet Management (Subn)
01h
LID-routed SMP.
All CAs, switches, and routers.
Subnet Management (Subn)
81h
Directed-route SMP.
All CAs, switches, and routers.
Subnet Administrator (SubnAdm)
03h
SA
GMP.
All CAs, switches, and routers hosting a SM.
Performance Manager (Perf)
04h
Performance Management GMP.
All CAs, switches, and routers.
Baseboard Manager (BM)
05h
Baseboard Management GMP.
All CAs, switches, and routers.
Device Manager (DevMgt)
06h
Device Management GMP.
Optional
Communications Manager (ComMgt)
07h
Communication Management GMP.
All CAs that support RC,UC, or RD and UD QPs not at fixed addresses.
SNMP
08h
SNMP Tunneling GMP (used to tunnel the SNMP protocol through the IBA fabric).
Optional
Vendor-supplied Manager
09h–0Fh
Vendor Specific GMP.
Optional
Application-specific Manager
10h–1Fh
Application Specific GMP.
Optional
00h, 20h–80h, 82h–FFh
Reserved.
Table 28-4. Methods Common to Multiple (but not necessarily all) Classes
Method Name
Type
Value
Description
Get()
Request
01h
Read a device attribute.
Set()
Request
02h
Write to a device attribute.
GetResp()
Response
81h
The response from an attribute Get or Set request.
Send()
Message
03h
Send a datagram. Does not require a response.
Trap()
Message
05h
An unsolicited MAD sent from a device indicating an event occurred that may be of interest to the targeted manager.
Report()
Request
06h
Used by a manager to forward the Notice attribute received in a Trap(Notice)
MAD to a device that subscribed for notices from that device.
ReportResp()
Response
86h
Sent by a subscribing device in response to receipt of a Report(Notice) from a manager.
TrapRepress()
Message
07h
Sent by a manager to instruct a device's MA to stop sending identical, repetitive Trap(Notice) MADs for the same event.
00h,04h, 08h–0Fh, 80h, 82h–85h, 87h–8Fh
Reserved
10h–7Fh, 90h–FFh
Class-specific methods. Use is defined by the class.
