Event Subscription and Event Forwarding

What Is Event Forwarding?

A device can subscribe to a particular manager to have it forward event notices received via traps from:

• a specific port on a CA or router, or from the management port on a switch.

• or from a collection of CAs, routers, or switches that reside within a specified LID address range.

Subscription Availability

Mandatory for the SA

Although SM-related traps are sent to the SM when an SM-related event is detected by a device's SMA, a subscription service is not available directly from the Master SM. It is, however, available from the SA (the SA's subscriber support is mandatory).

Optional for GSMs

It is optional whether or not the GSMs provide a subscription service. This ability is verified by performing a Get(InformInfo) from the respective GSM. The SA may be queried to determine the existence and location of the GSMs. A successful read indicates the subscription service is supported.

How the SA's Location Is Determined

The SA is either located at the same port as the SM or in another location. It is located in the following manner. The entity desiring the location of the SA sends a SubnAdmGet(ClassPortInfo) to the Master SM's port address (indicated in PortInfo.MasterSMLID). This GMP has the following characteristics:

• DLID = LID address indicated in the originating port's PortInfo.MasterSMLID attribute element.

• Destination QP specified in the BTH:DestQP field is QP1 (i.e., the GSI).

• DETH:Q_Key = 80010000h (the GSI's controlled Q_Key).

• SLID = the originating port's base LID address.

• LRH:SL = the SL value found in the originating port's PortInfo.MasterSMSL attribute element.

• BTH:P_Key = the default P_Key (FFFFh or 7FFFh) from the originating port's P_KeyTable attribute.

The specification states that the ClassPortInfo data structure returned (see Table 28-7 on page 794) “shall return all information needed to communicate to Subnet Administration.” However, it doesn't say what field(s) of the data structure contain this information. It is the author's opinion that it works as follows:

• If the ClassPortInfo.RedirectGID and ClassPortInfo.RedirectLID fields are both zero, redirection is not in effect. All SA accesses are therefore sent to the same port that the SM resides on (i.e., the one identified by the issuing port's PortInfo.MasterSMLID attribute element).

• If, on the other hand, either of those ClassPortInfo attribute elements contain non-zero values, redirection is in force, and all SA request MADs should be sent to the indicated redirect address. For more information on redirection, refer to “GMP Redirection” on page 175 and “Additional Information Regarding Redirection” on page 914.

How to Subscribe

Subscribing to a GSM

To subscribe to a GSM for the forwarding of event notifications, the prospective subscriber sends a Set(InformInfo) to the GSM with the following information (see Table 28-10 on page 804):

• Identify CA, router, or switch port via:

  - its GID

  - or its LID

• or identify a set of CAs, switches, or routers by defining a range of LID addresses.

• Set InformInfo.Subscribe to 1.

The GSM responds by returning a GetResp(InformInfo) with the InformInfo.Subscribe attribute element set as follows:

• 0 = Subscription request denied.

• 1 = Subscription request accepted.

It should be noted that the manager memorizes the SLID (or, if it's a global packet, the SLID and SGID addresses) in the packet and records it as the address to which the Notice should be sent when a trap is received.

Subscribing to the SA

To subscribe to the SA for trap forwarding, the prospective subscriber sends a SubnAdmSet(InformInfo) to the SA with the same information shown in the previous section (also see Table 28-10 on page 804). The SA responds by returning a SubnAdmGetResp(InformInfo) with the InformInfo.Subscribe attribute element set as follows:

• 0 = Subscription request denied.

• 1 = Subscription request accepted.

Once again, it should be noted that the manager memorizes the SLID (or, if it's a global packet, the SLID and SGID addresses) in the packet and records it as the address to which the Notice should be sent when a trap is received.

How the Manager Forwards a Trap

When the SA or a GSM receives a Trap(Notice) from a port notifying the manager of a specific event within that device, the manager performs a lookup in its subscriber list and, if someone had subscribed for notification of this event type from this port, the Notice attribute delivered in the Trap(Notice) is delivered to the subscriber via one of the following:

• If the manager is the SA, it sends a SubnAdmReport(Notice) to the subscriber containing the Notice attribute.

• If the manager is a GSM, it sends a Report(Notice) to the subscriber containing the Notice attribute.

Table 28-10. InformInfo Attribute Format

Item Name	R/W?	Description
GID	RW	Specifies specific port to subscribe for via its assigned GID address. Set to all zeroes if not desired.
LIDRangeBegin	RW	Specifies the lowest LID in a range of port LID addresses to subscribe for. Address FFFFh denotes all LID addresses.
LIDRangeEnd	RW	Specifies the highest LID in a range of LID addresses to subscribe for. Set to zero if no range desired. Ignored if LIDRangeBegin is FFFFh.
P_Key	RW	A partition key assigned to the prospective subscriber.
IsGeneric	RW	If = 1, this is a request to forward generic traps to the subscriber. If = 0, this is a request to forward all vendor specific traps to the subscriber. Values above 1 are undefined.
Subscribe	RW	If = 1, this is a subscription request. If = 0, this is a request to unsubscribe. Values above 1 are undefined.
ClassRange	RW	Indicating the type of events to be notified of: 0000h - Fatal 0001h - Urgent 0002h - Security 0003h - Subnet Management 0004h - Informational FFFFh - Forward All
DeviceID/TrapNumber	RW	If IsGeneric = 0, this is the device ID assigned by the manufacturer. If IsGeneric = 1, this is a specific trap number. Value of FFFFh means forward any Device ID or TrapNumber.
RespTimeValue	RO	Maximum time from request receipt to the transmission of the response or between port's transmission of successive MADs that are part of same multiple-MAD sequence. Time = 4.096us X 2RespTimeValue
Reserved	RO
VendorID/NodeType	RW	If IsGeneric = 1, indicates device type: - 000000h - Reserved - 000001h - Channel Adapter - 000002h - Switch - 000003h - Router - 000004h - Subnet Management - 000005h-FFFFFFh - Reserved If IsGeneric = 0, indicates the 24 bit IEEE-assigned vendor ID.