Definitions of Managed Objects for the Internet Small Computer System Interface (iSCSI)
obsoletes
- rfc-4544 — Definitions of Managed Objects for Internet Small Computer System Interface (iSCSI)
Extracted elements (30)
Digest method attributes use OIDs (object identities from the iscsiDescriptors subtree) rather than enumerated integers so that vendors can define additional digest methods in enterprise MIB modules and return those OIDs without modifying the base ISCSI-MIB.
Each iSCSI MIB object exposes one attributes table and zero or more separate statistics tables that AUGMENT it. The separation allows attributes and statistics to be extended independently as the iSCSI standard evolves, without requiring restructuring of a single combined table.
iscsiInstXNodeArchitecture was added to InstanceAttributes to expose node architecture details (vendor software, firmware, hardware, OS versions) to management stations, mirroring the X#NodeArchitecture key defined in RFC 7143 Section 13.26 for iSCSI login negotiation.
iscsiTgtPortalNodeIndexOrZero uses zero to handle the common implementation case where the same Target Portal Group Tag and port apply to all nodes on a portal; non-zero values index per-(portal, node) tuples for implementations that vary the tag or port by node.
The 3-in-10-second notification throttle was chosen because three notifications per 10 seconds allows short bursts of concurrent notifications (e.g., simultaneous authentication and negotiation failures) without suppressing them, while preventing sustained flooding of the management network.
RFC 7147 incorporates fixes to errata present in RFC 4544 as part of the revision aligned with RFC 7143. Specific corrected items are not enumerated in the document text but are reflected in the updated MIB definition.
iSCSI instances do not replace SNMP contexts but complement them by providing a simple way to assign virtual or physical partitions of a device to one or more SNMP contexts without configuring each node, portal, and session row individually.
The iSCSI MIB is designed to layer between the SCSI MIB (RFC 4455) and TCP MIB (RFC 4022). Each iscsiNode links to a SCSI device via iscsiNodeTransportType (a RowPointer), and each iscsiConnection is correlated to a TCP MIB entry using the 5-tuple (protocol, src addr, src port, dst addr, dst port).
The iscsiPortalRecvMarker object is deprecated in this revision (aligned with RFC 7143 Section 13.25 which obsoletes iSCSI marker keys). Agents SHOULD report it but the field has no operational effect.
An SNMP agent implementing the iSCSI MIB module SHOULD NOT send more than three iSCSI notifications in any 10-second period, to prevent flooding the network or notification host during burst error conditions.
Individual objects within an active iscsiPortalAttributesEntry row may not be modified while the row is active. Changing attributes such as the IP address requires deleting and recreating the rows associated with the old values.
The iscsiInstIndex value MUST NOT be modified or reused by an agent unless a reboot has occurred, and an agent SHOULD attempt to keep this value persistent across reboots to maintain stable management references.
When an iscsiPortalAttributesTable row is deleted, all connections associated with that row are terminated — either immediately or via clean shutdown per RFC 7143. Matching for outbound connections uses iscsiCxnLocalAddr; inbound connections additionally match iscsiCxnLocalPort.
iscsiConnectionAttributesTable lists active TCP connections within each session, including local and remote IP addresses and port numbers (for correlation with TCP MIB) and a simplified high-level connection state not directly mapping to the iSCSI specification state tables.
iscsiDescriptors defines OID-based identifiers (iscsiHeaderIntegrityTypes and iscsiDataIntegrityTypes subtrees) for digest methods. Attributes using these types store an OID rather than an enumerated integer, allowing vendor extension without modifying the base MIB.
iscsiInstance is the top-level indexing object; every other table in the MIB uses iscsiInstIndex as its primary index. It supports multiple virtual instances within a single device, enabling partitioned or hierarchical storage management.
iscsiInstanceSsnErrorStatsTable (augmenting iscsiInstanceAttributesTable) tracks session failures by type: digest errors (iscsiInstSsnDigestErrors), connection timeout errors (iscsiInstSsnCxnTimeoutErrors), format errors (iscsiInstSsnFormatErrors), and target-unmapped errors (iscsiInstSsnTgtUnmappedErrors).
iscsiNodeAttributesTable holds per-node login negotiation preferences including InitialR2T, ImmediateData, MaxBurstLength (default 262144 bytes), FirstBurstLength (default 65536 bytes), MaxConnections, DataPDUInOrder, DataSequenceInOrder, DefaultTime2Wait, DefaultTime2Retain, and ErrorRecoveryLevel (0–2).
iscsiPortalAttributesTable lists transport endpoints (IP address plus transport protocol) used by an iSCSI instance for listening to incoming target connections, initiating outbound connections, or both. The iscsiPortalRoles BITS field determines which sub-tables are created automatically.
iscsiSessionAttributesTable records active sessions with type (normal or discovery SendTargets), direction (Inbound from outside initiator, or Outbound to outside target), and negotiated operational parameters. Discovery sessions not belonging to any particular node use a node index of zero.
iscsiTgtAuthAttributesTable and iscsiIntrAuthAttributesTable implement access control lists via RowPointer references into the IPS Authorization MIB (RFC 4545), which holds iSCSI name, IP address, and credential information for authenticating initiators to targets and vice versa.
iscsiTgtPortalAttributesTable contains target-portal-specific attributes including TCP listen port (iscsiTgtPortalPort) and aggregation tag (iscsiTgtPortalTag, range 1..65535). Portals sharing the same tag can aggregate connections within the same multi-connection session.
The iSCSI MIB object hierarchy is rooted at iscsiInstance, which contains iscsiPortal (with iscsiTargetPortal and iscsiInitiatorPortal sub-objects), iscsiNode (with iscsiTarget, iscsiInitiator, iscsiTgtAuthorization, iscsiIntrAuthorization sub-objects), and iscsiSession (containing iscsiConnection).
Three SNMP notifications are defined: iscsiTgtLoginFailure (sent by a target on critical login failure), iscsiIntrLoginFailure (sent by an initiator on critical login failure), and iscsiInstSessionFailure (sent on abnormal session termination due to digest or connection errors). Critical failures include authentication, authorization, and negotiation failures.
The ISCSI-MIB module is assigned OID mib-2 142, establishing the authoritative SNMP Management Information Base for managing iSCSI protocol devices. It obsoletes RFC 4544 and is the second version of the iSCSI MIB module.
Notifications for critical login failures (authentication, authorization, negotiation) are defined to expose security-related problems requiring immediate operator action. The iscsiTgtLoginAuthenticateFails and iscsiTgtLoginAuthorizeFails counters SHOULD trigger iscsiTgtLoginFailure notifications when incremented.
Several read-write objects in the iSCSI MIB (portal creation/deletion, node negotiation parameters, authorization entries) can alter the operational behavior of iSCSI devices if accessed by unauthorized parties, requiring SNMP access control (e.g., SNMP view-based access control, SNMPv3 authentication and privacy) to protect them.
IscsiDigestMethod is an INTEGER enumeration with values none(1), other(2), noDigest(3), and crc32c(4), used to represent header and data digest negotiation preferences per RFC 7143 Section 13.1.
IscsiName is an OCTET STRING of SIZE(0 | 16..223) encoded as UTF-8, where a zero-length string indicates absence of an iSCSI name. The 16-byte minimum and 223-byte maximum match the iSCSI name format specified in RFC 7143 Section 4.2.7.
IscsiTransportProtocol is encoded as Unsigned32 (0..255) using IANA-assigned protocol numbers. Currently only TCP (protocol number 6) is defined for iSCSI, but the range accommodates future transport protocols.