RFC 4544
Definitions of Managed Objects for Internet Small Computer System Interface (iSCSI)
Network Working Group M. Bakke Request for Comments: 4544 Cisco Systems Category: Standards Track M. Krueger Hewlett-Packard T. McSweeney IBM J. Muchow Qlogic Corp. May 2006 Definitions of Managed Objects for Internet Small Computer System Interface (iSCSI) Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2006).Abstract
This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in TCP/IP-based internets. In particular, it defines objects for managing a client using the Internet Small Computer System Interface (iSCSI) protocol (SCSI over TCP).
Table of Contents
1. Introduction ....................................................3 2. Specification of Requirements ...................................3 3. The Internet-Standard Management Framework ......................3 4. Relationship to Other MIB Modules ...............................3 5. Relationship to SNMP Contexts ...................................4 6. Discussion ......................................................4 6.1. iSCSI MIB Object Model .....................................5 6.2. iSCSI MIB Table Structure ..................................6 6.3. iscsiInstance ..............................................7 6.4. iscsiPortal ................................................7 6.5. iscsiTargetPortal ..........................................9 6.6. iscsiInitiatorPortal .......................................9 6.7. iscsiNode .................................................10 6.8. iscsiTarget ...............................................10 6.9. iscsiTgtAuthorization .....................................11 6.10. iscsiInitiator ...........................................11 6.11. iscsiIntrAuthorization ...................................11 6.12. iscsiSession .............................................11 6.13. iscsiConnection ..........................................12 6.14. IP Addresses and TCP Port Numbers ........................12 6.15. Descriptors: Using OIDs in Place of Enumerated Types .....13 6.16. Notifications ............................................13 7. MIB Definitions ................................................14 8. Security Considerations ........................................79 9. IANA Considerations ............................................80 10. Normative References ..........................................80 11. Informative References ........................................81 12. Acknowledgements ..............................................81
1. Introduction
This document defines a MIB module for iSCSI [RFC3720], used to manage devices that implement the iSCSI protocol.2. Specification of Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].3. The Internet-Standard Management Framework
For a detailed overview of the documents that describe the current Internet-Standard Management Framework, please refer to section 7 of RFC 3410 [RFC3410]. Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. MIB objects are generally accessed through the Simple Network Management Protocol (SNMP). Objects in the MIB are defined using the mechanisms defined in the Structure of Management Information (SMI). This memo specifies a MIB module that is compliant to the SMIv2, which is described in STD 58, RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580 [RFC2580].4. Relationship to Other MIB Modules
The iSCSI MIB module is normally layered between the SCSI MIB module [RFC4455] and the TCP MIB module [RFC4022], and makes use of the IP Storage (IPS) Identity Authentication MIB module [RFC4545]. Here is how these modules are related: SCSI MIB Within systems where a SCSI layer is present, each iscsiNode, whether it has an initiator role, target role, or both, is related to one SCSI device within the SCSI MIB module. In this case, the iscsiNodeTransportType attribute points to the SCSI transport object within the SCSI MIB module, which in turn contains an attribute that points back to the iscsiNode. In this way, a management station can navigate between the two MIB modules. In systems where a SCSI layer is not present, such as within an iSCSI proxy device, the iscsiNodeTransportType attribute points to the appropriate corresponding object within the appropriate MIB, or is left blank.
TCP MIB Each iSCSI connection is related to one transport-level
connection. Currently, iSCSI uses only TCP; the iSCSI
connection is related to a TCP connection using its normal
(protocol, source address, source port, destination
address, destination port) 5-tuple.
AUTH MIB Each iSCSI node that serves a target role can have a list
of authorized initiators. Each of the entries in this list
points to an identity within the IPS Identity
Authentication MIB module that will be allowed to access
the target. iSCSI nodes that serve in an initiator role
can also have a list of authorized targets. Each of the
entries in this list points to an identity within the Auth
MIB module to which the initiator should attempt to
establish sessions. The Auth MIB module includes
information used to identify initiators and targets by
their iSCSI name, IP address, and/or credentials.
This MIB module imports objects from RFCs 2578 [RFC2578], 2579
[RFC2579], 2580 [RFC2580], and 3411 [RFC3411]. It also imports
textual conventions from the INET-ADDRESS-MIB [RFC4001].
5. Relationship to SNMP Contexts
Each non-scalar object in the iSCSI MIB module is indexed first by an
iSCSI Instance. Each instance is a collection of nodes, portals,
sessions, etc., that can define a physical or virtual partitioning of
an iSCSI-capable device. The use of an instance works well with
partitionable or hierarchical storage devices and fits in logically
with other management schemes. Instances do not replace SNMP
contexts, however they do provide a very simple way to assign a
virtual or physical partition of a device to one or more SNMP
contexts, without having to do so for each individual node, portal,
and session row.
6. Discussion
This MIB module structure supplies configuration, fault, and
statistics information for iSCSI devices [RFC3720]. It is structured
around the well-known iSCSI objects, such as targets, initiators,
sessions, connections, and the like.
This MIB module may also be used to configure access to iSCSI
targets, by creating iSCSI Portals and authorization list entries.
It is worthwhile to note that this is an iSCSI MIB module and as such reflects only iSCSI objects. This module does not contain information about the SCSI-layer attributes of a device. If a SCSI layer is present, the SCSI MIB module, currently under development, may be used to manage SCSI information for a device. The iSCSI MIB module consists of several "objects", each of which is represented by one or more tables. This section contains a brief description of the "object" hierarchy and a description of each object, followed by a discussion of the actual table structure within the objects.6.1. iSCSI MIB Object Model
The top-level object in this structure is the iSCSI instance, which "contains" all of the other objects. iscsiInstance -- A distinct iSCSI entity within the managed system. iscsiPortal -- An IP address used by this instance iscsiTargetPortal -- Contains portal information relevant when the portal -- is used to listen for connections to its targets. iscsiInitiatorPortal -- Contains portal information relevant when the portal -- is used to initiate connections to other targets. iscsiNode -- An iSCSI node can act as an initiator, a target, or both. -- Contains generic (non-role-specific) information. iscsiTarget -- Target-specific iSCSI node information. iscsiTgtAuth -- A list of initiator identities that are allowed -- access to this target. iscsiInitiator -- Initiator-specific iSCSI node information. iscsiIntrAuth -- A list of target identities to which this initiator -- is configured to establish sessions. iscsiSession -- An active iSCSI session between an initiator and target. -- The session's direction may be Inbound (outside -- initiator to our target) or Outbound (our initiator to -- an outside target). iscsiConnection -- An active TCP connection within an iSCSI session.
An iSCSI node can be an initiator, a target, or both. The iSCSI node's portals may be used to initiate connections (initiator) or listen for connections (target), depending on whether the iSCSI node is acting as an initiator or target. The iSCSI MIB module assumes that any target may be accessed via any portal that can take on a target role, although other access controls not reflected in the module might limit this.6.2. iSCSI MIB Table Structure
Each iSCSI object exports one or more tables: an attributes table, and zero or more statistics tables, which augment the attributes table. Since iSCSI is an evolving standard, it is much cleaner to provide statistics and attributes as separate tables, allowing attributes and statistics to be added independently. In a few cases, there are multiple categories of statistics that will likely grow; in this case, an object will contain multiple statistics tables. iscsiObjects iscsiDescriptors iscsiInstance iscsiInstanceAttributesTable iscsiInstanceSsnErrorStatsTable -- Counts abnormal session terminations iscsiPortal iscsiPortalAttributesTable iscsiTargetPortal iscsiTgtPortalAttributesTable iscsiInitiatorPortal iscsiIntrPortalAttributesTable iscsiNode iscsiNodeAttributesTable iscsiTarget iscsiTargetAttributesTable iscsiTargetLoginStatsTable -- Counts successful and unsuccessful logins iscsiTargetLogoutStatsTable -- Counts normal and abnormal logouts iscsiTgtAuthorization iscsiTgtAuthAttributesTable iscsiInitiator iscsiInitiatorAttributesTable iscsiInitiatorLoginStatsTable -- Counts successful and unsuccessful logins iscsiInitiatorLogoutStatsTable -- Counts normal and abnormal logouts iscsiIntrAuthorization iscsiIntrAuthAttributesTable
iscsiSession
iscsiSessionAttributesTable
iscsiSessionStatsTable
-- Performance-related counts (requests, responses, bytes)
iscsiSessionCxnErrorStatsTable
-- Counts digest errors, connection errors, etc.
iscsiConnection
iscsiConnectionAttributesTable
Note that this module does not attempt to count everything that could
be counted; it is designed to include only those counters that would
be useful for identifying performance, security, and fault problems
from a management station.
6.3. iscsiInstance
The iscsiInstanceAttributesTable is the primary table of the iSCSI
MIB module. Every table entry in this module is "owned" by exactly
one iSCSI instance; all other table entries in the module include
this table's index as their primary index.
Most implementations will include just one iSCSI instance row in this
table. However, this table exists to allow for multiple virtual
instances. For example, many IP routing products now allow multiple
virtual routers. The iSCSI MIB module has the same premise; a large
system could be "partitioned" into multiple, distinct virtual
systems.
This also allows a single SNMP agent to proxy for multiple
subsystems, perhaps a set of stackable devices, each of which has one
or even more instances.
The instance attributes include the iSCSI vendor and version, as well
as information on the last target or initiator at the other end of a
session that caused a session failure.
The iscsiInstanceSsnErrorStatsTable augments the attributes table and
provides statistics on session failures due to digest, connection, or
iSCSI format errors.
6.4. iscsiPortal
The iscsiPortalAttributesTable lists iSCSI portals that can be used
to listen for connections to targets, to initiate connections to
other targets, or to do both.
Each row in the table includes an IP address (either v4 or v6), and a transport protocol (currently only TCP is defined). Each portal may have additional attributes, depending on whether it is an initiator portal, a target portal, or both. Initiator portals also have portal tags; these are placed in corresponding rows in the iscsiIntrPortalAttributesTable. Target portals have both portal tags and ports (e.g., TCP listen ports if the transport protocol is TCP); these are placed in rows in the iscsiTgtPortalAttributesTable. Portal rows, along with their initiator and target portal counterparts, may be created and destroyed through this MIB module by a management station. Rows in the initiator and target portal tables are created and destroyed automatically by the agent, whenever a row is created or destroyed in the iscsiPortalAttributesTable, or if the value of iscsiPortalRoles changes. Attributes in these tables may then be modified by the management station if the agent implementation allows. When created by a management station, the iscsiPortalRoles attribute is used to control row creation in the initiator and target portal tables. Creating a row with the targetTypePortal bit set in iscsiPortalRoles will cause the implementation to start listening for iSCSI connections on the portal. Creating a row with the initiatorTypePortal bit set in iscsiPortalRoles will not necessarily cause connections to be established; it is left to the implementation whether and when to make use of the portal. Both bits may be set if the portal is to be used by both initiator and target nodes. When deleting a row in the iscsiPortalAttibutesTable, all connections associated with that row are terminated. The implementation may either terminate the connection immediately or request a clean shutdown as specified in [RFC3720]. An outbound connection (when an iscsiInitiatorPortal is deleted) matches the portal if its iscsiCxnLocalAddr matches the iscsiPortalAddr. An inbound connection (when an iscsiTargetPortal is deleted) matches the portal if its iscsiCxnLocalAddr matches the iscsiPortalAddr, and its iscsiCxnLocalPort matches the iscsiTargetPortalPort. Individual objects within a row in this table may not be modified while the row is active. For instance, changing the IP address of a portal requires that the rows associated with the old IP address be deleted, and new rows be created (in either order).
6.5. iscsiTargetPortal
The iscsiTgtPortalAttributesTable contains target-specific attributes for iSCSI portals. Rows in this table use the same indices as their corresponding rows in the iscsiPortalAttributesTable, with the addition of iscsiNodeIndex. Rows in this table are created when the targetTypePortal bit is set in the iscsiPortalRoles attribute of the corresponding iscsiPortalAttributesEntry; they are destroyed when this bit is cleared. This table contains the TCP (or other protocol) port on which the socket is listening for incoming connections. It also includes a portal group aggregation tag; iSCSI target portals within this instance sharing the same tag can contain connections within the same session. This table will be empty for iSCSI instances that contain only initiators (such as iSCSI host driver implementations). Many implementations use the same target portal tag and protocol port for all nodes accessed via a portal. These implementations will create a single row in the iscsiTgtPortalAttributeTable, with an iscsiNodeIndex of zero. Other implementations do not use the same tag and/or port for all nodes; these implementations will create a row in this table for each (portal, node) tuple, using iscsiNodeIndex to designate the node for this portal tag and port.6.6. iscsiInitiatorPortal
The iscsiIntrPortalAttributesTable contains initiator-specific objects for iSCSI portals. Rows in this table use the same indices as their corresponding entries in the iscsiPortalAttributesTable. A row in this table is created when the initiatorTypePortal bit is set in the iscsiPortalRoles attribute; it is destroyed when this bit is cleared. Each row in this table contains a portal group aggregation tag, indicating which portals an initiator may use together within a multiple-connection session. This table will be empty for iSCSI instances that contain only targets (such as most iSCSI devices).
Many implementations use the same initiator tag for all nodes accessing targets via a given portal. These implementations will create a single row in iscsiIntrPortalAttributeTable, with an iscsiNodeIndex of zero. Other implementations do not use the same tag and/or port for all nodes; these implementations will create a row in this table for each (portal, node) tuple, using iscsiNodeIndex to designate the node for this portal tag and port.6.7. iscsiNode
The iscsiNodeAttributesTable contains a list of iSCSI nodes, each of which may have an initiator role, a target role, or both. This table contains the node's attributes that are common to both roles, such as its iSCSI name and alias string. Attributes specific to initiators or targets are available in the iscsiTarget and iscsiInitiator objects. Each row in this table that can fulfill a target role has a corresponding row in the iscsiTarget table; each entry that fulfills an initiator role has a row in the iscsiInitiator table. Nodes such as copy managers that can take on both roles have a corresponding row in each table. This table also contains the login negotiations preferences for this node. These objects indicate the values this node will offer or prefer in the operational negotiation phase of the login process. For most implementations, each entry in the table also contains a RowPointer to the transport table entry in the SCSI MIB module that this iSCSI node represents. For implementations without a standard SCSI layer above iSCSI, such as an iSCSI proxy or gateway, this RowPointer can point to a row in an implementation-specific table that this iSCSI node represents.6.8. iscsiTarget
The iscsiTargetAttributesTable contains target-specific attributes for iSCSI nodes. Each entry in this table uses the same index values as its corresponding iscsiNode entry. This table contains attributes used to indicate the last failure that was (or should have been) sent as a notification. This table is augmented by the iscsiTargetLoginStatsTable and the iscsiTargetLogoutStatsTable, which count the numbers of normal and abnormal logins and logouts to this target.
6.9. iscsiTgtAuthorization
The iscsiTgtAuthAttributesTable contains an entry for each initiator identifier that will be allowed to access the target under which it appears. Each entry contains a RowPointer to a user identity in the IPS Authorization MIB module, which contains the name, address, and credential information necessary to authenticate the initiator.6.10. iscsiInitiator
The iscsiInitiatorAttributesTable contains a list of initiator- specific attributes for iSCSI nodes. Each entry in this table uses the same index values as its corresponding iscsiNode entry. Most implementations will include a single entry in this table, regardless of the number of physical interfaces the initiator may use. This table is augmented by the iscsiInitiatorLoginStatsTable and the iscsiInitiatorLogoutStatsTable, which count the numbers of normal and abnormal logins and logouts from this initiator.6.11. iscsiIntrAuthorization
The iscsiIntrAuthAttributesTable contains an entry for each target identifier to which the initiator is configured to establish a session. Each entry contains a RowPointer to a user identity in the IPS Authorization MIB module, which contains the name, address, and credential information necessary to identify (for discovery purposes) and authenticate the target.6.12. iscsiSession
The iscsiSessionAttributesTable contains a set of rows that list the sessions known to be existing locally for each node in each iSCSI instance. The session type for each session indicates whether the session is used for normal SCSI commands or for discovery using the SendTargets text command. Discovery sessions that do not belong to any particular node have a node index attribute of zero.
The session direction for each session indicates whether it is an Inbound session or an Outbound session. Inbound sessions are from some other initiator to the target node under which the session appears. Outbound sessions are from the initiator node under which the session appears to a target outside this iSCSI instance. Many attributes may be negotiated when starting an iSCSI session. Most of these attributes are included in the session object. Some attributes, such as the integrity and authentication schemes, have some standard values that can be extended by vendors to include their own schemes. These contain an object identifier, rather than the expected enumerated type, to allow these values to be extended by other MIB modules, such as an enterprise MIB module. The iscsiSessionStatsTable includes statistics related to performance; it counts iSCSI data bytes and PDUs. For implementations that support error recovery without terminating a session, the iscsiSessionCxnErrorStatsTable contains counters for the numbers of digest and connection errors that have occurred within the session.6.13. iscsiConnection
The iscsiConnectionAttributesTable contains a list of active connections within each session. It contains the IP addresses and TCP (or other protocol) ports of both the local and remote sides of the connection. These may be used to locate other connection-related information and statistics in the TCP MIB module [RFC4022]. The attributes table also contains a connection state. This state is not meant to directly map to the state tables included within the iSCSI specification; they are meant to be simplified, higher-level definitions of connection state that provide information more useful to a user or network manager. No statistics are kept for connections.6.14. IP Addresses and TCP Port Numbers
The IP addresses in this module are represented by two attributes, one of type InetAddressType, and the other of type InetAddress. These are taken from [RFC4001], which specifies how to support addresses that may be either IPv4 or IPv6.
The TCP port numbers that appear in a few of the structures are described as simply port numbers, with a protocol attribute indicating whether they are TCP ports or something else. This will allow the module to be compatible with iSCSI over transports other than TCP in the future.6.15. Descriptors: Using OIDs in Place of Enumerated Types
The iSCSI MIB module has a few attributes, namely, the digest method attributes, where an enumerated type would work well, except that an implementation may need to extend the attribute and add types of its own. To make this work, this MIB module defines a set of object identities within the iscsiDescriptors subtree. Each of these object identities is basically an enumerated type. Attributes that make use of these object identities have a value that is an Object Identifier (OID) instead of an enumerated type. These OIDs can indicate either the object identities defined in this module or object identities defined elsewhere, such as in an enterprise MIB module. Those implementations that add their own digest methods should also define a corresponding object identity for each of these methods within their own enterprise MIB module, and return its OID whenever one of these attributes is using that method.6.16. Notifications
Three notifications are provided. One is sent by an initiator detecting a critical login failure, another is sent by a target detecting a critical login failure, and the third is sent upon a session being terminated due to an abnormal connection or digest failure. Critical failures are defined as those that may expose security-related problems that may require immediate action, such as failures due to authentication, authorization, or negotiation problems. Attributes in the initiator, target, and instance objects provide the information necessary to send in the notification, such as the initiator or target name and IP address at the other end that may have caused the failure. To avoid sending an excessive number of notifications due to multiple errors counted, an SNMP agent implementing the iSCSI MIB module SHOULD NOT send more than three iSCSI notifications in any 10-second period. The 3-in-10 rule was chosen because one notification every three seconds was deemed often enough, but should two or three different notifications happen at the same time, it would not be desirable to suppress them. Three notifications in 10 seconds is a happy medium,
where a short burst of notifications is allowed, without inundating the network and/or notification host with a large number of notifications.
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