Definitions of Managed Objects for Data Link Switching using SMIv2
Extracted elements (29)
DLSw MIB objects do not duplicate information from the underlying DLC layer MIBs (LLC, SDLC). Instead, circuit table entries use RowPointer (dlswCircuitS1Dlc) to reference conceptual rows in the appropriate enterprise-specific or standard DLC MIB, avoiding redundancy.
The recommended technique for grouping run-time capabilities exchange is to defer sending a capabilities message until no further capabilities-related SNMP SET changes have arrived for a pre-defined period, thereby batching multiple variable changes into a single over-the-wire message.
To keep the MIB small, information exchanged between partner DLSw nodes (e.g., SAP lists, NetBIOS names, MAC address lists from Capabilities Exchange) is only stored at the receiving end. There are no objects for what was sent, requiring managers to query both partners to get a complete picture.
A transport connection in 'connected' state with a zero-length dlswTConnOperPartnerVersion indicates the partner is a pre-standard RFC 1434+ DLSw node, not an AIW Version 1 DLSw Standard node. Managers can use this distinction to infer whether xBusy or standard pacing flow control is in use.
The DLSw MIB uses ifIndex (from IF-MIB / RFC 1573) as the index into dlswIfTable and as a reference from circuit entries (dlswCircuitS1Index) and SDLC link station entries (dlswSdlcLsTable). Implementations must also support the Interface Group MIB.
When coexisting with RFC 1747 (SDLC MIB), dlswSdlcLsTable uses the same interface/link-station-address indices as RFC 1747, providing a mapping between native SDLC addressing and DLSw domain addressing (local MAC and SAP). Circuit entries with SDLC use dlswCircuitS1DlcType=sdlc and dlswCircuitS1Dlc pointing to sdlcLSAdminTable, sdlcLSOperTable, or sdlcLSStatsTable rows.
All MAC addresses, SAPs, and ring numbers in the DLSw MIB are in non-canonical (most-significant-bit-first) form. Implementations must use this encoding consistently throughout.
Because DLSw is the user of LLC services, administrative actions such as disconnecting a hung circuit should be performed via dlswCircuitState in the DLSw MIB rather than directly via the LLC MIB (e.g., setting llcCcAdminStatus). The DLSw MIB is the preferred management point.
To take a TConnConfig row out of service, the manager should set dlswTConnConfigRowStatus to notInService rather than using the excluded setup type. Changes to capabilities-exchange-related MIB objects should be grouped into as few SNMP SET requests as possible to reduce network traffic from run-time capabilities exchange messages.
When multiple TConnConfigTable rows match an incoming transport connection (e.g., individual, group, and global rows overlap), the DLSw node must apply the 'most specific match wins' rule. For equal-specificity matches, the choice of row is implementation-defined. Managers should never create two rows with duplicate remote addressing values.
dlswNodeStatus (dlswNode 5) is read-write with values active(1) and inactive(2). Setting to inactive disconnects all circuits, all transport connections, all local DLC connections, and stops processing DLC connection setup traffic. Setting to active restores DLSw to its initial state.
dlswNodeVersion (dlswNode 1) is a 2-octet read-only OCTET STRING: the first octet is the DLSw standard Version number and the second is the Release number, as exchanged in DLSw Capabilities Exchange messages per RFC 1795.
dlswNodeVirtualSegmentLFSize (dlswNode 7) is a read-write LFSize value, defaulting to lfs65535, that constrains the maximum frame size DLSw can forward on any path through itself; it affects LF size negotiation during circuit creation.
dlswTConnConfigInitCirRecvWndw (0–65535 SSP messages, default 1) sets the initial circuit receive pacing window sent in the capabilities exchange for future transport connections. A larger value is appropriate for partners reachable via high-latency paths.
dlswTConnConfigSapList (16 octets) controls which SAPs are advertised per partner transport connection. Changes affect only new circuit establishments, not existing ones. The default value ('AA000000000000000000000000000000'H) enables SAPs 0, 4, 8, and C.
dlswTConnConfigSetupType controls connection behavior: activePersistent (initiate and retry), activeOnDemand (initiate only on directory cache hit), passive (accept only), excluded (reject the specified partner), or other. Default is passive.
dlswTConnOperFlowCntlMode reports whether the flow control in use is undetermined(1), standard RFC 1795 pacing(2), or other(3) (which covers RFC 1434+ xBusy or vendor-specific methods). Whether 'other' is xBusy can be inferred from dlswTConnOperPartnerVersion.
dlswTConnOperPartnerVersion is a 0- or 2-octet read-only string identifying the partner's DLSw standard version and release from its Capabilities Exchange message. A zero-length string with state 'connected' indicates a non-standard (RFC 1434+) partner DLSw.
dlswTConnTcpConfigTcpConnections (1–16, default 2) is the preferred number of TCP connections within one DLSw transport connection; the actual count is negotiated at capabilities exchange. dlswTConnTcpConfigMaxSegmentSize (default 4096 bytes) sets the receive TCP segment size limit.
Five compliance levels are defined: dlswCoreCompliance (minimum for all implementations), dlswTConnTCPCompliance (TCP transport support), dlswDirCompliance (directory function), dlswDirLocateCompliance (directory with ordered retrieval), and dlswSdlcCompliance (SDLC end-station support). NetBIOS-related objects are grouped separately in each because DLSw Version 1 does not require NetBIOS support.
The DLSw MIB is structured into six object groups: dlswNode (node identity, configuration, control), dlswTConn (transport connections to partner DLSw nodes), dlswInterface (interfaces where DLSw is active), dlswDirectory (MAC and NetBIOS name caches), dlswCircuit (end-station circuits), and dlswSdlc (SDLC-attached end stations).
The DLSw MIB module is assigned the OBJECT IDENTIFIER { mib-2 46 }, establishing the dlsw subtree under the standard MIB-II hierarchy. The dlswMIB object and dlswDomains object are defined under this root.
Security considerations for the DLSw MIB are addressed in Section 6.0 of the document. Read-write and read-create objects in this MIB (such as dlswNodeStatus, dlswTConnConfigTable, and dlswTConnOperState) can cause significant operational disruption if accessed by unauthorized parties, including disconnecting all circuits and transport connections.
Transport connection operational states are: connecting (connection request sent to transport), initCapExchange (initial Capabilities Exchange sent), connected (ready for CanUReach messages), quiescing (no new circuits, disconnect when last circuit leaves), disconnecting (force-disconnect all circuits), and disconnected. Manager may SET only quiescing or disconnecting.
DlswTCPAddress encodes a DLSw partner's IP address as a 4-octet OCTET STRING in network-byte order. The dlswTCPDomain OID identifies this transport domain. Display hint is '1d.1d.1d.1d'.
LFSize is an INTEGER textual convention enumerating exactly 64 valid largest-frame sizes (in octets, including DLC header and INFO field but excluding MAC framing), as defined by IEEE 802.1D Addendum, ranging from lfs516(516) to lfs65535(65535).
MacAddressNC is a 6-octet (or zero-length) OCTET STRING representing an 802 MAC address in non-canonical (most-significant-bit-first) format. All MAC addresses, SAPs, and ring numbers throughout the MIB use this non-canonical form.
NBName is an OCTET STRING of 0–16 octets representing a qualified NetBIOS name with optional wildcards: '?' means don't-care for that character position, and '*' at the end means the remainder of the name is don't-care.
The SAP list (dlswTConnConfigSapList, dlswTConnOperPartnerSapList) is a 16-octet OCTET STRING where each bit represents one even SAP value: the MSB of octet 1 is SAP 0, next bit is SAP 2, ..., LSB of octet 16 is SAP 254. A set bit means DLSw is active for that SAP.