DECnet Phase IV MIB Extensions
obsoletes
- rfc-1289 — DECnet Phase IV MIB Extensions
Extracted elements (29)
Buffer size parameters (phivRouteBuffSize and phivRouteSegBuffSize) both include a constant 6-byte addend not associated with actual Routing or Data Link overhead. This extra 6 is retained for backward compatibility with the Phase III parameter definition, which historically included Routing overhead in the buffer size field.
Object names and definitions are derived directly from the DIGITAL Network Architecture Network Management Functional Specification Version 4.0.0 (July 1983) and then massaged to conform to Internet MIB naming conventions, preserving original DECnet semantics while fitting the Internet SMI.
The term EXECUTOR in this MIB refers exclusively to the DECnet software entity on the managed node and is explicitly not intended to affect or reference any other protocol stacks (e.g., TCP/IP) that may coexist on the same system.
Throughout the MIB, enumeration values are incremented by one relative to the native DECnet (NICE protocol) coded values. This is required because the Internet SMI (RFC 1155) does not permit enumerated integers with the value zero, and DECnet natively encodes several states as zero.
phivEthHardwareAddr (6-octet Ethernet hardware address as seen by DECnet software) is explicitly noted to differ from ifPhysAddress, because DECnet may present a different address view than the standard MIB-II interface layer.
The InterfaceIndex textual convention is explicitly defined as sharing the range of ifIndex (1..2147483647) from MIB-II, and phivCircuitLineIndex is set equal to the corresponding ifIndex value, enabling cross-referencing between the DECnet Phase IV MIB and the standard interfaces table.
Implementation of the Circuit Group is mandatory for all systems. It covers circuit parameters, circuit counters, and associated control objects.
Implementation of the Ethernet Group is mandatory for all systems that support Ethernet links.
Implementation of the Routing Layer Group is mandatory for all systems that implement level 1 routing layer communications.
Implementation of the System Group is mandatory for all systems. It exposes the executor node's operational state (phivSystemState) and text identifier (phivExecIdent).
The Session Layer Group and End Communication Layer Group are each optional, but a system is considered to implement a group if and only if all objects within that group are implemented — partial implementation is not permitted.
Circuit type (phivCircuitCommonType) enumerates: ddcmp-point (1), ddcmp-control (2), ddcmp-tributary (3), x25 (4), ddcmp-dmc (5), ethernet (6), ci (7), qp2-dte20 (8), bisync (9), other (14), and fddi (15).
Counter-zeroing is exposed as write-only control objects (phivEndCountZeroCount, phivRouteCountZeroCount, phivCircuitCountZeroCount): setting the value to 2 (reset) zeros all counters in the respective table; the value 1 (other) is the read-back state.
NSP retransmission behavior is tunable via phivEndRetransmitFactor (max restarts of retransmit timer before Session Control disconnects the link), phivEndDelayFact (multiplier for round-trip delay estimate), phivEndDelayWeight (exponential smoothing weight for RTT), and phivEndInactivityTimer (idle-link check interval in seconds).
PhivCounter is an INTEGER textual convention for DECnet counters that latch at their maximum specified value until the system is restarted or the counter is manually reset to zero by the user or management software.
Routing buffer sizing is controlled by two separate parameters: phivRouteBuffSize (maximum Routing-layer forwarding message size) and phivRouteSegBuffSize (maximum end-to-end segment size). Both include an extra 6 bytes for Phase III compatibility; SegBuffSize must be less than or equal to BuffSize.
Routing node type (phivRouteRoutingType) is a read-write enumeration with values routing-III (1), nonrouting-III (2), area (3), routing-IV (4), nonrouting-IV (5). The obsolete phivRouteType carried the same semantics but was read-only.
Routing parameters include phivRouteMaxAddr (max node number, 1–1023), phivRouteMaxHops (max path hops, 1–30), phivRouteMaxCost (max path cost, 1–1022), and phivRouteMaxVisits (max nodes a transit packet may have visited, 1–63) — each must not be less than the corresponding network-wide maximum for correct routing.
The DDCMP Multipoint Control Group exposes per-tributary polling algorithm parameters: dead/dying/inactive thresholds (counts of receive timeouts before state change), base priorities and increments for each polling state, babble timer (max transmit window in ms), and a transmission delay timer.
The DECnet Phase IV MIB subtree is assigned the OID { mib-2 18 } (phiv), establishing it as a named branch within the standard Internet MIB-II hierarchy.
The End System Counter Table (phivEndCountTable) tracks per-remote-node byte and message counts for both user-level and total traffic, plus connect counts, response timeouts, and connect resource errors, all using latching PhivCounter integers.
The Ethernet Group exposes phivEthDesigRouterNodeAddr (current designated router address, read-only), phivEthMaxRouters (max peer routers on circuit, 0–255), phivEthRouterPri (designated-router election priority, 0–127, default 64), and phivEthHardwareAddr (6-octet hardware address as seen by DECnet software, distinct from ifPhysAddress).
The Level 1 Route Table (phivLevel1RouteTable) is indexed by PhivAddr and contains per-destination entries with circuit index, path cost (sum of circuit costs), hop count, and the next-hop node address.
The MIB is organized into 14 groups: System, Network Management, Session, End, Routing, Circuit, DDCMP, DDCMP Multipoint Control, Ethernet, Counters, Adjacency, Line, Non Broadcast Line, and Area, each assigned a sub-OID under phiv (1–15, skipping 13).
Section 9 addresses security considerations for the DECnet Phase IV MIB. The MIB exposes numerous read-write objects (executor state, routing parameters, circuit costs, polling thresholds) that, if modified by unauthorized parties via SNMP, could disrupt DECnet routing and end-system connectivity; access control relies on the SNMP community-based security model of RFC 1157.
Circuit operational state (phivCircuitCommonState) has four values: on, off, service, cleared. The circuit substate (phivCircuitCommonSubState) further refines this with 13 values including starting, reflecting, looping, loading, dumping, triggering, synchronizing, failed, and running.
DDCMP multipoint polling state (phivControlPollingState) has five values: automatic (algorithm-controlled), active, inactive, dying, and dead. When automatic, the read-only substate (phivControlPollingSubState) reflects the algorithm's current determination and is displayed as a tag, e.g., AUTOMATIC-INACTIVE.
The executor node (phivSystemState) and remote node (phivEndRemoteState) share four operational states: ON (allows logical links), OFF (terminates all links and stops routing), SHUT (no new links; waits for existing links to close before going OFF), and RESTRICTED (no new incoming links from other nodes).
PhivAddr is a 2-octet OCTET STRING encoding a DECnet Phase IV node address. The most significant 6 bits of the first octet hold the area number; the next 2 bits of the first octet plus all 8 bits of the second octet hold the 10-bit host address.