Definition of Managed Objects for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)
Extracted elements (20)
For link layers using the 6LoWPAN dispatch byte, only datagrams with dispatch byte matching 01xxxxxx, 10xxxxxx, or 11xxxxxx are counted as 6LoWPAN datagrams. Datagrams with pattern 00xxxxxx (NALP) are explicitly excluded from all counters.
Objects are defined twice: once for global statistics (lowpanStats) and once for per-interface statistics (lowpanIfStatsTable). Per-interface statistics are optional to implement, allowing constrained devices to implement only global counters.
The fragmentation-related counters were modeled after those in the IP-MIB (RFC 4293) for consistency. The discard counters are placed at the end of input and output chains but can be incremented at any time a datagram is discarded for reasons not covered by more specific counters.
While the LOWPAN-MIB provides direct SNMP binding, SNMP may not be affordable on constrained devices. Proposals exist to provide bindings to CoAP (RFC 7252) for accessing MIB-modeled data on constrained nodes.
Implementations that do not support mesh forwarding MUST count received 6LoWPAN datagrams with a MESH header in lowpanInMeshReceives, but MUST NOT increment lowpanInMeshReceives and lowpanInMeshDelivers if those datagrams are dropped.
Header decompression counters: lowpanInCompReqds counts datagrams requiring decompression; lowpanInCompFails counts failures (e.g., missing context); lowpanInCompOKs counts successful decompressions.
lowpanIfStatsTable is an optional per-interface statistics table indexed by ifIndex (from IF-MIB), containing the same 29 counters as the global lowpanStats group but scoped to individual interfaces.
lowpanInDiscards counts received datagrams discarded for reasons such as lack of buffer space, explicitly excluding datagrams discarded due to reassembly or compression failures. lowpanInDelivers counts IPv6 packets successfully delivered to the IPv6 layer.
lowpanInReceives (Counter32) counts total 6LoWPAN datagrams received including those in error; lowpanInHdrErrors (Counter32) counts those discarded due to header errors including unknown dispatch values.
lowpanReasmTimeout (OID lowpanStats.1) is an Unsigned32 in seconds representing the maximum time received fragments are held awaiting reassembly. A per-interface counterpart lowpanIfReasmTimeout exists in lowpanIfStatsEntry.1.
Mesh output counters: lowpanOutMeshHopLimitExceeds counts MESH-header datagrams dropped due to hop limit exceeded; lowpanOutMeshNoRoutes counts drops due to no forwarding information; lowpanOutMeshRequests, lowpanOutMeshForwds, and lowpanOutMeshTransmits track MESH encapsulation pipeline.
Mesh-related input counters: lowpanInMeshReceives counts datagrams with a MESH header; lowpanInMeshForwds counts those requiring mesh forwarding; lowpanInMeshDelivers counts MESH-header datagrams delivered to the local system.
Output compression counters: lowpanOutCompReqds counts IPv6 packets for which header compression was attempted; lowpanOutCompFails counts compression failures; lowpanOutCompOKs counts successful compressions.
Output fragmentation counters: lowpanOutFragReqds counts IPv6 packets requiring fragmentation; lowpanOutFragFails counts packets discarded due to fragmentation failure; lowpanOutFragOKs counts successfully fragmented packets; lowpanOutFragCreates counts generated FRAG1 and FRAGN datagrams.
Reassembly counters: lowpanInReasmReqds counts fragments (FRAG1 and FRAGN) needing reassembly; lowpanInReasmFails counts reassembly algorithm failures (e.g., timeouts, not necessarily discarded fragment count); lowpanInReasmOKs counts successfully reassembled IPv6 packets.
The conformance statement defines four OBJECT-GROUPs: lowpanStatsGroup (mandatory baseline, excludes mesh counters), lowpanStatsMeshGroup (mandatory if MESH processing supported), lowpanIfStatsGroup (mandatory if per-interface stats exposed), lowpanIfStatsMeshGroup (mandatory if both).
The LOWPAN-MIB module is assigned OID { mib-2 226 } and provides monitoring and troubleshooting support for the 6LoWPAN layer, filling the gap between IF-MIB (link layer) and IP-MIB (IPv6 layer) in the protocol stack.
IANA assigned the OBJECT IDENTIFIER value { mib-2 226 } with descriptor 'lowpanMIB' in the SMI Numbers registry for use by the LOWPAN-MIB module defined in this document.
All objects in this MIB are read-only (no read-write or read-create), so there is no risk of an intruder altering management objects via SNMP SET operations. However, GET access to traffic counters should still be controlled as they reveal communication patterns, and reassembly counters could inform denial-of-service attacks on the reassembly mechanism.
SNMPv3 with cryptographic mechanisms for authentication and privacy is RECOMMENDED. Deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED. Operators must configure SNMP entities to restrict access to legitimate principals.