Network Working Group M. St. Johns, Ed. Request for Comments: 2669 @Home Network Category: Proposed Standard August 1999 DOCSIS Cable Device MIB Cable Device Management Information Base for DOCSIS compliant Cable Modems and Cable Modem Termination Systems 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 (1999). All Rights Reserved. Abstract This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it defines a basic set of managed objects for SNMP- based management of DOCSIS 1.0 compliant Cable Modems and Cable Modem Termination Systems. This memo specifies a MIB module in a manner that is compliant to the SNMP SMIv2 [5][6][7]. The set of objects is consistent with the SNMP framework and existing SNMP standards. This memo is a product of the IPCDN working group within the Internet Engineering Task Force. Comments are solicited and should be addressed to the working group's mailing list at ipcdn@terayon.com and/or the author. Table of Contents 1 The SNMP Management Framework ................................... 2 2 Glossary ........................................................ 3 2.1 CATV .......................................................... 3 2.2 CM ............................................................ 3 2.3 CMTS .......................................................... 4 2.4 DOCSIS ........................................................ 4 St. Johns Standards [Page 1] RFC 2669 DOCSIS Cable Device MIB August 1999 2.5 Downstream .................................................... 4 2.6 Head-end ...................................................... 4 2.7 MAC Packet .................................................... 4 2.8 MCNS .......................................................... 4 2.9 RF ............................................................ 4 2.10 Upstream ..................................................... 4 3 Overview ........................................................ 4 3.1 Structure of the MIB .......................................... 5 3.2 Management requirements ....................................... 6 3.2.1 Handling of Software upgrades ............................... 6 3.2.2 Events and Traps ............................................ 6 3.2.3 Trap Throttling ............................................. 8 3.2.3.1 Trap rate throttling ...................................... 8 3.2.3.2 Limiting the trap rate .................................... 8 3.3 Protocol Filters .............................................. 9 3.3.1 Inbound LLC Filters - docsDevFilterLLCTable ................ 10 3.3.2 Special Filters ............................................ 10 3.3.2.1 IP Spoofing Filters - docsDevCpeTable .................... 10 3.3.2.2 SNMP Access Filters - docsDevNmAccessTable ............... 10 3.3.3 IP Filtering - docsDevIpFilterTable ........................ 11 3.3.4 Outbound LLC Filters ....................................... 13 4 Definitions .................................................... 13 5 Acknowledgments ................................................ 51 6 References ..................................................... 51 7 Security Considerations ........................................ 52 8 Intellectual Property .......................................... 54 9 Author's Address ............................................... 54 10 Full Copyright Statement ...................................... 55 1. The SNMP Management Framework The SNMP Management Framework presently consists of five major components: o An overall architecture, described in RFC 2571 [1]. o Mechanisms for describing and naming objects and events for the purpose of management. The first version of this Structure of Management Information (SMI) is called SMIv1 and described in STD 16, RFC 1155 [2], STD 16, RFC 1212 [3] and RFC 1215 [4]. The second version, called SMIv2, is described in STD 58, RFC 2578 [5], STD 58, RFC 2579 [6] and STD 58, RFC 2580 [7]. o Message protocols for transferring management information. The first version of the SNMP message protocol is called SNMPv1 and described in STD 15, RFC 1157 [8]. A second version of the SNMP message protocol, which is not an Internet standards track protocol, is called SNMPv2c and described in RFC 1901 [9] and RFC St. Johns Standards [Page 2] RFC 2669 DOCSIS Cable Device MIB August 1999 1906 [10]. The third version of the message protocol is called SNMPv3 and described in RFC 1906 [10], RFC 2572 [11] and RFC 2574 [12]. o Protocol operations for accessing management information. The first set of protocol operations and associated PDU formats is described in STD 15, RFC 1157 [8]. A second set of protocol operations and associated PDU formats is described in RFC 1905 [13]. o A set of fundamental applications described in RFC 2573 [14] and the view-based access control mechanism described in RFC 2575 [15]. Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the mechanisms defined in the SMI. This memo specifies a MIB module that is compliant to the SMIv2. A MIB conforming to the SMIv1 can be produced through the appropriate translations. The resulting translated MIB must be semantically equivalent, except where objects or events are omitted because no translation is possible (use of Counter64). Some machine readable information in SMIv2 will be converted into textual descriptions in SMIv1 during the translation process. However, this loss of machine readable information is not considered to change the semantics of the MIB. 2. Glossary The terms in this document are derived either from normal cable system usage, or from the documents associated with the Data Over Cable Service Interface Specification process. 2.1. CATV Originally "Community Antenna Television", now used to refer to any cable or hybrid fiber and cable system used to deliver video signals to a community. 2.2. CM Cable Modem. A CM acts as a "slave" station in a DOCSIS compliant cable data system. St. Johns Standards [Page 3] RFC 2669 DOCSIS Cable Device MIB August 1999 2.3. CMTS Cable Modem Termination System. A generic term covering a cable bridge or cable router in a head-end. A CMTS acts as the master station in a DOCSIS compliant cable data system. It is the only station that transmits downstream, and it controls the scheduling of upstream transmissions by its associated CMs. 2.4. DOCSIS "Data Over Cable Interface Specification". A term referring to the ITU-T J.112 Annex B standard for cable modem systems [20]. 2.5. Downstream The direction from the head-end towards the subscriber. 2.6. Head-end The origination point in most cable systems of the subscriber video signals. Generally also the location of the CMTS equipment. 2.7. MAC Packet A DOCSIS PDU. 2.8. MCNS "Multimedia Cable Network System". Generally replaced in usage by DOCSIS. 2.9. RF Radio Frequency. 2.10. Upstream The direction from the subscriber towards the head-end. 3. Overview This MIB provides a set of objects required for the management of DOCSIS compliant Cable Modems (CM) and Cable Modem Termination Systems (CMTS). The specification is derived from the DOCSIS Radio Frequency Interface specification [16]. Please note that the DOCSIS 1.0 standard only requires Cable Modems to implement SNMPv1 and to St. Johns Standards [Page 4] RFC 2669 DOCSIS Cable Device MIB August 1999 process IPv4 customer traffic. Design choices in this MIB reflect those requirements. Future versions of the DOCSIS standard are expected to require support for SNMPv3 and IPv6 as well. 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 [19]. 3.1. Structure of the MIB This MIB is structured into seven groups: o The docsDevBase group extends the MIB-II 'system' group with objects needed for cable device system management. o The docsDevNmAccessGroup provides a minimum level of SNMP access security (see Section 3 of [18]). o The docsDevSoftware group provides information for network- downloadable software upgrades. See "Handling of Software Upgrades" below.. o The docsDevServer group provides information about the progress of the interaction between the CM or CMTS and various provisioning servers. o The docsDevEvent group provides control and logging for event reporting. o The docsDevFilter group configures filters at link layer and IP layer for bridged data traffic. This group consists of a link-layer filter table, docsDevFilterLLCTable, which is used to manage the processing and forwarding of non-IP traffic; an IP packet classifier table, docsDevFilterIpTable, which is used to map classes of packets to specific policy actions; a policy table, docsDevFilterPolicyTable, which maps zero or more policy actions onto a specific packet classification, and one or more policy action tables. At this time, this MIB specifies only one policy action table, docsDevFilterTosTable, which allows the manipulation of the type of services bits in an IP packet based on matching some criteria. The working group may add additional policy types and action tables in the future, for example to allow QOS to modem service identifier assignment based on destination. St. Johns Standards [Page 5] RFC 2669 DOCSIS Cable Device MIB August 1999 o The docsDevCpe group provides control over which IP addresses may be used by customer premises equipment (e.g. PCs) serviced by a given cable modem. This provides anti-spoofing control at the point of origin for a large cable modem system. This group is separate from docsDevFilter primarily as this group is only implemented on the Cable Modem (CM) and MUST NOT be implemented on the Cable Modem Termination System (CMTS). 3.2. Management requirements 3.2.1. Handling of Software upgrades The Cable Modem software upgrade process is documented in [16]. From a network management station, the operator: o sets docsDevSwServer to the address of the TFTP server for software upgrades o sets docsDevSwFilename to the file pathname of the software upgrade image o sets docsDevSwAdminStatus to upgrade-from-mgt One reason for the SNMP-initiated upgrade is to allow loading of a temporary software image (e.g., special diagnostic software) that differs from the software normally used on that device without changing the provisioning database. Note that software upgrades should not be accepted blindly by the cable device. The cable device may refuse an upgrade if: o The download is incomplete. o The file contents are incomplete or damaged. o The software is not intended for that hardware device (may include the case of a feature set that has not been purchased for this device). 3.2.2. Events and Traps This MIB provides control facilities for reporting events through syslog, traps, and non-volatile logging. If events are reported through traps, the specified conventions must be followed. Other means of event reporting are outside the scope of this document. St. Johns Standards [Page 6] RFC 2669 DOCSIS Cable Device MIB August 1999 The definition and coding of events is vendor-specific. In deference to the network operator who must troubleshoot multi-vendor networks, the circumstances and meaning of each event should be reported as human-readable text. Vendors SHOULD provide time-of-day clocks in CMs to provide useful timestamping of events. For each vendor-specific event that is reportable via TRAP, the vendor must create an enterprise-specific trap definition. Trap definitions MUST include the event reason encoded as DisplayString and should be defined as: trapName NOTIFICATION-TYPE OBJECTS { ifIndex, eventReason, other useful objects } STATUS current DESCRIPTION "trap description" ::= Object Id Note that ifIndex is only included if the event or trap is interface related. An example (fake) vendor defined trap might be: xyzVendorModemDropout NOTIFICATION-TYPE OBJECTS { eventReason, xyzModemHighWatermarkCount } STATUS current DESCRIPTION "Sent by a CMTS when a configurable number of modems (xyzModemHysteresis) de-register or become unreachable during the sampling period (5 minutes). Used to warn a management station about a catastrophic cable plant outage." ::= { xyzTraps 23 } In this example eventReason is a DisplayString providing a human readable error message, and xyzModemHighWatermarkCount is a Gauge32 which indicates the maximum number of modems during the epoch. St. Johns Standards [Page 7] RFC 2669 DOCSIS Cable Device MIB August 1999 The last digit of the trap OID for enterprise-specific traps must match docsDevEvId. For SNMPv1-capable Network Management systems, this is necessary to correlate the event type to the trap type. Many Network Management systems are only capable of trap filtering on an enterprise and single-last-digit basis. 3.2.3. Trap Throttling The CM and CMTS MUST provide support for trap message throttling as described below. The network operator can employ message rate throttling or trap limiting by manipulating the appropriate MIB variables. 3.2.3.1. Trap rate throttling Network operators may employ either of two rate control methods. In the first method, the device ceases to send traps when the rate exceeds the specified maximum message rate. It resumes sending traps only if reactivated by a network management station request. In the second method, the device resumes sending traps when the rate falls below the specified maximum message rate. The network operator configures the specified maximum message rate by setting the measurement interval (in seconds), and the maximum number of traps to be transmitted within the measurement interval. The operator can