INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 Management Information Base for Data Over Cable Service Interface Specification (DOCSIS) Cable Modem Termination Systems for Subscriber Management draft-ietf-ipcdn-subscriber-mib-11.txt Wed May 28 15:00:00 EST 2003 Wilson Sawyer ARRIS wsawyer@ieee.org Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at: http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at: http://www.ietf.org/shadow.html. 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 set of managed objects for SNMP-based management of Data-over-Cable Service Interface Specification (DOCSIS)-compliant Cable Modem Termination Systems. These managed objects facilitate protection of the cable network from misuse by subscribers. 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@ietf.org and/or the author. Expires November 2003 [Page 1] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 Table of Contents 1. The Internet-Standard Management Framework.........................2 2. Overview...........................................................2 2.1. Structure of the MIB.............................................3 2.1.1. docsSubMgtFilterGroupTable.....................................4 2.2. Management requirements..........................................4 2.2.1. Interaction with DOCSIS provisioning for CPE address control...5 2.2.2. Interaction with DOCSIS provisioning for filtering.............5 2.2.3. Distinguishing Modem from Subscriber Traffic...................6 2.3. Relationship to the Differentiated Services MIB [RFC3289]........6 2.4. Filtering and the Tiny Fragment Attack...........................7 3. Definitions........................................................7 4. Acknowledgments...................................................16 5. Normative References..............................................16 6. Informative References............................................17 7. Security Considerations...........................................17 8. Author's Address..................................................19 9. Intellectual Property.............................................19 10. Full Copyright Statement.........................................19 1. 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]. 2. Overview This MIB provides a set of objects required for the management of DOCSIS Cable Modem Termination Systems (CMTS). The specification is derived in part from the operational model described in the DOCSIS Radio Frequency Interface Specification [DOCSRFI]. These managed objects facilitate protection of the cable network from misuse by subscribers. The following figure illustrates the operational and physical deployment relationships between elements in a cable modem network. This MIB resides at the CMTS, which is the first point in the public data network at which the cable operator controls physical access. The CMTS (possibly assisted by other IP services devices) acts as a network edge, separating the physical outside-plant cable television network from the operator's IP network. Expires November 2003 [Page 2] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 | operator's IP network +------+ --------------------- | CMTS | operator's cable head-end +------+ --------------------- | +--------+--------+ CATV physical network | | | +----+ +----+ +----+ ------------------ | CM | | CM | | CM | subscriber premises +----+ +----+ +----+ ------------------ | | | subscriber host or network This MIB controls IP packet forwarding to and from each cable modem, at the CMTS. Different modems may be accorded different treatment. Much of this MIB duplicates capabilities found in the DOCSIS Cable Device MIB [RFC2669]. While it is expected that the Cable Device MIB will be used to prevent unwanted traffic from entering the cable network, it is also possible that a malicious user might tamper with cable modem software, disabling its filtering policies. This MIB provides a more secure mechanism, since physical access to the CMTS is controlled by the network operator. In particular, this MIB provides two capabilities: first, to limit the IP addresses behind a modem, and, second, to provide protocol filtering to and from a modem. The first duplicates the capabilities of the docsDevCpe group [RFC2669]. This provides for either learned or provisioned subscriber premises host IP addresses behind a cable modem. The filtering capability makes use of the Classification, Counting, and Drop facilities of the Differentiated Services MIB [RFC3289]. In order to provide different filtering for various classes of subscribers, this MIB defines the docsSubMgtFilterGroupTable which specifies which filters are to apply to each subscriber packet. This table is used by RFC3289 as a first pass of classification, to then choose a second pass of classification using the diffServMultiFieldClfrTable: diffServDataPathStart --> diffServClfrEntry(1) diffServClfrElementSpecific(1) --> docsSubMgtFilterGroupIndex diffServClfrElementNext(1) --> diffServClfrEntry(2) diffServClfrElementSpecific(2)--> diffServMultiFieldClfrEntry diffServClfrElementNext(2) --> difServActionEntry (count or algDrop) Rather than maintaining a separate list of filters for each modem at the CMTS, it is assumed that large numbers of modems will share filtering characteristics. Therefore, DOCSIS signaling defines filter groups by which cable modems share common filter lists. 2.1. Structure of the MIB Expires November 2003 [Page 3] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 This MIB is structured in four tables: o The docsSubMgtCpeControlTable controls the acceptance of subscriber host addresses behind a cable modem. o The docsSubMgtCpeIpTable monitors the subscriber host addresses which the CMTS believes to exist behind the cable modem. o The docsSubMgtCmFilterTable binds a cable modem to a set of filters in diffServMultiFieldClfrTable. o The docsSubMgtFilterGroupTable provides the OIDs by which the diffServClfrElementTable selects a filter group. The docsSubMgtCpeControlTable and docsSubMgtCmFilterTable AUGMENT the docsIfCmtsCmStatusTable from [RFC2670]. Similarly, docsSubMgtCpeIpTable expands this table (an additional index is used). As such, each entry in these tables is bound to a registered cable modem, as perceived by the CMTS. 2.1.1. docsSubMgtFilterGroupTable The docsSubMgtFilterGroupTable is unusual in that it might be viewed not so much as an array of single-object entries as an array of OBJECT-IDENTIFIER conventions. Each instance of docsSubMgtFilterGroupIndex serves as an OID reference for diffServClfrElementSpecific. The index value corresponds to the filter group identifier signaled by the cable modem [DOCSRFI]. An entry exists in this Table if a reference to it exists in diffServClfrElementSpecific. As such, contrary to common practice, the index for the table is read-only, and is both the Entry's index and its only value. 2.2. Management requirements The DOCSIS cable modem provisioning model [DOCSRFI] requires that cable modems use TFTP to acquire a list of parameters. The modem then passes many of these parameters to the CMTS in the DOCSIS Registration message. The parameter values are digitally signed by the creator of the TFTP contents, and the signature is verified by the CMTS. In general, then, the CMTS need not itself be configured with the attributes of its cable modems. It will acquire these values through the Registration process that is secured by the digital signature. Cable modem subscriber management, as described here, modifies this process slightly for reasons of data reduction and ease of administrative control. In the case of filtering management, for example, the tables are maintained through SNMP at the CMTS, and the modem registration merely signals the index values for the rows that apply to that modem. Expires November 2003 [Page 4] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 2.2.1. Interaction with DOCSIS provisioning for CPE address control Rows in docsSubMgtCpeControlTable are created by the CMTS for each modem as a result of the DOCSIS registration process. The DOCSIS registration attributes may include items semantically equivalent to those in the DocsDevCpe branch of the DOCSIS Cable Device MIB [RFC2669]: o docsDevCpeEnroll o docsDevCpeIpMax o docsDevCpeIp Successful DOCSIS registration shall have the effect of setting the corresponding fields in the docsSubMgtCpeControlTable and the docsSubMgtCpeIpTable. If not present, the default at registration shall be to set docsSubMgtCpeControlActive to false. Rows in docsSubMgtCpeIpTable are created through any of three ways: DOCSIS registration (as described above), learning by the CMTS, or through some unspecified administrative mechanism on the CMTS. The docsDevCpeIpMax table bound applies only to the first two. The CMTS may learn addresses by simply snooping source IP addresses from each cable modem. Other learning mechanisms (for example, ARP snooping) may be used. The learning mechanism is not defined by this document. 2.2.2. Interaction with DOCSIS provisioning for filtering Rows in docsSubMgtCmFilterTable are created by the CMTS for each modem as a result of the DOCSIS registration process. The DOCSIS registration attributes may include four indices (see section C.1.1.18.3 of [DOCSRFI]): o one identifying the upstream filter group for packets originating from the cable modem (i.e., those packets whose source MAC address matches that of the cable modem). o one identifying the upstream filter group for packets originating from subscribers attached to the cable modem (i.e., those packets whose source MAC address does not match that of the cable modem). o one identifying the downstream filter group for packets destined to the cable modem (i.e., those packets whose destination MAC address matches that of the cable modem). o one identifying the downstream filter group for packets destined to subscribers attached to the cable modem (i.e., those packets whose destination MAC address does not match that of the cable modem). Successful registration shall have the effect of setting docsSubMgtCmFilterDownstream, docsSubMgtCmFilterUpstream, docsSubMgtSubFilterDownstream, and docsSubMgtSubFilterUpstream, for that modem (just as if set through the SNMP protocol). If the DOCSIS Expires November 2003 [Page 5] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 attributes are not present, the effect shall be to use the default entry (diffServClfrElementSpecific=zeroDotZero) specified in the diffServClfrElementTable. 2.2.3. Distinguishing Modem from Subscriber Traffic All traffic originating from or destined to a subscriber site is potentially suspect, and subject to suppression by the network operator. This is true even if the traffic is ostensibly sourced or sunk by the cable modem itself, rather than the subscriber hosts behind the modem. To provide more nuanced administrative control, this document allows separate filter policies for modems and hosts. For example, modem policies may limit modems to server-subnet-only access, while allowing a different scope to subscribers. The CMTS chooses the filter set to apply based solely on the MAC address (source MAC upstream, destination MAC downstream). If the MAC address matches that of the modem, then the docsSubMgtCmFilterUp/Downstream pair is used; otherwise the docsSubMgtSubFilterUp/Downstream pair is applied. If the CM acts as a router rather than as a DOCSIS bridging forwarder, then the network operator will only use the docsSubMgtCmFilterUp/Downstream pair. 2.3. Relationship to the Differentiated Services MIB [RFC3289] DOCSIS CMTSs rely on the classification, counting, and drop facilities of the Differentiated Services MIB to screen subscriber packets for IP, TCP, and UDP characteristics. It is expected that any implementation of this MIB also include at least the following from RFC 3289: o diffServDataPathTable o diffServClfrTable o diffServClfrElementTable o diffServMultiFieldClfrTable o diffServActionTable o diffServCountActTable o diffServAlgDropTable (diffServAlgDropType=alwaysDrop) The use of other facilities from RFC 3289 is not precluded, but is beyond the scope of this specification. The base capability of RFC 3289 assumes that all packets on the same direction of the same interface will be classified by the same criteria. Filter Groups, introduced in this document, expand on RFC 3289 to allow various subscribers to receive different classification (filtering) treatment. One way to view filter groups is as sub- interfaces within the physical DOCSIS channel. Another way to view them is as values of a field logically prepended to the packet prior to classification: Expires November 2003 [Page 6] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 [filter group][docsis MAC header][IP header]... Of course this 'logical' field has no existence outside of the CMTS. The diffServClfrTable and diffServClfrElementTable are then used twice: the first classifiers select among filter groups, using OIDs from docsSubMgtFilterGroupTable. The 'next' action on matching a filter group is to select a diffServClfrEntry which now classifies on IP/TCP/UDP criteria (the diffServMultiFieldClfrTable_. The 'next' action on this second match may be a 'count' (and accept), a 'drop', or some other feature from RFC 3289. 2.4. Filtering and the Tiny Fragment Attack It is recommended that the implementers prevent the "tiny fragment" and "overlapping fragment" attacks for the TCP filtering tables in this MIB, as discussed in RFC 1858 [RFC1858] and RFC 3128 [RFC3128]. Prevention of these attacks can be implemented with the following rules, when filtering is enabled: o admit all packets with fragment offset >= 2 o discard all packets with fragment offset = 1, or with fragment offset = 0 AND fragment payload length < 16. o apply filtering rules to all packets with fragment offset = 0. 3. Definitions DOCS-IETF-SUBMGT-MIB DEFINITIONS ::= BEGIN IMPORTS MODULE-IDENTITY, OBJECT-TYPE, Integer32, mib-2 FROM SNMPv2-SMI TruthValue, TimeStamp FROM SNMPv2-TC OBJECT-GROUP, MODULE-COMPLIANCE FROM SNMPv2-CONF InetAddressType, InetAddress FROM INET-ADDRESS-MIB docsIfCmtsCmStatusIndex, docsIfCmtsCmStatusEntry FROM DOCS-IF-MIB; -- RFC2670 docsSubMgt MODULE-IDENTITY LAST-UPDATED "200305280000Z" -- May 28, 2003 Expires November 2003 [Page 7] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 ORGANIZATION "IETF IPCDN Working Group" CONTACT-INFO " Wilson Sawyer Postal: ARRIS 50 Kelly Brook Lane East Hampstead, NH 03826 U.S.A. Phone: +1 603 382 7080 E-mail: wsawyer@ieee.org IETF IPCDN Working Group General Discussion: ipcdn@ietf.org Subscribe: http://www.ietf.org/mailman/listinfo/ipcdn Archive: ftp://ftp.ietf.org/ietf-mail-archive/ipcdn Co-chairs: Richard Woundy, Richard_Woundy@cable.comcast.com Jean-Francois Mule, jf.mule@cablelabs.com" DESCRIPTION "This is the CMTS centric subscriber management MIB for DOCSIS compliant CMTS. Copyright (C) The Internet Society (2003). This version of this MIB module is part of RFC xxxx; see the RFC itself for full legal notices." REVISION "200305280000Z" -- May 28, 2003 DESCRIPTION "Initial version, published as RFC xxxx." -- RFC editor to assign xxxx ::= { mib-2 xx } -- xx to be assigned by IANA docsSubMgtObjects OBJECT IDENTIFIER ::= { docsSubMgt 1 } docsSubMgtCpeControlTable OBJECT-TYPE SYNTAX SEQUENCE OF DocsSubMgtCpeControlEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table AUGMENTs the docsIfCmtsCmStatusTable and adds four WRITEable objects which reflect the state of subscriber management on a particular CM." ::= { docsSubMgtObjects 1 } docsSubMgtCpeControlEntry OBJECT-TYPE SYNTAX DocsSubMgtCpeControlEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A row in the docsSubMgtCpeControlTable. All values are set at successful modem registration, either from the system default, or from objects included in the DOCSIS registration request sent upstream to the CMTS from the CM. The contents of this entry are meaningless unless the corresponding docsIfCmtsCmStatusValue is registrationComplete(6). The persistence of this row is determined solely by the lifespan of the corresponding docsIfCmtsCmStatusEntry (normally StorageType=volatile)." Expires November 2003 [Page 8] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 AUGMENTS { docsIfCmtsCmStatusEntry } ::= {docsSubMgtCpeControlTable 1 } DocsSubMgtCpeControlEntry ::= SEQUENCE { docsSubMgtCpeControlMaxCpeIp Integer32, docsSubMgtCpeControlActive TruthValue, docsSubMgtCpeControlLearnable TruthValue, docsSubMgtCpeControlReset TruthValue, docsSubMgtCpeControlLastReset TimeStamp } docsSubMgtCpeControlMaxCpeIp OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-write STATUS current DESCRIPTION "The number of simultaneous IP addresses permitted behind the CM. If this is set to zero, all CPE traffic from the CM is dropped. If the provisioning object corresponding to docsSubMgtCpeIpTable includes more CPE IP address entries for this modem than the value of this object, then this object is set to the count of the number of rows in docsSubMgtCpeIpTable that have the same docsIfCmtsCmStatusIndex value. (E.g. if the CM has 5 IP addresses specified for it, this value is 5). This limit applies to learned and docsis-provisioned entries, but does not limit entries added through some administrative process at the CMTS. If not set through DOCSIS provisioning, this object defaults to docsSubMgtCpeMaxIpDefault. Note that this object is only meaningful if docsSubMgtCpeControlActive is true." ::= { docsSubMgtCpeControlEntry 1 } docsSubMgtCpeControlActive OBJECT-TYPE SYNTAX TruthValue MAX-ACCESS read-write STATUS current DESCRIPTION "If this is set to true, CMTS based CPE control is active and all the actions required by the various filter tables and controls apply at the CMTS. If this is set to false, no subscriber management filtering is done at the CMTS (but other filters may apply). If not set through DOCSIS provisioning, this object defaults to docsSubMgtCpeActiveDefault." ::= { docsSubMgtCpeControlEntry 2 } docsSubMgtCpeControlLearnable OBJECT-TYPE SYNTAX TruthValue MAX-ACCESS read-write STATUS current DESCRIPTION "If this is set to true, the CMTS may learn up to docsSubMgtMaxCpeIp addresses (less any DOCSIS-provisioned Expires November 2003 [Page 9] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 entries) related to this CM. Those IP addresses are added (by internal process) to the docsSubMgtCpeIpTable. The nature of the learning mechanism is not specified here. If not set through DOCSIS provisioning, this object defaults to docsSubMgtCpeLearnableDefault. Note that this object is only meaningful if docsSubMgtCpeControlActive is true." ::= { docsSubMgtCpeControlEntry 3 } docsSubMgtCpeControlReset OBJECT-TYPE SYNTAX TruthValue MAX-ACCESS read-write STATUS current DESCRIPTION "This object always returns false on read. If this object is set to true, the rows with 'learned' addresses in docsSubMgtCpeIpTable for this CM are deleted from that table." ::= { docsSubMgtCpeControlEntry 4 } docsSubMgtCpeControlLastReset OBJECT-TYPE SYNTAX TimeStamp MAX-ACCESS read-only STATUS current DESCRIPTION "The value of sysUpTime when docsSubMgtCpeControlReset was last set true. Zero if never reset." ::= { docsSubMgtCpeControlEntry 5 } docsSubMgtCpeMaxIpDefault OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-write STATUS current DESCRIPTION "The default value for docsSubMgtCpeControlMaxCpeIp if not signaled in the DOCSIS Registration request. Upon initial CMTS initialization, this defaults to 16." ::= { docsSubMgtObjects 2 } docsSubMgtCpeActiveDefault OBJECT-TYPE SYNTAX TruthValue MAX-ACCESS read-write STATUS current DESCRIPTION "The default value for docsSubMgtCpeControlActive if not signaled in the DOCSIS Registration request. Upon initial CMTS initialization, this defaults to false." ::= { docsSubMgtObjects 3 } docsSubMgtCpeLearnableDefault OBJECT-TYPE SYNTAX TruthValue MAX-ACCESS read-write STATUS current DESCRIPTION "The default value for docsSubMgtCpeControlLearnable if not Expires November 2003 [Page 10] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 signaled in the DOCSIS Registration request. Upon initial CMTS initialization, this defaults to true." ::= { docsSubMgtObjects 4 } docsSubMgtCpeIpTable OBJECT-TYPE SYNTAX SEQUENCE OF DocsSubMgtCpeIpEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A table of CPE IP addresses known on a per CM basis." ::= { docsSubMgtObjects 5 } docsSubMgtCpeIpEntry OBJECT-TYPE SYNTAX DocsSubMgtCpeIpEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "An entry in the docsSubMgtCpeIpTable. The first index is the specific modem we're referring to, the second index is the specific CPE IP entry." INDEX { docsIfCmtsCmStatusIndex, docsSubMgtCpeIpIndex } ::= {docsSubMgtCpeIpTable 1 } DocsSubMgtCpeIpEntry ::= SEQUENCE { docsSubMgtCpeIpIndex Integer32, docsSubMgtCpeIpAddressType InetAddressType, docsSubMgtCpeIpAddr InetAddress, docsSubMgtCpeIpLearned TruthValue } docsSubMgtCpeIpIndex OBJECT-TYPE SYNTAX Integer32(1..2147483647) MAX-ACCESS not-accessible STATUS current DESCRIPTION "The index of this CPE IP address relative to the indexed CM. An entry is created either through the included CPE IP addresses in the provisioning object, or via learning. If a CMTS receives an IP packet from a CM that contains a source IP address which does not match one of the docsSubMgtCpeIpAddr entries for this CM, one of two things occurs. If the number of entries is less than docsSubMgtCpeControlMaxCpeIp, the source address is added to the table and the packet is forwarded. If the number of entries equals the docsSubMgtCpeControlMaxCpeIp, AND docsSubMgtCpeControlActive is true, then the packet is dropped. Otherwise the packet is forwarded. " ::= { docsSubMgtCpeIpEntry 1 } docsSubMgtCpeIpAddressType OBJECT-TYPE SYNTAX InetAddressType Expires November 2003 [Page 11] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 MAX-ACCESS read-only STATUS current DESCRIPTION "The type of internet address of docsSubMgtCpeIpAddr." ::= { docsSubMgtCpeIpEntry 2 } docsSubMgtCpeIpAddr OBJECT-TYPE SYNTAX InetAddress MAX-ACCESS read-only STATUS current DESCRIPTION "The IP address either set from provisioning or learned via address gleaning or other forwarding means. See docsSubMgtCpeIpIndex for the mechanism." ::= { docsSubMgtCpeIpEntry 3 } docsSubMgtCpeIpLearned OBJECT-TYPE SYNTAX TruthValue MAX-ACCESS read-only STATUS current DESCRIPTION "If true, this entry was learned from IP packets sent upstream rather than from the provisioning objects." ::= { docsSubMgtCpeIpEntry 4 } docsSubMgtCmFilterTable OBJECT-TYPE SYNTAX SEQUENCE OF DocsSubMgtCmFilterEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Binds filter groups to modems. This table identifies for each modem the upstream and downstream filter groups that apply to packets for that modem. Zero is used as a distinguished value to mean no filter group." ::= { docsSubMgtObjects 6 } docsSubMgtCmFilterEntry OBJECT-TYPE SYNTAX DocsSubMgtCmFilterEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Binds a filter group to each direction of traffic for a modem. The filters in this entry apply if docsSubMgtCpeControlActive is true. The contents of this entry are meaningless unless the corresponding docsIfCmtsCmStatusValue is registrationComplete(6). The persistence of this row is determined solely by the lifespan of the corresponding docsIfCmtsCmStatusEntry (normally StorageType=volatile)." AUGMENTS { docsIfCmtsCmStatusEntry } ::= {docsSubMgtCmFilterTable 1 } DocsSubMgtCmFilterEntry ::= SEQUENCE { Expires November 2003 [Page 12] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 docsSubMgtSubFilterDownstream Integer32, docsSubMgtSubFilterUpstream Integer32, docsSubMgtCmFilterDownstream Integer32, docsSubMgtCmFilterUpstream Integer32 } docsSubMgtSubFilterDownstream OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-write STATUS current DESCRIPTION "The filter group applied to traffic destined for subscribers attached to the referenced CM. This is set upon row creation to either zero (use default classification), or to the value in the provisioning object sent upstream from the CM to the CMTS during registration. The value of this object is the same as the filter group index appearing as docsSubMgtFilterGroupIndex." ::= { docsSubMgtCmFilterEntry 1 } docsSubMgtSubFilterUpstream OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-write STATUS current DESCRIPTION "The filter group applied to traffic originating from subscribers attached to the referenced CM. This is set upon row creation to either zero (use default classification), or to the value in the provisioning object sent upstream from the CM to the CMTS. The value of this object is the same as the filter group index appearing as docsSubMgtFilterGroupIndex." ::= { docsSubMgtCmFilterEntry 2 } docsSubMgtCmFilterDownstream OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-write STATUS current DESCRIPTION "The filter group applied to traffic destined for the referenced CM itself. This is set upon row creation to either zero (use default classification), or to the value in the provisioning object sent upstream from the CM to the CMTS during registration. The value of this object is the same as the filter group index appearing as docsSubMgtFilterGroupIndex." ::= { docsSubMgtCmFilterEntry 3 } docsSubMgtCmFilterUpstream OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-write STATUS current DESCRIPTION "The filter group applied to traffic originating from the referenced CM itself. This is set upon row creation to either zero use default classification), or to the value in Expires November 2003 [Page 13] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 the provisioning object sent upstream from the CM to the CMTS during registration. The value of this object is the same as the filter group index appearing as docsSubMgtFilterGroupIndex." ::= { docsSubMgtCmFilterEntry 4 } docsSubMgtFilterGroupTable OBJECT-TYPE SYNTAX SEQUENCE OF DocsSubMgtFilterGroupEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Provides a collection of OIDs to which diffServClfrElementSpecific refers. This table provides filter group indices which can be compared with those signaled during Docsis registration. A packet matches an entry from this table if the packet originated from or is destined to a cable modem which registered this index as one of its four filter groups (see docsSubMgtCmFilterTable) and if the packet direction and MAC address select the use of this index among the four." ::= { docsSubMgtObjects 7 } docsSubMgtFilterGroupEntry OBJECT-TYPE SYNTAX DocsSubMgtFilterGroupEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "An entry only exists if needed by the diffServClfrElementEntry. A packet matches this entry if the packet's cable modem registered this index as one of its four filter groups (see docsSubMgtCmFilterTable) and if the packet direction and MAC address select the use of this index among the four." INDEX { docsSubMgtFilterGroupIndex } ::= { docsSubMgtFilterGroupTable 1 } DocsSubMgtFilterGroupEntry ::= SEQUENCE { docsSubMgtFilterGroupIndex Integer32 } docsSubMgtFilterGroupIndex OBJECT-TYPE SYNTAX Integer32(0..2147483647) MAX-ACCESS read-only STATUS current DESCRIPTION "Provides an OID to which diffServClfrElementSpecific refers. A packet matches this entry if the packet's cable modem registered this index value as one of its four filter groups and if the packet direction and MAC address select the use of this index among the four. Because this is the only field in this table, it is read-only, contrary to the usual SNMP custom of making indices not-accessible." ::= { docsSubMgtFilterGroupEntry 1 } Expires November 2003 [Page 14] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 docsSubMgtConformance OBJECT IDENTIFIER ::= { docsSubMgt 2 } docsSubMgtCompliances OBJECT IDENTIFIER ::= { docsSubMgtConformance 1 } docsSubMgtGroups OBJECT IDENTIFIER ::= { docsSubMgtConformance 2 } docsSubMgtBasicCompliance MODULE-COMPLIANCE STATUS current DESCRIPTION "The compliance statement for CMTS devices that implement CMTS centric subscriber management." MODULE MANDATORY-GROUPS { docsSubMgtGroup } OBJECT docsSubMgtCpeControlMaxCpeIp SYNTAX Integer32(0..16) DESCRIPTION "An implementation is only required to support up to sixteen addresses per modem." OBJECT docsSubMgtCpeMaxIpDefault SYNTAX Integer32(0..16) DESCRIPTION "An implementation is only required to support up to sixteen addresses per modem." OBJECT docsSubMgtCpeIpAddressType SYNTAX InetAddressType { ipv4(1) } DESCRIPTION "An implementation is only required to support IPv4 addresses." OBJECT docsSubMgtCpeIpAddr SYNTAX InetAddress (SIZE(4)) DESCRIPTION "An implementation is only required to support IPv4 addresses." OBJECT docsSubMgtSubFilterDownstream SYNTAX Integer32(0..30) DESCRIPTION "An implementation is only required to support thirty filter groups." OBJECT docsSubMgtSubFilterUpstream SYNTAX Integer32(0..30) DESCRIPTION "An implementation is only required to support thirty filter groups." Expires November 2003 [Page 15] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 OBJECT docsSubMgtCmFilterDownstream SYNTAX Integer32(0..30) DESCRIPTION "An implementation is only required to support thirty filter groups." OBJECT docsSubMgtCmFilterUpstream SYNTAX Integer32(0..30) DESCRIPTION "An implementation is only required to support thirty filter groups." ::= { docsSubMgtCompliances 1 } docsSubMgtGroup OBJECT-GROUP OBJECTS { docsSubMgtCpeControlMaxCpeIp, docsSubMgtCpeControlActive, docsSubMgtCpeControlLearnable, docsSubMgtCpeControlReset, docsSubMgtCpeControlLastReset, docsSubMgtCpeMaxIpDefault, docsSubMgtCpeActiveDefault, docsSubMgtCpeLearnableDefault, docsSubMgtCpeIpAddressType, docsSubMgtCpeIpAddr, docsSubMgtCpeIpLearned, docsSubMgtSubFilterDownstream, docsSubMgtSubFilterUpstream, docsSubMgtCmFilterDownstream, docsSubMgtCmFilterUpstream, docsSubMgtFilterGroupIndex } STATUS current DESCRIPTION "The objects use to managed host-based cable modems via a set of CMTS enforced controls." ::= { docsSubMgtGroups 1 } END 4. Acknowledgments This document is based on work by Michael St.Johns, then at Excite@Home. Thanks to Guenter Roeck, Julie McGray, and Bert Wijnen for reviewing earlier drafts. 5. Normative References [RFC2578] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Structure of Management Information for Version 2 (SMIv2)", STD 58, RFC 2578, April 1999. Expires November 2003 [Page 16] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 [RFC2579] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999. [RFC2580] McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999. [DOCSRFI] "Data-Over-Cable Service Interface Specifications: Cable Modem Radio Frequency Interface Specification SP-RFIv2.0-I03-021218", DOCSIS, December 2002, available at http://www.cablemodem.com/. [RFC2669] StJohns, M. , "Cable Device Management Information Base for DOCSIS Compliant Cable Modems and Cable Modem Termination Systems", RFC2669, August 1999. [RFC2670] StJohns, M. , "Radio Frequency (RF) Interface Management Information Base for MCNS/DOCSIS compliant RF interfaces", RFC2670, August 1999. [RFC3289] Baker, F., Chan, K., and A. Smith, "Management Information Base for the Differentiated Services Architecture", RFC3289, May 2002. 6. Informative References [RFC1858] Ziemba, G., Reed, D., and P. Traina, "Security Considerations for IP Fragment Filtering", RFC1858, October 1995. [RFC3128] Miller, I., "Protection against a Variant of the Tiny Fragment Attack". RFC3128, June 2001. [RFC3410] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction and Applicability Statements for Internet- Standard Management Framework", RFC 3410, December 2002. [DOCSBPI] "Data-Over-Cable Service Interface Specifications: Baseline Privacy Plus Interface Specification SP-BPI+-I09-020830", DOCSIS, August 2002, available at http://www.cablemodem.com/. 7. Security Considerations This MIB is intended to limit certain kinds of network behavior by subscriber hosts attached to cable modems, including, for example, IP spoofing. These limitations may be compromised, however, if the cable Expires November 2003 [Page 17] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 modem's identity or registration process is spoofed. The DOCSIS RFI and privacy specifications [DOCSRFI] and [DOCSBPI] define a number of mechanisms for assuring modem identity. The filtering mechanism defined here can be defeated through the "tiny fragment" and "overlapping fragment" attacks if the recommendations in section 2.2.6 are omitted. See [RFC1858] and [RFC3128] for discussion of these attacks. There are a number of management objects defined in this MIB that have a MAX-ACCESS clause of read-write and/or read-create. Such objects may be considered sensitive or vulnerable in some network environments. The support for SET operations in a non-secure environment without proper protection can have a negative effect on network operations. Unauthorized SETs to this MIB can permit two major security problems with public cable network operation: IP address spoofing, and defeat of operator-defined packet filtering. The following objects, if SET maliciously, would evade controls on address spoofing: docsSubMgtCpeControlMaxCpeIp docsSubMgtCpeControlActive docsSubMgtCpeControlLearnable docsSubMgtCpeControlReset docsSubMgtCpeMaxIpDefault docsSubMgtCpeActiveDefault docsSubMgtCpeLearnableDefault The following objects could also permit packet filtering to be defeated: docsSubMgtSubFilterDownstream docsSubMgtSubFilterUpstream docsSubMgtCmFilterDownstream docsSubMgtCmFilterUpstream Some of the readable objects in this MIB module (i.e., objects with a MAX-ACCESS other than not-accessible) may be considered sensitive or vulnerable in some network environments. It is thus important to control even GET access to these objects and possibly to even encrypt the values of these objects when sending them over the network via SNMP. The most sensitive is docsSubMgtCpeIpAddr within docsSubMgtCpeIpTable. While docsSubMgtCpeIpTable is intended to control address spoofing, it includes information about the current subscriber address pool. This information may itself be valuable to would-be spoofers. SNMP versions prior to SNMPv3 did not include adequate security. Even if the network itself is secure (for example by using IPSec), even then, there is no control as to who on the secure network is Expires November 2003 [Page 18] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 allowed to access and GET/SET (read/change/create/delete) the objects in this MIB module. It is RECOMMENDED that implementers consider the security features as provided by the SNMPv3 framework (see [RFC3410], section 8), including full support for the SNMPv3 cryptographic mechanisms (for authentication and privacy). Further, deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to enable cryptographic security. It is then a customer/operator responsibility to ensure that the SNMP entity giving access to an instance of this MIB module, is properly configured to give access to the objects only to those principals (users) that have legitimate rights to indeed GET or SET (change/create/delete) them. 8. Author's Address Wilson Sawyer ARRIS 50 Kelly Brook Lane East Hampstead NH 03826 Phone: +1 603 382 7080 Email: wsawyer@ieee.org 9. Intellectual Property The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 10. Full Copyright Statement Expires November 2003 [Page 19] INTERNET-DRAFT DOCSIS Subscriber Management MIB May 2003 Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Expires November 2003 [Page 20]