RFC4036
Network Working Group W. Sawyer Request for Comments: 4036 April 2005 Category: Standards Track
Management Information Base for
Data Over Cable Service Interface Specification (DOCSIS)
Cable Modem Termination Systems for Subscriber Management
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 (2005).
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 Simple Network Management Protocol (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. The Differentiated Services MIB (RFC 3289) provides the filtering functions needed here, making use of classification items defined in this specification.
3.2.1. Interaction with DOCSIS Provisioning for CPE
3.2.2. Interaction with DOCSIS Provisioning for
3.3. Relationship to the Differentiated Services MIB
3.3.1. Using the Filter Group to Extend Packet
Contents
- 1 The Internet-Standard Management Framework
- 2 Conventions
- 3 Overview
- 4 Definitions
- 5 Acknowledgements
- 6 IANA Considerations
- 7 Normative References
- 8 Informative References
- 9 Security Considerations
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.
Conventions
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 BCP 14, RFC 2119 RFC2119.
Overview
This MIB module 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 [ITU-T-J122]. These managed objects facilitate protection of the cable network from misuse by subscribers. This misuse might include, for example, address spoofing, service spoofing, or operation of unauthorized services.
The following figure illustrates the operational and physical deployment relationships between elements in a cable modem network. This MIB module 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 service devices) acts as a network edge, separating the physical outside-plant cable television network from the operator's IP network.
| operator's IP network
+------+ ---------------------
| CMTS | operator's cable head-end
+------+ ---------------------
|
+--------+--------+ CATV physical network
| | |
+----+ +----+ +----+ ------------------
| CM | | CM | | CM | subscriber premises
+----+ +----+ +----+ ------------------
| | | subscriber host or network
This MIB module controls IP packet forwarding to and from each cable modem, at the CMTS. Different modems may be accorded different treatment.
Much of this module duplicates capabilities found in the DOCSIS Cable Device MIB RFC2669. Although 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, as 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 address and 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 address and protocol filtering capability is similar to that performed by the cable modem itself. It differs in several respects because it is intended to control subscriber traffic at the CMTS, rather than at the individual CM. First, the MIB structure must be indexed appropriately at the CMTS to indicate which cable modem subscriber is intended. Second, 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, modems are grouped so as to share common filter lists.
The filtering capability is implemented using 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 apply to each subscriber packet. This table is used by RFC 3289 as a first pass of classification, and also to 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)
Because it is assumed that large numbers of modems will share filtering characteristics, DOCSIS signaling defines filter groups according to which cable modems share common filter lists. The operator creates references to these groups in the diffServClfrElementSpecific(1) entries above.
Structure of the MIB
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
that the CMTS believes 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.
docsSubMgtFilterGroupTable
The docsSubMgtFilterGroupTable links the filter group (signaled by DOCSIS as a small integer) to the diffServClfrElementEntry for the first pass of filter classification. diffServClfrElementSpecific
requires a RowPointer. Thus, this table exists to provide referenced objects for diffServClfrElementSpecific. The classification method is as follows:
o Use the DOCSIS filter group, as inferred from the sending or
receiving modem, as the classification criterion.
o Use docsSubMgtFilterGroupIndex as the value to match.
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.
IPv4 Compliance
Please note that the compliance statements in this version of the MIB module require support only for IPv4 addresses. That is because the current version of the DOCSIS protocols (1.0, 1.1, and 2.0) are not IPv6 capable. Although support for IPv6 will require changes to the DOCSIS protocols, it is expected that the only changes to the MIB module itself will be the addition of new compliance statements that mandate support for IPv6 addresses. All IP addresses that appear in this document conform to the textual conventions specified in RFC4001.
Management Requirements
The DOCSIS cable modem provisioning model [ITU-T-J122] 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 itself need not 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 to reduce data and to ease administrative control. Filtering criteria, for example, are maintained through SNMP at the CMTS, and the modem registration merely signals the index values for the rows that apply to that modem.
Interaction with DOCSIS Provisioning for CPE Address Control
The CMTS creates rows in docsSubMgtCpeControlTable 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 section of the DOCSIS Cable Device MIB RFC2669:
o docsDevCpeEnroll o docsDevCpeIpMax o docsDevCpeIp
Successful DOCSIS registration will have the effect of setting the corresponding fields in the docsSubMgtCpeControlTable and the docsSubMgtCpeIpTable. If they are not present at modem registration, the CMTS shall apply the following:
o docsSubMgtCpeControlActive <-- docsSubMgtCpeActiveDefault o docsSubMgtCpeControlMaxCpeIp <-- docsSubMgtCpeMaxIpDefault o docsSubMgtCpeControlLearnable <-- docsSubMgtCpeLearnableDefault
Rows in docsSubMgtCpeIpTable are created through any of three ways: DOCSIS registration (as described above), learning by the CMTS, or some unspecified administrative mechanism on the CMTS. The docsDevCpeIpMax table bound applies only to the first two.
The CMTS may learn addresses simply by snooping source IP addresses from traffic originating from each cable modem. Other learning mechanisms (for example, ARP snooping) may be used. The learning mechanism is not defined by this document.
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 [ITU-T-J122]):
o One identifying the upstream (ingress with respect to the CMTS
interface) 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 (egress with respect to the CMTS
interface) 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 will have the effect of setting docsSubMgtCmFilterCmDownstream, docsSubMgtCmFilterCmUpstream, docsSubMgtCmFilterSubDownstream, and docsSubMgtCmFilterSubUpstream, for that modem (just as if they were set through the SNMP protocol). If the DOCSIS attributes are not present, the four values are set to zero. The effect will be to use the default entry (diffServClfrElementSpecific=zeroDotZero) specified in the diffServClfrElementTable. Note that omission of the DOCSIS-signaled values results in application of the default filtering entry, not in omission of filtering.
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 by 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 docsSubMgtCmFilterCmUp/Downstream pair is used; otherwise, the docsSubMgtCmFilterSubUp/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 docsSubMgtCmFilterCmUp/Downstream pair.
Relationship to the Differentiated Services MIB RFC3289
DOCSIS CMTSes 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 includes at least the following from RFC 3289:
o diffServDataPathTable o diffServClfrTable o diffServClfrElementTable o diffServMultiFieldClfrTable o diffServActionTable o diffServCountActTable o diffServAlgDropTable (diffServAlgDropType=alwaysDrop)
The corresponding "next-free" objects are also required.
The use of other facilities from RFC 3289 is not precluded but is beyond the scope of this specification.
Using the Filter Group to Extend Packet Classification
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, which are 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:
[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 that 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.
Interface Usage
For the purposes of DOCSIS subscriber management, only the DOCSIS MAC cable interface(s) are used. The interface appears as the index to diffServDataPathEntry, which is the starting point for diffserv MIB table traversal.
The use of the diffserv MIB for other purposes, both on the DOCSIS MAC interfaces and on other network interfaces, is not precluded by this document.
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.
Definitions
DOCS-IETF-SUBMGT-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY,
OBJECT-TYPE,
Integer32,
mib-2
FROM SNMPv2-SMI
RowStatus,
TruthValue,
TimeStamp,
StorageType
FROM SNMPv2-TC
OBJECT-GROUP,
MODULE-COMPLIANCE
FROM SNMPv2-CONF
InetAddressType,
InetAddress
FROM INET-ADDRESS-MIB
docsIfCmtsCmStatusIndex,
docsIfCmtsCmStatusEntry
FROM DOCS-IF-MIB -- RFC2670
diffServMIBDataPathGroup,
diffServMIBClfrGroup,
diffServMIBClfrElementGroup,
diffServMIBMultiFieldClfrGroup,
diffServMIBActionGroup,
diffServMIBAlgDropGroup,
diffServMIBCounterGroup,
diffServDataPathStatus,
diffServClfrStatus,
diffServClfrElementStatus,
diffServMultiFieldClfrAddrType,
diffServMultiFieldClfrSrcAddr,
diffServMultiFieldClfrDstAddr,
diffServAlgDropStatus,
diffServDataPathStorage,
diffServClfrStorage,
diffServClfrElementStorage,
diffServMultiFieldClfrStorage,
diffServActionStorage,
diffServCountActStorage,
diffServAlgDropStorage,
diffServAlgDropType
FROM DIFFSERV-MIB -- RFC3289
;
docsSubMgt MODULE-IDENTITY
LAST-UPDATED "200503290000Z" -- March 29, 2005
ORGANIZATION "IETF IP over Cable Data Network (IPCDN) Working
Group"
CONTACT-INFO
" Wilson Sawyer
Postal: 50 Kelly Brook Lane
East Hampstead, NH 03826
U.S.A.
Phone: +1 603 382 7080
E-mail: [email protected]
IETF IPCDN Working Group
General Discussion: [email protected]
Subscribe: http://www.ietf.org/mailman/listinfo/ipcdn
Archive: ftp://ftp.ietf.org/ietf-mail-archive/ipcdn
Co-chairs: Richard Woundy, [email protected]
Jean-Francois Mule, [email protected]"
DESCRIPTION
"This is the CMTS centric subscriber management MIB for
DOCSIS-compliant CMTS. It provides the objects to allow a Cable
Modem Termination operator to control the IP addresses and
protocols associated with subscribers' cable modems.
Copyright (C) The Internet Society (2005). This version of this MIB module is part of RFC 4036; see the RFC itself for full legal notices." REVISION "200503290000Z" -- March 29, 2005 DESCRIPTION "Initial version, published as RFC 4036. Note that the compliance statements in this version apply only to implementations that support DOCSIS 1.0/1.1/2.0, which are not IPv6-capable." ::= { mib-2 125 }
docsSubMgtObjects OBJECT IDENTIFIER ::= { docsSubMgt 1 }
docsSubMgtCpeControlTable OBJECT-TYPE
SYNTAX SEQUENCE OF DocsSubMgtCpeControlEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table AUGMENTs the docsIfCmtsCmStatusTable, adding
four WRITEable objects, as well as a read-only object, all of
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 (see
reference) is registrationComplete(6). The persistence of this
row is determined solely by the lifespan of the corresponding
docsIfCmtsCmStatusEntry (normally StorageType=volatile)."
REFERENCE
"RFC 2670"
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. (For example,
if the CM has 5 IP addresses specified for it, this value is 5.)
This limit applies to learned and DOCSIS-provisioned entries
but not to 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
"Controls the application of subscriber management to
this cable modem. 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
"Controls whether the CMTS may learn (and pass traffic
for) CPE IP addresses associated with a cable modem. If this is
set to true, the CMTS may learn up to docsSubMgtMaxCpeIp
addresses (less any DOCSIS-provisioned 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."
DEFVAL { 0 }
::= { 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. This value should
be treated as nonvolatile; if set, its value should persist
across device resets."
DEFVAL { 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. This value should
be treated as nonvolatile; if set, its value should persist
across device resets."
DEFVAL { false }
::= { docsSubMgtObjects 3 }
docsSubMgtCpeLearnableDefault OBJECT-TYPE
SYNTAX TruthValue
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The default value for docsSubMgtCpeControlLearnable if not
signaled in the DOCSIS Registration request. This value should
be treated as nonvolatile; if set, its value should persist
across device resets."
DEFVAL { 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, and 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 docsSubMgtCpeControlActive is true and a CMTS receives
an IP packet from a CM that contains a source IP address that
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, then the packet is
dropped."
::= { docsSubMgtCpeIpEntry 1 }
docsSubMgtCpeIpAddressType OBJECT-TYPE
SYNTAX InetAddressType
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.
The type of this address is determined by the value of
docsSubMgtCpeIpAddressType."
::= { 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, identifying for each modem
the upstream and downstream filter groups that apply to packets
for that modem. Normally, this table reflects the filter group
values signaled by DOCSIS Registration, although values may be
overridden by management action.
For each of the columns in this table, zero is a distinguished
value, indicating that the default filtering action is to be
taken rather than that associated with a filter group number.
Zero is used if the filter group is not signaled by DOCSIS
registration."
::= { 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 (see reference) is
registrationComplete(6). The persistence of this row is
determined solely by the lifespan of the corresponding
docsIfCmtsCmStatusEntry (normally StorageType=volatile)."
REFERENCE
"RFC 2670"
AUGMENTS { docsIfCmtsCmStatusEntry }
::= {docsSubMgtCmFilterTable 1 }
DocsSubMgtCmFilterEntry ::= SEQUENCE
{
docsSubMgtCmFilterSubDownstream Integer32,
docsSubMgtCmFilterSubUpstream Integer32,
docsSubMgtCmFilterCmDownstream Integer32,
docsSubMgtCmFilterCmUpstream Integer32
}
docsSubMgtCmFilterSubDownstream OBJECT-TYPE
SYNTAX Integer32(0..65535) MAX-ACCESS read-write STATUS current
DESCRIPTION
"The filter group applied to traffic destined for subscribers
attached to the referenced CM. Upon row creation, this is set
either to zero (use default classification, the
diffServClfrElementSpecific=zeroDotZero row of
diffServClfrElementTable) 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 that of the filter group
index appearing as docsSubMgtFilterGroupIndex."
::= { docsSubMgtCmFilterEntry 1 }
docsSubMgtCmFilterSubUpstream OBJECT-TYPE
SYNTAX Integer32(0..65535)
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The filter group applied to traffic originating from
subscribers attached to the referenced CM. Upon row creation
this is set to either zero (use default classification, the
diffServClfrElementSpecific=zeroDotZero row of
diffServClfrElementTable), 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 that of the filter group index appearing as
docsSubMgtFilterGroupIndex."
::= { docsSubMgtCmFilterEntry 2 }
docsSubMgtCmFilterCmDownstream OBJECT-TYPE
SYNTAX Integer32(0..65535)
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The filter group applied to traffic destined for the
referenced CM itself. Upon row creation this is set either to
zero (use default classification, the
diffServClfrElementSpecific=zeroDotZero row of
diffServClfrElementTable), 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 that of the filter group
index appearing as docsSubMgtFilterGroupIndex."
::= { docsSubMgtCmFilterEntry 3 }
docsSubMgtCmFilterCmUpstream OBJECT-TYPE
SYNTAX Integer32(0..65535)
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, the
diffServClfrElementSpecific=zeroDotZero row of
diffServClfrElementTable), 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 4 }
docsSubMgtFilterGroupTable OBJECT-TYPE
SYNTAX SEQUENCE OF DocsSubMgtFilterGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Provides a collection of referenceable entries to which
diffServClfrElementSpecific refers. This table provides filter
group indices that 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
that 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(1..65535)
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The filter group index, from the set signaled at DOCSIS
Registration. Provides a referenceable entry to which diffServClfrElementSpecific points. A packet matches this classifier 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 SMI custom of making indices not-accessible.
Note that although zero may be signaled (or defaulted) at DOCSIS
Registration to indicate a default filtering group, no such entry
appears in this table, as diffServClfrElementSpecific will
use a zeroDotZero pointer for that classification."
::= { docsSubMgtFilterGroupEntry 1 }
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.
This compliance statement applies to implementations that support DOCSIS 1.0/1.1/2.0, which are not IPv6 capable."
MODULE DIFFSERV-MIB -- RFC3289
MANDATORY-GROUPS {
diffServMIBDataPathGroup,
diffServMIBClfrGroup,
diffServMIBClfrElementGroup,
diffServMIBMultiFieldClfrGroup,
diffServMIBActionGroup,
diffServMIBAlgDropGroup,
diffServMIBCounterGroup
}
OBJECT diffServDataPathStatus -- same as RFC3289
SYNTAX RowStatus { active(1) }
WRITE-SYNTAX RowStatus { createAndGo(4), destroy(6) }
DESCRIPTION
"Support for createAndWait and notInService is not required."
OBJECT diffServClfrStatus -- same as RFC3289
SYNTAX RowStatus { active(1) }
WRITE-SYNTAX RowStatus { createAndGo(4), destroy(6) }
DESCRIPTION
"Support for createAndWait and notInService is not required."
OBJECT diffServClfrElementStatus -- same as RFC3289
SYNTAX RowStatus { active(1) }
WRITE-SYNTAX RowStatus { createAndGo(4), destroy(6) }
DESCRIPTION
"Support for createAndWait and notInService is not required."
OBJECT diffServMultiFieldClfrAddrType
SYNTAX InetAddressType { ipv4(1) }
DESCRIPTION
"An implementation is only required to support IPv4
addresses."
OBJECT diffServMultiFieldClfrSrcAddr
SYNTAX InetAddress (SIZE(4))
DESCRIPTION
"An implementation is only required to support IPv4
addresses."
OBJECT diffServMultiFieldClfrDstAddr
SYNTAX InetAddress (SIZE(4))
DESCRIPTION
"An implementation is only required to support IPv4
addresses."
OBJECT diffServAlgDropStatus -- same as RFC3289
SYNTAX RowStatus { active(1) }
WRITE-SYNTAX RowStatus { createAndGo(4), destroy(6) }
DESCRIPTION
"Support for createAndWait and notInService is not required."
OBJECT diffServDataPathStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServClfrStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServClfrElementStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServMultiFieldClfrStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServActionStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServCountActStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServAlgDropStorage
SYNTAX StorageType { nonVolatile(3) }
DESCRIPTION
"An implementation is only required to support nonvolatile
storage."
OBJECT diffServAlgDropType
SYNTAX INTEGER { alwaysDrop(5) }
DESCRIPTION
"For DOCSIS subscriber management, this object is
only used to provide packet filtering. Implementations
need not support other values of this enumeration."
MODULE -- This module i.e., DOCS-IETF-SUBMGT-MIB
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 docsSubMgtCmFilterSubDownstream
SYNTAX Integer32(0..30)
DESCRIPTION
"An implementation is only required to support thirty
filter groups."
OBJECT docsSubMgtCmFilterSubUpstream
SYNTAX Integer32(0..30)
DESCRIPTION
"An implementation is only required to support thirty
filter groups."
OBJECT docsSubMgtCmFilterCmDownstream
SYNTAX Integer32(0..30)
DESCRIPTION
"An implementation is only required to support thirty
filter groups."
OBJECT docsSubMgtCmFilterCmUpstream
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,
docsSubMgtCmFilterSubDownstream,
docsSubMgtCmFilterSubUpstream,
docsSubMgtCmFilterCmDownstream,
docsSubMgtCmFilterCmUpstream,
docsSubMgtFilterGroupIndex
}
STATUS current
DESCRIPTION
"The objects used to manage host-based cable modems
via a set of CMTS enforced controls."
::= { docsSubMgtGroups 1 }
END
Acknowledgements
This document is based on work by Michael St. Johns, then at Excite@Home. Thanks to Guenter Roeck and Julie McGray for reviewing earlier versions. Thanks to Bert Wijnen, Mike Heard, and Harrie Hazewinkel for extensive later review. Thanks to the working group chairs, Richard Woundy and Jean-Francois Mule, for their extensive support.
IANA Considerations
The MIB module defined in this document uses the following IANA- assigned OBJECT IDENTIFIER value recorded in the SMI Numbers registry:
Descriptor OBJECT IDENTIFIER value
-----------------------
docsSubMgt { mib-2 125}
Normative References
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
RFC2578 McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Structure of Management Information Version 2 (SMIv2)",
STD 58, RFC 2578, April 1999.
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.
[ITU-T-J122] Second-Generation Transmission Systems for Interactive
Cable Television Services, J.122, ITU-T, December, 2002.
RFC2670 St. Johns, M., "Radio Frequency (RF) Interface
Management Information Base for MCNS/DOCSIS compliant RF
interfaces", RFC 2670, August 1999.
RFC3289 Baker, F., Chan, K., and A. Smith, "Management
Information Base for the Differentiated Services
Architecture", RFC 3289, May 2002.
RFC4001 Daniele, M., Haberman, B., Routhier, S., and J.
Schoenwaelder, "Textual Conventions for Internet Network
Addresses", RFC 4001, February 2005.
Informative References
RFC1858 Ziemba, G., Reed, D., and P. Traina, "Security
Considerations for IP Fragment Filtering", RFC 1858, October 1995.
RFC2669 St. Johns, M., "DOCSIS Cable Device MIB Cable Device
Management Information Base for DOCSIS compliant Cable
Modems and Cable Modem Termination Systems", RFC 2669,
August 1999.
RFC3128 Miller, I., "Protection Against a Variant of the Tiny
Fragment Attack (RFC 1858)", RFC 3128, 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+-
I11-040407", DOCSIS, April 2004, available at
http://www.cablemodem.com/ and at
http://www.cablelabs.com/specifications/archives.
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 modem's identity or registration process is spoofed. The DOCSIS RFI and privacy specifications [ITU-T-J122] and [DOCSBPI] define a number of mechanisms for assuring modem identity.
For network filtering of TCP traffic to be effective, implementors MUST follow the recommendations in section 3.4.
There are a number of management objects defined in this MIB that have a MAX-ACCESS clause of read-write and/or read-create. These 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:
docsSubMgtCmFilterSubDownstream docsSubMgtCmFilterSubUpstream docsSubMgtCmFilterCmDownstream docsSubMgtCmFilterCmUpstream
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 even to encrypt the values of these objects when they are sent over the network via SNMP. The most sensitive is docsSubMgtCpeIpAddr within docsSubMgtCpeIpTable. Although docsSubMgtCpeIpTable is intended to control address spoofing, it includes information about the current subscriber address pool. This information may in 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), there is no control as to who on the secure network is 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) who have legitimate rights to GET or SET (change/create/delete) them.
Author's Address
Wilson Sawyer 50 Kelly Brook Lane East Hampstead NH 03826
Phone: +1 603 382 7080 EMail: [email protected]
Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
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Acknowledgement
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