Network Working Group W. Sawyer

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.

Table of Contents

1. The Internet-Standard Management Framework.................... 2
2. Conventions................................................... 2
3. Overview...................................................... 2
3.1. Structure of the MIB.................................... 4
3.1.1. docsSubMgtFilterGroupTable...................... 4
3.1.2. IPv4 Compliance................................. 5
3.2. Management Requirements................................. 5
3.2.1. Interaction with DOCSIS Provisioning for CPE
Address Control................................. 6
3.2.2. Interaction with DOCSIS Provisioning for
Filtering....................................... 6
3.2.3. Distinguishing Modem from Subscriber Traffic.... 7

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3.3. Relationship to the Differentiated Services MIB
[RFC3289]............................................... 7
3.3.1. Using the Filter Group to Extend Packet
Classification.................................. 8
3.3.2. Interface Usage................................. 8
3.4. Filtering and the Tiny Fragment Attack.................. 9
4. Definitions................................................... 9
5. Acknowledgements.............................................. 23
6. IANA Considerations........................................... 23
7. Normative References.......................................... 23
8. Informative References........................................ 24
9. Security Considerations....................................... 25
Author's Address.................................................. 26
Full Copyright Statement.......................................... 27

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. 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].

3. 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.

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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.

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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.

3.1. 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.

3.1.1. 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

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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.

3.1.2. 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].

3.2. 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.

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3.2.1. 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.

3.2.2. 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 [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).

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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.

3.2.3. 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 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.

3.3. 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

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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.

3.3.1. 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.

3.3.2. 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.

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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.

3.4. 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.

4. 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,

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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.

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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,

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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

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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

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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)

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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

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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

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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

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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."

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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."

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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."

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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,

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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

5. 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.

6. 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}

7. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

[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.

8. 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.

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

[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.

9. 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

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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]

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RFC 4036 DOCSIS Subscriber Management MIB April 2005

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.

This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM 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.

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pertain to the implementation or use of the technology described in
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made any independent effort to identify any such rights. Information
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this standard. Please address the information to the IETF at ietf-
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Acknowledgement

Funding for the RFC Editor function is currently provided by the
Internet Society.

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