One document matched: draft-ietf-rap-pr-02.txt
Differences from draft-ietf-rap-pr-01.txt
Internet Draft Kwok Ho Chan
Expiration: September 2000 Nortel Networks
File: draft-ietf-rap-pr-02.txt David Durham
Intel
Silvano Gai
Cisco
Shai Herzog
IPHighway
Keith McCloghrie
Cisco
Francis Reichmeyer
IPHighway
John Seligson
Nortel Networks
Andrew Smith
Extreme Networks
Raj Yavatkar
Intel
COPS Usage for Policy Provisioning
March 10, 2000
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
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Abstract
This draft describes the use of the COPS protocol [COPS] for
support of policy provisioning. This specification is independent
of type of policy being provisioned (QoS, Security, etc.) but
focuses on the mechanisms and conventions used to communicate
provisioned information between PDPs and PEPs. The protocol
extensions described in this document do not make any assumptions
about the policy data being communicated, but describe the message
formats and objects that carry policy data.
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Table of Contents
Abstract..............................................................3
Table of Contents.....................................................4
Glossary..............................................................5
1. Introduction.....................................................5
1.1. Why not SNMP?..................................................6
1.2. Interaction between the PEP and PDP............................7
2. Policy Information Base (PIB)....................................8
2.1. Rules for Modifying and Extending PIBs.........................9
2.2. Adding PRCs to, or deprecating from, a PIB.....................9
2.2.1. Adding or Deprecating Attributes of a PRC......................9
2.2.2. Augmenting a PRC with another PRC.............................10
2.3. COPS Operations Supported for a Policy Rule Instance..........10
3. Message Content.................................................11
3.1. Request (REQ) PEP -> PDP.....................................11
3.2. Decision (DEC) PDP -> PEP....................................12
3.3. Report State (RPT) PEP -> PDP................................14
4. COPS-PR Protocol Objects........................................14
4.1. Complete Policy Rule Identifier (PRID)........................15
4.2. Prefix PRID (PPRID)...........................................16
4.3. Encoded Policy Instance Data (EPD)............................16
4.4. Provisioning Error Object (PERR)..............................18
4.5. Error PRID Object (ErrorPRID).................................19
5. COPS-PR Client-Specific Data Formats............................19
5.1. Named Decision Data...........................................20
5.2. ClientSI Request Data.........................................20
5.3. Policy Provisioning Report Data...............................20
5.3.1. Success and Failure Report-Type Data Format...................21
5.3.2. Accounting Report-Type Data Format............................21
6. Common Operations...............................................22
7. Fault Tolerance.................................................24
7.1. Security Considerations.......................................25
8. Acknowledgements................................................25
9. References......................................................26
10. Author Information..............................................27
11. Full Copyright Notice...........................................28
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Glossary
PRC Policy Rule Class. A type of policy data.
PRI Policy Rule Instance. An instance of a PRC.
PIB Policy Information Base. The database of policy
information.
PDP Policy Decision Point. See [RAP-FRAMEWORK].
PEP Policy Enforcement Point. See [RAP-FRAMEWORK].
PRID Policy Rule Instance Identifier. Uniquely identifies an
instance of a PRC.
1. Introduction
The IETF Resource Allocation Protocol (RAP) WG has defined the
COPS (Common Open Policy Service) protocol [COPS] as a scalable
protocol that allows policy servers (PDPs) to communicate policy
decisions to network devices (PEP). COPS was designed to support
multiple types of policy clients.
COPS is a query/response protocol that supports two common models
for policy control: Outsourcing and Configuration.
The Outsourcing model addresses the kind of events at the PEP that
require instantaneous policy decision (authorization). The PEP,
being aware that it must perform a policy decision. However, being
unable to carry the task itself, the PEP delegates responsibility
to an external policy server (PDP). For example, in [COPS-RSVP]
when a reservation message arrives, the PEP is aware that it must
decide whether to admit or reject the request. It sends a specific
query to the PDP, and in most case, waits for a decision before
admitting the outstanding reservation.
The COPS Configuration model (herein described as the Provisioning
model), on the other hand, makes no assumptions of such direct 1:1
correlation between PEP events and PDP decisions. The PDP may
proactively provision the PEP reacting to external events (such as
user input), PEP events, and any combination thereof (N:M
correlation). Provisioning may be performed in bulk (e.g., entire
router QoS configuration) or in portions (e.g., updating a
DiffServ marking filter).
Network resources are often provisioned based on relatively static
SLAs (Service Level Agreements) at network boundaries. While the
Outsourcing model is dynamically paced by the PEP in real-time,
the Provisioning model is paced by the PDP in somewhat flexible
timing over a wide range of configurable aspects of the PEP.
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Edge Device Policy Server
+--------------+ +-----------+ +-----------+
| | | | | External |
| | COPS | | | Events |
| +-----+ | REQ() | +-----+ | +---+-------+
| | |----|----------|->| | | |
| | PEP | | | | PDP |<-|---------+
| | |<---|----------|--| | |
| +-----+ | COPS | +-----+ |
| | DEC() | |
+--------------+ +-----------+
Figure 1: COPS Provisioning Model
In COPS-PR, policy requests describe the PEP and its configurable
parameters (rather than an operational event). If a change occurs
in these basic parameters, an updated request is sent. Hence,
requests are issued quite infrequently. Decisions are not
necessarily mapped directly to requests, and are issued mostly
when the PDP responds to external events or PDP events (policy/SLA
updates).
This draft describes the use of the COPS protocol [COPS] for
support of policy provisioning. This specification is independent
of the type of policy being provisioned (QoS, Security, etc.) but,
rather, focuses on the mechanisms and conventions used to
communicate provisioned information between PDPs and PEPs. The
model described in this document is based on the concept of Policy
Information Bases (PIBs) that define the policy data. There may be
one or more PIBs for given area of policy and different areas of
policy will have different sets of PIBs.
In order to support a model that includes multiple PDPs
controlling non-overlapping areas of policy on a single PEP, the
client type specified by the PEP to the PDP is unique for the area
of policy being managed. A single client type for a given area of
policy (eg. QoS) will be used for all PIBs that exist in that
area. The client should treat all the COPS-PR client-types it
supports as non-overlapping and independent namespaces where
instances MUST NOT be shared.
The Examples used in this document are biased toward QoS Policy
Provisioning in a Differentiated Services (DiffServ) environment.
However, COPS-PR can be used for other types of provisioning
policies under the same framework.
1.1. Why not SNMP?
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SNMP is a very popular network management protocol. One may
question using COPS-PR, rather than extending SNMP for policy
provisioning.
SNMP is designed for low-level access at very fine levels of
granularity. When configuring large amounts of policy
information, the low-level, granular access makes it inefficient
and cumbersome.
COPS-PR has been designed within a framework which is less
general-purpose and more optimized for configuration to overcome
these shortcomings, based on the requirements defined in [RAP]. It
has a single connection between client and server, it guarantees
only one server updates the policy configuration at any given time
(and these are locked, even from console configuration, while COPS
is connected to a server). COPS uses reliable TCP transport and
thus uses a state sharing/synchronization mechanism and exchanges
differential updates only. If either the server or client are
rebooted (or restarted) the other would know about it quickly.
Last, it is defined as a real-time mechanism for the PEP device.
The COPS protocol is already used for policy control over RSVP. It
is highly desirable to use a single policy control protocol for
Quality of Service (QoS) mechanisms (if possible), rather than
invent a new one for each type of policy problem.
At the same time, useful mechanisms from SNMP were adopted. COPS-
PR uses a named Policy Information Base (PIB), which can be
described using the SMI [V2SMI] and encoded using BER [BER] data
encoding. This allows reuse of experience, knowledge, tools and
some code from the SNMP world.
1.2. Interaction between the PEP and PDP
When a device boots, it opens a COPS connection to its Primary
PDP. When the connection is established, the PEP sends information
about itself to the PDP in the form of a configuration request.
This information includes client specific information (e.g.,
hardware type, software release, configuration information).
During this phase the client may also specify the maximum COPS-PR
message size supported.
In response, the PDP downloads all provisioned policies that are
currently relevant to that device. On receiving the provisioned
policies, the device maps them into its local QoS mechanisms, and
installs them. If conditions change at the PDP such that the PDP
detects that changes are required in the provisioned policies
currently in effect, then the PDP sends the changes (installs
and/or deletes) in policy to the PEP, and the PEP updates its
local QoS mechanisms appropriately.
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If, subsequently, the configuration of the device changes (board
removed, board added, new software installed, etc.) in ways not
covered by policies already known to the PEP, then the PEP sends
this unsolicited new information to the PDP. On receiving this new
information, the PDP sends to the PEP any additional provisioned
policies now needed by the PEP.
2. Policy Information Base (PIB)
The data carried by COPS-PR is a set of policy rules. The protocol
uses a named data structure, known as a Policy Information Base
(PIB), to identify the type and purpose of unsolicited policy
information that is "pushed" from the PDP to the PEP for
provisioning policy. The PIB name space is common to both the PEP
and the PDP and data instances within this space are unique within
the scope of a given PDP/PEP/Client-Type communication channel.
Note that a given device might implement multiple PEPs or multiple
Client-Types and the name space is then only relevant within each
separate channel (there is no sharing of instance data across the
PDP/PEP/Client-Types).
The PIB can be described as a conceptual tree data structure where
the branches of the tree represent types of rules or Policy Rule
Classes (PRCs), while the leaves represent the contents of Policy
Rule Instances (PRIs). There may be multiple instances of rules
(PRIs) for any given rule type (PRC). For example, if one wanted
to install multiple access control filters, the PRC might
represent a generic access control filter type and each PRI might
represent an individual access control filter to be applied. The
tree might be represented as follows:
-------+-------+----------+---PRC--+--PRI
| | | +--PRI
| | |
| | +---PRC-----PRI
| |
| +---PRC--+--PRI
| +--PRI
| +--PRI
| +--PRI
| +--PRI
|
+---PRC---PRI
Figure 2: The PIB Tree
Instances of the policy rules (PRIs) are each identified by a
Policy Rule Identifier (PRID). A PRID is a name, carried in a COPS
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<Named ClientSI> or <Named Decision Data> object, which identifies
a particular instance of a rule.
2.1. Rules for Modifying and Extending PIBs
As experience is gained with policy management, and as new
requirements arise, it will be necessary to make changes to PIBs.
Changes to an existing PIB can be made in several ways.
(1) Additional PRCs can be added to a PIB or an existing one
deprecated.
(2) Attributes can be added to, or deprecated from an existing
PRC.
(3) An existing PRC can be extended by "augmenting" it with a new
PRC defined in another (perhaps enterprise specific) PIB.
The rules for each of these extension mechanisms is described in
this sub-section. All of these mechanisms for modifying a PIB
allow for interoperability between PDPs and PEPs even when one
party is using a new version of the PIB while the other is using
an old version.
2.2. Adding PRCs to, or deprecating from, a PIB
A published PIB can be extended with new PRCs by simply revising
the document and adding additional PRCs. These additional PRCs
are easily identified with new PRIDs under the module's PRID
Prefix.
In the event that a PEP implementing the new PIB is being
configured by a PDP implementing the old PIB, the PEP will simply
not receive any instances of the new PRC. In the event that the
PEP is implementing the old PIB and the PDP the new one, the PEP
may receive PRIs for the new PRC. The PEP SHOULD ignore these
unsupported PRI. However, it MAY return and error to the PDP. In
the latter case, the PDP must restructure its policy decisions to
exclude the unsupported PRCs.
Similarly, existing PRCs can be deprecated from a PIB. In this
case, the PEP ignores any PRIs sent it by a PDP implementing the
old (non- deprecated) version of the PIB. A PDP implementing the
new version of the PIB simply does not send any instances of the
deprecated class.
2.2.1. Adding or Deprecating Attributes of a BER Encoded PRC
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A PIB can be modified to deprecate existing attributes of a PRC or
add new ones.
When deprecating the attributes of a PRC, it must be remembered
that, with the COPS-PR protocol, the attributes of the PRC are
identified by their order in the sequence rather than an explicit
label (or attribute OID). Consequently, an ASN.1 value MUST be
sent even for deprecated attributes so that a PDP and PEP
implementing different versions of the PIB are inter-operable.
For a deprecated attribute, if the PDP is using a BER encoded PIB,
the PDP MUST send either an ASN.1 value of the correct type, or it
may send an ASN.1 NULL value. A PEP that receives an ASN.1 NULL
for an attribute that is not deprecated SHOULD substitute a
default value. If it has no default value to substitute it MUST
return an error to the PDP.
When adding new attributes to a PIB, these new attributes must be
added in sequence after the existing ones. A PEP that receives a
PRI with more attributes than it is expecting MUST ignore the
additional attributes. It MAY send a warning back to the PDP.
A PEP that receives a PRI with fewer attributes than it is
expecting SHOULD assume default values for the missing attributes.
It MAY send a warning back to the PDP. If the missing attributes
are required and there is no suitable default, the PEP MUST send
and error back to the PDP. In all cases the missing attributes
are assumed to correspond to the last attributes of the PRC.
2.3. COPS Operations Supported for a Policy Rule Instance
A Policy Rule Instance (PRI) typically contains a value for each
attribute defined for the PRC of which it an instance and is
identified uniquely, within the scope of a given COPS Client-Type on
a PEP, by a Policy Rule Identifier (PRID). The following COPS
operations are supported on a PRI:
o Install - This operation creates or updates a named instance of
a PRC. It includes two parameters: a PRID object to name the PRI
and an Encoded Policy Instance Data (EPD) object with the
new/updated values. The PRID value MUST uniquely identify a
single PRI (i.e. PRID/PRC prefix values are illegal).
o Remove - This operation is used to delete an instance of a PRC.
It includes one parameter, a PRID object, which names either the
individual PRI to be deleted or a PRID prefix naming one or more
complete classes of PRIs. Prefix-based deletion supports
efficient bulk policy removal.
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3. Message Content
The COPS protocol provides for different COPS clients to define
their own "named", i.e. client-specific, information for various
messages. This section describes the messages exchanged between a
COPS server (PDP) and COPS Policy Provisioning clients (PEP) that
carry client-specific data objects. All the COPS messages used by
COPS-PR conform to the message specifications defined in the COPS
base protocol [COPS].
Note: The use of the '*' character represented throughout this
document is consistent with the ABNF [RFC2234] and means 0 or more
of the following entities.
3.1. Request (REQ) PEP -> PDP
The REQ message is sent by policy provisioning clients to issue a
'configuration request' to the PDP as specified in the COPS
Context Object. The Client Handle associated with the REQ message
originated by a provisioning client must be unique for that
client. The Client Handle is used to identify a specific request
state. Thus, one client can potentially open several configuration
request states, each uniquely identified by its handle. Different
request states are used to isolate similarly named configuration
information into non-overlapping contexts (or logically isolated
namespaces). Thus, a piece of named information is unique relative
to a particular client-type and is unique relative to a particular
request state for that client-type, even if the information was
similarly identified in other request states. Thus, the Client
Handle is part of the instance identification of the communicated
configuration information.
The config request message serves as a request from the PEP to the
PDP for provisioning policy data which the PDP may have for the
PEP, such as access control lists, etc. This includes policy the
PDP may have at the time the REQ is received as well as any future
policy data or updates to this data.
The config request message should include provisioning client
information to provide the PDP with client-specific configuration
or capability information about the PEP. The information provided
by the PEP should include client resource (e.g. queuing
capabilities) and default policy configuration (e.g. default role
combinations) information as well as references to existing policy
(i.e. PIB) incarnation data. This information typically does not
include all the information previously installed by a PDP but
rather should include checksums or shortened references to
previously installed information for synchronization purposes.
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This information from the client assists the server in deciding
what types of policy the PEP can install and enforce. The format
of the information encapsulated in the provisioning Named ClientSI
data is described in section 5. Note that the config request
message is regenerated and sent to the PDP in response to the
receipt of a Synchronize State Request (SSQ) message.
The policy information supplied by the PDP must be consistent with
the named decision data defined for the policy provisioning
client. The PDP responds to the config request with a DEC message
containing any available provisioning policy data.
The REQ message has the following format:
<Request> ::= <Common Header>
<Client Handle>
<Context = config request>
[<Named ClientSI: Provisioning >]
[<Integrity>]
Note that the COPS objects IN-Int, OUT-Int and LDPDecisions are
not included in a COPS-PR Request.
3.2. Decision (DEC) PDP -> PEP
The DEC message is sent from the PDP to a policy provisioning
client in response to the REQ message received from the PEP. The
Client Handle must be the same Handle that was received in the
corresponding REQ message.
The DEC message is sent as an immediate response to a
configuration request with the solicited message flag set in the
COPS message header. Subsequent DEC messages may also be sent at
any time after the original DEC message to supply the PEP with
additional/updated policy information without the solicited
message flag set in the COPS message header (as they are
unsolicited decisions).
Each DEC message may contain multiple decisions. This means a
single message can install some policies and delete others. In
general a COPS-PR decision message should contain at most one or
more deletes followed by one or more install decisions. This is
used to solve a precedence issue, not a timing issue: the delete
decision deletes what it specifies, except those items that are
installed in the same message.
The DEC message can also be used by the PDP to command the PEP to
open a new Request State or Delete an existing Request State as
identified by the Client-Handle. To accomplish this, COPS-PR
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defines a new flag for the COPS Decision Flags object. The flag
0x02 is to be used by COPS-PR client-types and is hereafter
referred to as the "Request-State" flag. An Install decision
(Decision Flags: Command-Code=Install) with the Request-State flag
set in the COPS Decision Flags object will cause the PEP to issue
a new Request with a new Client Handle or else specify the
appropriate error in a COPS Report message. A Remove decision
(Decision Flags: Command-Code=Remove) with the Request-State flag
set in the COPS Decision Flags object will cause the PEP to send a
COPS Delete Request State (DRQ) message for the request state
identified by the Client Handle in the DEC message. Whenever the
Request-State flag is set in the COPS Decision Flags object in the
DEC message, no COPS Named Decision Data object can be included in
the corresponding decision (as it serves no purpose for this
decision flag).
A COPS-PR DEC message must be treated as a single "transaction",
i.e. either all the decisions in a DEC message succeed or they all
fail. This allows the PDP to delete some policies only if other
policies can be installed in their place. The DEC message has the
following format:
<Decision Message> ::= <Common Header>
<Client Handle>
*(<Decision(s)>) | <Error>
[<Integrity>]
<Decision> ::= <Context>
<Decision: Flags>
[<Named Decision Data: Provisioning >]
Note that the Named Decision Data (Provisioning) object is
included in a COPS-PR Decision when it is an Install or Remove
decision with no Decision Flags set. Other types of COPS decision
data objects (e.g. Stateless, Replacement) are not supported by
COPS-PR client-types. The Named Decision Data object MUST NOT be
included in the decision if the Decision Flags object Command-Code
is NULL (meaning there is no configuration information to install
at this time) or if the Request-State flag is set in the Decision
Flags object.
For each decision on the DEC message, the PEP performs the
operation specified in the Command-Code and Flags field in the
Decision Flags object on the Named Decision Data. For the policy
provisioning clients, the format for this data is defined in the
context of the Policy Information Base (see section 5). In
response to a DEC message, the policy provisioning client sends a
RPT message with the solicited message flag set back to the PDP to
inform the PDP of the action taken.
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3.3. Report State (RPT) PEP -> PDP
The RPT message is sent from the policy provisioning clients to
the PDP to report accounting information associated with the
provisioned policy, or to notify the PDP of changes in the PEP
(Report-Type = 'Accounting') related to the provisioning client.
RPT is also used as a mechanism to inform the PDP about the action
taken at the PEP, in response to a DEC message. For example, in
response to an 'Install' decision, the PEP informs the PDP if the
policy data is installed (Report-Type = 'Success') or not (Report-
Type = 'Failure'). Reports that are in response to a DEC message
MUST set the solicited message flag in their COPS message header.
Reports can also be unsolicited and all unsolicited Reports MUST
NOT set the solicited message flag in their COPS message header.
Examples of unsolicited reports include 'Accounting' Report-Types,
that were not triggered by a specific DEC messages, or 'Failure'
Report-Types that indicate a change of state in a previously
successfully installed configuration.
The RPT message may contain provisioning client information such
as accounting parameters or errors/warnings related to a decision.
The data format for this information is defined in the context of
the policy information base (see section 5). The RPT message has
the following format:
<Report State> ::= <Common Header>
<Client Handle>
<Report Type>
[<Named ClientSI: Provisioning >]
[<Integrity>]
4. COPS-PR Protocol Objects
The COPS Policy Provisioning clients encapsulate several new
objects within the existing COPS Named Client-specific information
object and Named Decision Data object. This section defines the
format of these new objects.
COPS-PR classifies policy data according to "bindings", where a
binding consists of a Policy Rule Identifier and the Policy Rule
Instance data, encoded within the context of the provisioning
policy information base (see section 5).
The format for these new objects is as follows:
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0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num | S-Type |
+---------------+---------------+---------------+---------------+
| 32 bit unsigned integer |
+---------------+---------------+---------------+---------------+
S-Num and S-Type are similar to the C-Num and C-Type used in the
base COPS objects. The difference is that S-Num and S-Type are
used only for COPS-PR clients and are encapsulated within the
existing COPS Named ClientSI or Named Decision Data objects. The
S-Num identifies the general purpose of the object, and the S-Type
describes the specific encoding used for the object. All the
object descriptions and examples in this document use the Basic
Encoding Rules as the encoding type (S-Type = 1). Additional
encodings can be defined for the remaining S-Types in the future
(for example, XML string based encodings).
Length is a two-octet value that describes the number of octets
(including the header) that compose the object. If the length in
octets does not fall on a 32-bit word boundary, padding must be
added to the end of the object so that it is aligned to the next
32-bit boundary before the object can be sent on the wire. On the
receiving side, a subsequent object boundary can be found by
simply rounding up the stated object length of the current object
to the next 32-bit boundary.
4.1. Complete Policy Rule Identifier (PRID)
S-Num = 1, S-Type = 1 (Complete BER PRID), Length = variable.
This object is used to carry the identifier, or PRID, of a Policy
Rule Instance. The identifier is encoded following the rules that
have been defined for encoding SNMP Object Identifier (OID)
values. Specifically, PRID values are encoded using the
Type/Length/Value (TLV) format and initial sub-identifier packing
that is specified by the binary encoding rules [BER] used for
Object Identifiers in an SNMP PDU.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = PRID | S-Type = BER |
+---------------+---------------+---------------+---------------+
... ...
| Policy Rule Identifier |
... ...
+---------------+---------------+---------------+---------------+
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For example, a (fictitious) PRID equal to 1.3.6.1.2.2.8.1 would be
encoded as follows (values in hex):
06 07 2B 06 01 02 02 08 01
The entire PRID object would be encoded as follows:
00 0D - Length
01 - S-Num
01 - S-Type (Complete PRID)
06 07 2B 06 01 02 02 08 01 - Encoded PRID
00 00 00 - Padding
4.2. PRID Prefix(PPRID)
Certain operations, such as decision removal, can be optimized by
specifying a PRID prefix with the intent that the requested
operation be applied to all PRIs matching the prefix. PRID prefix
objects MUST only be used in the COPS protocol <Remove Decision>
operation where it may be more optimal to perform bulk decision
removal using class prefixes instead of a sequence of individual
<Remove Decision> operations. Other COPS operations, e.g. <Install
Decision> operations always require individual PRID specification.
S-Num = 2, S-Type = 1 (BER PRID Prefix), Length = variable.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = PPRID | S-Type = BER |
+---------------+---------------+---------------+---------------+
... ...
| PRID Prefix |
... ...
+---------------+---------------+---------------+---------------+
Continuing with the previous example, a PRID prefix that is
equal to 1.3.6.1.2.2 would be encoded as follows (values in hex):
06 05 2B 06 01 02 02
The entire PRID object would be encoded as follows:
00 0B - Length
02 - S-Num = PRID Prefix
01 - S-Type = BER
06 05 2B 06 01 02 02 - Encoded PRID Prefix
00 - Padding
4.3. Encoded Policy Instance Data (EPD)
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S-Num = 3, S-Type = 1, Length = variable.
This object is used to carry the encoded value of a Policy Rule
Instance. The PRI value, which contains all of the individual
values of the attributes that comprise the class, is encoded as a
series of TLV sub-components. Each sub-component represents the
value of a single attribute and is encoded following the BER.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = EPD | S-Type = BER |
+---------------+---------------+---------------+---------------+
... ...
| BER Encoded PRI Value |
... ...
+---------------+---------------+---------------+---------------+
As an example, an instance of the filter class, defined in the QoS
Policy IP PIB [PIB], would be encoded as follows:
02 01 08 :filterIndex/INTEGER/Value = 8
40 04 C0 39 01 05 :filterDstAddr/IpAddress/Value = 192.57.1.5
40 04 FF FF FF FF :filterDstMask/IpAddress/Value = 255.255.255.255
40 04 00 00 00 00 :filterSrcAddr/IpAddress/Value = 0.0.0.0
40 04 00 00 00 00 :filterSrcMask/IpAddress/Value = 0.0.0.0
02 01 FF :filterDscp/Integer32/Value = -1 (not used)
02 01 06 :filterProtocol/INTEGER/Value = 6 (TCP)
05 00 :filterDstL4PortMin/NULL/not supported
05 00 :filterDstL4PortMax/NULL/not supported
05 00 :filterSrcL4PortMin/NULL/not supported
05 00 :filterSrcL4PortMax/NULL/not supported
02 01 01 :filterPermit/TruthValue/Value = 1 (true)
The entire EPD object would be encoded as follows:
00 30 - Length
03 - S-Num = EPD
01 - S-Type = BER
02 01 08 - filterIndex
40 04 C0 39 01 05 - filterDstAddr
40 04 FF FF FF FF - filterDstMask
40 04 00 00 00 00 - filterSrcAddr
40 04 00 00 00 00 - filterSrcMask
02 01 FF - filterDscp
02 01 06 - filterProtocol
05 00 - filterDstL4PortMin
05 00 - filterDstL4PortMax
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05 00 - filterSrcL4PortMin
05 00 - filterSrcL4PortMax
02 01 01 - filterPermit
Note that attributes not supported within a class are still
returned in the EPD for a PRI. By convention, a NULL value is
returned for attributes that are not supported. In the previous
example, source and destination port number attributes are not
supported.
4.4. Global Provisioning Error Object (GPERR)
S-Num = 4, S-Type = 1, Length = 8.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = GPERR | S-Type = BER |
+---------------+---------------+---------------+---------------+
| Error-Code | Error Sub-code |
+---------------+---------------+---------------+---------------+
The global provisioning error object has the same format as the
Error object in COPS [COPS], except with C-Num and C-Type replaced
by the S-Num and S-Type values shown. The global provision error
object is used to communicate general errors that do not map to a
specific PRC.
The following global error codes are defined:
availMemLow(1),
availMemExhausted(2),
unknownASN.1Tag(3),
maxMsgSizeExceeded(4),
unknownError(5)
Note: For the unknownASN.1Tag, the erroneous tag type
MUST be specified in the Error Sub-Code field
4.5. PRC Class Provisioning Error Object (CPERR)
S-Num = 5, S-Type = 1, Length = 8.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = CPERR | S-Type = BER |
+---------------+---------------+---------------+---------------+
| Error-Code | Error Sub-code |
+---------------+---------------+---------------+---------------+
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The class-specific provisioning error object has the same format
as the Error object in COPS [COPS], except with C-Num and C-Type
replaced by the S-Num and S-Type values shown. The class-specific
error object is used to communicate errors relating to specific
PRCs and MUST have an associated Error PRID Object.
The following Generic Class-Specific errors are defined:
priSpaceExhausted(1),
priInstanceInvalid(2),
attrValueInvalid(3),
attrValueSupLimited(4),
attrEnumSupLimited(5),
attrMaxLengthExceeded(6),
attrReferenceUnknown(7),
priNotifyOnly(8),
unknownPrc(9), -- install a PRI of a class not supported by PEP
noAccess(10), -- install a PRI of a class whose access is notify
tooFewAttrs(11), -- recvd PRI has fewer attributes than required.
invalidAttrType(12), -- recvd PRI has an attribute of the wrong
type.
deletedInRef(13), -- deleted PRI is still referenced by other
(non) deleted PRIs
priSpecificError(14)
Note: For the priSpecificError code the Error Sub-code field
contains the PRC specific error code
4.6. Error PRID Object (ErrorPRID)
S-Num = 6, S-Type = 1 (BER ErrorPRID), Length = variable.
This object is used to carry the identifier, or PRID, of a Policy
Rule Instance that caused an installation error or could not be
installed or removed. The identifier is encoded and formatted
exactly as in the PRID object as described in section 4.1.
5. COPS-PR Client-Specific Data Formats
This section describes the format of the named client specific
information for the COPS policy provisioning client. ClientSI
formats are defined for Decision message's Named Decision Data
object, the Request message's Named ClientSI object and Report
message's Named ClientSI object. The actual content of the data is
defined by the policy information base for a specific provisioning
client type (see below).
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5.1. Named Decision Data
The formats encapsulated by the Named Decision Data object for the
policy provisioning client-types depends on the type of decision.
Install and Remove are the two types of decisions that dictate the
internal format of the COPS Named Decision Data object and require
its presence. Install and Remove refer to the 'Install' and
'Remove' Command-Code, respectively, specified in the COPS
Decision Flags Object when no Decision Flags are set. The data,
in general, is composed of one or more bindings. Each binding
associates a PRID object and a EPD object. The PRID object is
always present in both install and remove decisions, the EPD
object MUST be present in the case of an install decision and MUST
NOT be present in the case of a remove decision.
The format for this data is encapsulated within the COPS Named
Decision Data object as follows:
< Decision: Named Data> ::= <<Install Decision> |
<Remove Decision>>
<Install Decision> ::= *(<PRID> <EPD>)
<Remove Decision> ::= *(<PRID>|<PPRID>)
Note that PRID objects in a Remove Decision may specify PRID
prefix values. Explicit and implicit deletion of installed
policies is supported by a client. Install Decision data MUST be
explicit (i.e., PRID prefix values are illegal and MUST be
rejected by a client).
5.2. ClientSI Request Data
The provisioning client request data will use same bindings as
described above. The format for this data is encapsulated in the
COPS Named ClientSI object as follows:
<ClientSI: Named Request> ::= <*(<PRID> <EPD>)>
5.3. Policy Provisioning Report Data
The COPS Named ClientSI object is used in the RPT message in
conjunction with the accompanying COPS Report Type object to
encapsulate COPS-PR report information from the PEP to the PDP.
Report types can be 'Success' or 'Failure', indicating to the PDP
that a particular set of provisioning policies has been either
successfully or unsuccessfully installed/removed on the PEP, or
'Accounting'.
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5.3.1. Success and Failure Report-Type Data Format
Report-types can be 'Success' or 'Failure' indicating to the PDP
that a particular set of provisioning policies has been either
successfully or unsuccessfully installed/removed on the PEP. The
provisioning report data consists of the bindings described above
and global and specific error/warning information.
Specific errors are associated with a particular policy rule. For
a 'Success' Report-Type, a specific error is an indication of a
warning related to a specific policy that has been installed, but
that is not fully implemented (e.g., its parameters have been
approximated) as identified by the ErrorPRID object. For a
'Failure' Report-Type, this is an error code specific to a
binding, again, identified by the ErrorPRID object. Specific
errors may also include regular <PRID><EPD> bindings to carry
additional information in a generic manner so that the specific
errors/warnings may be more verbosely described and associated
with the erroneous ErrorPRID object.
Global errors are not tied to a specific ErrorPRID. In a 'Success'
RPT message, a global error is an indication of a general warning
at the PEP level (e.g., memory low). In a 'Failure' RPT message,
this is an indication of a general error at the PEP level (e.g.,
memory exhausted).
In the case of a 'Failure' Report-Type the PEP MUST report at
least the first error and should report as many errors as
possible. In this case the PEP MUST roll-back its configuration to
the last good transaction before the erroneous Decision message
was received.
The format for this data is encapsulated in the COPS Named
ClientSI object as follows:
<ClientSI: Named Report> ::= <[<GPERR>] *(<report>)>
<report> ::= <ErrorPRID> <CPERR> *(<PRID><EPD>)
5.3.2. Accounting Report-Type Data Format
Additionally, reports can be used to carry accounting information
when specifying the 'Accounting' Report-Type. This accounting report
message will typically carry statistical or event information
related to the installed configuration for use at the PDP. This
information is encoded as one or more <PRID><EPD> bindings that
generally describe the accounting information being reported from
the PEP to the PDP.
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The format for this data is encapsulated in the COPS Named ClientSI
object as follows:
<ClientSI: Named Report> ::= <*(<PRID><EPD>)>
6. Common Operations
This section describes, in general, typical exchanges between a
PDP and Policy Provisioning COPS client.
First, a TCP connection is established between the client and
server and the PEP sends a Client-Open message specifying a COPS-
PR client-type, Policy Provisioning client. If the PDP supports
the specified provisioning client type, the PDP responds with a
Client-Accept (CAT) message. If the client-type is not supported,
a Client-Close (CC) message is returned by the PDP to the PEP,
possibly identifying an alternate server that is known to support
the policy for the provisioning client-type specified.
After receiving the CAT message, the PEP can send requests to the
server. The REQ from a policy provisioning client contains a COPS
'Configuration Request' context object and, optionally, any
relevant named client specific information from the PEP. The
information provided by the PEP should include available client
resources (e.g., supported classes/attributes) and default policy
configuration information as well as references to existing policy
(i.e., PIB) incarnation data. The configuration request message
from a provisioning client serves two purposes. First, it is a
request to the PDP for any provisioning configuration data which
the PDP may currently have that is suitable for the PEP, such as
access control filters, etc., given the information the PEP
specified in its REQ. Also, the configuration request effectively
opens a channel that will allow the PDP to asynchronously send
policy data to the PEP, as the PDP decides is necessary, as long
as the PEP keeps its request state open (ie. As long as the PEP
does not send a DRQ with the request state's Client Handle). This
asynchronous data may be new policy data or an update to policy
data sent previously.
After the PEP sends a REQ, if the PDP has Policy Provisioning
policy configuration information for the client, that information
is returned to the client in a DEC message containing the Policy
Provisioning client policy data within the COPS Named Decision
Data object and specifying an "Install" Command-Code in the
Decision Flags object. If no filters are defined, the DEC message
will simply specify that there are no filters using the "NULL
Decision" Command-Code in the Decision Flags object. As the PEP
MUST specify a Client Handle in the request message, the PDP MUST
process the Client Handle and copy it in the corresponding
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decision message. A DEC message must be issued by the PDP with the
Solicited Message Flag set in the COPS message header, regardless
of whether or not the PDP has any configuration information for
the PEP at the time of the request. This is to prevent the PEP
from timing out the REQ and deleting the Client Handle.
The PDP can then add new policy data or update/delete existing
state by sending subsequent unsolicited DEC message(s) to the PEP,
with the same Client Handle. The PEP is responsible for removing
the Client handle when it is no longer needed, for example when
the interface goes down, and informing the PDP that the Client
Handle is to be deleted via the COPS DRQ message.
For Policy Provisioning purposes, access state, and access
requests to the policy server can be initiated by other sources
besides the PEP. Examples of other sources include attached users
requesting network services via a web interface into a central
management application, or H.323 servers requesting resources on
behalf of a user for a video conferencing application. When such a
request is accepted, the edge device affected by the decision (the
point where the flow is to enter the network) must be informed of
the decision. Since the PEP in the edge device did not initiate
the request, the specifics of the request, e.g. flowspec, packet
filter, and PHB to apply, must be communicated to the PEP by the
PDP. This information is sent to the PEP using the Decision
message containing Policy Provisioning Named Decision Data objects
in the COPS Decision object as specified. Any updates to the state
information, for example in the case of a policy change or call
tear down, is communicated to the PEP by subsequent DEC messages
containing the same Client Handle and the updated Policy
Provisioning request state. Updates can specify that policy data
is to be deleted or installed.
PDPs may also command the PEP to open a new Request State or
delete an exiting one by issuing a decision with the Decision
Flags object's Request-State flag set. If the command-code is
"install", then the PDP is commanding the PEP to create a new
Request State, and therefore issue a new REQ message specifying a
new Client Handle or otherwise issue a "Failure" RPT specifying an
error condition. Each request state represents an independent and
logically non-overlapping namespace, identified by the Client
Handle, on which transactions may be performed. Other existing
Request States will be unaffected by the new request state as they
are independent (thus, no instances of configuration data within
one Request State can be affected by DECs for another Request
State as identified by the Client Handle). If the command-code is
"Remove", then the PDP is commanding the PEP to delete the
existing Request-State specified by the DEC message's Client
Handle, thereby causing the PEP to issue a DRQ message for this
Handle.
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The PEP acknowledges the DEC message and action taken by sending a
RPT message with a "Success" or "Failure" Report-Type object with
the Solicited Message Flag set in the COPS message header. This
serves as an indication to the PDP that the requestor (e.g. H.323
server) can be notified that the request has been accepted by the
network. If the PEP needs to reject the DEC operation for any
reason, a RPT message is sent with a Report-Type of value
"Failure" and optionally a Client Specific Information object
specifying the policy data that was rejected. The PDP can then
respond to the requestor accordingly.
The PEP can report to the PDP the local status of any installed
request state when appropriate. This information is sent in a
Report-State (RPT) message with the "Accounting" flag set. The
request state being reported is referenced by the Client Handle
associated with the request state and the client specific data
identifier.
Finally, Client-Close (CC) messages are used to cancel the
corresponding Client-Open message. The CC message informs the
other side that the client type specified is no longer supported.
7. Fault Tolerance
When communication is lost between PEP and PDP, the PEP attempts
to re-establish the TCP connection with the PDP it was last
connected to. If that server cannot be reached, then the PEP
attempts to connect to a secondary PDP, assumed at this time to be
manually configured at the PEP.
When a connection is finally re-established with a PDP, the PEP
sends a OPN message with a <LastPDPAddr> object providing the
address of the most recent PDP for which it is still caching
decisions. If no decisions are being cached on the PEP (due to
reboot or TTL timeout of state) the PEP must not include the last
PDP address information. Based on this information, the PDP may
request the PEP to re-synch its current state information (by
issuing a COPS SSQ message). If, after re-connecting, the PDP does
not request the synchronization, the client can assume the server
recognizes it and the current state at the PEP is correct. Any
state changes which occurred at the PEP while the connection was
lost must be reported to the PDP via the PEP sending an updated
REQ message. On the other hand, if re-synchronization is
requested, the PEP MUST reissue any REQ messages it generated
during initial connection establishment and the PDP MUST issue DEC
messages to delete either individual PRIDs or prefixes as
appropriate to ensure a consistent known state at the PEP.
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While the PEP is disconnected from the PDP, the request state at
the PEP is to be used for policy decisions. If the PEP cannot re-
connect in some pre-specified period of time, the request state is
to be deleted and the associated Handles removed. The same holds
true for the PDP; upon detecting a failed TCP connection, the
time-out timer is started for the request state associated with
the PEP and the state is removed after the specified period
without a connection.
7.1. Security Considerations
The use of COPS for Policy Provisioning introduces no new security
issues over the base COPS protocol [COPS]. The security mechanism
described in that document should be deployed in a COPS-PR
environment.
8. Acknowledgements
This document has been developed with active involvement
from a number of sources. The authors would specifically like to
acknowledge the valuable input given by Michael Fine and Scott Hahn.
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9. References
[COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja, R.,
Sastry, A., "The COPS (Common Open Policy Service)
Protocol", IETF RFC 2748, Proposed Standard, January 2000.
[RAP] Yavatkar, R., et al., "A Framework for Policy Based
Admission Control",IETF RFC 2753, January 2000.
[RSVP] Braden, R., Zhang, L., Berson, S., Herzog, S., and Jamin,
S., "Resource Reservation Protocol (RSVP) Version 1
Functional Specification", IETF RFC 2205, Proposed
Standard, September 1997.
[ASN1] Information processing systems - Open Systems
Interconnection, "Specification of Abstract Syntax Notation
One (ASN.1)", International Organization for
Standardization, International Standard 8824, December
1987.
[BER] Information processing systems - Open Systems
Interconnection - Specification of Basic Encoding Rules for
Abstract Syntax Notation One (ASN.1), International
Organization for Standardization. International Standard
8825, (December, 1987).
[RFC2475] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W.
Weiss, "An Architecture for Differentiated Service," RFC
2475, December 1998.
[PIB] M. Fine, K. McCloghrie, S. Hahn, K. Chan, A. Smith, "An
Initial Quality of Service Policy Information Base for
COPS-PR Clients and Servers", draft-mfine-cops-pib-02.txt,
October 1999.
V2SMI] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Structure of Management
Information Version 2(SMIv2)", STD 58, RFC 2578, April
1999.
[RFC2234] D. Crocker, P. Overell, " Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
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10. Author Information
Francis Reichmeyer IPHighway Inc.
Phone: (201) 585-0800 Parker Plaza, 16th Floor
Email: FranR@iphighway.com 400 Kelby St.
Fort-Lee, NJ 07024
Shai Herzog
Phone: (201) 585-0800
Email: Herzog@iphighway.com
Kwok Ho Chan Nortel Networks, Inc.
Phone: (978) 916-8175 600 Technology Park Drive
Email: kchan@nortelnetworks.com Billerica, MA 01821
David Durham Intel
Phone: (503) 264-6232 2111 NE 25th Avenue
Email: david.durham@intel.com Hillsboro, OR 97124
Raj Yavatkar
Phone: (503) 264-9077
Email: raj.yavatkar@intel.com
Silvano Gai Cisco Systems, Inc.
Phone: (408) 527-2690 170 Tasman Dr.
Email: sgai@cisco.com San Jose, CA 95134-1706
Keith McCloghrie
Phone: (408) 526-5260
Email: kzm@cisco.com
Andrew Smith Extreme Networks
Phone: +1 408 579 2821 3585 Monroe St.
Email: andrew@extremenetworks.com Santa Clara CA 95051
USA
John Seligson Nortel Networks, Inc.
Phone: (408) 495-2992 4401 Great America Parkway
Email:jseligso@nortelnetworks.com Santa Clara, CA 95054
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11. Full Copyright Notice
Copyright (C) The Internet Society (1997). 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.
Chan et al. Expires June 2000 [Page 28]
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