Internet Draft Francis Reichmeyer
Expiration: June 2000 Shai Herzog
File: draft-ietf-rap-pr-01.txt IPHighway
Kwok Ho Chan
John Seligson
Nortel Networks
David Durham
Raj Yavatkar
Intel
Silvano Gai
Keith McCloghrie
Cisco Systems
Andrew Smith
Extreme Networks
COPS Usage for Policy Provisioning
October 22, 1999
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
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Internet Draft COPS Usage for Policy Provisioning 22-Oct-99
Abstract
This document introduces a new client type for the COPS protocol to
support policy provisioning. Use of this new client type is
independent of the type of policy being managed and it assumes a
data model that is based on the concept of named policy information
as found in a Policy Information Base, or PIB.
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Table of Contents
Abstract..............................................................2
Table of Contents.....................................................3
Glossary..............................................................4
1. Introduction.....................................................4
1.1. Why not SNMP? ..................................................5
1.2. Interaction between the PEP and PDP ............................6
2. Policy Information Base (PIB)....................................7
2.1. PIB Syntax .....................................................8
2.2. PIB Example ....................................................8
2.3. Rules for Modifying and Extending PIBs ........................10
2.3.1.Adding PRCs to, or deprecating from, a PIB ....................10
2.3.2.Adding or Deprecating Attributes of a PRC .....................11
2.3.3.Augmenting a PRC with another PRC .............................12
2.4. COPS Operations Supported for a Policy Rule Instance ..........12
3. Message Content.................................................13
3.1. Request (REQ) PEP -> PDP .....................................13
3.2. Decision (DEC) PDP -> PEP ....................................14
3.3. Report State (RPT) PEP -> PDP ................................15
4. COPS-PR Protocol Objects........................................15
4.1. Binding Count (BC) ............................................16
4.2. Policy Rule Identifier (PRID) .................................16
4.2.1.Complete PRID .................................................16
4.2.2.Prefix PRID ...................................................17
4.3. BER Encoded Policy Instance Data (BPD) ........................18
4.4. Provisioning Error Object (PERR) ..............................19
5. COPS-PR Client-Specific Data Formats............................20
5.1. Named Decision Data ...........................................20
5.2. ClientSI Request Data .........................................21
5.3. Policy Provisioning Report Data ...............................21
6. Common Operations...............................................21
7. Fault Tolerance.................................................23
7.1. Security Considerations .......................................24
8. References......................................................25
9. Author Information..............................................26
10. Full Copyright Notice...........................................27
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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 a PRC.
1. Introduction
The IETF RSVP Admission Policy (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 Provisioning.
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 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 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 | | | | PDD<|--|---------+
| | |<---|----------|--| | |
| +-----+ | 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 cannot be mapped
directly to requests, and are issued mostly when the PDP responds
to external events or PDP events (policy/SLA updates).
This draft describes a new client type ("Provisioning") for COPS
to support policy provisioning. This new client type is
independent of the type of policy (QoS, VPNs, Security, etc.) and
it is based on the concept of PIBs (Policy Information Bases
[PIB]).
The Examples used in this document are biased toward QoS Policy
Provisioning in a Differentiated Services (DiffServ) environment.
However, the COPS-PR client type can be used for other types of
provisioning policies under the same framework.
1.1. Why not SNMP?
SNMP is a very popular network management protocol. One may
question using COPS-PR, rather than extending SNMP for policy
provisioning.
There are several aspects intrinsic to SNMP that prevents it from
being a successful policy protocol.
SNMP uses a transactional model, and does not support the concept
of long term Client/Server connection. As a by product, servers
may not know that devices failed and vice versa. A hello polling
may be a cumbersome replacement, however it may not solve the
problem if a device may reboot in between polling messages.
The SNMP transactional model allows multiple servers to
simultaneously modify state of a network device. Given that SNMP
does not have resource locking facilities, a policy server would
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have to constantly poll and verify that no other networking
management software or humans changed ANY of the configured
resources.
SNMP is based on UDP and is thus unreliable. The lack of
reliability is unacceptable for a policy protocol [RAP].
Provisioning policy is assumed quite large and diverse. It is
desired that a provisioning protocol would be based on state
sharing between client and server such that only differential
updates are sent. Such state sharing requires a reliable transport
mechanism.
Last, SNMP was not designed as a real-time operations protocol.
Its trap mechanism is inefficient and cumbersome and there is no
performance guarantees.
COPS was designed 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 high priority (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 the model of
SMI and MIB and 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 which are
currently relevant to that device. On receiving the provisioned
policies, the device maps them into its local QoS mechanisms, and
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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.
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 names within this space are unique within the
scope of a given PDP/PEP/ClientType communication channel. Note
that a give device might implement multiple PEPs or multiple
ClientTypes and the name space then only has uniqueness within
each separate channel.
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
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Instances of the policy rules (PRIs) are each identified by a
Policy Rule Identifier (PRID). A PRID is a name, carried in a COPS
<Named ClientSI> object, which identifies a particular instance of
a rule.
2.1. PIB Syntax
The provisioning PIB syntax is based on SMI and MIBs, based on the
ASN.1 data definition language [ASN1]. The decision to use this
format as a basis opens-up the possibility of leveraging SNMP SMI
and MIB knowledge, experience and tools. In order to simplify the
implementation and allow re-use of SNMP encoding/decoding code,
the wire representation of the policy information (PRIDs and BPDs)
in the COPS protocol objects follows the Basic Encoding Rules
(BER) [BER] - the object syntax definitions appear in section 4.
PRCs and their PRIs are identified by PRIDs, which are unique
within the scope of a given PDP/PEP/ClientType channel. PRIDs have
a hierarchical structure of the form a.b.c.d (e.g. 1.3.4.7), where
a prefix identifies the PRC (e.g., 1.3 or 1.3.4) and the last
component identifies the individual instance (e.g. 7).
Note that the instance values do not have to be consecutive
although they must be unique to this PDP/PEP/ClientType
communication. The actual values for the indices may be chosen by
the PDP and they may or may not have significance to the PDP as
real values; they have no significance to the PEP other than as
instance identifiers. Note also the intentional similarity to
SNMP's SMI syntax and semantics [V2SMI]. There is no need for a
"context" mechanism, such as that in SNMP, to disambiguate
different PRIs containing the same data: the instance numbers are
chosen by the PDP and the semantics of contexts can, therefore, be
encoded in the PRC definitions themselves.
Given that most provisioning operations require multiple
attributes, COPS-PR does not support operations on individual
attributes within a PRC (e.g. filterSrcPort above). Updates and
deletions are performed on a granularity of per-PRC only.
The policy tree names all the policy rule classes and instances
and this creates a common view of the policy organization between
the client (PEP) and the server (PDP). The PIB data on its own
is self- descriptive such that the receiving PEP understands the
required provisioning.
2.2. PIB Example
Consider the following simple example of a set of policy rule
class to represent filters for marking IP traffic with a certain
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diff-serv code point (DSCP). Each filter has the following
attributes: Protocol number, source address, source port,
destination address, destination port, and DSCP value to set. This
might be represented by the following class definition:
filterTable OBJECT-TYPE
SYNTAX SEQUENCE OF FilterEntry
POLICY-ACCESS install
STATUS current
DESCRIPTION
"Filter PRC."
::= { pib 1 }
filterEntry OBJECT-TYPE
SYNTAX FilterEntry
STATUS current
DESCRIPTION
"An instance of the filter class."
INDEX { filterIndex }
::= { filterTable 1 }
FilterEntry ::= SEQUENCE {
filterIndex INTEGER, -- arbitrary index
filterProtocol INTEGER,
filterSrcAddr IpAddress,
filterSrcPort INTEGER,
filterDstAddr IpAddress,
filterDstL4Port INTEGER,
filterDscp Integer32
}
etc.
Let us assume that the base "pib" has a prefix in the policy tree
of 1.2.3. So, the first filter instance might have a PRID of
pib.filterTable.filterEntry.10, or 1.2.3.1.1.10. The next filter
instance might then get the PRID 1.2.3.1.1.99. This PIB segment
might be shown diagramatically as:
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(1.2.3) (1.2.3.1) (1.2.3.1.1) (1.2.3.1.1.10)
pib---+-filterTable-+-filterEntry-+-----10-------+-filterProtocol
| | |
| | +-filterSrcAddr
etc. | |
| +-filterSrcPort
| |
| etc.
|
|(1.2.3.1.1.99)
+-----99-------+-filterIndex
| |
| +-filterProtocol
etc. |
etc.
{_______________________________} {___________}
\/ \/
PRC branches PRI leaves
Figure 3: A PIB Example for a DiffServ Filter
The numbers in parentheses represent the location of the PRC or
PRI in the tree. Note that the last digit of the PRCs (which in
SMI would describe the individual class attributes) is dropped
from the PRID since COPS-PR only supports operations on complete
classes, not on individual attributes.
2.3. 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 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.
2.3.1. Adding PRCs to, or deprecating from, a PIB
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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 OIDs under the module OID.
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.
2.3.2. Adding or Deprecating Attributes of a PRC
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, 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.
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2.3.3. Augmenting a PRC with another PRC
Rather than extending a PRC by modifying the PIB and adding
attributes to that PRC, a new PRC can be defined, perhaps in a
different PIB module to augment an existing PRC. This is
especially useful for independent enterprises to independently
augment an existing class.
An augmenting PRC has its own OID. However, an instance of this
PRC can only be created if there is a corresponding instance (with
the same instance ID) of the base PRC. The base PRC, on the other
hand, can be configured by a PDP without the PDP also configuring
the augmenting PRC (or PRCs). In this case, the PEP MUST asume
some default values for the attributes of the augmenting PRC.
When the PDP deletes an instance of a base PRC, the instances of
the corresponding augmented PRCs are also deleted.
Augmenting standard PIB attributes with enterprise specific
extensions introduces interoperability issues regarding policy
servers that are unaware of the proprietary additions. Under this
scenario, the DEFVAL clause SHOULD be used to provide default values
for the proprietary attributes. All attribute definitions in a class
the augments a base class SHOULD include a DEFVAL clause specifying
a reasonable default value. This helps to ensure that a PDP may
adequately provision a PEP based solely on standard PIB attributes.
Rules governing the usage and specification of the DEFVAL clause are
defined in the SMIv2 [SNMP-SMI].
2.4. COPS Operations Supported for a Policy Rule Instance
A Policy Rule Instance (PRI) may contain multiple leaf attributes
and is identified uniquely, within the scope of a given COPS
ClientType 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 a BER-encoded Policy Instance Data (BPD) 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.
3.1. Request (REQ) PEP -> PDP
The REQ message is sent by policy provisioning clients to issue a
'config request' to the PDP. The Client Handle associated with the
REQ message originated by a provisioning client must be unique for
that client but otherwise has no protocol significance at this
time.
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.
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 existing policy (i.e. PIB)
incarnation data. This information typically does not include
state previously installed by a PDP. This information from the
client assists the server in deciding what types of policy the PEP
can install and enforce. The format of the Provisioning ClientSI
data is described in the policy information base (see 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>]
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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 REQ
message.
The DEC message is sent as an immediate response to a config
request with the solicited decision flag set. Subsequent DEC
messages may also be sent at any time after the original DEC
message to supply the PEP with additional/updated policy
information. Updated policy data carried in DEC message is
correlated with the previous DEC by matching the policy ID
information in the provisioning client decision data.
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.
A COPS-PR DEC message contains 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 only Named Decision Data (Provisioning) is included in a
COPS-PR Decision. Other types of COPS decision data (e.g.
Stateless, Replacement) are not supported.
For each decision on the DEC message, the PEP performs the
operation specified in the Flags field on the Named decision data.
For the policy provisioning clients, the format for this data is
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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 back to the PDP to inform the PDP of the
action taken.
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 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 = 'Installed') or not
(Report-Type = 'Not Installed').
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
We define a new COPS client type for the policy provisioning
client:
Client Type = 2; Policy Provisioning Client
COPS messages sent between a Policy Provisioning client and a COPS
server contain a COPS Common Header with this Policy Provisioning
Client type specified:
0 1 2 3
+---------------+---------------+---------------+---------------+
| Version| Flag | Op Code | Client Type = 0x02 |
+---------------+---------------+---------------+---------------+
| Message Length |
+---------------+---------------+---------------+---------------+
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The COPS Policy Provisioning client uses several new COPS protocol
objects that carry named client-specific information. This section
defines those 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 next section).
The format for these new objects is as follows:
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = BC | S-Type = 1 |
+---------------+---------------+---------------+---------------+
| 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 ClientSI specific objects.
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 previous stated object length to the next
32-bit boundary.
4.1. Binding Count (BC)
S-Num = 1, S-Type = 1, Length = 8.
This object specifies the number of Bindings that are contained in
the message.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = BC | S-Type = 1 |
+---------------+---------------+---------------+---------------+
| 32 bit unsigned integer |
+---------------+---------------+---------------+---------------+
4.2. Policy Rule Identifier (PRID)
4.2.1. Complete PRID
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S-Num = 2, S-Type = 1 (Complete 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 = 1 |
+---------------+---------------+---------------+---------------+
... ...
| Policy Rule Identifier |
... ...
+---------------+---------------+---------------+---------------+
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
02 - S-Num
01 - S-Type (Complete PRID)
06 07 2B 06 01 02 02 08 01 - Encoded PRID
00 00 00 - Padding
4.2.2. Prefix PRID
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.
The specification of a prefix is performed using the Policy Rule
Identifier object with an S-Type equal to 2 (Prefix PRID).
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S-Num = 2, S-Type = 2 (Prefix PRID), Length = variable.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = PRID | S-Type = 2 |
+---------------+---------------+---------------+---------------+
... ...
| Prefix PRID |
... ...
+---------------+---------------+---------------+---------------+
Continuing with the previous example, a PRC 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
02 - S-Type = Prefix PRID
06 05 2B 06 01 02 02 - Encoded Prefix
00 - Padding
4.3. BER Encoded Policy Instance Data (BPD)
S-Num = 3, S-Type = 1, Length = variable.
This object is used to carry the BER encoded value of a Policy
Data Instance. This object is used to carry the BER 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 = BPD | S-Type = 1 |
+---------------+---------------+---------------+---------------+
... ...
| BER Encoded PRI Value |
... ...
+---------------+---------------+---------------+---------------+
As an example, an instance of the qosIpAce class, defined in the
QoS Policy IP PIB [PIB], would be encoded as follows:
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02 01 08 :qosIpAceIndex/INTEGER/Value = 8
40 04 C0 39 01 05 :qosIpAceDstAddr/IpAddress/Value =
192.57.1.5
40 04 FF FF FF FF :qosIpAceDstMask/IpAddress/Value =
255.255.255.255
40 04 00 00 00 00 :qosIpAceSrcAddr/IpAddress/Value = 0.0.0.0
40 04 00 00 00 00 :qosIpAceSrcMask/IpAddress/Value = 0.0.0.0
02 01 FF :qosIpAceDscp/Integer32/Value = -1 (not used)
02 01 06 :qosIpAceProtocol/INTEGER/Value = 6 (TCP)
05 00 :qosIpAceDstL4PortMin/NULL/not supported
05 00 :qosIpAceDstL4PortMax/NULL/not supported
05 00 :qosIpAceSrcL4PortMin/NULL/not supported
05 00 :qosIpAceSrcL4PortMax/NULL/not supported
02 01 01 :qosIpAcePermit/TruthValue/Value = 1 (true)
The entire BPD object would be encoded as follows:
00 30 - Length
03 - S-Num = BPD
01 - S-Type
02 01 08 - qosIpAceIndex
40 04 C0 39 01 05 - qosIpAceDstAddr
40 04 FF FF FF FF - qosIpAceDstMask
40 04 00 00 00 00 - qosIpAceSrcAddr
40 04 00 00 00 00 - qosIpAceSrcMask
02 01 FF - qosIpAceDscp
02 01 06 - qosIpAceProtocol
05 00 - qosIpAceDstL4PortMin
05 00 - qosIpAceDstL4PortMax
05 00 - qosIpAceSrcL4PortMin
05 00 - qosIpAceSrcL4PortMax
02 01 01 - qosIpAcePermit
Note that attributes not supported within a class are still
returned in the BPD 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. Provisioning Error Object (PERR)
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S-Num = 4, S-Type = 1, Length = 8.
0 1 2 3
+---------------+---------------+---------------+---------------+
| Length | S-Num = PERR | S-Type = 1 |
+---------------+---------------+---------------+---------------+
| Error-Code | Error Sub-code |
+---------------+---------------+---------------+---------------+
The 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 policy provisioning client also adds the following error code:
Error Code 14 = Provisioning Error
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 named decision data, request data and
report data. The actual content of the data is defined by the
policy information base for the provisioning client type (see
below).
5.1. Named Decision Data
The Named Decision Data for the policy provisioning client
consists of two types of decisions: Install and Remove, used with
the 'Install' and 'Remove' Command-Code, respectively, in the COPS
Decision Object. The data, in general, is composed of one or more
bindings. Each binding associates a PRID object and a BPD object.
The PRID object is always present in both install and remove
decisions, the BPD 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 the provisioning client named decision data is as
follows:
< Decision: Named Data> ::= <Install Decision> |
<Remove Decision>
<Install Decision> ::= <BC> <PRID> <BPD> [<PRID> <BPD>]+
<Remove Decision> ::= <BC> <PRID> [<PRID>]+
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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 as follows:
<ClientSI: Named Request> ::= <BC> <PRID> <BPD> [<PRID> <BPD>]+
5.3. Policy Provisioning Report Data
The provisioning client report data is used in the RPT message in
conjunction with the accompanying COPS Report Type object. Report
types can be 'Commit' or 'No-Commit' 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. In a
'Commit' RPT message, 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). In a 'No Commit' RPT message, this is an error code
specific to a binding.
Global errors are not tied to a specific PRID. In a 'Commit' RPT
message, a global error is an indication of a general warning at
the PEP level (e.g., memory low). In a 'No Commit' RPT message,
this is an indication of a general error at the PEP level (e.g.,
memory exhausted).
In the case of a 'No Commit' the PEP MUST report at least the
first error and should report as many errors as possible.
<ClientSI: Named Report> ::= [<global-error>] [report]+
<global-error> ::= <Error>
<report> ::= <PRID> <specific-error>
[<BC>[<PRID><BPD>[<PRID><BPD>]+]]
<specific-error> ::= <Error>
6. Common Operations
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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 with the Client-
Type = 2, Policy Provisioning client. If the PDP supports the
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.
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 with and, optionally, any
relevant client specific information for the PEP. The information
provided by the PEP should include client resource (e.g.,
supported classes/attributes) and default policy configuration
information as well as existing policy (i.e., PIB) incarnation
data. The config 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.
Also, the config request is a request to asynchronously send
policy data to the PEP, as the PDP decides is necessary. This
asynchronous data may be new policy data or an update to policy
data sent previously.
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 Decision object. If no filters are defined, the
DEC message will simply specify that there are no filters using
the "NULL Decision" Decision Flags object. The PEP MUST specify a
client handle in the request message. The PDP MUST process the
client handle and copy it in the decision message. 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 existing state by
sending subsequent 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 handle is to be deleted.
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
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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 client specific 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.
The PEP acknowledges the DEC message and action taken by sending a
RPT message with a "Commit" or "No-Commit" Report-Type object.
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 "No-
Commit" 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
state being reported on 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 included the last
PDP address information. Based on this information, the PDP may
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request the PEP to re-synch its current state information (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 in a RPT message. 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.
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 (TTL: Time To Live,
see Section 3.3), 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.
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8. References
[COPS] Boyle, J., Cohen, R., Durham, D., Herzog, S., Raja, R.,
Sastry, A., "The COPS (Common Open Policy Service)
Protocol", IETF <draft-ietf-rap-cops-07.txt>, August 1999.
[RAP] Yavatkar, R., et al., "A Framework for Policy Based
Admission Control",IETF <draft-ietf-rap-framework-03.txt>,
April 1999.
[E2E] Bernet, Y., Yavatkar R., Ford, P., Baker, F., Nichols, K.,
Speer, M., "A Framework for End-to-End QoS Combining
RSVP/Intserv and Differentiated Services", IETF <draft-
ietf-DiffServ-rsvp-01.txt>, November 1998.
[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.
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9. 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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10. 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.
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