COPS Usage for Policy Provisioning February 1999
Network Working Group Francis Reichmeyer
Internet Draft Kwok Ho Chan
draft-sgai-cops-provisioning-00.txt Nortel Networks, Inc.
Expiration Date: August 1999 David Durham
Raj Yavatkar
Intel
Silvano Gai
Keith McCloghrie
Cisco Systems, Inc.
Shai Herzog
IPHighway
Andrew Smith
Extreme Networks
February 1999
COPS Usage for Policy Provisioning
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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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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COPS Usage for Policy Provisioning February 1999
Abstract
There is a clear need for a standard way to provision policies to
network devices. These policies may be related to QoS (Quality of
Service), Security, VPNs (Virtual Private Networks), etc.
The IETF RSVP Admission Policy (RAP) WG has defined the COPS (Common
Open Policy Service) protocol [COPS] and a scalable policy control
model for RSVP [RSVP].
This document describes a new client type ("Provisioning") for the
Common Open Policy Service (COPS) protocol to support policy
provisioning. This new client type is independent of the type of
policy and it is based on the concept of PIBs (Policy Information
Bases [PIB].
The example of provisioning used in this document is QoS Policy
Provisioning in a Differentiated Services (DiffServ) environment.
Table of contents
1. Terminology ......................................................3
2. Introduction .....................................................4
2.1 Basic Model...................................................6
2.2 Interaction between the PDP and the PEP.......................8
3. The definition of the Policy Tree ................................9
3.1 Description of the Policy Tree...............................10
3.2 Operations Supported On a PRI................................10
3.3 PIB general information......................................10
4. COPS Policy Provisioning Client Data ............................11
4.1 Policy Identifier (PRID).....................................11
4.2 BER encoded Policy instance Data (BPD).......................12
4.3 Binding Count (BC)...........................................13
4.4 Error Object.................................................13
4.5 Policy Provisioning Decision Data............................13
4.6 Policy Provisioning Request Data.............................14
4.7 Policy Provisioning Report Data..............................14
4.7.1 Commit Data .............................................15
4.7.2 No-Commit Data ..........................................15
4.7.3 Accounting Data .........................................15
5. Message Content .................................................16
5.1 Request (REQ) PEP -> PDP...................................16
5.2 Decision (DEC) PDP -> PEP..................................16
5.3 Report State (RPT) PEP -> PDP..............................18
6. Common Operation ................................................18
7. Fault Tolerance .................................................20
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8. Security ........................................................21
9. References ......................................................21
10. Author Information .............................................22
11. Full Copyright Statement .......................................23
1. Terminology
o ClientSI: Client Specific Information Object.
o COPS (Common Open Policy Service): client/server model for
supporting policy control [COPS].
o Object: this term is used in the same sense as in COPS
specification. A COPS object is identified by its C-Num and C-Type,
a ClientSI object by its S-Num, S-Type.
o PDP (Policy Decision Point): a network entity where policy
decisions are made.
o PEP (Policy Enforcement Point): network device where policy
decisions are enforced.
o Policy Rule: policy information specified by the PDP to be enforced
at the PEP.
o PRC (Policy Rule Class): a type of policy rule data item. In object
oriented terminology this is equivalent to a class. A PRC defines a
vector of attributes. Each attribute has a syntax type.
o PRI (Policy Rule Instance): an instance of a PRC. Potentially there
are multiple instances of the same PRC. The value of a PRI consist
of a vector of values, one value for each attribute in the PRC's
vector of attributes.
o PII (Policy Instance Identifier): one or more of the PRC attributes
the values of which are used as part of the identification of a
PRI.
o PIB (Policy Information Base): policy objects are accessed via a
virtual information store, termed the Policy Information Base or
PIB [PIB]. Objects in the PIB are defined using a subset of
Abstract Syntax Notation One (ASN.1) [ASN1].
o PRID (Policy Rule IDentifier): the name which identifies a
particular PRI or PRC. It has a hierarchical structure of the form
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1.3.4.2.7, where the first part identifies the PRC (i.e., 1.3.4)
and the last part is the value of the PII (Policy Instance
Identifier), which identifies the instance (i.e. 2.7). The PII is
null in the case of a PRC. PRIDs are represented as a BER encoded
OIDs (Object Identifiers).
o BPD: BER (ASN.1 [ASN1] Basic Encoding Rule [BER]) encoded Policy
Instance Data.
2. Introduction
The Common Open Policy Service (COPS) protocol is a query response
protocol used to exchange policy information between a network policy
server and a set of clients [COPS]. COPS is being developed within
the RSVP Admission Policy Working Group (RAP WG) of the IETF,
primarily for use as a mechanism for providing policy-based admission
control over requests for network resources [RAP].
The underlying assumption in the RAP framework is that applications
or end systems use the RSVP [RSVP] signaling protocol to communicate
Integrated Services (IntServ) reservation requests to the network
nodes along the path of a flow. These reservation requests carry
necessary flow specifications and requests for a flow to receive one
of the defined Integrated Services, Controlled Load or Guaranteed. In
the IntServ model, the RSVP messages themselves contain all the
necessary information needed at the networking device to classify and
service the flow [RSVP]. This information includes the session
identifier (source and destination addresses, port numbers, and
transmission protocol), flowspec token bucket parameters, and
requested service.
Edge Device Policy Server
+--------------+ +-----------+
| | | |
| | COPS | |
| +-----+ | REQ() | +-----+ |
RSVP | | |----|----------|->| | |
--------|-->| PEP | | | | PDP | |
| | |<---|----------|--| | |
| +-----+ | COPS | +-----+ |
| | DEC() | |
+--------------+ +-----------+
Figure 1: COPS with RSVP/IntServ
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As shown in Figure 1, the network device contacts a Policy Decision
Point (PDP) to make the policy-based admission control decision. The
PDP is simply required to return a Decision, such as "accept" and the
network device acts as a Policy Enforcement Point (PEP) and uses the
session information and IntServ service parameters to classify and
service the packets belonging to the flow.
Providing policy services in a DiffServ environment requires some
different assumptions about the admission control mechanisms used in
the network. First, there might be no explicit dynamic signaling from
sources of traffic requesting a particular service, as in the case of
an IntServ network. Network resources are provisioned based on static
SLAs (Service Level Agreements) at network boundaries. Second, where
requests for allocation of resources to differentiated services are
used, they may arrive at the PDP from network entities other than the
PEP. Examples of such sources include attached users requesting
network services via a web interface into a central management
application, or H.323 gatekeeper requesting resources on behalf of a
user for a video conferencing application, as shown in Figure 2.
+----------+
Edge Device Policy Server | H.323 |
+--------------+ +-----------+ |Gatekeeper|
| | | | | |
| | | | +----------+
| ----- | COPS | ----- | |
| | | | DECs() | | | | |
| | PEP |<---|----------|--| PDP |<----------+
| | | | | | | | Service
| ----- | | ----- | Request
| | | |
+--------------+ +-----------+
Figure 2: COPS Example with DiffServ
Requests of this sort still require some policy decision to be made
to ensure the requesting user/application has permission to use the
requested services and that the resources are available. Once the
decision is made, the PDP must configure one or more PEPs to allocate
necessary resources for services requested. In addition, the PDP may
also pass to the PEP provisioning decisions about resources related
to flows of a more static nature, such as long-term SLAs established
across boundaries of adjacent ISP networks.
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In summary, the interaction between the PDP and PEP is different in
at least two respects from that in the case of the IntServ
environment. First, the resource provisioning requests may originate
at places other than a PEP. Second, once the PDP makes a policy
decision to allocate resources for a service class or a flow
aggregate, it must pass sufficient information (such as packet
classification filters, traffic shaper parameters) in the decision
message to the PEPs so that PEPs can enforce policy decisions.
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]).
Adding a new client type to COPS is much easier than designing a new
protocol and allows us to reuse all the COPS code. Moreover, for QoS
Provisioning it has the additional advantage to adopt a single
protocol for RSVP and provisioned QoS. We have taken another
important decision to simplify the implementation of Provisioning,
i.e., to reuse the BER [BER] encoding and therefore part of the code
already available for SNMP.
2.1 Basic Model
Figure 3 shows a sample network configuration for a DiffServ
environment.
+-----+ +-----+
| BB/ | | BB/ |
| PS | | PS |
+-----+ +-----+
\ |
| /
| /
/ Stub \ / Transit \ / Stub \
/ Network \ / Network \ / Network \
+---+ | +---\ /---+ +---\ /---+ | +---+
|Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx |
+---+ | +---/ \---+ ---/ \---+ | +---+
\ / \ / \ /
\ / \ / \ /
Figure 3: Sample DiffServ Network Configuration
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Edge routers and boundary routers are located at the boundary of
DiffServ domains as described in [RFC 2475]. The BB/PS is responsible
for admission control functions and resource provisioning.
In the COPS model, the PDP is part of the bandwidth broker/policy
server that manages policy information and resources within a
DiffServ domain. Both edge routers and boundary routers act as PEPs
and communicate with BB/PS using COPS for exchange of policy
information. The internal organization of the bandwidth broker
functionality and policy functionality may vary and the policy server
and BB may be separate entities. In that case, either the BB or the
PS may communicate with the edge devices. The BB, upon receiving COPS
messages from the PEP, would consult the policy server to make its
final admission control decision. Similarly, if the PS receives COPS
messages directly from PEP, the PS would consult the BB to verify
available resources before making a final admission control decision.
To allow for use of COPS for policy provisioning and to distinguish
this usage from other uses of COPS, we have added a new client type
to COPS (client type = Provisioning client). It is possible for an
edge device to contain both a COPS-PR (COPS-Provisioning) and a COPS-
RSVP client. Each COPS clients can communicate with different PDPs,
or they can connect to the same PDP which supports both client types,
as shown in Figure 4.
Edge Device
+-----------------+
| | PS/BB
| +---------+ | +-------------+
| | | | | |
RSVP | |COPS-RSVP| | COPS-RSVP | +-----+ |
<-------|-->| Client |<--|-----------|-->| | |
| | | | | | | |
| |---------| | | | PDP | |
| | | | | | | |
| |COPS-PR |<--|-----------|-->| | |
| | Client | | COPS-PR | +-----+ |
| | | | | |
| +---------+ | +-------------+
| |
+-----------------+
Figure 4: COPS-PR and RSVP Clients in Same Edge Device
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Allowing multiple COPS client types to co-exist in a single PEP means
that the same PDP can coordinate policy decisions in an environment
where, say, both RSVP/IntServ and DiffServ QoS mechanisms need to be
managed. For example, in a stub network that uses IntServ with RSVP
signaling internally and is connected to a DiffServ transit network
externally. In this case, the edge device that connects the stub
network to the transit network may require policy decisions from the
same PDP for both RSVP requests as well as for policy rules to
enforce on the egress (DiffServ is with respect to the ingress)
interface.
The two decisions may very well need to be coordinated to ensure
proper provisioning and allocation of network resources. For example,
the decision of whether to admit an RSVP flow, or not, would depend
on the provisioning policy in place at the egress interface where the
flow is leaving the stub network, and vice versa. The issue of
combining IntServ and DiffServ to provide an end-to-end QoS solution
is discussed in the draft [E2E]. Also, the RSVP WG is currently
planning on addressing the use of RSVP within the differentiated
services QoS model.
2.2 Interaction between the PDP and the PEP
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 (see Section 3.3).
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
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.
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3. The definition of the Policy Tree
This section defines data format for the Provisioning client specific
information carried in the Decision, Request ClientSI, and Report
ClientSI objects. Provisioning client specific data may be defined
for the other objects in the future. COPS-PR data is represented by a
policy tree containing Policy Rule Classes (PRCs) and Instances of
those classes (PRIs), as shown in Figure 5.
-------+-------+----------+---PRC--+--PRI
| | | +--PRI
| | +---PRC-----PRI
| +---PRC--+--PRI
| | +--PRI
| | +--PRI
| | +--PRI
| | +--PRI
| +---PRC-----PRI
+---PRC---PRI
Figure 5: Example of a Policy Tree
The policy tree is based on SMI and MIBs. COPS for RSVP does not need
a policy tree, since the information exchanged has a simple format
and is defined by existing RSVP objects. COPS for Policy Provisioning
needs much more structure, since it needs to represent policies,
mappings, Access Control Lists, interfaces, etc.
PRIs (Policy Rule Instances) and PRCs (Policy Rule Classes) have
names called PRIDs (Policy Rule IDentifiers). PRIDs have a
hierarchical structure of the form 1.3.4.2.7, where the first part
identifies the PRC (e.g., 1.3.4) and the last part identifies the
instance (e.g. 2.7).
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). Therefore, when the PEP receives
data from the PDP, the data itself specifies what a PEP is supposed
to do with the data. The current granularity of access, i.e., the
atomicity of replacement, is proposed as a vector of values.
Note that the PRCs/PRIs in the above diagram are each a vector of
values. This proposal is that the hierarchy of PRCs/PRIs is for
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benefit of human understanding, not for programmatic understanding,
or inheritance.
3.1 Description of the Policy Tree
The Policy Tree is described using SMI and PIBs. SMI and PIBs are
defined based on the ASN.1 data definition language [ASN1]. To
simplify the implementation and re-use the SNMP encoding/decoding
code, the representation of the policy information on the wire must
follow BER both for the PRID and for the BPD (BER encoded Policy
Instance Data [BER]).
3.2 Operations Supported On a PRI
The following operations are supported on a PRI:
o Install - creates a new instance of a PRC, i.e. a new PRI, or
modifies an existing instance. The instance is automatically
enabled. Parameters to this operation are a PRID (see Section 4.1)
and an "BPD (BER encoded Policy instance Data)" containing the
value to assign to the new PRI see (Section 4.2). The BPD specifies
all the attributes of the new PRI.
o Delete - This operation is used to delete an instance of a PRC. The
parameter is a PRID (see Section 4.1).
3.3 PIB general information
The PIB has a branch that contains general information. Examples of
information stored in this branch are:
o TTL (Time To Live): a period of time in seconds. In the event the
PEP looses the COPS-PR connection with the PDP, it tries to re-
establish the connection with the primary and secondary PDPs. If
this fails for a period of time greater than the TTL, the
provisioning policies are discarded. The TTL specified in this
branch is the default TTL and may be overridden by TTLs present in
specific branches. A TTL = 0 means infinite.
o MCMS (Maximum COPS-PR Message Size): an optional maximum message
size in bytes. If the COPS-PR client has a fixed MCMS, it must
specify it. A value of zero means unknown MCMS.
o Interface to be provisioned.
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o Capability information: this may include what filters the PEP
supports, what kind of profiles or dispositions it can perform.
For a more detailed description of the PIB, see [PIB].
4. COPS Policy Provisioning Client Data
The COPS-PR extensions define a new client type:
Client Type = 2; Policy Provisioning Client
Policy Provisioning specific information is sent in a COPS message
containing a Common Header with the Policy Provisioning Client type
specified:
0 1 2 3
+----------------+----------------+----------------+----------------+
| Version| Flag | Op Code | Client Type = 0x02 |
+----------------+----------------+----------------+----------------+
| Message Length |
+----------------+----------------+----------------+----------------+
Setting flags to 0x01 implies it is a solicited message.
The COPS protocol specification defines several objects which may
carry client specific information between PDP and PEP:
o Context Object (Context)
o Reason code Object (Reason code)
o Decision Object (Decision)
o Error Object (Error)
o Client Specific Info Object (ClientSI) which includes:
o Request ClientSI
o Report ClientSI
o Client-Open ClientSI
4.1 Policy Identifier (PRID)
This object is used to carry the PRID of the Policy Rule Instance to
be installed or deleted.
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0 1 2 3
+----------------+----------------+----------------+----------------+
| Length | S-Num = PRID | S-Type = 1 |
+----------------+----------------+----------------+----------------+
... ...
| Policy Rule Identifier |
... ...
+----------------+----------------+----------------+----------------+
The 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.)
S-Num and S-Type have the same meaning of C-Num and C-Type, but they
are ClientSI specific. The value for PRID is S-Num = 1.
4.2 BER encoded Policy instance Data (BPD)
This object is used to carry the value of a Policy Data Instance to
be installed, It contains an BER coding of the Policy Data Instance
[BER].
0 1 2 3
+----------------+----------------+----------------+----------------+
| Length | S-Num = BPD | S-Type = 1 |
+----------------+----------------+----------------+----------------+
... ...
| BER Encoded PRI Value |
... ...
+----------------+----------------+----------------+----------------+
The 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.)
The value for BPD is S-Num = 2.
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4.3 Binding Count (BC)
This object is used to specify the number of Bindings that follow.
0 1 2 3
+----------------+----------------+----------------+----------------+
| Length | S-Num = BC | S-Type = 1 |
+----------------+----------------+----------------+----------------+
| 32 bit unsigned integer |
+----------------+----------------+----------------+----------------+
The length is equal to 8.
The value for BC is S-Num = 3.
4.4 Error Object
The Error object as the same format as in COPS [COPS], but C-Num and
C-Type are replaced by S-Num and S-Type. The value of S-Num = 4 and
S-Type = 1.
4.5 Policy Provisioning Decision Data
The Policy Provisioning Named Decision Data (<Decision: Named Data>,
see Section 5.2) is composed of one or more bindings. Each binding
associates a PRID object and an BPD object. The PRID object is always
present, the BPD object MUST be present in the case of an install
decision and MUST NOT be present in the case of a delete decision.
The BPD object contains the value to be assigned to the PRI that is
created or updated.
The Policy Provisioning specific decision data uses the following
format:
C-Num = 7
C-Type = 5
<Decision: Named Data> ::= <Install Decision> |
<Remove Decision>
This depends from the <Decision: Flag>, see Section 5.2.
<Install Decision> :: = [<Binding>]+
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<Binding> ::= <PRID> <BPD>
<Remove Decision> ::= [<PRID>]+
Please note that the delete has the capability of deleting an entire
table with a single operation.
4.6 Policy Provisioning Request Data
The Policy Provisioning Configuration request will utilize the COPS
Named ClientSI (C-Num=10 C-Type=2) object to carry the same bindings
as described above. The Policy Provisioning request Named ClientSI
data has the following format:
<ClientSI: Named> ::= < Policy Provisioning Request Data>
<Policy Provisioning Request Data (Named ClientSI)> ::= [Binding]+
4.7 Policy Provisioning Report Data
The Policy Provisioning specific report data is used in the RPT
message. The format of the report data is independent on the value of
the accompanying COPS Report Type object. Report types can be
"Commit" or "No-Commit" indicating to the PDP that a particular set
of policies has been either successfully or unsuccessfully
installed/deleted on the PEP.
<ClientSI: Named> ::= <Policy Provisioning Report Data>
<Policy Provisioning report data> ::= [<global-error>] [report]+
<global-error> ::= <Error>
where <global-error> is a global error or warning (i.e., not tied to
a specific PRID).
<report> ::= <PRID> <specific-error> [<Binding-Count> [<Binding]+]
<specific-error> ::= <Error>
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The RPT message can be solicited (in answer to a Decision Data) or
unsolicited (e.g., due to a change in the interfaces to be
provisioned).
The COPS-PR adds also the following error code:
- 14 Client-Type Specific Error Code;
4.7.1 Commit Data
When used with the "Commit" report type, the objects in the Policy
Provisioning Named ClientSI object in the Report Message have the
following meaning:
o <global-error> is a global warning, i.e. an indication of a general
warning at the PEP level (e.g., memory low);
o <specific-error> is a warning indication, i.e. 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);
o <PRID> is a PRID successfully installed/deleted.
4.7.2 No-Commit Data
When used with the "No-Commit" report type, the objects in the Policy
Provisioning Named ClientSI object in the Report Message have the
following meaning:
o <global-error> is a global error, i.e. an indication of a general
error at the PEP level (e.g., memory exhausted);
o <PRID> is the PRID of the unsuccessful install/delete;
o <specific-error> is an error code specific to a binding and is
followed by an optional set of <Binding> that caused the error due
to conflicts.
In the case of "no commit" the PEP MUST report at least the first
error and should report as many errors as possible.
4.7.3 Accounting Data
TBD
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5. Message Content
This section describes the COPS messages exchanged between a PEP and
PDP for use with Policy Provisioning policy services.
5.1 Request (REQ) PEP -> PDP
The REQ message is used by COPS Policy Provisioning clients for
issuing a config request to the PDP, as described in the COPS
protocol. The Client Handle is associated with request state
originated by the PEP and the PEP is responsible for notifying the
PDP when the Handle is no longer in use and can be deleted.
The Policy Provisioning request data, defined above, may be included
in the config request from the PEP to the PDP. Currently, the request
data is defined for carrying configuration/feature negotiation
information from the PEP. This provides the server with information
on the types of policy that the interface can enforce and the types
of policy data the PEP can install.
The config request message serves as a request from the PEP to the
PDP for any Policy Provisioning configuration data which the PDP may
have pre-defined for the PEP device, such as access control lists,
etc., and any future access data or updates. The pre-configured and
any asynchronous Policy Provisioning configuration data can then be
sent to the PEP over time via decisions, as decided by the PDP. The
configuration information supplied by the PDP is of the consistent
client specific format defined above. The PDP responds to the config
request with a DEC message containing any available configuration
information.
<Request> ::= <Common Header>
<Client Handle>
<Context = config request>
<ClientSI: Named>
For <ClientSI: Named> see Section 4.6.
5.2 Decision (DEC) PDP -> PEP
The DEC message (<Decision Message>) is sent from the PDP to a Policy
Provisioning client in response to a config REQ received from the
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PEP. The Client Handle must be the same Handle that was received in
the REQ message. The Client Specific Decision Data for Policy
Provisioning clients (<Decision: ClientSI Data>), to be used in the
DEC message, is defined in Section 4.5.
The DEC message is sent as an immediate response to a config request
with the solicited decision flag set, used to carry pre-defined
configuration information set in the PDP, to the PEP. Subsequent DEC
messages may also be sent at any time after the original DEC message
to continue supplying the PEP with additional/updated policy
information. The state carried in the DEC message is correlated with
an initial request state by the Client Handle and provides the
appropriate PRID information.
Each DEC message may contain multiple decisions. This allows with a
single message to install some policies and delete some 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 decision message is also a "transaction", i.e. all the
bindings in a message either succeed or fail. This allow to delete
some policies only if other policies can be installed in their place.
Associating a transaction semantic to a COPS message, instead of
defining a specific transaction construct, is not a limitation: in
fact the COPS message may have an arbitrary size, only limited either
by the PEP memory or by the MCMS parameter, if specified (see Section
3.3).
For each decision (<Decision>), the PEP performs the operation
specified in the Decision Flags object (<Decision: Flags>) on the
decision data (<Decision: ClientSI Data>]).
<Decision Message> ::= <Common Header>
<Client Handle>
[<Decision>]+ | <Error>
<Decision> ::= <Context>
<Decision: Command-Code>
[<Decision: Named Data>]
If no configuration state is available when the config REQ is
processed by the PDP, a DEC is sent with the "No Configuration Data"
decision flag set.
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In response to a DEC message, the Policy Provisioning client sends a
solicited RPT back to the PDP to inform the PDP of the actual action
taken. For example, in response to an Install Decision (see Section
4.5), the PEP informs the PDP if the decision data can be installed,
based on the other policy data on the device (are there conflicts,
etc.).
5.3 Report State (RPT) PEP -> PDP
The RPT message is sent from the Policy Provisioning client to the
PDP to report accounting information from PEP to PDP or notify
changes in the PEP (unsolicited report). It is also used as a
mechanism to inform the PDP about the action taken at the PEP, in
response to a DEC message (solicited report). The Policy Provisioning
report data format, as defined above, depends on the Report Type
included in the RPT message.
<Report State> ::= <Common Header>
<Client Handle>
<Report Type>
[<Policy Provisioning report data>]
6. Common Operation
This section describes, in general, typical exchanges between a PDP
and Policy Provisioning COPS client.
First, a connection is established between the PEP and PDP and the
PEP sends a Client-Open message with the Client-Type = 2, Policy
Provisioning client. If the PDP supports the Policy Provisioning
client, 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 Policy Provisioning client.
Once the CAT message is received, the client can send requests to the
server. The request a COPS-PR client sends to the server is for
configuration information, that is a REQ with "Configuration Request"
set in the context object that identifies a specific interface/module
and any relevant client specific information (see also Section 3.3).
The config request message serves two purposes in COPS-PR. First, it
is a request from the PEP to the PDP for any Policy Provisioning
configuration data which the PDP may have pre-defined for the PEP
device, such as acces control lists, etc. Also, the config request is
a request to the PDP to send asynchronous Policy Provisioning
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configuration data to the PEP, as it is received by the PDP. This
asynchronous data may be new policy data or an update to policy data
sent previously.
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 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 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
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COPS Usage for Policy Provisioning February 1999
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, either with the primary
PDP or a secondary PDP, the PEP should provide the last PDP address
of the PDP for which it is still caching decisions. Based on this
information, the PDP may request the PEP to re-synch its current
state information (SSQ message). 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. 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 changes state changes which occurred at the PEP while connection
was lost must be reported to the PDP in a RPT message. If re-
synchronization is requested, the PEP should reissue its
configuration requests and the PDP should delete the appropriate PRCs
on the PEP (thus, removing all previous decisions below the PRC,
effectively resetting all state, and reverting to some static or
preconfigured decisions).
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.
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8. Security
The use of COPS for Policy Provisioning introduce no new security
issues over the base COPS protocol. The use of IPSEC between PDP and
PEP, as described in [COPS] is sufficient.
9. 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-05.txt>, December
1998.
[RAP] Yavatkar, R., et al., "A Framework for Policy Based
Admission Control",IETF <draft-ietf-rap-framework-01.txt>,
November, 1998.
[E2E] Bernet, Y., Yavatka,r 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
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COPS Usage for Policy Provisioning February 1999
COPS-PR Clients and Servers", draft-mfine-cops-pib-00.txt,
February 1999.
10. Author Information
Francis Reichmeyer
Nortel Networks, Inc.
3 Federal Street
Billerica, MA 01821
Phone: (978) 916-3352
Email: freichmeyer@nortelnetworks.com
Kwok Ho Chan
Nortel Networks, Inc.
600 Technology Park Drive
Billerica, MA 01821
Phone: (978) 916-8175
Email: khchan@nortelnetworks.com
David Durham
Intel
2111 NE 25th Avenue
Hillsboro, OR 97124
Phone: (503) 264-6232
Email: david.durham@intel.com
Raj Yavatkar
Intel
2111 NE 25th Avenue
Hillsboro OR 97124
Phone: (503) 264-9077
Email: yavatkar@ibeam.intel.com
Silvano Gai
Cisco Systems, Inc.
170 Tasman Dr.
San Jose, CA 95134-1706
Phone: (408) 527-2690
email: sgai@cisco.com
Keith McCloghrie
Cisco Systems, Inc.
170 Tasman Dr.
San Jose, CA 95134-1706
Phone: (408) 526-5260
email: kzm@cisco.com
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COPS Usage for Policy Provisioning February 1999
Shai Herzog,
IPHighway
Parker Plaza, Suite 1500
400 Kelby St.
Fort-Lee, NJ 07024
Phone: (201) 585-0800
email: herzog@iphighway.com
Andrew Smith
Extreme Networks
10460 Bandley Drive
Cupertino, CA 95014
Phone: (408) 342-0999
Email: andrew@extremenetworks.com
11. Full Copyright Statement
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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