COPS Usage for Differentiated Services December 1998 Network Working Group Francis Reichmeyer Internet Draft Kwok Chan draft-ietf-rap-cops-ds-01.txt Bay Networks, Inc. Expiration Date: May 1999 David Durham Raj Yavatkar Intel Silvano Gai Keith McCloghrie Cisco Systems, Inc. Shai Herzog IPHighway December 1998 COPS Usage for Differentiated Services Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Abstract There is a clear need for relatively simple and coarse methods of providing differentiated classes of service for Internet traffic, to support various types of services, and specific business requirements. The IETF has chartered the Differentiated Service WG to define the differentiated services architecture and a common language for differentiated services. Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 1] COPS Usage for Differentiated Services December 1998 In parallel, the IETF RSVP Admission Policy (RAP) WG has defined the COPS (Common Open Policy Service) protocol [COPS]. This document describes enhancements to the Common Open Policy Service (COPS) protocol to support policy services in a Differentiated Services (DiffServ) environment. Further modifications to COPS for DiffServ may be proposed in the future, but what is presented here is thought to be the minimum necessary additions. 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 ................................8 3.1 Description of the Policy Tree................................9 3.2 Operations Supported On a PRI................................10 3.3 PIB general information......................................10 3.4 An example of a PIB..........................................10 4. COPS DiffServ Client Data .......................................13 4.1 Policy Identifier (PRID).....................................13 4.2 BER encoded Policy instance Data (BPD).......................14 4.3 DiffServ Decision Data.......................................14 4.4 DiffServ Request Data........................................15 4.5 DiffServ Report Data.........................................15 4.5.1 Successfully Installed/Removed Data .....................15 4.5.2 Unsuccessfully Installed/Removed Data ...................15 4.5.3 Accounting Data .........................................16 5. Message Content .................................................16 5.1 Request (REQ) PEP -> PDP...................................16 5.2 Decision (DEC) PDP -> PEP..................................17 5.3 Report State (RPT) PEP -> PDP..............................18 6. Common Operation ................................................18 7. Fault Tolerance .................................................20 8. Security ........................................................21 9. References ......................................................21 10. Author Information .............................................22 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 2] COPS Usage for Differentiated Services December 1998 1. Terminology o ACL: Access Control List. 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. An object is identified by its C-num and C-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. It inherits from PRC. A PRC defines a vector of attributes. Each attribute has a syntax type that is either primitive or refined. It also overrides the READ and WRITE methods and defines new error sub- codes. 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. 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 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 3] COPS Usage for Differentiated Services December 1998 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 As shown in Figure 1, the network device contacts a Policy Decision Point (PDP) to make the policy-based admission control decision. The Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 4] COPS Usage for Differentiated Services December 1998 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. 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 5] COPS Usage for Differentiated Services December 1998 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 the usage of the COPS protocol for communicating this information between DiffServ clients (PEPs) and the policy servers (PDPs). 2.1 Basic Model Figure 2 shows a sample network configuration for a DiffServ environment. Edge routers and boundary routers are located at the boundary of DiffServ domains as described in [Nichols]. The BB/PS is responsible for admission control functions and resource provisioning. +-----+ +-----+ | BB/ | | BB/ | | PS | | PS | +-----+ +-----+ \ | | / | / / Stub \ / Transit \ / Stub \ / Network \ / Network \ / Network \ +---+ | +---\ /---+ +---\ /---+ | +---+ |Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx | +---+ | +---/ \---+ ---/ \---+ | +---+ \ / \ / \ / \ / \ / \ / Figure 3: Sample DiffServ Network Configuration 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 6] COPS Usage for Differentiated Services December 1998 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 DiffServ specific communication and to distinguish DiffServ usage from other uses of COPS, we have added a new client type to COPS (client type = DiffServ client). It is possible for an edge device to contain both a COPS-DS 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-DS |<--|-----------|-->| | | | | Client | | COPS-DS | +-----+ | | | | | | | | +---------+ | +-------------+ | | +-----------------+ Figure 4: COPS DS and RSVP Clients in Same Edge Device 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 7] COPS Usage for Differentiated Services December 1998 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 (hardware type, software release, configuration information). During this phase the client also specifies the maximum COPS-DS 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 at the PEP, then the PDP sends the changes (installs/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 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. 3. The definition of the Policy Tree This section defines data format for the DiffServ client specific information carried in the Decision, Request ClientSI, and Report ClientSI objects. DiffServ client specific data may be defined for the other objects in the future. COPS-DS data is represented by a policy tree containing Policy Rule Classes (PRCs) and Instances of those classes (PRIs), as shown in Figure 5. Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 8] COPS Usage for Differentiated Services December 1998 -------+-------+----------+---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 DiffServ needs much more structure, since it needs to represent policies, mappings, ACLs, 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 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 9] COPS Usage for Differentiated Services December 1998 code, the representation of the policy information on the wire must follow BER both for the PRID and for the BPD [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-DS 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 DS 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-DS Message Size): a message size in bytes. The COPS-DS Client-Open ClientSI MUST specify the MCMS supported by the client. This value must be in the range 4KB - 64KB. o Interface to be provisioned. o Capability information: This may include what filters the PEP supports, what kind of profiles or dispositions it can perform. 3.4 An example of a PIB This section contains a simple example of a PIB describing a simple set of filters for IP packets. Each filter is able to match either the source IP address, the destination IP address or both. This Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 10] COPS Usage for Differentiated Services December 1998 example is provided only for the benefit of understanding how a PIB is structured. It is not necessarily supposed to describe any actual policy data. policyFilterPIB OBJECT IDENTIFIER ::= { policyPIB 1 } ipHeaderFilterTable OBJECT-TYPE SYNTAX SEQUENCE OF IpHeaderFilterEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "This table contains a simple ACL, i.e. one or more IP filters." ::= {policyFilterPIB 1} ipHeaderFilterEntry OBJECT-TYPE SYNTAX IpHeaderFilterEntry MAX-ACCESS write-only STATUS current DESCRIPTION "Each row of the table has four columns. The ipHeaderFilterIndex uniquely identifies a particular IP filter. The ipHeaderFilterMatchType specifies the type of match (source only, destination only, source and destination). The ipHeaderFilterSourceAddress and ipHeaderFilterDestinationAddress contain the source and destination IP addresses." INDEX {ipHeaderFilterIndex} ::= {ipHeaderFilterTable 1} IpHeaderFilterEntry ::= SEQUENCE { ipHeaderFilterIndex INTEGER, ipHeaderFilterMatchType BITS, ipHeaderFilterSourceAddress IpAddress, ipHeaderFilterDestinationAddress IpAddress } ipHeaderFilterIndex OBJECT-TYPE SYNTAX INTEGER MAX-ACCESS not-accessible STATUS current DESCRIPTION "The index of the table, used to identify each Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 11] COPS Usage for Differentiated Services December 1998 individual IP filter" ::= {ipHeaderFilterEntry 1} ipHeaderFilterMatchType OBJECT-TYPE SYNTAX BITS { matchSource (0), matchDestination (1) } MAX-ACCESS not-accessible STATUS current DESCRIPTION "This field indicates which one or more of the addresses are required to match the corresponding addresses of the IP packet." ::= {ipHeaderFilterEntry 2} ipHeaderFilterSourceAddress OBJECT-TYPE SYNTAX IpAddress MAX-ACCESS not-accessible STATUS current DESCRIPTION "IP source address to be matched against the packet in the event the ipHeaderFilterMatchType has the corresponding bit set. ::= {ipHeaderFilterEntry 3} ipHeaderFilterDestinationAddress OBJECT-TYPE SYNTAX IpAddress MAX-ACCESS not-accessible STATUS current DESCRIPTION "IP destination address to be matched against the packet in the event the ipHeaderFilterMatchType has the corresponding bit set. ::= {ipHeaderFilterEntry 4} Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 12] COPS Usage for Differentiated Services December 1998 4. COPS DiffServ Client Data The COPS-DS extensions define a new client type: Client Type = 2; DiffServ Client DiffServ specific information is sent in a COPS message containing a Common Header with the DiffServ Client type specified: 0 1 2 3 +----------------+----------------+----------------+----------------+ | Version| //// | Op Code | Client Type = 0x02 | +----------------+----------------+----------------+----------------+ | Message Length | +----------------+----------------+----------------+----------------+ 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. 0 1 2 3 +----------------+----------------+----------------+----------------+ | Length | Type = PRID | +----------------+----------------+----------------+----------------+ | Policy Rule Identifier | +----------------+----------------+----------------+----------------+ Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 13] COPS Usage for Differentiated Services December 1998 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 | Type = "BER type" | +----------------+----------------+----------------+----------------+ | BER Encoded PRI Value | +----------------+----------------+----------------+----------------+ 4.3 DiffServ Decision Data The DiffServ Named Decision 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 DiffServ specific decision data uses the following format: C-Num = 7 C-Type = 5 ::= | This depends from the , see Section 5.2. :: = ::= | ::= ::= ::= | Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 14] COPS Usage for Differentiated Services December 1998 Please note that the delete has the capability of deleting an entire table with a single operation. 4.4 DiffServ Request Data The diffServ Configuration request will utilize the COPS Named ClientSI (C-Num=10 C-Type=2) object to carry the same bindings as described above. The DiffServ request Named ClientSI data has the following format: ::= ::= 4.5 DiffServ Report Data DiffServ specific report data is used in the RPT message. The format of the report data is dependant on the value of the accompanying COPS Report Type object. Report types can be Installed/Removed or NotInstalled/NotRemoved indicating to the PDP that a particular set of policies has been either successfully or unsuccessfully installed/deleted on the PEP. 4.5.1 Successfully Installed/Removed Data When used with the "Installed" or "Removed" report type, the DiffServ Named ClientSI object in the Report Message has the following format: ::= ::= [] where is the set of PRID successfully installed/deleted. 4.5.2 Unsuccessfully Installed/Removed Data When used with the "Not Installed" or "Not Removed" report type, the DiffServ specific report data has the following format: ::= Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 15] COPS Usage for Differentiated Services December 1998 ::= ::= | ::= [] where: is the PRID of the unsuccessful install/delete, is the error code and are conflicting bindings that caused the error. The COPS-DS adds also the following two error codes: - 12 COPS Client Specific Error Code; - 13 Vendor Specific Error Code. In the case of "no commit" the PEP MUST report at least the first error and should report as many errors as possible. 4.5.3 Accounting Data TBD 5. Message Content This section describes the COPS messages exchanged between a PEP and PDP for use with DiffServ policy services. 5.1 Request (REQ) PEP -> PDP The REQ message is used by COPS DiffServ 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 DiffServ request data, defined above, may be included in the config request form PEP to 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. Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 16] COPS Usage for Differentiated Services December 1998 The config request message serves as a request from the PEP to the PDP for any DiffServ 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 DiffServ 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. ::= [ ] 5.2 Decision (DEC) PDP -> PEP The DEC message () is sent from the PDP to a DiffServ client in response to a config REQ received from the PEP. The Client Handle must be the same Handle that was received in the REQ message. The Client Specific Decision Data for DiffServ clients (), to be used in the DEC message, is defined in Section 4.3. 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-DS decision message should contain at most one delete decision followed by at most one install decision. 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-DS 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. Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 17] COPS Usage for Differentiated Services December 1998 For each decision (), the PEP performs the operation specified in the Decision Flags object () on the decision 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. In response to a DEC message, the DiffServ client sends a RPT back to the PDP to inform the PDP of the actual action taken. For example, in response to a DEC with the "Install" flag (only) set, 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 DiffServ client to the PDP to report accounting information from PEP to PDP on request state installed at the PEP. It is also used as a mechanism to inform the PDP about the action taken at the PEP, in response to a DEC message. The DiffServ report data format, as defined above, depends on the Report Type included in the RPT message. ::= [] 6. Common Operation This section describes, in general, typical exchanges between a PDP and DiffServ 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, DiffServ Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 18] COPS Usage for Differentiated Services December 1998 client. If the PDP supports the DiffServ 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 (believed?) to support the policy for the DiffServ client. Once the CAT message is received, the client can send requests to the server. The request a COPS DiffServ 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-DS. First, it is a request from the PEP to the PDP for any DiffServ 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 DiffServ 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 DiffServ QoS policy configuration information for the client, that information is returned to the client in a DEC message containing the DiffServ 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 "No Configuration" Decision Flags object. The PEP MUST specify a client handle (which can be zero) 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 DiffServ 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 19] COPS Usage for Differentiated Services December 1998 PEP using the Decision message containing DiffServ 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 DiffServ 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 "Installed" or "Removed" 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 "Not Installed" or "Not Removed" 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, 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- Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 20] COPS Usage for Differentiated Services December 1998 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). 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 (some multiple of the keep-alive time? - TBD), 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. 8. Security The use of COPS for DiffServ 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 , December 1998. [RAP] Yavatkar, R., et al., "A Framework for Policy Based Admission Control",IETF , November, 1997. [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 , March 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 Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 21] COPS Usage for Differentiated Services December 1998 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). [Nichols] K. Nichols, V. Jacobson, L. Zhang, " A Two-bit Differentiated Services Architecture for the Internet," draft-nichols-diff-svc-arch-00.txt 10. Author Information Francis Reichmeyer Bay Networks, Inc. 3 Federal Street Billerica, MA 01821 Phone: (978) 916-3352 Email: freichmeyer@baynetworks.com Kwok Ho Chan Bay Networks, Inc. 600 Technology Park Billerica, MA 01821 Phone: (978) 916-8175 Email: khchan@baynetworks.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. Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 22] COPS Usage for Differentiated Services December 1998 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 Shai Herzog IPHighway 400 Kelby St., Suite 1500 Parker Plaza Fort Lee, NJ 07024 Phone: (201) 585-0800 Email: herzog@iphighway.com Reichmeyer, Chan, Durham, Gai, McCloghrie [Page 23]