Network Working Group M. Boucadair, Ed.
Internet-Draft C. Jacquenet
Intended status: Informational Orange
Expires: September 7, 2020 D. Zhang
Huawei Technologies
P. Georgatsos
CERTH
March 6, 2020

Dynamic Service Negotiation
draft-boucadair-connectivity-provisioning-protocol-19

Abstract

This document specifies the Connectivity Provisioning Negotiation Protocol (CPNP) which is designed to facilitate the dynamic negotiation of service parameters.

CPNP is a generic protocol that can be used for various negotiation purposes that include (but are not necessarily limited to) connectivity provisioning services, storage facilities, Content Delivery Networks, etc.

Status of This Memo

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This Internet-Draft will expire on September 7, 2020.

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Table of Contents

1. Introduction

This document defines the Connectivity Provisioning Negotiation Protocol (CPNP) that is meant to dynamically exchange and negotiate connectivity provisioning parameters and other service-specific parameters between a Customer and a Provider. CPNP is a tool that introduces automation in the service negotiation and activation procedures, thus fostering the overall service provisioning process. CPNP can be seen as a component of the dynamic negotiation meta-domain described in Section 3.4 of [RFC7149].

CPNP is a generic protocol that can be used for other negotiation purposes than connectivity provisioning. For example, CPNP can be used to request extra storage resources, to extend the footprint of a CDN (Content Delivery Networks), to enable additional features from a cloud Provider, etc. CPNP can be extended with new Information Elements (IEs). Sample negotiation uses cases are described in Section 5.

[RFC7297] describes a Connectivity Provisioning Profile (CPP) template to capture connectivity requirements to be met by a transport infrastructure for the delivery of various services such as Voice over IP (VoIP), IPTV, and Virtual Private Network (VPN) services [RFC4026]. The CPP document defines the set of IP transfer parameters that reflect the guarantees that can be provided by the underlying transport network together with reachability scope and capacity needs. CPNP uses the CPP template to encode connectivity provisioning clauses that are subject to negotiation. The agreed CPP will be then passed to other functional elements that are responsible for the actual service activation and provisioning. For example, NETCONF [RFC6241] or RESTCONF [RFC8040] can be used to activate adequate network features that are required to deliver the agreed service. How the outcome of CPNP negotiation is translated into service and network provisioning actions is out of scope of this document.

As a reminder, several proposals have been made in the past by the (research) community (e.g., COPS-SLS [I-D.nguyen-rap-cops-sls], Service Negotiation Protocol (SrNP) [TEQUILA], Dynamic Service Negotiation Protocol (DSNP) [I-D.itsumo-dsnp], Resource Negotiation and Pricing Protocol (RNAP) [Xin], Service Negotiation and Acquisition Protocol (SNAP) [Karl]). CPNP leverages the experience of the authors with SrNP by separating the negotiation primitives from the service under negotiation. Moreover, careful examination of the other proposals revealed certain deficiencies that were easier to address through the creation of a new protocol rather than modifying existing protocols. For example:

One of the primary motivations of this document is to provide a permanent reference to exemplify how service negotiation can be automated.

This document is organized as follows:

Implementation details are out of scope. An example of required modules and interfaces to implement this specification is sketched in Section 4 of [AGAVE]. This specification builds on that effort.

2. Terminology

This document makes use of the following terms:

Customer:
Is a business role which denotes an entity that is involved in the definition and the possible negotiation of a contract, including a Connectivity Provisioning Agreement, with a Provider. A connectivity provisioning contract is captured in a dedicated CPP template-based document, which may specify (among other information): the sites to be connected, border nodes, outsourced operations (e.g., routing, force via points).

The right to invoke the subscribed service may be delegated by the Customer to third-party End Users, or brokering services.

A Customer can be a Service Provider, an application owner, an enterprise, a user, etc.
Network Provider (or Provider):
Owns and administers one or many transport domain(s) (typically Autonomous System (AS)) composed of (IP) switching and transmission resources (e.g., routing, switching, forwarding, etc.). Network Providers are responsible for delivering and operating connectivity services (e.g., offering global or restricted reachability at specific rates). Offered connectivity services may not necessarily be restricted to IP.

The policies to be enforced by the connectivity service delivery components can be derived from the technology-specific clauses that might be included in contracts agreed with the Customers. If no such clauses are included in the agreement, the mapping between the connectivity requirements and the underlying technology-specific policies to be enforced is deployment-specific.
Quotation Order:
Denotes a request made by the Customer to the Provider that includes a set of requirements. The Customer may express its service-specific requirements by assigning (strictly or loosely defined) values to the information items included in the commonly understood template (e.g., CPP template) describing the offered service. These requirements constitute the parameters to be mutually agreed upon.
Offer:
Refers to a response made by the Provider to a Customer's quotation order that describes the ability of the Provider to satisfy the order at the time of its receipt. Offers reflect the capability of the Provider in accommodating received Customer orders beyond monolithic ‘yes/no’ answers.

An offer may fully or partially meet the requirements of the corresponding order. In the latter case, it may include alternative suggestions which the Customer may take into account by issuing a new order.
Agreement:
Refers to an order placed by the Customer and accepted by the Provider. It signals the successful conclusion of a negotiation cycle.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here.

3. CPNP Functional Elements

The following functional elements are defined:

CPNP client (or client):
Denotes a software instance that sends CPNP requests and receives CPNP responses. The current operations that can be performed by a CPNP client are listed below:
  1. Create a quotation order (Section 9.2.1).
  2. Cancel an ongoing quotation order under negotiation (Section 9.2.7).
  3. Accept an offer made by a server (Section 9.2.4).
  4. Withdraw an agreement (Section 9.2.8).
  5. Update an agreement (Section 9.2.9).
CPNP server (or server):
Denotes a software instance that receives CPNP requests and sends back CPNP responses accordingly. The CPNP server is responsible for the following operations:
  1. Process a quotation order (Section 9.2.2).
  2. Make an offer (Section 9.2.3).
  3. Cancel an ongoing quotation order (Section 11.2.3).
  4. Process an order withdrawal (Section 11.2.3).

4. Order Processing Models

For preparing their service orders, Customers may need to be aware of the offered services. Therefore, Providers should first proceed with the announcement (or the exposure) of the services they can provide. The service announcement process may take place at designated global or Provider-specific service markets, or through explicit interactions with the Providers. The details of this process are outside the scope of this document.

With or without such service announcement/exposure mechanisms in place, the following order processing models can be distinguished:

Frozen model:


The Customer cannot actually negotiate the parameters of the service(s) offered by a Provider. After consulting the Provider's service portfolio, the Customer selects the service offer he/she wants to subscribe and places an order to the Provider. Order handling is quite simple on the Provider side because the service is not customized as per Customer's requirements, but rather pre-designed to address a Customer base that shares the same requirements (i.e., these customers share the same Customer Provisioning Profile). This mode can be implemented using existing tools such as [RFC8309].
Negotiation-based model:


Unlike the frozen model, the Customer documents his/her requirements in a request for a quotation, which is then sent to one or several Providers. Solicited Providers check whether they can address these requirements or not, and get back to the Customer accordingly, possibly with an offer that may not exactly match customer's requirements (e.g., a 100 Mbps connection cannot be provisioned given the amount of available resources, but an 80 Mbps connection can be provided). A negotiation between the Customer and the Provider(s) then follows until both parties reach an agreement (or do not).

Both frozen and negotiation-based models require the existence of appropriate service templates like a CPP template and their instantiation for expressing specific offerings from Providers and service requirements from Customers, respectively. CPNP can be used in either model for automating the required Customer-Provider interactions. Since the frozen model can be seen as a special case of the negotiation-based model, not only ‘yes/no’ answers but also counter-proposals may be offered by the Provider in response to Customer orders. This document focuses on the negotiation-based model.

Order processing management on the Network Provider's side usually solicits features supported by the following functional blocks:

CPNP does not assume any specific knowledge about these functional blocks, drawing an explicit line between protocol operation and the logic for handling connectivity provisioning requests. An order processing logic is typically fed with the information manipulated by the aforementioned functional blocks. For example, the resources that can be allocated to accommodate Customer's requirements may depend on network availability estimates as calculated by the planning functions and related policies, as well as the number of orders to be processed simultaneously over a given period of time.

This document does not elaborate on how Customers are identified and subsequently managed by the Provider's Information System.

5. Sample Use Cases 

       ,--,--,--.             ,--,--,--.
    ,-'          `-.       ,-'          `-.
   (CDN Provider 'A')=====(CDN Provider 'B')
    `-.  (CDN-A) ,-'       `-. (CDN-B)  ,-'
       `--'--'--'             `--'--'--'

Figure 1: CDN Interconnection

       ,--,--,--.             ,--,--,--.
    ,-'          `-.       ,-'          `-.
   (Mapping System 'A')===(Mapping System 'B')
    `-.          ,-'       `-.           ,-'
       `--'--'--'             `--'--'--'

Figure 2: LISP Mapping System Interconnect

A non-exhaustive list of CPNP use cases is provided below:

  1. [RFC4176] introduces the L3VPN Service Order Management functional block which is responsible for managing the requests initiated by the Customers and tracks the status of the completion of the related operations. CPNP can be used between the Customer and the Provider to negotiate L3VPN service parameters.

    A CPNP server could therefore be part of the L3VPN Service Order Management functional block discussed in [RFC4176]. Once an agreement is reached, the service can be provisioned using, e.g., [I-D.ietf-opsawg-l3sm-l3nm].
  2. CPNP can be used between two adjacent domains to deliver IP interconnection services (e.g., enable, update, disconnect). For example, two Autonomous Systems (ASes) can be connected via several interconnection points. CPNP can be used between these ASes to upgrade existing links, request additional resources, provision a new interconnection point, etc.

    See, for example, the framework documented in [ETICS].
  3. An integrated Provider can use CPNP to rationalize connectivity provisioning needs related to its service portfolio. A CPNP server function is used by network operations teams. A CPNP interface to trigger CPNP negotiation cycles is exposed to service management teams.
  4. Service Providers can use CPNP to initiate connectivity provisioning requests towards a number of Network Providers so as to optimize the cost of delivering their services. Although multiple CPNP ordering cycles can be initiated by a Service Provider towards multiple Network Providers, a subset of these orders may actually be put into effect.

    For example, a cloud Service Provider can use CPNP to request more resources from Network Providers.
  5. CPNP can also be used in the context of network slicing ([I-D.geng-netslices-architecture]) to request network resources together with a set of requirements that need to be satisfied by the Provider. Such requirements are not restricted to basic IP forwarding capabilities, but may also include a characterization of a set of service functions that may be invoked. For the network slicing case, the instances of a CPP template could be derived from the network slice templates inputs as documented in [I-D.contreras-teas-slice-nbi].
  6. CPNP can be used in Machine-to-Machine (M2M) environments to dynamically subscribe to M2M services (e.g., access to data retrieved by a set of sensors, extend sensor coverage, etc.).

    Also, Internet of Things (IoT, [RFC6574]) domains may rely on CPNP to enable dynamic access to data produced by involved objects, according to their specific policies, to various external stakeholders such as data analytics and business intelligence companies. Direct CPNP-based interactions between IoT domains and interested parties enable open access to diverse sets of data across the Internet, e.g., from multiple types of sensors, user groups and/or geographical areas.
  7. CPNP can be used in the context of I2NSF ([RFC8329]) to capture the customer-driven policies to be enforced by a set of Network Security Functions.
  8. A Provider offering cloud services can expose a CPNP interface to allow Customers to dynamically negotiate typical data center resources, such as additional storage, processing and networking resources, enhanced security filters, etc.

    Cloud computing providers typically structure their computation service offerings by bundling CPU, RAM, and storage units as quotas, instances, or flavors that can be consumed in an ephemeral or temporal fashion during the lifetime of the required function. A similar approach is followed by CPNP (see for example, Section 9.2.11).
  9. In the inter-cloud context (also called cloud of clouds or cloud federation), CPNP can be used to reserve computing and networking resources hosted by various cloud infrastructures.
  10. CDN Providers can use CPNP to extend their footprint by interconnecting their respective CDN infrastructures [RFC6770] (see Figure 1).

  11. Mapping Service Providers (MSPs, [RFC7215]) can use CPNP to enrich their mapping database by interconnecting their mapping system (see Figure 2). This interconnection allows to relax the constraints on PxTR (Proxy Ingress/Egress Tunnel Router) in favour of native LISP (Locator/ID Separation Protocol) forwarding [RFC6830]. Also, it prevents the fragmentation of the LISP mapping database. A framework is described in [I-D.boucadair-lisp-idr-ms-discovery].

  12. CPNP may also be used between SDN (Software-Defined Networking) controllers in contexts where Cooperating Layered Architecture for Software-Defined Networking (CLAS) is enabled [RFC8597].

6. CPNP Deployment Models

Several CPNP deployment models can be envisaged. Two examples are listed below:

Once the negotiation of connectivity provisioning parameters is successfully concluded, that is, an order has been placed by the Customer, the actual network provisioning operations are initiated. The specification of related dynamic resource allocation and policy enforcement schemes, as well as how CPNP servers interact with the network provisioning functional blocks at Provider sides are out of the scope of this document.

This document does not make any assumption about the CPNP deployment model either.

7. CPNP Negotiation Model

CPNP runs between a Customer and a Provider carrying service orders from the Customer and corresponding responses from the Provider to the end of reaching a service provisioning agreement. As the services offered by the Provider are well-described, by means of the CPP template for connectivity matters, the negotiation process is essentially a value-settlement process, where an agreement is pursued on the values of the commonly understood information items (service parameters) included in the service description template (Section 9.1.9).

The protocol is transparent to the content that it carries and to the negotiation logic invoked at Customer and Provider sides, and which manipulates the content (i.e., the information carried in CPNP messages to proceed with the negotiation).

The protocol aims at facilitating the execution of the negotiation logic by providing the required generic communication primitives.

Since negotiations are initiated and primarily driven by the Customer's negotiation logic, it is reasonable to assume that the Customer is the only party that can call for an agreement. An implicit approach is adopted for not overloading the protocol with additional messages. In particular, the acceptance of an offer made by the Provider signals a call for agreement from the Customer. Note that it is almost certain the Provider to accept this call since it refers to an offer that itself made. Of course, at any point the Provider or the Customer may quit the negotiations, each on its own grounds.

Based on the above, CPNP adopts a Quotation Order/Offer/Answer model, which proceeds through the following basic steps (Figure 3):

  1. The CPNP client specifies its service requirements via a Provision Quotation Order (PQO). The order may include strictly or loosely defined values in the clauses describing service provisioning characteristics.
  2. The CPNP server declines the PQO, or makes an offer to address the requirements of the PQO, or suggests a counter-proposal that partially addresses the requirements of the PQO in case specific requirements cannot be accommodated.
  3. The CPNP client either accepts or declines the offer. Accepting the offer by the CPNP client implies a call for agreement; thus the agreement between both parties and the conclusion of the negotiation.
+------+                     +------+ 
|Client|                     |Server| 
+------+                     +------+ 
   |=====Requested Service=====>|  
   |<=====Offered Service=======|  
   |======Agreed Service=======>|

Figure 3: Simplified Service Negotiation

Multiple instances of CPNP may run at Customer's or Provider's domains. A CPNP client may be engaged in multiple, simultaneous negotiations with the same or different CPNP servers (parallel negotiations, see Section 8.10) and a CPNP server may need to negotiate with other Provider(s) as part of negotiations that are ongoing with a CPNP client (cascaded negotiations, see Section 8.8).

CPNP relies on various timers to run its operations. Two types of timers are defined: those that are specific to CPNP message transmission and those that are specific to the negotiation logic. The latter are used to guide the negotiation logic at both CPNP client and CPNP server sides, particularly in cases where the CPNP client is involved in parallel negotiations with several CPNP servers or in cases where the CPNP server is in turn involved in negotiations with other Providers for processing a given customer-originated quotation order. CPNP allows a CPNP server to request an extra time to proceed with the negotiation. This request may be accepted or rejected by the CPNP client.

Providers may need to publish available services to the Customers (see Section 4). CPNP may optionally support this functionality. Dedicated templates can be defined for the purpose of service announcement, which will be used by the CPNP clients to initiate their CPNP negotiation cycles.

For the sake of simplicity, a single Offer/Answer stage is assumed within one CPNP negotiation cycle. Nevertheless, as already stated, multiple CPNP negotiation cycles can be undertaken by a CPNP client (see Figure 4).

The model is flexible enough to accommodate changing conditions during the lifetime of a service (e.g., introduction of an additional VPN site).

+------+                  +------+ +------+                  +------+
|Client|                  |Server| |Client|                  |Server|
+------+                  +------+ +------+                  +------+
   |=====Quotation Order=====>|       |=====Quotation Order=====>|
   |<==========Offer==========|       |<==========Offer==========|
   |===========Accept========>|       |==========Decline========>|

  1-Step Successful Negotiation         1-Step Failed Negotiation
            Cycle                               Cycle

+------+                  +------+ +------+                  +------+
|Client|                  |Server| |Client|                  |Server|
+------+                  +------+ +------+                  +------+
   |===Quotation Order(a)====>|       |===Quotation Order(i)====>|
   |<==========Offer==========|       |<==========Offer==========|   
   |==========Decline========>|       |==========Decline========>|
   |===Quotation Order(b)====>|       |===Quotation Order(j)====>|
   |<==========Offer==========|       |<==========Offer==========|   
   |===========Accept========>|       |==========Decline========>|
                                      |===Quotation Order(k)====>|
                                      |<==========Offer==========| 
                                      |==========Decline========>|
                                      |===Quotation Order(l)====>|
                                      |<==Fail to make an offer==| 

    N-Step Negotiation Cycle:         N-Step Negotiation Cycle:
      Successful Negotiation              Failed Negotiation

Figure 4: Overall Negotiation Process

Means used by a CPNP client to retrieve a list of active/agreed offers are not defined in this document.

An order can be implicitly or explicitly activated. Section 3.1 of [RFC7297] specifies a dedicated clause called activation Means. Such clause indicates the required action(s) to be undertaken to activate access to the (IP connectivity) service. This document defines a dedicated CPNP message that can be used for explicit activation (Section 9.2.11)).

8. Protocol Overview

8.1. Client/Server Communication

CPNP is a client/server protocol that can run over any transport protocol. Yet, UDP is the default transport mode secured with Datagram Transport Layer Security (DTLS) [RFC6347]. No permanent CPNP transport session needs to be maintained between the client and the server.

The CPNP client can be configured with the CPNP server(s). Typically, an IP address together with a port number are configured to the CPNP client, based upon manual or dynamic configuration means (e.g., DHCP). Alternatively, a Provider may advertise the port number (CPNP_PORT) it uses to bind the CPNP service using SRV [RFC2782].

The client sends CPNP requests using CPNP_PORT as the destination port number. The same port number used as the source port number of a CPNP request sent to a CPNP server is used by the server to reply to that request.

CPNP is independent of the IP address family.

CPNP retransmission is discussed in Section 11.4 for unreliable transports.

Considerations related to mutual authentication are discussed in Section 13.

8.2. Policy Configuration on the CPNP Server

As an input to its decision-making process, the CPNP server may be connected to various external modules such as: Customer Profiles, Network Topology, Network Resource Management, Order Repositories, AAA and Network Provisioning Manager (an example is shown in Figure 5).

These external modules provide inputs to the CPNP server, so that it can:

The above list of CPNP server operations is not exhaustive.

       . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
       .Business & Administrative Management                   .      
       .+------------------------++---------------------------+.  
       .| Business Guidelines    ||    Billing & Charging     |.
       .+-----------+------------++-----------+---------------+.
       .            |                         |                .
       .            +-------------------+     |                .
       . . . . . . . . . . . . . . . . .|. . .|. . . . . . . . .
       . . . . . . . . . . . . . . . . .|. . .|. . . . . . . . .
       .Order Handling Management       |     |                .
       . +-------------------+  +-------+-----+--------------+ .
       . |Network Topology DB+--+        CPNP Server         | .
       . +-------------------+  +-+---+---+---+---+-----+----+ . 
       .                          |   |   |   |   |     |      .
       . +------------------------+-+ |   |   |   |     |      .
       . |   Network Dimensioning   | |   |   |   |     |      .
       . |        & Planning        | |   |   |   |     |      .
       . +--------------------------+ |   |   |   |     |      .
       . +----------------------------+-+ |   |   | +---+----+ .
       . |                              | |   |   | |   AAA  | .
       . |   Network       +------------+ |   |   | +--------+ .
       . |  Resource       | +------------+-+ | +-+----------+ .
       . |  Management     | |   Customer   | | |   Orders   | .
       . |                 | |   Profiles   | | | Repository | .
       . +-----------------+ +--------------+ | +------------+ .
       . . . . . . . . . . . . . . . . . . . .|. . . . . . . . .
       +--------------------------------------+----------------+
       |             Network Provisioning Manager              |   
       +-------------------------------------------------------+

Figure 5: Order Handling Management Functional Block (Focus on Internal Interfaces)

The following order handling modes can also be configured on the server:

  1. Fully automated mode: This mode does not require any action from the administrator when receiving a request for a service. The server can execute its decision-making process related to the orders received and generate corresponding offers.
  2. Administrative validation checking: Some or all of the server's operations are subject to administrative validation procedures. This mode requires an action from the administrator for every request received. To that aim, the CPNP methods which can be automatically handled by the server (or are subject to one or several validation administrative checks) can be configured on the server.

8.3. CPNP Session Entries

A CPNP session entry is denoted by a tuplet defined as follows:

8.4. CPNP Transaction

A CPNP transaction occurs between a client and a server for completing, modifying, withdrawing a service agreement, and comprises all CPNP messages exchanged between the client and the server, from the first request sent by the client to the final response sent by the server. A CPNP transaction is bound to a CPNP session (Section 8.3).

Because multiple CPNP transactions can be maintained by the CPNP client, the client must assign an identifier to uniquely identify a given transaction. This identifier is denoted as Transaction-ID.

The Transaction-ID must be randomly assigned by the CPNP client, according to the best current practice for generating random numbers [RFC4086] that cannot be guessed easily. Transaction-ID is used for validating CPNP responses received by the client.

In the context of a transaction, the client needs to randomly select a sequence number and assign it to the first CPNP message to send. This number is then incremented for each request message that is subsequently sent within the ongoing CPNP transaction (see Section 11.3).

8.5. CPNP Timers

CPNP adopts a simple retransmission procedure which relies on a retransmission timer denoted as RETRANS_TIMER and a maximum retry threshold. The use of RETRANS_TIMER and a maximum retry threshold are described in Section 11.

The response timer (EXPECTED_RESPONSE_TIME) is set by the client to denote the time, in seconds, the client will wait for receiving a response from the server to a provisioning quotation order request (see Section 9.1.6). If the timer expires, the respective quotation order is cancelled by the client and a CANCEL message is generated accordingly.

The expected offer timer (EXPECTED_OFFER_TIME) is set by the server to indicate the time by when the CPNP server is expecting to make an offer to the CPNP client (see Section 9.1.7). If no offer is received by then, the CPNP client will consider the order as rejected.

An offer expiration timer (VALIDITY_OFFER_TIME) is set by the server to represent the time, in minutes, after which an offer made by the server becomes invalid (see Section 9.1.8).

8.6. CPNP Operations

CPNP operations are listed below. They may be augmented, depending on the nature of some transactions or because of security considerations that may necessitate a distinct CPNP client/server authentication phase before negotiation begins.

The above CPNP primitives are service-independent. CPNP messages may transparently carry service-specific objects which are handled by the negotiation logic at either side.

The document specifies the service objects that are required for connectivity provisioning negotiation (see Section 8.7) purposes. Additional service-specific objects to be carried in CPNP messages can be defined in the future for accommodating alternative deployment schemes or other service provisioning needs.

8.7. Connectivity Provisioning Documents

CPNP makes use of several flavors of Connectivity Provisioning Documents (CPD). These documents follow the same CPP template described in [RFC7297].

Requested Connectivity Provisioning Document (Requested CPD):
Refers to the CPD included by a CPNP client in a QUOTATION request.
Offered Connectivity Provisioning Document (Offered CPD):
This document is included by a CPNP server in an OFFER message. Its information reflects the proposal of the server to accommodate all or a subset of the clauses depicted in a Requested CPD. A validity time is associated with the offer made.
Agreed Connectivity Provisioning Document (Agreed CPD):
If the client accepts an offer made by the server, the Offered CPD is included in an ACCEPT message. This CPD is also included in an ACK message. Thus, a 3-way handshake procedure is followed for successfully completing the negotiation.

Figure 6 shows a typical CPNP negotiation cycle and the use of the different types of Connectivity Provisioning Documents.

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |======QUOTATION (Requested CPD)=====>|
   |<============PROCESSING==============|
   |<========OFFER (Offered CPD)=========|
   |=============PROCESSING=============>|
   |=========ACCEPT (Agreed CPD)========>|
   |<=========ACK (Agreed CPD)===========|
   |                                     |

Figure 6: Connectivity Provisioning Documents

A provisioning document can include parameters with fixed values, loosely-defined values, or any combination thereof. A provisioning document is said to be concrete if all clauses have fixed values.

A typical evolution of a negotiation cycle would start with a quotation order with loosely-defined parameters, and then, as offers are made, it would conclude with concrete provisioning document for calling for the agreement.

8.8. Child Provisioning Quotation Orders

If the server detects that network resources from another Network Provider need to be allocated in order to accommodate the requirements described in a PQO (e.g., in the context of an inter-domain VPN service, additional PE router resources need to be allocated), the server may generate child PQOs to request the appropriate network provisioning operations (see Figure 7). In such situation, the server behaves also as a CPNP client. The server associates the parent order with its child PQOs. How this is achieved is implementation-specific (e.g., this can be typically achieved by locally adding the reference of the child PQO to the parent order).

+------+            +--------+          +--------+
|Client|            |Server A|          |Server B|
+------+            +--------+          +--------+
   |                    |                    |
   |=====QUOTATION=====>|                    |
   |<====PROCESSING=====|                    |
   |                    |=====QUOTATION=====>|
   |                    |<====PROCESSING=====|
   |                    |<=======OFFER=======|
   |                    |=====PROCESSING====>|
   |                    |=======ACCEPT======>|
   |                    |<=======ACK=========|
   |<=======OFFER=======|                    |
   |=====PROCESSING====>|                    |
   |=======ACCEPT======>|                    |
   |<=======ACK=========|                    |
   |                    |                    |

Figure 7: Example of Child Orders

8.9. Multi-Segment Service

A composite service (e.g., connectivity) requested by a customer could imply multi-segment services (e.g., multi-segment connectivity spanning an end-to-end scope), in the sense that one single CPNP request is decomposed into N connectivity requests at the provider's side (thereby leading to child orders). The Provider is in charge of handling the complexity of splitting the generic provisioning order in a multi-segment context. Such complexity is local to the Provider.

8.10. Negotiating with Multiple CPNP Servers

A CPNP client may undertake multiple negotiations in parallel with several servers for various reasons, such as cost optimization and fail-safety. These multiple negotiations may lead to one or many agreements.

The salient point underlining the parallel negotiation scenarios is that, although the negotiation protocol is strictly between two parties, this may not be the case of the negotiation logic. The CPNP client negotiation logic may need to collectively drive parallel negotiations, as the negotiation with one server may affect the negotiation with other servers; for example, it may need to use the responses from all servers as an input for determining the messages (and their content) to subsequently send within the course of each individual negotiation. Timing is therefore an important aspect at the client's side. The CPNP client needs to have the ability to synchronize the receipt of the responses from the servers. CPNP takes into account this requirement by allowing clients to specify in the QUOTATION message the time by which the server needs to respond (see Section 9.1.6).

8.11. State Management

Both the client and the server maintain repositories to store ongoing orders. How these repositories are maintained is deployment-specific. It is out of scope of this document to elaborate on such considerations. Timestamps are also logged to track state change. Tracking may be needed for various reasons, including regulatory or billing ones.

In order to accommodate failures that may lead to the reboot of the client or the server, the use of permanent storage is recommended, thereby facilitating state recovery.

8.11.1. On the Client Side

This is the list of the typical states that can be associated with a given order on the client's side:

Sub-states may be defined (e.g., to track failed vs. cancelled orders) but those are not shown in Figure 8.

+------------------+
|     Created      |-----------------+
+------------------+                 |
        |                            |
        v                            |
+------------------+                 |
|AwaitingProcessing|----------------+|
+------------------+                || 
        |                           ||
   QUOTATION/UPDATE                 ||
        v                           ||
+------------------+                ||
|     PQOSent      |---CANCEL------+||
+------------------+               vvv
        |                        +-----+
    PROCESSING                   |     |
        v                        |     |
+------------------+   CANCEL    |  C  |
| ServerProcessing |------------>|  A  |
+------------------+    FAIL     |  N  |
        |                        |  C  |
        |                        |  E  | 
      OFFER                      |  L  |
        |                        |  L  |
        v                        |  E  |
+------------------+             |  D  |
|  OfferReceived   |---CANCEL--->|     |
+------------------+             |     |
        | PROCESSING             +-----+
        v                          ^^^
+------------------+               |||
|  OfferProcessing |---DECLINE-----+||
+------------------+                ||
        | ACCEPT                    ||
        v                           ||
+------------------+                ||
|    AcceptSent    |---CANCEL-------+|
+------------------+                 |
        | ACK                        |
        v                            |
+------------------+                 |
|   Completed      |---WITHDRAW------+
+------------------+

Figure 8: Example of a CPNP Finite State Machine (Client Side)

8.11.2. On the Server Side

The following lists the states which can be associated with a given order and a corresponding offer on the server's side:

+------------------+           +------------------+    
|AwaitingProcessing|<----------|    ChildCreated  |                        
+------------------+           +------------------+                   
        |                            |      ^ 
        v                            |      |                                                
+------------------+                 |      |           
|   ChildPQOSent   |----------------+|      Q     
+------------------+                ||      U              
        |                           ||      O                 
     QUOTATION/UPDATE               ||      T                  
        v                           ||      A  +--------------------+ 
+---------------------+   CANCEL    ||      T  |     PQOReceived    |      
|ChildServerProcessing|------------+||      I  +--------------------+ 
+---------------------+    FAIL    vvv      O       |      |  
        |                        +-----+    N    CANCEL    |
    PROCESSING                   |     |<---|-------+  PROCESSING
        v                        |     |    |              v
+------------------+             |     |   +------------------------+            
|ChildOfferReceived|----CANCEL---|  C  |<--|   AwaitingProcessing   |  
+------------------+             |  A  |   +------------------------+ 
        |                        |  N  |       ^          | OFFER
      OFFER                      |  C  |       | +------------------+ 
        |                        |  E  |<DECLINE-|   OfferProposed  |
        |                        |  L  |       | +------------------+     
        v                        |  L  |       |          |
+------------------+             |  E  |       |      PROCESSING
|ChildOfferReceived|---CANCEL----|  D  |       |          v
+------------------+             |     |       | +------------------+      
        |                        |     |<DECLINE-| Proc'ingReceived |     
   PROCESSING                    |     |       |+------------------+       
        |                        +-----+       |          | ACCEPT
        v                         ^^^^^        |          v  
+------------------+              |||||        | +------------------+
|ChildOfferProc'ing|---DECLINE----+|||+-CANCEL-|-|  AcceptReceived  |       
+------------------+               |||         | +------------------+ 
        |ACCEPT                    |||         |          |ACK
        v                          |||         |          v   
+------------------+               |||         | +------------------+
|  ChildAcceptSent |---CANCEL------+|+-WITHDRAW|-|    Completed     |       
+------------------+                |          | +------------------+                  
        | ACK                       |          |
        v                           |          |
+------------------+                |          |
|  ChildCompleted  |---WITHDRAW-----+          |
|                  +---------------------------+
+------------------+

Figure 9: CPNP Finite State Machine (Server Side)

9. CPNP Objects

This section defines CPNP objects using the RBNF format defined at [RFC5511].

9.1. Attributes

9.1.1. CUSTOMER_AGREEMENT_IDENTIFIER

CUSTOMER_AGREEMENT_IDENTIFIER is an identifier which is assigned by a client to identify an agreement. This identifier must be unique to the client.

Rules for assigning this identifier are specific to the client (Customer). The value of CUSTOMER_AGREEMENT_IDENTIFIER is included in all CPNP messages.

The client (Customer) assigns an identifier to an order under negotiation before an agreement is reached. This identifier will be used to unambiguously identify the resulting agreement at the client side (Customer).

The server handles CUSTOMER_AGREEMENT_IDENTIFIER as an opaque value.

9.1.2. PROVIDER_AGREEMENT_IDENTIFIER

PROVIDER_AGREEMENT_IDENTIFIER is an identifier which is assigned by a server to identify an order. This identifier must be unique to the server.

Rules for assigning this identifier are specific to the server (Provider). PROVIDER_AGREEMENT_IDENTIFIER is included in all CPNP messages, except QUOTATION messages (because the state is only present at the client side).

The server (Provider) assigns an identifier to an order under negotiation before an agreement is reached. This identifier will be used to unambiguously identify the resulting agreement at the server side (Provider).

The client handles PROVIDER_AGREEMENT_IDENTIFIER as an opaque value.

9.1.3. TRANSACTION_ID

This object conveys the Transaction-ID introduced in Section 8.4.

9.1.4. SEQUENCE_NUMBER

Sequence Number is a number that is monotonically incremented in every new CPNP message pertaining to a given CPNP transaction. This number is used to avoid reply attacks.

Refer to Section 11.3.

9.1.5. NONCE

NONCE is a random value assigned by the CPNP server. It is RECOMMENDED to assign unique NONCE values for each order.

NONCE is then mandatory to be included in subsequent CPNP client operations on the associated order (including the resulting agreement) such as: withdraw the order or update the order.

If the NONCE validation checks fail, the server rejects the request with a FAIL message including the appropriate failure reason code.

9.1.6. EXPECTED_RESPONSE_TIME

This attribute indicates the time by when the CPNP client is expecting to receive a response from the CPNP server to a given PQO. If no offer is received by then, the CPNP client will consider the quotation order as rejected.

EXPECTED_RESPONSE_TIME follows the date format specified in [RFC3339].

9.1.7. EXPECTED_OFFER_TIME

This attribute indicates the time by when the CPNP server is expecting to make an offer to the CPNP client. If no offer is received by then, the CPNP client will consider the order as rejected.

The CPNP server may propose an expected offer time that does not match the expected response time indicated in the quotation order message. The CPNP client can accept or reject the proposed expected time by when the CPNP server will make an offer.

The CPNP server can always request extra time for its processing, but this may be accepted or rejected by the CPNP client.

EXPECTED_OFFER_TIME follows the date format specified in [RFC3339].

9.1.8. VALIDITY_OFFER_TIME

This attribute indicates the time of validity of an offer made by the CPNP server. If the offer is not accepted before this date expires, the CPNP server will consider the CPNP client has rejected the offer; the CPNP server will silently remove this order from its base.

VALIDITY_OFFER_TIME follows date format specified in [RFC3339].

9.1.9. SERVICE_DESCRIPTION

This document specifies a machinery to negotiate any aspect subject to negotiation. Service clauses that are under negotiation are conveyed using this attribute.

The structure of the connectivity provisioning clauses is provided in the following sub-section.

9.1.9.1. CONNECTIVITY_PROVISIONING_DOCUMENT

The RBNF format of the Connectivity Provisioning Document (CPD) is shown in Figure 10:

<CONNECTIVITY_PROVISIONING_DOCUMENT> ::= 
                           <Connectivity Provisioning Component> ...
<Connectivity Provisioning Component> ::= 
                           <CONNECTIVITY_PROVISIONING_PROFILE> ...
<CONNECTIVITY_PROVISIONING_PROFILE> ::= 
                           <Customer Nodes Map>
                           <SCOPE>
                           <QoS Guarantees>
                           <Availability>
                           <CAPACITY>
                           <Traffic Isolation>
                           <Conformance Traffic>
                           <Flow Identification>
                           <Overall Traffic Guarantees>
                           <Routing and Forwarding>
                           <Activation Means>
                           <Invocation Means>
                           <Notifications>
<Customer Nodes Map> ::=  <Customer Node> ...
<Customer Node> ::=  <IDENTIFIER>
                     <LINK_IDENTIFIER>
                     <LOCALISATION>

Figure 10: The RBNF format of the Connectivity Provisioning Document (CPD)

9.1.10. CPNP Information Elements

An Information Element (IE) is an optional object which can be included in a CPNP message.

9.1.10.1. Customer Description

The client may include administrative information such as:

The format of this Information Element is as follows:

<Customer Description> ::= [<NAME>] [<Contact Information>]
<Contact Information> ::=  [<EMAIL_ADDRESS>] [<POSTAL_ADDRESS>]
                           [<TELEPHONE_NUMBER> ...]

9.1.10.2. Provider Description

The server may include administrative information in an offer such as:

The format of this Information Element is as follows:

<Provider Description> ::= [<NAME>][<Contact Information>][<AS_NUMBER>]

9.1.10.3. Negotiation Options

The client may include some negotiation options such as:

The format of this Information Element is as follows:

<Negotiation Options> ::= [<PURPOSE>]

9.2. Operation Messages

This section specifies the RBNF format of CPNP operation messages. The following operation codes are used:

1:
QUOTATION (Section 9.2.1)
2:
PROCESSING (Section 9.2.2)
3:
OFFER (Section 9.2.3)
4:
ACCEPT (Section 9.2.4)
5:
DECLINE (Section 9.2.5)
6:
ACK (Section 9.2.6)
7:
CANCEL (Section 9.2.7)
8:
WITHDRAW (Section 9.2.8)
9:
UPDATE (Section 9.2.9)
10:
FAIL (Section 9.2.10)
11:
ACTIVATE (Section 9.2.11)

These codes are used to unambiguously identify a CPNP operation; the operation code is conveyed in the "METHOD_CODE" attribute mentioned in the following sub-sections.

In the following, "VERSION" refers to the CPNP version number. This attribute MUST be set to 1.

9.2.1. QUOTATION

The format of the QUOTATION message is shown below:

<QUOTATION Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
[<EXPECTED_RESPONSE_TIME>]
<REQUESTED_CONNECTIVITY_PROVISIONING_DOCUMENT>
[<INFORMATION_ELEMENT>...]

The message MAY include an EXPECTED_RESPONSE_TIME which indicates by when the client is expecting to receive an offer from the server. QUOTATION message MUST also include a requested service description (that is, requested connectivity provisioning document for connectivity services).

The message MAY include ACTIVATION_TYPE to request a permanent or scheduled activation type (e.g., using the ACTIVATE method defined in Section 9.2.11). If no such clause is included, the default mode is to assume that the order will be active once the agreed activation means are successfully invoked (e.g., Section 3.11 of [RFC7297]).

When the client sends the QUOTATION message to the server, the state of the order changes to "PQOSent" at the client side.

9.2.2. PROCESSING

The format of the PROCESSING message is shown below:

<PROCESSING Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
[<EXPECTED_OFFER_TIME>]

Section 10). If no error is encountered, the server generates a PROCESSING response to the client to indicate the PQO has been received and it is being processed. The server MUST generate an order identifier which identifies the order in its local order repository. The server MUST copy the content of CUSTOMER_AGREEMENT_IDENTIFIER and TRANSACTION_ID fields as conveyed in the QUOTATION message. The server MAY include an EXPECTED_OFFER_TIME by when it expects to make an offer to the client.

Upon receipt of a PROCESSING message, the client verifies whether it has issued a PQO to that server and which contains the CUSTOMER_AGREEMENT_IDENTIFIER and TRANSACTION_ID. If no such PQO is found, the PROCESSING message MUST be silently ignored. If a PQO is found, the client may check whether it accepts the EXPECTED_OFFER_TIME and then, it changes to state of the order to "ServerProcessing".

If more time is required by the server to process the quotation order, it MAY send a PROCESSING message that includes a new EXPECTED_OFFER_TIME. The client can answer with an ACK message if more time is granted (Figure 11) or with a FAIL message if the time extension request is rejected (Figure 12).

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |=======QUOTATION(Requested CPD)=====>|
   |<========PROCESSING(time1)===========|
                     ...
   |<========PROCESSING(MoreTime)========|
   |============ACK(TimeGranted)========>|
                     ...
   |<=========OFFER(Offered CPD)=========|
   |=============PROCESSING=============>|
   |==========ACCEPT(Agreed CPD)========>|
   |<==========ACK(Agreed CPD)===========|
   |                                     |

Figure 11: Request More Negotiation Time: Granted

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |=======QUOTATION(Requested CPD)=====>|
   |<========PROCESSING(time1)===========|
                     ...
   |<========PROCESSING(MoreTime)========|
   |=====FAIL(More Time Rejected)=======>|

Figure 12: Request More Negotiation Time: Rejected

9.2.3. OFFER

The format of the OFFER message is shown below:

<OFFER Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<NONCE>
<VALIDITY_OFFER_TIME>
<OFFERED_CONNECTIVITY_PROVISIONING_DOCUMENT>
[<INFORMATION_ELEMENT>...]

The server MAY include ACTIVATION_TYPE to indicate whether the offer is about a permanent or scheduled activation type. The message MAY include ACTIVATION_SCHEDULE to indicate when the order is to be activated. If no such clause is included, the default mode is to assume that the order will be active once the agreed activation means are successfully invoked (e.g., Section 3.11 of [RFC7297] or Section 9.2.11).

9.2.4. ACCEPT

The format of the ACCEPT message is shown below:

<ACCEPT Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<NONCE>
<AGREED_CONNECTIVITY_PROVISIONING_DOCUMENT>
[<INFORMATION_ELEMENT>...]

Section 9.2.3).

9.2.5. DECLINE

The format of the DECLINE message is shown below:

<DECLINE Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<NONCE>
[<REASON>...]

A DECLINE message MAY include an information to indicate the reason for declining an offer. The following codes are defined:

If no order is found, the server returns a FAIL message to the requesting client. In order to prevent DDoS (Distributed Denial of Service) attacks, the server SHOULD restrict the number of FAIL messages sent to a requesting client. It MAY also rate-limit FAIL messages.

A flow example is shown in Figure 13.

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |=======QUOTATION(Requested CPD)=====>|
   |<============PROCESSING==============|
   |<=========OFFER(Offered CPD)=========|
   |=============PROCESSING=============>|
   |===============DECLINE==============>|
   |<================ACK=================|
   |                                     |

Figure 13: DECLINE Flow Example

9.2.6. ACK

The format of the ACK message is shown below:

<ACK Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
[<EXPECTED_RESPONSE_TIME>]
[<CONNECTIVITY_PROVISIONING_DOCUMENT>]
[<INFORMATION_ELEMENT>...]

This message is sent by the server as a response to an ACCEPT, WITHDRAW, DECLINE, or CANCEL message. In this case, the ACK message MUST include the copy of the service description document as stored by the server. In particular, the following considerations are taken into account for connectivity provisioning services:

A client may issue an ACK message as a response to a time extension request (conveyed in PROCESSING) received from the server. In such case, the ACK message MUST include an EXPECTED_RESPONSE_TIME that is likely to be set to the time extension requested by the server.

9.2.7. CANCEL

The format of the CANCEL message is shown below:

<CANCEL Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
[<CONNECTIVITY_PROVISIONING_DOCUMENT>]

If no quotation order is found, the server returns a FAIL message to the requesting client.

9.2.8. WITHDRAW

The format of the WITHDRAW message is shown below:

<WITHDRAW Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<NONCE>
[<AGREED_CONNECTIVITY_PROVISIONING_DOCUMENT>]
[<INFORMATION_ELEMENT>...]

Figure 14 shows a typical usage of this message.

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |============WITHDRAW(CPD)===========>|
   |<============PROCESSING==============|
   |<===========ACK(Empty CPD)===========|
   |                                     |

Figure 14: WITHDRAW Flow Example

The CPNP MUST include the same CUSTOMER_AGREEMENT_IDENTIFIER, PROVIDER_AGREEMENT_IDENTIFIER, and NONCE as those used when creating the order.

Upon receipt of a WITHDRAW message, the server checks whether an order matching the request is found. If an order is found, the state of the order is changed to "Cancelled" and an ACK message including an Empty CPD is returned to the requesting client. If no order is found, the server returns a FAIL message to the requesting client.

9.2.9. UPDATE

The format of the UPDATE message is shown below:

<UPDATE Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<NONCE>
<EXPECTED_RESPONSE_TIME>
<REQUESTED_CONNECTIVITY_PROVISIONING_DOCUMENT>
[<INFORMATION_ELEMENT>...]

Upon receipt of an UPDATE message, the server checks whether an order, having state "Completed", matches CUSTOMER_AGREEMENT_IDENTIFIER, PROVIDER_AGREEMENT_IDENTIFIER, and NONCE. 

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |=========UPDATE(Requested CPD)======>|
   |<============PROCESSING==============|
   |<=========OFFER(Updated CPD)=========|
   |=============PROCESSING=============>|
   |==========ACCEPT(Updated CPD)=======>|
   |<==========ACK(Updated CPD)==========|
   |                                     |

Figure 15: UPDATE Flow Example

A flow chart that illustrates the use of UPDATE operation is shown in Figure 15.

9.2.10. FAIL

The format of the FAIL message is shown below:

<FAIL Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<STATUS_CODE>

The status code indicates the error code. The following codes are supported:

1 (Message Validation Error):

The message cannot be validated (see Section 10).
2 (Authentication Required):

The request cannot be handled because authentication is required.
3 (Authorization Failed):

The request cannot be handled because authorization failed.
4 (Administratively prohibited):

The request cannot be handled because of administrative policies.
5 (Out of Resources):

The request cannot be honored because resources (e.g., capacity) are insufficient.
6 (Network Presence Error):

The request cannot be honored because there is no network presence.
7 (More Time Rejected):

The request to extend the time for negotiation is rejected by the client.
8 (Unsupported Activation Type):

The request cannot be handled because the requested activation type is not supported.

9.2.11. ACTIVATE

The format of the ACTIVATE message is shown below:

<ACTIVATE Message> ::=
<VERSION>
<METHOD_CODE>
<SEQUENCE_NUMBER>
<TRANSACTION_ID>
<CUSTOMER_AGREEMENT_IDENTIFIER>
<PROVIDER_AGREEMENT_IDENTIFIER>
<NONCE>
<ACTIVATION_SCHEDULE>
[<INFORMATION_ELEMENT>...]

Upon receipt of an UPDATE message, the server checks whether an order, having state "Completed", matches CUSTOMER_AGREEMENT_IDENTIFIER, PROVIDER_AGREEMENT_IDENTIFIER, and NONCE. 

+------+                              +------+
|Client|                              |Server|
+------+                              +------+
   |================ACTIVATE()==========>|
   |<==============ACK()=================|
   |                                     |

Figure 16: ACTIVATE Flow Example

Figure 16 illustrates the use of ACTIVATE operation.

10. CPNP Message Validation

Both client and server proceed with CPNP message validation. The following tables summarize the validation checks to be followed.

10.1. On the Client Side

Operation Validation Checks
PROCESSING {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier} must match an existing PQO with a state set to "PQOSent". The sequence number carried in the packet must be larger than the sequence number maintained by the client.
OFFER {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier} must match an existing order with state set to "PQOSent" or {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier} must match an existing order with a state set to "ServerProcessing". The sequence number carried in the packet must be larger than the sequence number maintained by the client.
ACK (QUOTATION Transaction) {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier, Offered Connectivity Provisioning Order} must match an order with a state set to "AcceptSent". The sequence number carried in the packet must be larger than the sequence number maintained by the client.
ACK (UPDATE Transaction) {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier, Updated Connectivity Provisioning Order} must match an order with a state set to "AcceptSent". The sequence number carried in the packet must be larger than the sequence number maintained by the client.
ACK (WITHDRAW Transaction) {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier, Empty Connectivity Provisioning Order} must match an order with a state set to "Cancelled". The sequence number carried in the packet must be larger than the sequence number maintained by the client.

10.2. On the Server Side

Method Validation Checks
QUOTATION The source IP address passes existing access filters (if any). The sequence number carried in the packet must not be lower than the sequence number maintained by the server.
PROCESSING The sequence number carried in the packet must be greater than the sequence number maintained by the server.
CANCEL {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier} must match an order with state set to "PQOReceived" or "OfferProposed" or "ProcessingReceived" or "AcceptReceived ". The sequence number carried in the packet must be greater than the sequence number maintained by the server.
ACCEPT {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier, Nonce, Offered Connectivity Provisioning Order} must match an order with state set to "OfferProposed" or "ProcessingReceived". The sequence number carried in the packet must be greater than the sequence number maintained by the server.
FAIL {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier} must match an order with state set to "AwaitingProcessing" and for which a request to grant more time to process an offer was requested. The sequence number carried in the packet must be greater than the sequence number maintained by the server.
DECLINE {Source IP address, source port number, destination IP address, destination port number, Transaction-ID, Customer Order Identifier, Provider Order Identifier, Nonce} must match an order with state set to "OfferProposed" or "ProcessingReceived". The sequence number carried in the packet must be greater than the sequence number maintained by the server.
UPDATE The source IP address passes existing access filters (if any) and {Customer Order Identifier, Provider Order Identifier, Nonce} must match an existing order with state "Completed".
WITHDRAW The source IP address passes existing access filters (if any) and {Customer Order Identifier, Provider Order Identifier, Nonce} must match an existing order with state "Completed".
ACTIVATE The source IP address passes existing access filters (if any) and {Customer Order Identifier, Provider Order Identifier, Nonce} must match an existing order with state "Completed" for which the activation procedure is tagged to be explicit.

11. Theory of Operation

Both CPNP client and server proceed with message validation checks as specified in Section 10.

11.1. Client Behavior

11.1.1. Order Negotiation Cycle

To place a provisioning quotation order, the client first initiates a local quotation order object identified by a unique identifier assigned by the client (Client Order Identifier). The state of the quotation order is set to "Created". The client then generates a QUOTATION request which includes the assigned identifier, possibly an expected response time, a Transaction-ID, and a Requested Service (e.g., Requested Connectivity Provisioning Document). The client may include additional Information Elements such as Negotiation Options or Activation Type.

The client may be configured to not enforce negotiation checks on EXPECTED_OFFER_TIME; if so, no EXPECTED_RESPONSE_TIME attribute (or EXPECTED_RESPONSE_TIME set to infinite) should be included in the quotation order.

Once the request is sent to the server, the state of the request is set to "PQOSent" and a timer, if a response time is included in the quotation order, is set to the expiration time as included in the QUOTATION request. The client also maintains a copy of the CPNP session entry details used to generate the QUOTATION request. The CPNP client must listen on the same port number that it used to send the QUOTATION request.

If no answer is received from the server before the retransmission timer expires (i.e., RETRANS_TIMER, Section 8.5), the client retransmits the message until maximum retry is reached (e.g., 3 times). The same sequence number is used for retransmitted packets.

If a FAIL message is received, the client may decide to issue another (corrected) request towards the same server, cancel the local order, or contact another server. The behavior of the client depends on the error code returned by the server in the FAIL message.

If a PROCESSING message matching the CPNP session entry (Section 8.3) is received, the client updates the CPNP session entry with the PROVIDER_AGREEMENT_IDENTIFIER information. If the client does not accept the expected offer time that may have been indicated in the PROCESSING message, the client may decide to cancel the quotation order. If the client accepts the EXPECTED_OFFER_TIME, it changes the state of the order to "ServerProcessing" and sets a timer to the value of EXPECTED_OFFER_TIME. If no offer is made before the timer expires, the client changes the state of the order to "Cancelled".

As a response to a time extension request (conveyed in a PROCESSING message that included a new EXPECTED_OFFER_TIME), the client may grant this extension by issuing an ACK message or reject the time extension with a FAIL message having a status code set to "More Time Rejected".

If an OFFER message matching the CPNP session entry is received, the client checks if a PROCESSING message having the same PROVIDER_AGREEMENT_IDENTIFIER has been received from the server. If a PROCESSING message was already received for the same order but the PROVIDER_AGREEMENT_IDENTIFIER does not match the identifier included in the OFFER message, the client silently ignores the message. If a PROCESSING message having the same PROVIDER_AGREEMENT_IDENTIFIER was already received and matches the CPNP transaction identifier, the client changes the state of the order to "OfferReceived" and sets a timer to the value of VALIDITY_OFFER_TIME indicated in the OFFER message.

If an offer is received from the server (i.e., as documented in an OFFER message), the client may accept or reject the offer. The client accepts the offer by generating an ACCEPT message which confirms that the client agrees to subscribe to the offer documented in the OFFER message; the state of the order is passed to "AcceptSent". The transaction is terminated if an ACK message is received from the server. If no ACK is received from the server, the client proceeds with the retransmission of the ACCEPT message until the maximum retry is reached (Section 11.4).

The client may also decide to reject the offer by sending a DECLINE message. The state of the order is set by the client to "Cancelled". If an offer is not acceptable by the client, the client may decide to contact a new server or submit another order to the same server. Guidelines to issue an updated order or terminate the negotiation are specific to the client.

An order can be activated (or de-activated) using the ACTIVATE message or other agreed activation means (Section 3.11 of [RFC7297]).

11.1.2. Order Withdrawal Cycle

A client may withdraw a completed order. This is achieved by issuing a WITHDRAW message. This message MUST include Customer Order Identifier, Provider Identifier, and Nonce returned during the order negotiation cycle, as specified in Section 11.1.1.

If no ACK is received from the server, the client proceeds with the retransmission of the message. If no ACK is received after the maximum retry is exhausted, the client should log the information and must send an alarm to the administrator. If there is no specific instruction from the administrator, the client SHOULD schedule another Withdrawal cycle. The client MUST NOT retry this Withdrawal cycle more frequently than every 300 seconds and MUST NOT retry more frequently than every 60 seconds.

11.1.3. Order Update Cycle

A client may update a completed order. This is achieved by issuing an UPDATE message. This message MUST include Customer Order Identifier, Provider Order Identifier and Nonce returned during the order negotiation cycle specified in Section 11.1.1. The client MUST include in the UPDATE message an updated CPD with the requested changes.

Subsequent messages exchange is similar to what is documented in Section 11.1.1.

11.2. Server Behavior

11.2.1. Order Processing

Upon receipt of a QUOTATION message from a client, the server sets a CPNP session, stores Transaction-ID and generates a Provider Order Identifier. Once preliminary validation checks are completed ( Section 10), the server may return a PROCESSING message to inform the client that the quotation order is received and it is under processing; the server may include an expected offer time to notify the client by when an offer will be proposed. An order with state "AwaitingProcessing" is created by the server. The server runs its decision-making process to decide which offer it can make to honor the received order. The offer should be made before the expected offer time expires.

If the server cannot make an offer, it sends backs a FAIL message with the appropriate error code.

If the server requires more negotiation time, it must send a PROCESSING message with a new EXPECTED_OFFER_TIME. The client may grant this extension by issuing an ACK message or reject the time extension with a FAIL message having a status code set to "More Time Rejected". If the client doesn't grant more time, the server must answer before the initial expected offer time; otherwise the client will decline the quotation order.

If the server can honor the request or it can make an offer that meets only some of the requirements, it creates an OFFER message. The server must indicate the Transaction-ID, Customer Order Identifier as indicated in the QUOTATION message, and the Provider Order Identifier generated for this order. The server must also include Nonce and the offered service document (e.g., offered Connectivity Provisioning Document). The server includes an offer validity time as well. Once sent to the client, the server changes the state of the order to "OfferProposed" and a timer set to the validity time is initiated.

If the server determines that additional network resources from another network provider are needed to accommodate a quotation order, it will create child PQO(s) and will behave as a CPNP client to negotiate child PQO(s) with possible partnering providers (see Figure 7).

If no PROCESSING, ACCEPT, or DECLINE message is received before the expiry of the RETRANS_TIMER, the server re-sends the same offer to the client. This procedure is repeated until maximum retry is reached.

If an ACCEPT message is received before the offered validity time expires, the server proceeds with validation checks as specified in Section 10. The state of the corresponding order is passed to "AcceptReceived". The server sends back an ACK message to terminate the order processing cycle.

If a CANCEL/DECLINE message is received, the server proceeds with the cancellation of the order. The state of the order is then passed to "Cancelled".

11.2.2. Order Withdrawal

A client may withdraw a completed order by issuing a WITHDRAW message. Upon receipt of a WITHDRAW message, the server proceeds with the validation checks, as specified in Section 10:

11.2.3. Order Update

A client may update an order by issuing an UPDATE message. Upon receipt of an UPDATE message, the server proceeds with the validation checks as specified in Section 10:

11.3. Sequence Numbers

In each transaction, sequence numbers are used to protect the transaction against replay attacks. Each communicating partner of the transaction maintains two sequence numbers, one for incoming packets and one for outgoing packets. When a partner receives a message, it will check whether the sequence number in the message is larger than the incoming sequence number maintained locally. If not, the message will be discarded. If the message is proved to be legitimate, the value of the incoming sequence number maintained locally will be replaced by the value of the sequence number in the message. When a partner sends out a message, it will insert the value of the outgoing sequence number into the message and increase the outgoing sequence number maintained locally by 1.

11.4. Message Re-Transmission

If a transaction partner sends out a message and does not receive any expected reply before the retransmission timer expires (i.e., RETRANS_TIMER), a transaction partner will try to re-transmit the message. The procedure is reiterated until a maximum retry is reached (e.g., 3 times). An exception is the last message (e.g., ACK) sent from the server in a transaction. After sending this message, the retransmission timer will be disabled since no additional feedback is expected.

In addition, if the partner receives a retransmission of a last incoming packet it handled, the partner can re-send the same answer to the incoming packet with a limited frequency. If no answer was generated at the moment, the partner needs to generate a PROCESSING message as the answer.

To optimize message retransmission, a partner could also store the last incoming packet and the associated answer. Note that the times of retransmission could be decided by the local policy and retransmission will not cause any change of sequence numbers.

12. Some Operational Guidelines

12.1. Logging on the CPNP Server

The CPNP server should be configurable to log various events and associated information. Such information may include:

12.2. Business Guidelines and Objectives

The CPNP server can operate in the following modes:

  1. Fully automated mode:

    The CPNP server is provisioned with a set of business guidelines and objectives that will be used as an input to the decision-making process. The CPNP server will service received orders that fall into these business guidelines; otherwise, requests will be escalated to an administrator that will formally validate/invalidate an order request. The set of policies to be configured to the CPNP server are specific to each administrative entity managing a CPNP server.
  2. Administrative-based mode:

    This mode assumes some or all CPNP server' operations are subject to a formal administrative validation. CPNP events will trigger appropriate validation requests that will be forwarded to the contact person(s) or department which is responsible for validating the orders. Administrative validation messages are relayed using another protocol (e.g., SMTP) or a dedicated tool.

Business guidelines are local to each administrative entity. How validation requests are presented to an administrator are out of scope of this document; each administrative entity may decide the appropriate mechanism to enable for that purpose.

13. Security Considerations

Means to defend the server against denial-of-service attacks must be enabled. For example, access control lists (ACLs) can be enforced on the client, the server or the network in between, to allow a trusted client to communicate with a trusted server.

The client and the server MUST be mutually authenticated. Authenticated encryption MUST be used for data confidentiality and message integrity.

The protocol does not provide security mechanisms to protect the confidentiality and integrity of the packets transported between the client and the server. An underlying security protocol such as (e.g., Datagram Transport Layer Security (DTLS) [RFC6347], Transport Layer Security (TLS) [RFC8446]) MUST be used to protect the integrity and confidentiality of protocol messages. In this case, if it is possible to provide an Automated Key Management (AKM) and associate each transaction with a different key, inter-transaction replay attacks can naturally be addressed. If the client and the server use a single key, an additional mechanism should be provided to protect inter-transaction replay attacks between them. Clients MUST implement DTLS record replay detection (Section 3.3 of [RFC6347]) or an equivalent mechanism to protect against replay attacks.

DTLS and TLS with a cipher suite offering confidentiality protection and the guidance given in [RFC7525] MUST be followed to avoid attacks on (D)TLS.

The client MUST silently discard CPNP responses received from unknown CPNP servers. The use of a randomly generated Transaction-ID makes it hard to forge a response from a server with a spoofed IP address belonging to a legitimate CPNP server. Furthermore, CPNP demands that messages from the server must include the correct identifiers of the orders. Two order identifiers are used: one generated by the client and a second one generated by the server.

The Provider MUST enforce means to protect privacy-related information included the documents (see Section 8.7) exchanged in CPNP messages [RFC6462]. In particular, this information MUST NOT be revealed to external parties without the consent of Customers. Providers should enforce policies to make Customer fingerprinting difficult to achieve. For more discussion about privacy, refer to [RFC6462][RFC6973].

The Nonce and the Transaction ID attributes provide sufficient randomness and can effectively tolerate attacks raised by off-line adversaries, who do not have the capability of eavesdropping and intercepting the packets transported between the client and the server. Only authorized clients must be able to modify agreed CPNP orders. The use of a randomly generated Nonce by the server makes it hard to modify an agreement on behalf of a malicious third-party.

14. IANA Considerations

This document does not request any IANA action.

15. Acknowledgements

Thanks to Diego R. Lopez and Adrian Farrel for the comments.

Thanks to the ISE reviewers.

Special thanks to Luis Miguel Contreras Murillo for the detailed review.

16. References

16.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002.
[RFC4086] Eastlake 3rd, D., Schiller, J. and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax Used to Form Encoding Rules in Various Routing Protocol Specifications", RFC 5511, DOI 10.17487/RFC5511, April 2009.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012.
[RFC7297] Boucadair, M., Jacquenet, C. and N. Wang, "IP Connectivity Provisioning Profile (CPP)", RFC 7297, DOI 10.17487/RFC7297, July 2014.
[RFC7525] Sheffer, Y., Holz, R. and P. Saint-Andre, "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2015.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018.

16.2. Informative References

[AGAVE] Boucadair, M., Georgatsos, P., Wang, N., Griffin, D., Pavlou, G., Howarth, M. and A. Elizondo, "The AGAVE Approach for Network Virtualization: Differentiated Services Delivery", April 2009.
[ETICS] EU FP7 ETICS Project, "Economics and Technologies of Inter-Carrier Services", January 2014.
[I-D.boucadair-lisp-idr-ms-discovery] Boucadair, M. and C. Jacquenet, "LISP Mapping Service Discovery at Large", Internet-Draft draft-boucadair-lisp-idr-ms-discovery-01, March 2016.
[I-D.contreras-teas-slice-nbi] Contreras, L., Homma, S. and J. Ordonez-Lucena, "Considerations for defining a Transport Slice NBI", Internet-Draft draft-contreras-teas-slice-nbi-00, November 2019.
[I-D.geng-netslices-architecture] 67, 4., Dong, J., Bryant, S., kiran.makhijani@huawei.com, k., Galis, A., Foy, X. and S. Kuklinski, "Network Slicing Architecture", Internet-Draft draft-geng-netslices-architecture-02, July 2017.
[I-D.ietf-opsawg-l3sm-l3nm] Aguado, A., Dios, O., Lopezalvarez, V., Voyer, D. and L. Munoz, "A Layer 3 VPN Network YANG Model", Internet-Draft draft-ietf-opsawg-l3sm-l3nm-01, November 2019.
[I-D.itsumo-dsnp] Chen, J., "Dynamic Service Negotiation Protocol (DSNP)", Internet-Draft draft-itsumo-dsnp-03, March 2006.
[I-D.nguyen-rap-cops-sls] Nguyen, T., "COPS Usage for SLS negotiation (COPS-SLS)", Internet-Draft draft-nguyen-rap-cops-sls-03, July 2002.
[Karl] Czajkowski, K., Foster, I., Kesselman, C., Sander, V. and S. Tuecke, "SNAP: A Protocol for Negotiating Service Level Agreements and Coordinating Resource Management in Distributed Systems"
[RFC2782] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, DOI 10.17487/RFC2782, February 2000.
[RFC3084] Chan, K., Seligson, J., Durham, D., Gai, S., McCloghrie, K., Herzog, S., Reichmeyer, F., Yavatkar, R. and A. Smith, "COPS Usage for Policy Provisioning (COPS-PR)", RFC 3084, DOI 10.17487/RFC3084, March 2001.
[RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned Virtual Private Network (VPN) Terminology", RFC 4026, DOI 10.17487/RFC4026, March 2005.
[RFC4176] El Mghazli, Y., Nadeau, T., Boucadair, M., Chan, K. and A. Gonguet, "Framework for Layer 3 Virtual Private Networks (L3VPN) Operations and Management", RFC 4176, DOI 10.17487/RFC4176, October 2005.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6462] Cooper, A., "Report from the Internet Privacy Workshop", RFC 6462, DOI 10.17487/RFC6462, January 2012.
[RFC6574] Tschofenig, H. and J. Arkko, "Report from the Smart Object Workshop", RFC 6574, DOI 10.17487/RFC6574, April 2012.
[RFC6770] Bertrand, G., Stephan, E., Burbridge, T., Eardley, P., Ma, K. and G. Watson, "Use Cases for Content Delivery Network Interconnection", RFC 6770, DOI 10.17487/RFC6770, November 2012.
[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet Autonomous System (AS) Number Space", RFC 6793, DOI 10.17487/RFC6793, December 2012.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D. and D. Lewis, "The Locator/ID Separation Protocol (LISP)", RFC 6830, DOI 10.17487/RFC6830, January 2013.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., Morris, J., Hansen, M. and R. Smith, "Privacy Considerations for Internet Protocols", RFC 6973, DOI 10.17487/RFC6973, July 2013.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined Networking: A Perspective from within a Service Provider Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014.
[RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo-Pascual, J. and D. Lewis, "Locator/Identifier Separation Protocol (LISP) Network Element Deployment Considerations", RFC 7215, DOI 10.17487/RFC7215, April 2014.
[RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for Application-Based Network Operations", RFC 7491, DOI 10.17487/RFC7491, March 2015.
[RFC8040] Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017.
[RFC8259] Bray, T., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017.
[RFC8309] Wu, Q., Liu, W. and A. Farrel, "Service Models Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018.
[RFC8329] Lopez, D., Lopez, E., Dunbar, L., Strassner, J. and R. Kumar, "Framework for Interface to Network Security Functions", RFC 8329, DOI 10.17487/RFC8329, February 2018.
[RFC8597] Contreras, LM., Bernardos, CJ., Lopez, D., Boucadair, M. and P. Iovanna, "Cooperating Layered Architecture for Software-Defined Networking (CLAS)", RFC 8597, DOI 10.17487/RFC8597, May 2019.
[TEQUILA] Georgatsos, P. and G. Giannakopoulos, "Service Negotiation Protocol (SrNP)"
[Xin] Wang, X., "Resource Negotiation and Pricing Protocol (RNAP)"

Authors' Addresses

Mohamed Boucadair (editor) Orange Rennes, 35000 France EMail: mohamed.boucadair@orange.com
Christian Jacquenet Orange Rennes, 35000 France EMail: christian.jacquenet@orange.com
Dacheng Zhang Huawei Technologies EMail: dacheng.zhang@huawei.com
Panos Georgatsos Centre for Research and Innovation Hellas 78, Filikis Etairias str. Volos, Hellas 38334 Greece Phone: +302421306070 EMail: pgeorgat@gmail.com