Internet Engineering Task Force X. Wei Internet-Draft L. Zhu Intended status: Informational Huawei Expires: April 4, 2014 Oct 2013 PAWS Database Discovery draft-wei-paws-database-discovery-02 Abstract This document provides a Database Discovery mechanism for PAWS. By this mechanism the master device gets the available WSDBs with which it should communicate as well as the regulatory domain information. The mechanism is based on the LoST protocol . Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on April 4, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Wei & Zhu Expires April 4, 2014 [Page 1] Internet-Draft Abbreviated Title Oct 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Motivations . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Mechanism overview . . . . . . . . . . . . . . . . . . . . 4 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 4 3. System Architecture Description . . . . . . . . . . . . . . . 5 4. Specification . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Brief introduction of LoST . . . . . . . . . . . . . . . . 8 4.2. Issues to be clarified . . . . . . . . . . . . . . . . . . 10 4.2.1. Service Identifier . . . . . . . . . . . . . . . . . . 10 4.2.2. Conveying of regulatory domain . . . . . . . . . . . . 10 4.2.3. URL-related information . . . . . . . . . . . . . . . 10 4.3. Discovery procedures . . . . . . . . . . . . . . . . . . . 11 4.3.1. Discovery Request procedure . . . . . . . . . . . . . 11 4.3.2. Discovery Response procedure . . . . . . . . . . . . . 11 4.3.3. Recursion and Iteration . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 14 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8.1. Normative references . . . . . . . . . . . . . . . . . . . 14 8.2. Informative References . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Wei & Zhu Expires April 4, 2014 [Page 2] Internet-Draft Abbreviated Title Oct 2013 1. Introduction 1.1. Motivations In the PAWS protocol, the master device queries the database for available spectrum, but the device MUST determine the URL for the database before it can send any PAWS messages. Brief discussions of database discovery can be found in [RFC6953] and [PAWS PROTOCOL]. Several different choices can be taken for the device to determine the appropriate URL(s) for connection. There are some possible methods for this purpose (not all methods are included here): (1) The manufacture or the user of device can manually pre-configure statically the URL(s) of one or more databases that is available for the device to query white space spectrum (e.g. the device and database have agreements with each other.), for example, if the device is to be used in US, it will be configured with the database of US, and then it directly connects to the database in US, or if the device is to be used in several countries it can be configured with different database for each country. (2) The device can be configured by certain provisioning process after attaching to operator's network. (3) An entity of Listing server[PAWS PROTOCOL], providing the URLs for one or more Spectrum Databases, could be deployed in a regulatory domain, then the device queries and checks available databases from the Listing server. (4) When the database which the device currently connects to cannot provide service for this device any more, it can redirects this device to anther database that can serve the master [PAWS PROTOCOL]. But in some scenarios the methods above may not work well: (1) To pre-configure device, the user has to know the available database(s) that can be used in the regulatory domain, it may be inconvenient especially when the device is moved to a different regulatory domain. (2) It is possible that some databases are not available any more or some new databases are setup, the pre-configuring and provisioning method may not cope with it very well. (3) It is possible that in pre-configuring method the available databases of several regulatory domains may be pre-configured in device, and whether it is convenient for a device to know which regulatory domain it currently locates at the beginning. (4) In the method that database provides redirecting to the master device some security related issues have to be considered. It might be ok for a database to provide master device with URL of another database in the same regulatory domain. But in case when master moves from regulatory domain A to regulatory domain B, it might not all seems right for database of A to provide regulatory domain information and available databases or Listing server of B to the device, because PAWS databases and master devices are each certified to operate in certain regulatory domains. Wei & Zhu Expires April 4, 2014 [Page 3] Internet-Draft Abbreviated Title Oct 2013 So a dynamic database discovery mechanism is provided here, the mechanism can be used independently or cooperate with other methods, e.g. device can first connect to the configured or provisioned databases, if that fails then the device can use the dynamic mechanism to find out available databases. The discovery mechanism discussed here will provide master device with two kind of information: the regulatory domain where the device locates now and the available list of DBs or a Listing server in that domain. The mechanism discussed in this memo will be provided as an OPTIONAL method as described in PAWS PROTOCOL [PAWS PROTOCOL]. 1.2. Mechanism overview The dynamic database discovery mechanism provided here is used by a device to discover the available white space databases for its current location and related regulatory domain information. In discovery procedure, the URI for the database SHOULD be obtained from an authorized and authenticated entity. The master device provides its current geo-location information to the entity in Database Discovery Request message, and the entity will return a list of available databases/or Listing server and the regulatory body related information that has jurisdiction over the master device's location. When the master device gets the information about available database and regulatory body, it can choose the proper database for querying white space spectrum by PAWS procedures. 2. Terminology and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [RFC2119]. The terminology from PAWS: problem statement, use cases and requirements RFC6953 [RFC6953] is applicable to this document. White Space Database (WSDB) In the context of white space and cognitive radio technologies, the database is an entity which contains, but is not limited to, current information as required by the regulatory policies about available spectrum at any given location and time, and other types of related Wei & Zhu Expires April 4, 2014 [Page 4] Internet-Draft Abbreviated Title Oct 2013 (to the white space spectrum) or relevant information. White Space Database Discovery Server (WSDB DS) A server function provided to a white space device, the client. The white space device contacts a white space database discovery server to receive the service of discovering or identifying one or more white space databases. The white space database discovery server is a known entity to the white space device, which knows at least a useable internet address for the white space database discovery server. The white space database discovery server takes as input positioning information from the white space device and returns both URLs of white space databases that cover white space device's current location and indication of the regulatory domain governing at the white space device's current location. A single white space database discovery server may have global scope, serving clients located globally. Mapping Mapping is a process that takes a location and a service identifier as inputs and returns one or more URLs. Those URLs can point either to a host providing that service or to a host that in turn routes the request to the final destination. Device The device in this memo is equivalent to the master device described in RFC6953 [RFC6953]. 3. System Architecture Description Before the WSD can query a trusted WSDB for a list of available frequencies or channels for use in the white space spectrum, the WSD must first discover the available databases and addresses serving the regulatory domain in which the device is currently located. At power-up the WSD does not reliably know the regulatory domain corresponding to its current location, and therefore does not reliably know with which white space database(s) it can communicate. Furthermore it is essential that the WSD connect with a trusted WSDB for proper operation and indeed regulatory compliance. The discovery system is based on client-server model; the basic model is shown in Figure 1. Wei & Zhu Expires April 4, 2014 [Page 5] Internet-Draft Abbreviated Title Oct 2013 +----------+ +----------+ | Master | <--------> | WSDB DS | +----------+ +----------+ Figure 1: DB discovery system model The WSDB DS takes as input location information from the WSD and returns to the WSD one or more addresses of WSDBs or WSDB Listing servers as appropriate to the WSD. For the discovery mechanism to work well, some assumptions have to be considered: (1) Master device can get its geo-location directly or indirectly. (2) Master device has gotten the URL (or IP address) of a trusted WSDB DS before starting the discovery procedure. The URL or IP address of WSDB DS can be found by any method such as DNS, manually configuring etc, and it is out of scope of this document. The WSDB DSs can be deployed independently without knowledge of each other; a lot of WSDB DS can be deployed all around the world. When the WSD does not have the address of a serviceable WSDB (e.g. at power-up or failed to get the current regulatory domain etc), the WSD sends a Discovery Request message to a WSDB DS. The WSD includes in the Discovery Request information about its current location. The WSDB DS uses this location information to determine the regulatory domain where the WSD is located, and returns a Discovery Response message which includes the address of one or more WSDBs (or WSDB listing server as appropriate) and regulatory domain related information to the WSD. An overview of procedures of how master device gets available spectrum from WSDB is depicted in Figure 2. Wei & Zhu Expires April 4, 2014 [Page 6] Internet-Draft Abbreviated Title Oct 2013 +-----------+ +-----------+ +----------+ | | | WSDB | | | | WSD | | Discovery | | WSDB | | | | Server | | | +-----------+ +-----------+ +----------+ | | | | | | 0.Discovery Trigger | | | 1.Discovery Request | | |(location information, etc) | | |--------------------------->| | | | | | 2.Discovery Response | | | (address information, etc) | | |<---------------------------| | | | | | | | | /--------------------------|-----------------------\ | |/ | \| |\ | 3.(PAWS) /| | \--------------------------|-----------------------/ | | | | | | | Figure 2: An overview of procedures of how master device gets available spectrum from WSDB (0) Discovery trigger. There are several conditions that could trigger the database discovery procedure, for example, after master device's power-up, or when master device moves into a new regulatory domain, or when master device fails to connect to all of the pre- configured databases etc. (1) Discovery Request procedure. This message is used by master device to query available WSDB from WSDB DS; it conveys master's location and some other related information to WSDB DS. (2) Discovery Response procedure. This procedure conveys the regulatory domain and either the address of a listing server or the address of one or more WSDB authorized to provide service where the WSD is physically located to the master device. If spectrum access is not authorized at the WSD physical location, the response will contain an error code and no address information. (3) After WSDB discovery procedure, the master device can query available white space spectrum from the WSDB using PAWS protocol. Wei & Zhu Expires April 4, 2014 [Page 7] Internet-Draft Abbreviated Title Oct 2013 Figure 3 shows at a high level how white space master devices discover a suitable trusted white space database. In this document we describe how the master device may collect the addresses of one or more white space database. Procedures to contact a white space database are specified in PAWS PROTOCOL. [PAWS PROTOCOL] +------+ +-------+ |Master| |WSDB DS| +---+--+ +---+---+ | | | 1.Request(location,service id) | ------------------------------------>| | | | 2.Response(a list of URLs of DB)| |<-----------------------------------| | | +-----------------------------------------+ | |3.Select an available DB that can be used| | | by master to query for white space | | +-----------------------------------------+ | | | | | | | Figure 3: High level view of white space database discovery After master device has selected a available database for service, it can then use the PAWS protocol [PAWS PROTOCOL] to retrieve the available spectrum for its location. 4. Specification In this document, a dynamic database discovery mechanism based on existing LoST protocol [RFC5222] is discussed. 4.1. Brief introduction of LoST LoST (Location-to-Service Translation Protocol) is an XML-based protocol for mapping service identifiers and geodetic or civic location information to service contact URIs and associated information. Wei & Zhu Expires April 4, 2014 [Page 8] Internet-Draft Abbreviated Title Oct 2013 +-----------+ +-----------+ |LoST client| |LoST server| +-----------+ +-----------+ | | | | 1.Request Message(Location info,service identifier | |--------------------------------------------------> | | | | +-------------------------------+ | |2.mapping location info+service| | |to service URL(s) | | +-------------------------------+ | | | | | 3.Response Message(Service URL(s)) | |<---------------------------------------------------| | | | | Figure 4: n overview of procedures in LoST protocol The LoST client sends its location information and service type it wants to LoST server to retrieve one or more service URIs. The LoST server maintains the mapping relationship between location and service URI, on receiving request message it maps the location and service identifier in the request to one or more service URLs that can offer the service in the location. LoST messages are carried in HTTP and HTTPS protocol exchanges, facilitating use of TLS for protecting the integrity and confidentiality of requests and responses. This discovery mechanism utilizes LoST to communicate between master device and WSDB DS, the master device acts as LoST client and WSDB DS plays the role of LoST server. The protocol stack is shown in Figure 5. To use LoST for this discovery mechanism, several issues have to be clarified. Wei & Zhu Expires April 4, 2014 [Page 9] Internet-Draft Abbreviated Title Oct 2013 +------------+ | LoST + +------------+ | HTTPS + +------------+ | TCP + +------------+ | IP + +------------+ Figure 5: Protocol stack for discovery mechanism 4.2. Issues to be clarified 4.2.1. Service Identifier A new service identifier for PAWS database discovery needs to be defined, according to RFC5031 [RFC5031], a top-level service and a sub-service are defined here. +----------------+-------------------------------------+ | Service | Description | +----------------+-------------------------------------+ | paws | top-level service of PAWS | | paws.discovery | the PAWS database discovery service | +----------------+-------------------------------------+ Table 1 So according to the service-identifying labels defined above, the service URN for PAWS database discovery service is as follow: urn:service:paws.discovery 4.2.2. Conveying of regulatory domain The name of regulatory domain can be conveyed using element in the LoST response message. [Note: the format and content of the regulatory domain information are TBD.] 4.2.3. URL-related information The WSDB DS may return database or Listing server to master device, but because the database and Listing server are all in the form of URL, so it may be difficult for mater device to distinguish between Wei & Zhu Expires April 4, 2014 [Page 10] Internet-Draft Abbreviated Title Oct 2013 database URL and Listing server URL. Here an extension to LoST is needed: for every element that used for conveying URL a new attribute ("indicator") which indicates whether it is a URL of database or a URL of Listing server. When the URL is for a database, then master device can run PAWS protocol to query white space spectrum from the database; or when the URL is for a Listing server, then master device connects to the Listing server for available database(s) in the domain. 4.3. Discovery procedures 4.3.1. Discovery Request procedure The discovery request procedure uses the query message of LoST for conveying parameters. Master device's location information will be included in the element. The service identifier defined in Section 4.2.1 is specified in the element. The following is an example of discovery request procedure message, using geodetic coordinates. 37.775 -122.422 urn:service:paws.discovery 4.3.2. Discovery Response procedure The discovery response procedure uses the response message of LoST for conveying parameters. After receiving the query message, the WSDB DS will map the location information and service identifier to one or more available WSDBs' URL. Wei & Zhu Expires April 4, 2014 [Page 11] Internet-Draft Abbreviated Title Oct 2013 Then in the message, a list of WSDBs' URL and regulatory domain that has jurisdiction over the current location will be conveyed to master device. The regulatory domain is contained in element. The service boundary of the WSDB can also be included in the response message to indicate the region for which the service URL returned would be the same as in the actual query. Or a service boundary reference can be returned to master device, and master device retrieve service boundary by this reference as needed. Next time when the master device powers up, if its location is within the service boundary it then may use the WSDB retrieved before. An example of discovery response procedure message is shown as follow: Wei & Zhu Expires April 4, 2014 [Page 12] Internet-Draft Abbreviated Title Oct 2013 Federal Communications Commission 37.775 -122.4194 37.555 -122.4194 37.555 -122.4264 37.775 -122.4264 37.775 -122.4194 urn:service:paws.discovery database1.example1.com database2.example2.com 4.3.3. Recursion and Iteration If the WSDB DS can not provide available WSDB for master device, then it may wish other WSDB DS to serve the master device's query request. In LoST, recursion and iteration patterns are provided for this purpose. In recursive mode, the LoST server initiates queries on behalf of the requester and returns the result to the requester. In iterative mode, the server contacted returns a redirection response indicating the next server to be queried if the server Wei & Zhu Expires April 4, 2014 [Page 13] Internet-Draft Abbreviated Title Oct 2013 contacted cannot provide an answer itself. 5. Security Considerations TBD. 6. IANA Consideration Registration of service URN for PAWS database discovery service. +----------------+-------------------------------------+ | Service | Description | +----------------+-------------------------------------+ | paws | top-level service of PAWS | | paws.discovery | the PAWS database discovery service | +----------------+-------------------------------------+ Table 2 7. Acknowledgements Thanks to my colleagues for their sincerely help and comments when drafting this document. 8. References 8.1. Normative references [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for Emergency and Other Well-Known Services", RFC 5031, January 2008. [RFC5222] Hardie, T., Newton, A., Schulzrinne, H., and H. Tschofenig, "LoST: A Location-to-Service Translation Protocol", RFC 5222, August 2008. 8.2. Informative References [PAWS PROTOCOL] Chen, V., Das, S., Zhu, L., McCann, P., and J. Malyar, "Protocol to Access Spectrum Database", Wei & Zhu Expires April 4, 2014 [Page 14] Internet-Draft Abbreviated Title Oct 2013 draft-ietf-paws-protocol-06 (work in progress), June 2013. [RFC6953] Mancuso, A., Probasco, S., and B. Patil, "Protocol to Access White-Space (PAWS) Databases: Use Cases and Requirements", RFC 6953, May 2013. Authors' Addresses Xinpeng Wei Huawei Phone: +86 134 3682 2355 Email: weixinpeng@huawei.com Lei Zhu Huawei Phone: +86 139 1015 7020 Email: lei.zhu@huawei.com Wei & Zhu Expires April 4, 2014 [Page 15]