The Web Uri Open Beacon specification for the Internet of Things
(pronounced YUR-ee-BEE-kun)
Note: this is a preview-release intended for comments and experimentation.
The Uniform Resource Identifier Beacon (UriBeacon) defines Bluetooth 4.0 Advertisement Data that contain Web Uris. UriBeacon provides a way for Bluetooth Low Energy devices to discover nearby Uris, for example, provides a way for a user to discover a short Url and then download it on their smartphone.
UriBeacon is an open specification that is:
- licensed under the Apache 2.0 License and adherent to the principles of the Open Internet and interoperable with the Open Web.
- not dependant on a specific hardware manufacturer, software vendor, mobile platform, user agent, web browser, or web service.
The UriBeacon Open Source Project aims to bring low power beacons into the family of Open Internet technologies. As such we forego private, exclusive and proprietary beacon solutions.
- Compliance with Bluetooth Specification Version 4.0 Advertising Packet Data Unit (PDU).
- Compatability with iOS and Android background scanning.
- Efficiency in terms of power and wireless network utilization.
A subgoal of #3 is to use the Advertisement PDU Type ADV_NONCONN_IND (non-connectable undirected advertising PDU Type) where the “advertiser” simply sends advertisements and doesn’t interact with the receivers, and avoid ADV_SCAN_IND and the SCAN_REQ SCAN_RSP message exchange.
The UriBeacon consists of two basic data types in an Advertising Data (AD) block: <<Service UUID>> and <<Service Data>. Both of these data types utilize a 16-bit Universally Unique Identifier (UUID) allocated by the Bluetooth standards body for this purpose:
| Assigned Number | Service Name | Service Description |
|---|---|---|
|
0xFED8 (65240) |
Uniform Resource Identifier Service | The Uniform Resource Identifier (Uri) Service provides a way for a Bluetooth Low Energy device to discover nearby identifiers for resources over a network, for example, provides a way for a user to discover a Url advertised by a Bluetooth Low Energy peripheral and then download it on their smartphone. |
**Table 2: 16-bit UUID Assigned Number for UriBeacon **
The <<Service UUID>> provides the mechanism for efficient, cross platform background scanning. Both Android and iOS allow background scanning for Services based on UUIDs.
The <<Service Data>> provides the mechanism for transporting the payload of Uri, Tx Power Level (for ranging), and flags.
The format for the Advertising Data that includes the <<Service UUID>> and <<Service Data>> basic types is shown in in Figure 1 and Table 3.
Figure 1: UriBeacon Advertisement Data Format
| Offset | Size | Value | Name | Description |
|---|---|---|---|---|
| 0 | 1 | 2 | AD Length | |
| 1 | 1 | 0x03 | AD Type | Complete List of 16-Bit Service |
| 2 | 2 | 0xFED8 | Service ID | Assigned Uri Service UUID |
| 4 | 1 | 5..23 | AD Length | |
| 5 | 1 | 0x16 | AD Type | Service Data |
| 6 | 2 | 0xFED8 | Service ID | Assigned Uri Service UUID |
| 8 | 1 | - | Flags | UriBeacon Flags |
| 9 | 1 | - | TX Power | UriBeacon Tx Power Level |
| 10 | 1 | - | Uri Scheme | UriBeacon Uri Scheme Prefix |
| 11 | 0..17 | octets | Encoded Uri | UriBeacon Uri |
Table 3: UriBeacon Advertisement Data Format
See Generic Access Profile (GAP) EIR Data Type and Advertising Data Type (AD Type) Values
| Bit | Description |
|---|---|
| 0 | Hidden |
| 1..7 | Reserved for future use. Must be zero. |
The Hidden flag is a command for the user-agent that tells it not to access a particular UriBeacon. This is a guideline only, and is not a blocking method. User agents may, with user approval, display hidden beacons.
The Transmit Power Level represents the transmit power level in dBm, and the value ranges from -100 dBm to +20 dBm to a resolution of 1 dBm.
The value is a signed 8 bit integer as specified by TX Power Level Bluetooth Characteristic.
- The value 0x12 is interpreted as +18dBm
- The value 0xEE is interpreted as -18dBm
The Uri Scheme Prefix byte defines the identifier scheme, an optional prefix and how the remainder of the Uri is encoded.
| Decimal | Hex | Expansion |
|---|---|---|
| 0 | 0x00 | http://www. |
| 1 | 0x01 | https://www. |
| 2 | 0x02 | http:// |
| 3 | 0x03 | https:// |
| 4 | 0x04 | urn:uuid: |
The urn:uuid identifier scheme is defined by RFC 2141, for example: urn:uuid:B1E13D51-5FC9-4D5B-902B-AB668DD54981.
The encoding consists of 16-octets representing the UUID in the form:
| Offset | Size | Description |
|---|---|---|
| 0..15 | 16 | UUID in byte order |
The HTTP URL scheme is defined by RFC 1738, for example
http://bit.ly/1tGYKCV and is used to designate Internet resources
accessible using HTTP (HyperText Transfer Protocol).
The encoding consists of a sequence of characters. Character codes excluded from the Url encoding are used as text expansion codes. When a user agent receives the UriBeacon the byte codes in the Url identifier are replaced by the expansion text according to the table below.
| Decimal | Hex | Expansion |
|---|---|---|
| 0 | 0x00 | .com/ |
| 1 | 0x01 | .org/ |
| 2 | 0x01 | .edu/ |
| 3 | 0x02 | .net/ |
| 4 | 0x03 | .info/ |
| 5 | 0x04 | .biz/ |
| 6 | 0x05 | .gov/ |
| 7 | 0x07 | .com |
| 8 | 0x08 | .org |
| 9 | 0x09 | .edu |
| 10 | 0x0a | .net |
| 11 | 0x0b | .info |
| 12 | 0x0c | .biz |
| 13 | 0x0d | .gov |
| 14..32 | 0x0e..0x20 | Reserved for Future Use |
| 127..255 | 0x7F..0xFF | Reserved for Future Use |
Note: URIs are written only with the graphic printable characters of the US-ASCII coded character set. The octets 00-20 and 7F-FF hexadecimal are not used. See “Excluded US-ASCII Characters” in RFC 2936.
Service UUIDtype is defined in Core Specification Supplement, Part A, section 1.1Service Datatype is defined in Core Specification Supplement, Part A, section 1.11