Create Source Route - 0x21

Description

This frame type is used to create an entry in the source route table of a local device. A source route specifies the complete route a packet traverses to get from source to destination. For best results, use source routing with many-to-one routing. See Source routing for more information.

In most cases, this frametype is used in combination with routing information received from a corresponding Route Record Indicator - 0xA1 frame. Route indicators are generated when a network device sends data to a concentrator. The order in which addresses are entered into the 0x21 frame are the same as provided by the 0xA1 frame—destination to source.

There is no response frame for this frame type. Take care when generating source routes as an incorrectly formatted frame will be silently rejected or may cause unexpected results.

Note Both the 64-bit and 16-bit destination addresses are required when creating a source route.

Format

The following table provides the contents of the frame. For details on frame structure, see API frame format.

Offset	Size	Frame Field	Description
0	8-bit	Start Delimiter	Indicates the start of an API frame.
1	16-bit	Length	Number of bytes between the length and checksum.
3	8-bit	Frame type	Create Source Route - 0x21
4	8-bit	Frame ID (reserved)	This frame type generates no response, so the Frame ID field is not used. Set this field to 0.
5	64-bit	64-bit destination address	Set to the 64-bit IEEE address of the destination device (required).
13	16-bit	16-bit destination address	Set to the 16-bit network address of the destination device (required).
15	8-bit	Options (reserved)	Source routing options are not available yet. This bit field is reserved for future functionality. Set this field to 0.
16	8-bit	Number of addresses	The number of addresses in the source route (excluding source and destination). A route can only traverse across a maximum of 30 hops. If this number is 0 or exceeds the maximum hop count, the frame is silently discarded and a route will not be created.
17-n	16-bit variable	Address	The 16-bit network address(es) of the devices along the source route, excluding the source and destination. The addresses should be entered in reverse order (from destination to source) to match the order provided in Route Record Indicator - 0xA1.
EOF	8-bit	Checksum	0xFF minus the 8-bit sum of bytes from offset 3 to this byte (between length and checksum).

Examples

Each example is written without escapes (AP = 1) and all bytes are represented in hex format. For brevity, the start delimiter, length, and checksum fields have been excluded.

4-hop route

A concentrator needs to send data to a device with a 64-bit address of 0013A20012345678 that is 4-hops away. Due to the size of the network, route discoveries need to be be minimized. The concentrator had previously received a Route Record Indicator - 0xA1 with the source route to this device and had stored this information.

The route looks like this:

Source (concentrator) <> Router A <> Router B <> Router C <> Destination (remote)

In this example, the network addresses are simplified.

7E 00 14 21 00 00 13 A2 00 12 34 56 78 DD DD 00 03 CC CC BB BB AA AA F6

Frame type	Frame ID	64-bit dest	16-bit dest	Options	Num of addresses	Address 1	Address 2	Address 3
0x21	0x00	0x0013A200 12345678	0xDDDD	0x00	0x03	0xCCCC	0xBBBB	0xAAAA
Route request	Not used	Destination IEEE address	Destination NWK address	Not used		Neighbor of dest	Intermediate hop	Neighbor of source