doc: start documenting the Layer 2 packets (WIP)
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@ -254,6 +254,157 @@ They therefore do not have a _TX sequence number_; this field is reserved and mu
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The _RX sequence number_ and all other header fields are used as usual.
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==== Connection Management
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Connection Management Frames control the Layer 2 connection between a client and the digipeater.
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They are especially important for connect and disconnect procedures.
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Connection Management Frames have at least one byte in the data field: the type of the management packet.
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The following types are defined:
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[cols="1,2,5", options="header"]
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.Connection Management Types
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|===
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|Type Indicator
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|Sent by
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|Description
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|`0x00`
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|Digipeater
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|Beacon
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|`0x01`
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|Client
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|Connection Request
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|`0x02`
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|Digipeater
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|Connection Parameters
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|`0x03`
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|Digipeater
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|Connection Reset
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|`0x04`
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|Digipeater
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|Disconnect Request
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|`0x05`
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|Client
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|Disconnect
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|===
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===== Beacons
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Beacons are sent periodically by the digipeater to show it’s presence to potential new clients.
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The layer 2 header is filled as follows:
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- Message Type: `001` (Connection Management)
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- TX Request: `1`
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- Source Address: the digipeater’s HAM-64 address
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- Destination Address: the HAM-64 broadcast address
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- TX sequence number: reserved, always 0
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- RX sequence number: reserved, always 0
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The message contains exactly 1 data byte: `0x00` to indicate that this is a Beacon packet.
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A Beacon packet shall always be sent as the last or only packet in a burst.
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After a Beacon is sent by the digipeater it listens for a short time for Connection Requests from new clients.
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A new client that intends to connect shall send the Connection Request as soon as possible after the beacon transmission ends.
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===== Connection Request
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A Connection Request is sent by a client that intends to connect to a digipeater.
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The layer 2 header is filled as follows:
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- Message Type: `001` (Connection Management)
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- TX Request: `1`
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- Source Address: the new client’s HAM-64 address
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- Destination Address: the digipeater’s HAM-64 address
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- TX sequence number: reserved, always 0
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- RX sequence number: reserved, always 0
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The message contains exactly 1 data byte: `0x01` to indicate that this is a Connection Request packet.
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A Connection Request is always a response to a Beacon packet.
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It shall be the only packet in a burst.
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When the digipeater receives a Connection Request it has two options for a response:
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. Accept the connection by sending a Connection Parameters packet to the client in the next burst.
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. Reject the connection by sending a Connection Reset packet to the client in the next burst.
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===== Connection Parameters
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The Connection Parameters packet has two functions: it indicates to a client that its Connection Request was accepted and tells it how to configure its network stack.
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This is the first packet in the regular Go-back-N data flow.
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The layer 2 header is filled as follows:
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- Message Type: `001` (Connection Management)
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- TX Request: `1`
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- Source Address: the digipeater’s HAM-64 address
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- Destination Address: the new client’s HAM-64 address
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- TX sequence number: 0 (the first packet)
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- RX sequence number: 0 (no packets received yet)
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The type indicator is `0x02`.
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After the type indicator follow one or more configuration blocks.
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Each block consists of three data fields:
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. Configuration Type: 1 byte
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. Configuration Data Length: 1 byte
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. Configuration data: variable number of bytes as indicated by Configuration Data Length
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The following Configuration Types are defined:
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[cols="1,1,5", options="header"]
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.Configuration Types
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|===
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|Type Indicator
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|Length
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|Description
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|`0x00`
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|16 Byte
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|IPv6 address
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|`0x01`
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|16 Byte
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|IPv6 gateway
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|`0x02`
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|16 Byte
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|IPv6 DNS server (may appear multiple times)
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|`0x03` - `0x07`
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|-
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|_reserved_
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|`0x08`
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|4 Byte
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|IPv4 address
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|`0x09`
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|4 Byte
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|IPv4 gateway
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|`0x0A`
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|4 Byte
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|IPv4 DNS server (may appear multiple times)
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|`0x0B` - `0xFF`
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|-
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|_reserved_
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|===
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If the client receives an unknown Configuration Type the corresponding block shall be skipped.
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The remaining blocks shall be parsed as usual.
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=== Ideas
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To be defined:
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@ -290,7 +441,7 @@ msc {
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digi box client [label="Connection established"];
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--- [label="Alternative 2: Connection is rejected"];
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digi -> client [label="Connection Refusal"];
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digi -> client [label="Connection Reset"];
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}
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....
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