Differences

This shows you the differences between two versions of the page.

--- packet:protocols [2024/04/18 09:10] – [AXUDP] Add diagram 2e0itb
+++ packet:protocols [2024/05/11 11:21] (current) – [AXTCP] 2e0itb
@@ Line 5: / Line 5: @@
 Keep It Simple Silly
-Protocol used between a TNC and a computer.  See [[packet:packet_documents|Packet Documents]].
+Protocol used between a TNC and a computer.  See [[packet:kiss-protocol|The KISS TNC: A simple Host-to-TNC communications protocol]], and [[packet:packet_documents|Packet Documents]].
 ====== AXIP ======
@@ Line 12: / Line 12: @@
 Appears to be an AX.25 frame in an IP packet with the IPPROTO field set to 93.
+| IP | AX.25 Frame | AX.25 CRC16 |
 ====== AXUDP ======
@@ Line 19: / Line 22: @@
 Appears to be an AX.25 frame in a UDP packet.  No common port number in usage.
-| IP | UDP | AX.25 Frame | CRC |
+| IP | UDP | AX.25 Frame | AX.25 CRC16 |
 ====== AXTCP ======
-AX.25 over TCP/IP
+There are (at least!) two variants of AXTCP in use.  A heuristic for telling them apart is to check the first byte.  If it's 0xC0 then it's BPQ (kiss over TCP), otherwise it's xrouter (AXTCP).
+===== as spoken by xrouter =====
 Appears to be two byte length (big endian), followed by an AX.25 packet.  No common port number in usage.
-| IP | TCP | 2 byte len (big endian) | AX.25 Packet | AX.25 CRC16 |
+| IP | TCP | 2 byte len (big endian) | AX.25 Frame | AX.25 CRC16 |
+For xrouter at least, the first packet needs to have your alias in the destination field, and your callsign in the source field, the control field can be anything, and the CRC must match.
+===== as spoken by bpq =====
+This is KISS over TCP.