bugs, mainly in disconnecting sessions (this bug appears to have slipped in over time due to maintenance by some people using it exclusively for APRS and not in virtual channel connected mode), and for example TAP interfaces not supporting the full 7 bytes of call sign string length as some interface drivers expect a 6 byte HW address (MAC), not an up-to-7 byte one like AX.25 use requires. Dire Wolf is a free open source replacement for the 1980s style TNC. It contains DSP software modems and a complete implementation of AX25 v2.2 plus FX.25 forward error correction. It can function as a digital repeater, GPS tracker, and APRS Internet Gateway (IGate) without any additional software. KISS-mode framing See full article at KISS (TNC) AX.25 is often used with a TNC that implements the KISS framing as a low-cost alternative to using expensive and uncommon HDLC controller cards. The KISS framing is not part of the AX.25 protocol itself nor is it sent over the air. It merely serves to encapsulate the protocol frames in a way that can successfully pass over a serial link to the TNC. The KISS framing is derived from SLIP, and makes many of the same assumptions, such as there only being two "endpoints" involved in the conversation. With SLIP, these were the two SLIP-connected hosts; with KISS, it is assumed that the KISS framing link is over serial with only the host computer and the TNC involved. Among other things, this makes it awkward to address multiple TNCs without having multiple (serial) data channels. Alternatives to KISS do exist that address these limitations, such as 6PACK. Applications AX.25 has most frequently been used to establish direct, point-to-point links between packet radio stations, without any additional network layers. This is sufficient for keyboard-to-keyboard contacts between stations and for accessing local bulletin board systems and DX clusters. In recent years, APRS has become a popular application. For tunneling of AX.25 packets over IP, AXIP and AXUDP are used to encapsulate AX.25 into IP or UDP packets. Limitations At the speeds commonly used to transmit packet radio data (rarely higher than 9,600 bit/s, and typically 1,200 bit/s), the use of additional network layers with AX.25 is impractical due to the data overhead involved. This is not a limitation of AX.25 per se, but places constraints on the sophistication of applications designed to use it. HDLC protocols identify