RFC 1123 INTRODUCTION October 1989 3. REMOTE LOGIN -- TELNET PROTOCOL ............................ 16 3.1 INTRODUCTION ........................................... 16 3.2 PROTOCOL WALK-THROUGH .................................. 16 3.2.1 Option Negotiation ................................ 16 3.2.2 Telnet Go-Ahead Function .......................... 16 3.2.3 Control Functions ................................. 17 3.2.4 Telnet "Synch" Signal ............................. 18 3.2.5 NVT Printer and Keyboard .......................... 19 3.2.6 Telnet Command Structure .......................... 20 3.2.7 Telnet Binary Option .............................. 20 3.2.8 Telnet Terminal-Type Option ....................... 20 3.3 SPECIFIC ISSUES ........................................ 21 3.3.1 Telnet End-of-Line Convention ..................... 21 3.3.2 Data Entry Terminals .............................. 23 3.3.3 Option Requirements ............................... 24 3.3.4 Option Initiation ................................. 24 3.3.5 Telnet Linemode Option ............................ 25 3.4 TELNET/USER INTERFACE .................................. 25 3.4.1 Character Set Transparency ........................ 25 3.4.2 Telnet Commands ................................... 26 3.4.3 TCP Connection Errors ............................. 26 3.4.4 Non-Default Telnet Contact Port ................... 26 3.4.5 Flushing Output ................................... 26 3.5. TELNET REQUIREMENTS SUMMARY ........................... 27 4. FILE TRANSFER .............................................. 29 4.1 FILE TRANSFER PROTOCOL -- FTP .......................... 29 4.1.1 INTRODUCTION ...................................... 29 4.1.2. PROTOCOL WALK-THROUGH ............................ 29 4.1.2.1 LOCAL Type ................................... 29 4.1.2.2 Telnet Format Control ........................ 30 4.1.2.3 Page Structure ............................... 30 4.1.2.4 Data Structure Transformations ............... 30 4.1.2.5 Data Connection Management ................... 31 4.1.2.6 PASV Command ................................. 31 4.1.2.7 LIST and NLST Commands ....................... 31 4.1.2.8 SITE Command ................................. 32 4.1.2.9 STOU Command ................................. 32 4.1.2.10 Telnet End-of-line Code ..................... 32 4.1.2.11 FTP Replies ................................. 33 4.1.2.12 Connections ................................. 34 4.1.2.13 Minimum Implementation; RFC-959 Section ..... 34 4.1.3 SPECIFIC ISSUES ................................... 35 4.1.3.1 Non-standard Command Verbs ................... 35 4.1.3.2 Idle Timeout ................................. 36 4.1.3.3 Concurrency of Data and Control .............. 36 4.1.3.4 FTP Restart Mechanism ........................ 36 4.1.4 FTP/USER INTERFACE ................................ 39 Internet Engineering Task Force