RFC 695

Official Change in Host-Host Protocol 💖

Okay bestie, this one is an official change to the Host to Host protocol 🧚 It's written by Mark Krilanovich, with a little note from Jon Postel at the end. The fix goes with the protocol spec (nic -- 8246) and lives in the Current Network Protocols Notebook (nic -- 7104) 📓

The copy I'm working from doesn't list a date, a category, or any "obsoletes" or "updates" info, so I'm not going to make any up 🙈

The Ambiguity 🔍

Okay so this doc fixes a confusing bit of the host-host protocol, specifically the ERR command. Paragraph f, page 35, of NIC 8246 says an ERR with error code 5 means "socket (link) not connected" 😬 That code was covering two totally different situations:

• a control command other than STR or RTS pointed at a socket that is neither fully open nor fully closed
• a (non-control) message showed up over a link that wasn't being used for a connection

Bestie, this is the problem 💀 In the first case the data field holds a host-host command, but in the second it holds a message header. The NCP that gets the ERR (or a human reading the error log) has no reliable way to tell which one happened, so the ERR command just can't be used to its full potential 😭

The Fix 🎀

Now each case gets its own error code, plus there's a brand new one meaning "invalid host leader received" ✨ So paragraph f under "ERR - Error detected" gets fully replaced with the stuff below. It's giving clarity, no cap 💅

f. Request on a non-open socket (Error code = 5) 🦋

A request other than an STR or RTS was made for a socket (perhaps referenced by link number) that is not party to an fully established connection. The socket's inappropriate state could either be that only one RFC has been sent (not yet open) or that only one CLS has been sent (not yet closed). The data field contains the command in error; the value of any fill necessary is zeros.

g. Message on an unknown link (Error code = 6) 🌸

A message was received over a user link which is not currently being used for any connection. The contents of the data field are the message header followed by the first eight bits of text, if any, or zeros.

h. Invalid host header (Error code = 7) 👑

A message was received either over the control link or a valid user link that had a host header with invalid format. Examples of when this subtype would be appropriate are the following: the M1 or M2 fields were non-zero, the byte size was invalid (not 8 for a control link, zero for any link), or the declared length (byte size times byte count) exceeded the actual length. The contents of the data field is the message header padded with eight bits of zeros.

— Jon Postel 🫶