Official change in Host-Host Protocol (RFC0695)

NWG/RFC# 695 MCK 5-JUL-75 15:38 32908 Official Change in Host-Host Protocol

Mark Krilanovich 1

Official Change in Host-Host Protocol 2

This is an official change to the Host to Host protocol, this document should be filed with the protocol specification (nic -- 8246,) in the Current Network Protocols Notebook (nic -- 7104,). 3

-- Jon Postel 3a

This document corrects an ambiguity in the current host-host protocol, concerning the ERR command. Paragraph "f", page 35, of NIC 8246 defines the meaning of an ERR command with error code of 5 to be "socket (link) not connected". The error code is stated to apply to two cases, one in which a control command other than STR or RTS refers to a socket that is neither fully open nor fully closed, and the other in which a (non-control) message arrives over a link not being used for a connection. 4

The difficulty arises from the fact that the contents of the "data" field of the ERR command has distinctly different formats in the two cases. In the first, it is a host-host command, and in the second it is a message header. There is no reliable way for the code in the NCP receiving the ERR command (or a human reviewing an error log) to distinguish between the two cases, and therefore fullest use cannot be made of the ERR command. 5

The two cases are now defined to have different error codes. In addition, a new error code is defined, meaning "invalid host leader received". Therefore, paragraph "f" under "ERR - Error detected" is now replaced by the following: 6

f. Request on a non-open socket (Error code = 5) 7

NWG/RFC# 695 MCK 5-JUL-75 15:38 32908 Official Change in Host-Host Protocol

A request other than an STR or RTS was made for a socket (perhaps referenced by link number) that is n...