System Administration Guide
Chapter 7, Connecting to other computers with UUCP

Defining a communications protocol

Defining a communications protocol

You can define the protocol to use with each device. In most cases it is not needed since you can use the default or define the protocol with the particular system you are calling (For more information on defining the protocol, see the Systems file ``type'' field.) To specify the protocol, use the form type,protocol (for example, ACU, g).

Alternatively, you can set up a Configuration file for your system. This file (/usr/lib/uucp/Configuration) contains the protocol configuration information used for contacting a specific system, or for use with a given device. You can specify different protocols in order of preference, and uucico will negotiate with the daemon at the other end of the session for the first protocol they have in common. In addition, the `g' and `G' protocols have configurable options. These are discussed in detail in the Configuration(F) manual page.

Table 7-2 UUCP communications protocols

 Protocol   Description
    g       standard UUCP protocol for connection
            over serial lines and modems. Uses error
            correction, provides variable packet and
            window size support and dynamic packet
            size adjustment.
    G       variant on ``g'' protocol used by SVR4
            systems.  Provides variable packet and
            window size support. (This is disabled
            on some old fashioned ``g'' protocol
    e       protocol for 8-bit error-free links
            (example: TCP, TLI, TLIS).  No error
    t       protocol for 8-bit error-free links
            (example: TCP, TLI, TLIS).  Checks
            received file size.  This protocol is
            provided for compatibility with BSD-
            derived systems.
    f       protocol for 7-bit only error-free links
            (for example, some X.25 PADs). Does a
            checksum on the entire file.
    x       protocol for 8-bit X.25 error-free
            links. Does not work on some X.25 packet
            switched networks (see t protocol).

NOTE: Changing the uucico window parameter for the ``g'' protocol can cause compatibility problems. Although the ``g'' protocol definition allows different window sizes, some implementations have a compiled-in size of 3 packets. If the local uucico is configured to use a different window size, the remote uucico daemon may die if it has a compiled-in limit. For example, it is best not to modify the default values if you plan on connecting to UUNET. See the Configuration(F) manual page for a full discussion of issues surrounding protocol packet and window sizes, and ``How a UUCP transmission proceeds'' for a demonstration of the debugging output from a ``g'' protocol session.