Point to Point Protocol for OS/2 TCP/IP 2.0

NAME

 * ppp - Point to Point Protocol for OS/2 TCP/IP 2.0

SYNOPSIS

 * ppp [ options ] [ com port ] [ speed ]

DESCRIPTION
The Point-to-Point Protocol (PPP) provides a method for transmitting datagrams over serial point-to-point links. PPP is composed of three parts: a method for encapsulating datagrams over serial links, an extensible Link Control Protocol (LCP), and a family of Network Control Protocols (NCP) for establishing and configuring different networklayer protocols.

The encapsulation scheme is provided by an OS/2 Ring 3 driver and an interface to the TCP/IP kernel. PPP provides the basic LCP, authentication support, and an NCP for establishing and configuring the Internet Protocol (IP) (called the IP Control Protocol, IPCP).

FREQUENTLY USED OPTIONS

 * :Communicate over the named com device. If no device name is given, ppp will use com1.
 * :Set the async port line speed to.
 * asyncmap :Set the async character map to . This map describes which control characters cannot be successfully received over the serial line. ppp will ask the peer to send these characters as a 2-byte "escape" sequence. The argument is a 32 bit hex number with each bit representing a character to escape. Bit 0 (00000001) represents the character 0x00; bit 31 (80000000) represents the character 0x1f or ^_. The default asyncmap is 0. If multiple asyncmap options are given, the values are ORed together.
 * auth:Require the peer to authenticate itself before allowing network packets to be sent or received.
 * connect :Use the executable or shell command specified by to set up the serial line. This script would typically use the "slattach" program or a REXX command file to dial the modem and start a remote ppp session.
 * defaultroute:Add a default route to the system routing tables, using the peer as the gateway, when IPCP negotiation is successfully completed. This entry is removed when the PPP connection is broken.
 * file :Read options from file (the format is described below).
 * help (-?):Display ppp usage information for the most common options.
 * mru :Set the MRU [Maximum Receive Unit] value to  for negotiation. ppp will ask the peer to send packets of no more than  bytes. The minimum MRU value is 128. The default MRU value is 1500. A value of 296 is recommended for slow interactive links (40 bytes for TCP/IP header + 256 bytes of data).
 * netmask :Set the interface netmask to , a 32 bit netmask in "decimal dot" notation (e.g. 255.255.255.0).
 * passive:Enables the "passive" option in the LCP. With this option, ppp will attempt to initiate a connection; if no reply is received from the peer, ppp will then just wait passively for a valid LCP packet from the peer (instead of exiting, as it does without this option).
 * restart:Restart LCP negotiation after link termination. This overrides the default behavior of terminating the ppp driver after disconnect.
 * rtscts:Use hardware flow control (i.e. RTS/CTS) to control the flow of data on the serial port.
 * silent:With this option, ppp will not transmit LCP packets to initiate a connection until a valid LCP packet is received from the peer.

OTHER OPTIONS
:
 * Set the local and/or remote interface IP addresses. Either one may be omitted. The IP addresses can be specified with a host name or in "decimal dot" notation (e.g. "150.203.23.247"). The default local address is the first IP address of the system. The remote address will be obtained from the peer if not specified in any option. Thus, in simple cases, this option is not required.

-all
 * Don't request or allow negotiation of any options for LCP and IPCP, use default values.

-ac
 * Disable Address/Control compression negotiation (use default, i.e. disabled).

-am
 * Disable asyncmap negotiation (use default, i.e. 0xffffffff).

-as 
 * Same as asyncmap 

-d
 * Increase debugging level.

-ip
 * Disable IP address negotiation. With this option, the remote IP address must be specified with an option on the command line or in an options file.

-mn
 * Disable magic number negotiation. With this option, ppp cannot detect a looped-back line.

-mru
 * Disable MRU [Maximum Receive Unit] negotiation (use default, i.e. 1500).

-p
 * Same as the passive option.

-pc
 * Disable protocol field compression negotiation (use default, i.e. disabled).


 * +ua 

Agree to authenticate using PAP [Password Authentication Protocol] if requested by the peer, and use the data in file for the user and password to send to the peer. The file contains the remote user name, followed by a newline, followed by the remote password, followed by a newline.

+pap
 * Require the peer to authenticate itself using PAP.

-pap
 * Don't agree to authenticate using PAP.

+chap
 * Require the peer to authenticate itself using CHAP [Cryptographic Handshake Authentication Protocol] authentication.

-chap
 * Don't agree to authenticate using CHAP.

-vj
 * Disable negotiation of Van Jacobson style IP header compression (use default, i.e. no compression).

debug
 * Increase debugging level (same as -d ).


 * domain 
 * Append the domain name  to the local host name for authentication purposes. For example, if gethostname returns the name foobar, but the fully qualified domain name is foobar.IBM.COM, you would use the domain option to set the domain name to IBM.COM.

exit
 * Causes the ppp driver to terminate on detecting loss of the modem Data Carrier Detect (DCD) signal.

idle 
 * Set the amount of inactivity time (no IP traffic) until the ppp driver hangs up the connection.

local
 * Don't use modem control lines.

name <n>
 * Set the name of the local system for authentication purposes to <n>.


 * user </PRE>
 * Set the user name to use for authenticating this machine with the peer using PAP to  </PRE>.


 * usehostname
 * Enforce the use of the hostname as the name of the local system for authentication purposes (overrides the name option).

remotename <n>
 * Set the assumed name of the remote system for authentication purposes to <n>.

proxyarp
 * Add an entry to this system's ARP [Address Resolution Protocol] table with the IP address of the peer and the Token-Ring/Ethernet address of this system.

login
 * Use the system password database for authenticating the peer using PAP.

secret
 * Use the secret for PAP and CHAP authentication with the peer.

lcp-restart <n>
 * Set the LCP restart interval (retransmission timeout) to <n> seconds (default 3).

lcp-max-terminate <n>
 * Set the maximum number of LCP terminate-request transmissions to <n> (default 3).

lcp-max-configure <n>
 * Set the maximum number of LCP configure-request transmissions to <n> (default 10).

lcp-max-failure <n>
 * Set the maximum number of LCP configure-NAKs returned before starting to send configure-Rejects instead to <n> (default 10).

ipcp-restart <n>
 * Set the IPCP restart interval (retransmission timeout) to <n> seconds (default 5 seconds).

ipcp-max-terminate <n>
 * Set the maximum number of IPCP terminate-request transmissions to <n> (default 3).

ipcp-max-configure <n>
 * Set the maximum number of IPCP configure-request transmissions to <n> (default 10).

ipcp-max-failure <n>
 * Set the maximum number of IPCP configure-NAKs returned before starting to send configure-Rejects instead to <n> (default 10).

pap-restart <n>
 * Set the PAP restart interval (retransmission timeout) to <n> seconds (default 5 seconds).

pap-max-authreq <n>
 * Set the maximum number of PAP authenticate-request transmissions to <n> (default 10).

chap-restart <n>
 * Set the CHAP restart interval (retransmission timeout for challenges) to <n> seconds (default 5 seconds).

chap-max-challenge <n>
 * Set the maximum number of CHAP challenge transmissions to <n> (default 10).

chap-interval <n>
 * If this option is given, ppp will rechallenge the peer every <n> seconds.

OPTIONS FILES
Options can be taken from files as well as the command line. ppp reads options from the files $ETC/ppp.cfg and $HOME/ppprc before looking at the command line. An options file is parsed into a series of words, delimited by whitespace. Whitespace can be included in a word by enclosing the word in quotes ("). A backslash (\) quotes the following character. A hash (#) starts a comment, which continues until the end of the line.

AUTHENTICATION
The PAP and CHAP secrets files can be setup to restrict the set of IP addresses which individual users may use.

The default behaviour of ppp is to agree to authenticate if requested, and to not require authentication from the peer. However, ppp will not agree to authenticate itself with a particular protocol if it has no secrets which could be used to do so.

Authentication is based on secrets, which are selected from secrets files, $ETC/pap.sct for PAP, and $ETC/chap.sct for CHAP. Both secrets files have the same format, and both can store secrets for several combinations of server (authenticating peer) and client (peer being authenticated). Note that ppp can be both a server and client, and that different protocols can be used in the two directions if desired.

A secrets file is parsed into words similar to the options file. A secret is specified by a line containing at least 3 words, in the order client, server, secret. Any following words on the same line are taken to be a list of acceptable IP addresses for that client. If there are only 3 words on the line, it is assumed that any IP address is OK. To disallow all IP addresses, use "-". If the secret starts with an `@', what follows is assumed to be the name of a file from which to read the secret. A "*" as the client or server name matches any name (wildcard). When selecting a secret, ppp takes the best match, i.e. the match with the fewest wildcards.

A secrets file contains both secrets for use in authenticating other hosts, plus secrets which can be used for authenticating ourselves to others. Which secret to use is chosen based on the names of the host (the `local name') and its peer (the `remote name'). The local name is set as follows:
 * if the usehostname option is given, then the local name is the hostname of this machine (with the domain appended, if supplied)
 * else if the name option is given, then use the argument of the first name option seen
 * else if the local IP address is specified with a hostname, then use that name
 * else use the hostname of this machine (with the domain appended, if given)
 * When authenticating ourselves using PAP, there is also a 'username' which is the local name by default, but can be set with the user option or the +ua option.

The remote name is set as follows:
 * if the remotename option is given, then use the argument of the last remotename option seen
 * else if the remote IP address is specified with a hostname, then use that host name
 * else the remote name is the null string "".

Secrets are selected from the PAP secrets file as follows:
 * For authenticating the peer, look for a secret with client == username specified in the PAP authenticate-request, and server == local name.
 * For authenticating ourselves to the peer, look for a secret with client == our username, server == remote name.

When authenticating the peer with PAP, a secret of "" matches any password supplied by the peer. If the password doesn't match the secret, the password is encrypted using crypt and checked against the secret again; thus secrets for authenticating the peer can be stored in encrypted form. If the login option was specified, the username and password are also checked against the system password database. Thus, the system administrator can set up the pap-secrets file to allow PPP access only to certain users, and to restrict the set of IP addresses that each user can use.

Secrets are selected from the CHAP secrets file as follows:
 * For authenticating the peer, look for a secret with client == name specified in the CHAP-Response message, and server == local name.
 * For authenticating ourselves to the peer, look for a secret with client == local name, and server == name specified in the CHAP-Challenge message.

Authentication must be satisfactorily completed before IPCP (or any other Network Control Protocol) can be started. If authentication fails, ppp will terminated the link by closing LCP. If IPCP negotiates an unacceptable IP address for the remote host, IPCP will be closed. IP packets can only be sent or received when IPCP is open.

ROUTING
When IPCP negotiation is completed successfully, ppp will inform the TCP/IP kernel of the local and remote IP addresses for the ppp interface. This is sufficient to create a host route to the remote end of the link, which will enable the peers to exchange IP packets. Communication with other machines generally requires further modification to routing tables and/or ARP (Address Resolution Protocol) tables. In some cases this may be done automatically through the actions of command scripts, but in most cases some further intervention is required.

Sometimes it is desirable to add a default route through the remote host, as in the case of a machine whose only connection to the Internet is through the ppp interface. The defaultroute option causes ppp to create such a default route when IPCP comes up, and delete it when the link is terminated.

In some cases it is desirable to use proxy ARP, for example on a server machine connected to a LAN, in order to allow other hosts to communicate with the remote host. The proxyarp option causes ppp to look for a network interface on the same subnet as the remote host, (an interface supporting broadcast and ARP, which is up and not a point-to-point or loopback interface). If found, ppp creates a permanent, published ARP entry with the IP address of the remote host and the hardware address of the network interface found.

EXAMPLES
In the simplest case, you can connect the serial ports of two machines via a NULL modem cable and issue a command like ppp com1 38400 passive to each machine.

The process of logging in to a host machine and starting ppp can be automated by using the connect option to run slattach or a REXX script, for example: ppp com1 38400 connect "slattach AT OK ATDT999-9999 CONNECT login: foobar Password: password" If your serial connection is any more complicated than a piece of wire, you may need to arrange for some control characters to be escaped. In particular, it is often useful to escape XON (^Q) and XOFF (^S), using asyncmap a0000. If the path includes a telnet, you probably should escape ^] as well (asyncmap 200a0000). Don't use an rlogin in the path - many implementations are not transparent; they will remove the sequence [0xff, 0xff, 0x73, 0x73, followed by any 8 bytes] from the stream.

DIAGNOSTICS
Messages are logged to both the console and the $ETC/ppp<n>.log file.

FILES
$ETC/ppp<n>.pid
 * Process-ID for ppp process on ppp interface unit n.

$ETC/pap.sct
 * Usernames, passwords and IP addresses for PAP authentication.

$ETC/chap.sct
 * Names, secrets and IP addresses for CHAP authentication.

$ETC/ppp.cfg
 * System default options for ppp, read before user default options or command-line options.

$HOME/ppprc
 * User default options, read before command-line options.

BUGS
Usability issues, several to be resolved prior to GA.