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

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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

<com port>
Communicate over the named com device. If no device name is given, ppp will use com1.
<speed>
Set the async port line speed to <speed>.
asyncmap <map>
Set the async character map to <map>. 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 <command>
             Use  the  executable  or shell command specified by
             <command> 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  negotia-
             tion  is  successfully  completed.   This  entry is
             removed when the PPP connection is broken.
file <filename>
             Read options from file <filename>  (the  format  is
             described below).
help (-?)
             Display  ppp  usage information for the most common
             options.
mru <n>
             Set the MRU [Maximum Receive Unit] value to <n> for
             negotiation.  ppp will ask the peer to send packets
             of no more than <n> 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 <n>
             Set  the interface netmask to <n>, 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 with-
             out 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

      <local_IP_address>:<remote_IP_address>
             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  sys-
             tem.   The remote address will be obtained from the
             peer if not specified in any option.  Thus, in sim-
             ple 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 <n>
             Same as asyncmap <n>
      -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 <p>

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 <d>

Append the domain name <d> to the local host name for authentication purposes. For example, if geth- ostname() 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 <n> 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 <u>

Set the user name to use for authenticating this machine with the peer using PAP to

<u>

.

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 Resolu-
             tion 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 <secret>
             Use  the secret <secret> for PAP and CHAP authenti-
             cation with the peer.
      lcp-restart <n>
             Set the LCP restart interval (retransmission  time-
             out) 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 time-
             out) 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  time-
             out) 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 time-
             out  for challenges) to <n> seconds (default 5 sec-
             onds).
      chap-max-challenge <n>
             Set the maximum number of CHAP challenge  transmis-
             sions 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 follow-
      ing 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  (wild-
      card).  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  authenti-
      cating  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 host-
         name,
         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 pass-
      word 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  cer-
      tain  users,  and to restrict the set of IP addresses that
      each user can use.
      Secrets are selected from the CHAP secrets  file  as  fol-
      lows:
  • For authenticating the peer, look for a secret with client == name specified in the CHAP-Response message, and server == local name.
      o  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.   Communica-
      tion  with other machines generally requires further modi-
      fication to routing tables and/or ARP (Address  Resolution
      Protocol) tables.  In some cases this may be done automat-
      ically 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  exam-
      ple  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 trans- parent; 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 authenti-
             cation.
      $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.

SEE ALSO

      RFC1144
             Jacobson, V.  Compressing TCP/IP headers  for  low-
             speed serial links.  1990 February.
      RFC1321
             Rivest, R.  The MD5 Message-Digest Algorithm.  1992
             April.
      RFC1331
             Simpson, W.A.  Point-to-Point  Protocol  (PPP)  for
             the  transmission  of multi-protocol datagrams over
             point-to-point links.  1992 May.
      RFC1332
             McGregor, G.  PPP Internet Protocol Control  Proto-
             col (IPCP).  1992 May.
      RFC1334
             Lloyd, B.; Simpson, W.A.  PPP authentication proto-
             cols.  1992 October.


NOTES

The following signals have the specified effect when sent to the ppp process.

      SIGINT, SIGTERM
             These  signals  cause ppp to terminate the link (by
             closing LCP), restore the serial  device  settings,
             and exit.

BUGS

Usability issues, several to be resolved prior to GA.