Defining Asynchronous Paths (dialup_path)

Asynchronous paths are identified in the file ppp.conf by the keyword dialup_path, which starts each definition. They can be associated with point-to-point and point-to-multipoint IP interfaces. Dynamic IP address allocation is supported over asynchronous paths only.

Synopsis

Asynchronous path definitions have the following general forms:

# Dialup path using static point-to-point IP interface
dialup_path
		ip_interface	ipdptpn
		expect_login_id	user_name
	.
	.
# Dialup path using dynamic point-to-point IP interface
dialup_path
		ip_interface	ipdptp*
		expect_login_id	user_name
	.
	.
# Dialup path using point-to-multipoint IP interface
dialup_path
	ip_interface	ipdn
		expect_login_id	user_name
		remote_ip_addr	ip_addr
	.
	.

Keywords

dialup_path

Mandatory parameter for asynchronous paths. Indicates the start of an asynchronous (or dialup) path definition.

ip_interface interface

Mandatory parameter for asynchronous paths. Associates the asynchronous path with one of the point-to-point (ipdptpn) or point-to-multipoint (ipdn) IP interfaces defined in the ifconfig section of the file.

Point-to-point IP interfaces may be static or dynamic. Static point-to-point IP interfaces are identified by a number (ipdptp0, ipdptp1, ..., ipdptpn), and associate the dialup path with exactly one pair of source and destination IP addresses. For example:

dialup_path
    ip_interface        ipdptp0

Dynamic IP interfaces are used for dynamic IP address allocation on the server side, and are identified by an asterisk (ipdptp*). An interface is assigned on demand, for as long as there are interfaces available in the pool. For example:

dialup_path
    ip_interface        ipdptp*

remote_host name

Mandatory parameter for asynchronous paths used to initiate calls. Associates the asynchronous path with the name of one of the remote hosts defined in the file link.conf. The value name can be any character string.

remote_ip_addr ip_addr

Mandatory parameter for point-to-multipoint connections. Not required for point-to-point connections. Specifies the IP address of the remote host associated with the asynchronous path. The value ip_addr can be an IP address (expressed using dot notation) or a hostname that appears in the file /etc/hosts.

expect_login_id login

Mandatory parameter for asynchronous paths used to accept incoming calls. Specifies the login id expected from the remote host. This parameter is used to associate an incoming call with a specific asynchronous path; therefore each remote host must have a unique login id.

The value login can be any lowercase string, between 1 and 8 characters in length. It must correspond to the login id which appears in the relevant connect script on the remote host.

You must also create a user account with this login id, using admintool(1M). See "Adding User Accounts for Incoming Connections" for detailed instructions.

default_route

Optional parameter for point-to-point IP interfaces. When the IP interface is marked up, the route is added to the routing table automatically as the default destination. It is removed from the routing table when the IP interface is marked down. This parameter is most commonly used in client configurations--that is, links configured for outgoing calls only. It should never be used in conjunction with a routing daemon running on the machine, because this generates unnecessary network traffic.

inactivity_timeout seconds

Optional parameter for asynchronous paths. Specifies the number of seconds of inactivity that elapse before an asynchronous connection is closed automatically.

The value seconds can be any integer. The default value is 120 seconds (2 minutes). If the value seconds is set to zero, the connection remains open until closed explicitly.

request_ip_addr state

Optional parameter for asynchronous paths. Enables dynamic IP address allocation at the client side only. When the value state is set to on, the client requests an IP address from a pool of interfaces assigned at the server side.

The value state can be on (enabled) or off (disabled). The default value is off.

private ip_interface

Optional parameter for asynchronous paths. Hides the specified IP interface from the interface pool defined for dynamic IP address allocation on the server side. Can be used to reserve point-to-point IP interfaces so they can be used for synchronous connections.

accept_any_ip_addr state

Optional parameter for asynchronous paths. Accepts the IP addresses provided by the remote host, even if they differ from the IP addresses assigned to the interface locally.

The value state can be on (enabled) or off (disabled). The default value is off.

lcp_async_map mask

Optional parameter for asynchronous paths. Specifies the LCP asynchronous map used by the remote host. The LCP asynchronous map is a negotiated parameter that defines which control characters are transposed for transmission in PPP frames.

Control characters in the range 0x00 to 0x1f, such as CTRL-S and CTRL-Q, are used by some devices to implement software flow control. These devices may interpret the control characters transmitted in PPP frames, and close the link as a result. To avoid problems interoperating with these devices, all 32 control characters are automatically transposed for transmission, so that they appear outside of the significant range. Encoding and decoding the control characters incurs a processing overhead at both ends of the link.

The LCP asynchronous map defines which of the control characters is transposed by the remote host. A bit set to 1 in the value mask tells the remote host to transpose the corresponding control character; a bit set to zero tells the remote host to leave the control character unchanged. Provided you can predict how each device in the link will respond to the control characters it receives in PPP frames, you can tell the remote host to transpose a subset of the control characters, by specifying a different mask value. For example, a mask value of 0x0000ffff tells the remote host to transpose the first 16 control characters only.

By default, the value mask is set to 0xffffffff, which tells the remote host to transpose all 32 control characters. A value of 0x0 leaves all control characters unchanged.

lcp_compression state

Optional parameter for asynchronous paths. Indicates whether the Address and Protocol fields in the PPP frame are compressed. See Appendix A, PPP Link Operation for more information.

The value state can be on (enabled) or off (disabled). The default value is on.

lcp_mru mru

Optional parameter for synchronous and asynchronous paths. Specifies the maximum receive unit (MRU) for the local machine. This parameter is carried in the LCP Configure-request frame, and sets the maximum transmission unit (MTU) for the remote host. See Appendix A, PPP Link Operation for more information.

By default, the value mru is set to 1500 bytes for Ethernet networks.

lcp_restart_timer seconds

Optional parameter for synchronous and asynchronous paths. Specifies the number of seconds which elapse between consecutive LCP Configure-Request frames. Increasing the LCP restart timer may be necessary when connecting over long delay networks, such as satellite connections. See Appendix A, PPP Link Operation for more information.

The value seconds can be any integer greater than zero. The default value is 3 seconds.

lcp_max_restart max_restart

Optional parameter for synchronous and asynchronous paths. Specifies the number of unanswered LCP Configure-Request frames generated before the endpoint is considered unreachable and the IP interface is marked as down. See Appendix A, PPP Link Operation for more information.

The value max_restart can be any integer in the range 1 to 255. The default value is 10. If the value max_restart is set to 255, LCP Configure-Request frames are generated periodically until the remote host finally responds.

ppp_link_name name

Optional parameter for synchronous and asynchronous paths. Assigns a name to the link, which is used by ppptrace and pppstat. The value name can be any character string.

ipcp_compression state

Optional parameter for synchronous and asynchronous paths. Indicates the current state of the header compression facility, which uses Van Jacobsen compression to improve performance over slow links. See Appendix A, PPP Link Operation for more information.

The value state can be vj (enabled) or off (disabled). The default value is vj.

expect_authentication mode

Optional parameter for synchronous and asynchronous paths. Indicates that the local host will request authentication from remote hosts, and the authentication protocol to be used. If authentication is enabled, remote hosts must authenticate themselves successfully, or the connection is closed.

The value mode can be off (no authentication), pap (authentication using PAP), chap (authentication using CHAP), or pap|chap (authentication using both PAP and CHAP). The default value is off.

If both PAP and CHAP are enabled, CHAP authentication is performed first. If the remote host does not support CHAP authentication, it is allowed to participate in PAP authentication only.

expect_pap_id pap_id

Mandatory parameter, if the local host requests PAP authentication. Specifies the PAP identifier expected from a remote host. The value pap_id can be any string between 0 and 255 characters in length. A zero length value is represented by: expect_pap_id ""

expect_pap_passwd pap_passwd

Mandatory parameter, if the local host requests PAP authentication. Specifies the PAP password expected from a remote host. The value pap_passwd can be any string, between 0 and 255 characters in length. A zero length value is represented by: expect_pap_passwd ""

expect_chap_name chap_name

Mandatory parameter, if the local host requests CHAP authentication. Specifies the CHAP name expected from a remote host. The value chap_name can be any string, between 1 and 255 characters in length.

chap_peer_secret chap_secret

Mandatory parameter, if the local host requests CHAP authentication. Specifies the CHAP secret that is used with the challenge value to generate the response expected from the remote host. The value chap_secret can be any string, between 1 and 255 characters in length.

send_authentication mode

Optional parameter. Indicates whether the local host will participate in authentication negotiation requested by remote hosts, and the authentication protocol used.

The value mode can be off (no authentication), pap (authentication using PAP), chap (authentication using CHAP), or pap|chap (authentication using both PAP and CHAP). The default value is off.

send_pap_id pap_id

Mandatory parameter, if the remote host requests PAP authentication. Specifies the PAP identifier sent to a remote host when it requests authentication. The value pap_id can be any string, between 0 and 255 characters in length. A zero length value is represented by: expect_pap_id ""

send_pap_passwd pap_passwd

Mandatory parameter, if the remote host requests PAP authentication. Specifies the PAP password sent to a remote host when it requests authentication. The value pap_passwd can be any string, between 0 and 255 characters in length. A zero length value is represented by: expect_pap_passwd ""

send_chap_name chap_name

Mandatory parameter, if the remote host requests CHAP authentication. Specifies the CHAP name sent to a remote host when it requests authentication. The value chap_name can be any string, between 1 and 255 characters in length.

chap_own_secret chap_secret

Mandatory parameter, if the remote host requests CHAP authentication. Specifies the CHAP secret that is used with the challenge value to generate the response sent to the remote host. The value chap_secret can be any string, between 1 and 255 characters in length.

Examples

The following asynchronous path definition shows a point-to-multipoint IP interface, and that the local host will request CHAP authentication from the remote host odyssey:

dialup_path
    ip_interface          ipd0
    expect_login_id       odyssey-login
    remote_host           odyssey
    remote_ip_addr        129.xxx.xxx.119
    inactivity_timeout    120
    expect_authentication chap
    expect_chap_name      odyssey_name
    chap_peer_secret      odyssey_secret

The following asynchronous path definition shows dynamic IP address allocation enabled at the client side:

dialup_path
    ip_interface	       ipdptp0
    remote_host         odyssey
    request_ip_addr     on

The following asynchronous path definitions show dynamic IP interfaces assigned to three dialup paths:

dialup_path
    ip_interface          ipdptp*
    expect_login_id       remote1
 
dialup_path
    ip_interface          ipdptp*
    expect_login_id       remote2
 
dialup_path
    ip_interface          ipdptp*
    expect_login_id       remote3