Defining Synchronous Paths (sync_path)

Synchronous paths are identified in the file ppp.conf by the keyword sync_path, which starts each definition. They are always associated with point-to-point IP interfaces.

Synopsis

Synchronous path definitions have the following general form:

sync_path
	ip_interface	ipdptpn
	unix_device	device_name
	.
	.
	.

Keywords

sync_path

Mandatory parameter for synchronous paths. Indicates the start of a synchronous path definition.

ip_interface ipdptpn

Mandatory parameter for synchronous paths. Associates the synchronous path with one of the point-to-point IP interfaces defined in the ifconfig section of the file. Load-sharing is enabled if two or more synchronous paths share the same IP interface.

unix_device device

Mandatory parameter for synchronous paths. Associates the synchronous path with one of the synchronous devices defined in the file link.conf. The value device must correspond to a synchronous serial interface installed in your machine.

For example, the device names of the form zshn associate the path with one of the on-board serial interfaces. The device names of the form hihn, associate the path with a high-speed serial interface (HSI).

default_route

Optional parameter for synchronous paths. Adds the route to the routing table as the default destination. The route is removed when the IP interface is marked down.

accept_any_ip_addr state

Optional parameter for synchronous 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.

link_monitor state

Optional parameter for synchronous paths. Indicates the current state of the link monitor. When enabled, the link monitor sends periodic echo requests to the remote host. If the remote host fails to respond after a specified number of requests, the link monitor assumes that the link has failed for some reason. It marks the IP interface associated with the synchronous path down to stop the transmission of more IP datagrams across the failed link.

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

link_monitor_timer seconds

Optional parameter for synchronous paths. Specifies the number of seconds which elapse between consecutive echo requests generated by the link monitor.

The value seconds can be any integer greater than zero. The default value is 5 seconds.

link_monitor_retries max_retries

Optional parameter for synchronous paths. Specifies the number of unanswered echo requests generated by the link monitor before the remote host is considered unreachable and the IP interface is disabled.

The value max_retries can be any integer greater than zero. The default value is 12.

ppp_link_name name

Optional parameter for synchronous and asynchronous paths. Assigns a name that is used by ppptrace and pppstat to identify the link. 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.

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

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.

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 synchronous path definition shows that the local host will request both PAP and CHAP authentication from remote hosts, but will only participate in PAP negotiation when authentication is requested by a remote host:

sync_path
    ip_interface            ipdptp0
    unix_device             zsh0
    expect_authentication   pap|chap
    expect_pap_id           epic_id
    expect_pap_passwd       epic_passwd
    expect_chap_name        epic_name
    chap_peer_secret        epic_secret
    send_authentication     pap
    send_pap_id             papyrus_id
    send_pap_passwd         papyrus_passwd

The following synchronous path definitions show load-sharing enabled between two synchronous paths that use the same IP interface:

sync_path
    ip_interface         ipdptp2
    unix_device          hih0
 
sync_path
    ip_interface         ipdptp2
    unix_device          hih1