39.1. Tunneling proprietary protocols

The Abilis supports two types of virtual tunneling, which can be applied to different level 2 links:

Both virtual tunnels support several operation modes:

39.1.1. Link check

Link check allows to automatically manage an eventual “True link backup” (onto ISDN line) in case of failure of the permanent VPN connection. When activating a packet voice or IP tunnel, Abilis checks continuously the link using the parameters below:


Link Check logging activation/deactivation.


Activates the multiplexing of DATA, “Link-Check”, VOICE frames type [NO: Abilis MPX multiplexing isn't active; YES: Abilis MPX multiplexing is active only for the data protocols LAPB and LINK-FR; EXT: Abilis MPX multiplexing is active for ANY data protocol]. The default value is YES;


Enables/disables the use of the “Link-Check” protocol, and consequently the transmission of “Link-check” frames. The link-check protocol is automatically disabled when MPX:NO. Note:with LC:NO the “true link backup” is disabled. The default value is YES;


Enables and selects the cryptography to be applied on the frames passing through the resource. Cryptography can be selectively applied to the different traffic types (VOICE and DATA). [NO: no cryptography is applied; DATA: cryptography is applied only on DATA traffic type; VOICE: cryptography is applied only on VOICE traffic type; ALL: cryptography is always in use, whatever is the traffic data type].


Selects the key to be used for cryptography operations. Users can choose either the default key supplied by the system (LCRKEY:DFT), or one of the keys defined in the cryptography keys table, in which case the numeric value (from 1 to 63) corresponding to the desired LCRKEY has to be specified. If the configured value refers to a missing LCRKEY it will be shown inside square brackets (e.g. CRKEY:[5] means that the key number 5 isn't present in the table). If the parameter LCR is set to NO, the value of LCRKEY is useless.


Maximum time to wait for a Link-Check “probe” acknowledge. If this time elapses without receiving the acknowledge the “probe” is immediately repeated, as a result “not acknowldged probes” are repeated every LT1 milliseconds. The default is 3000;


This is the time interval between a correctly sent and acknowledged Link-Check “probe” and the next one to send while the link is regularly working (e.g. P-LINK state is READY). It has relationships with the parameter LT1: and it has to satisfy the simple rule: LT3 > LT1 * 2. The default is 9000;


Sets the maximum number of Link-Check “probes” retransmission. The default is 3.


Refer to chapter Section 39.5, “Appendix - LN2 parameter” to have more information about LN2 parameter.


Set the compression type to use for an ip resource with subtype AIPT[-BCK], DL[-BCK], ML, BCH. Data Compression is available only under licence.[NO: compression not active, LZO1X: is often the best choice of all, LZO1B: is good with a large blocksize or with very redundant data, LZO1F: s good with a small blocksize or with binary data]

These parameters are in the link section:

[10:42:48] ABILIS_CPX:d p ip-5

RES:Ip-5 - Not Saved (SAVE CONF), Not Refreshed (INIT) ------------------------
       - IP over IP (Abilis tunnel) (AIPT) ------------------------------------
New    DESCR:
       OPSTATE:UP             LOG:NO               STATE-DETECT:NORMAL
       IPADD:  MASK:   NEIGH:
       REDIS:YES     HIDE:NO         RP:NONE            IPSEC:NO       VRRP:NO
       NAT:NO                        DIFFSERV:NO        DDNS:NO
       OUTBUF:100    OUTQUEUE:FAIR   MTU:1500
       INBUF:0                      mru:1500           SRCV:NO
       - TRFA section ---------------------------------------------------------
       - Link -----------------------------------------------------------------
       LLOG:DS       LMPX:YES         LC:YES         LCOMP:NO      LCR:NO
       LT1:3000      LT3:9000         LN2:3                        LCRKEY:DFT
       - IP Tunnel ------------------------------------------------------------
       TLOG:NO       MODE:STD         D-TOS:0-N      V-TOS:0-D     C-TOS:0-D
                     LOCPORT:2105     REMPORT:2100   CR:NO         CRKEY:DFT

The Abilis sends a link-check every LT3 msec. If there's no response, Abilis sends it again every LT1 msec for LN2 times. Using the default values it can take from 9 to 18 seconds to consider the link down.

The default values can be changed using the syntax:

  • s p pv-<id> par:<value> for a PV tunnel

  • s p ip-<id> par:<value> for an AIPT tunnel.


LT1 parameter has relationships with the parameter T1: and it has to satisfy the simple rule: T3 > T1 * 2.