38.1. Tunneling proprietary protocols

38.1. Tunneling proprietary protocols
	Chapter 38. Tunneling proprietary protocols

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

PV (Packet Voice): for UDP packetized voice only.
AIPT (Abilis IP Tunnel): for data and voice exchange.

Both virtual tunnels support several operation modes:

Tunnelling Mode

Table 38.1. Tunnelling modes

Mode	Description	Note
`STD`	Standard	No out-of-sequence packet reordering! Use `STD` only for tunnels through LAN and high quality WAN.
`EXT`	Extended	`EXT` supports out-of-sequence packet reordering, extended statistics and diagnostics. Use `EXT` for PV or AIPT tunnels through WAN, when both linked Abilis have a static IP Address.
`EXT-SERVER`	Extended Server	Use the combination of `EXT-SERVER` and `EXT-CLIENT,` for PV or AIPT tunnels, when one side has a dynamic IP address (client) and the other side has a static address (the server must have a static IP address).
`EXT-CLIENT`	Extended Client	`EXT` client is also to be used in PV or AIPT tunnels when Abilis is placed behind a router doing NAT/PAT

ART Protocol: “Abilis Redundant Tunneling” sends the same information on two different lines. The receiving Abilis discards the packet which arrives second (out-of sequence). The probability that the same packet is lost on both links equals the product of the original probabilities. Example: two links with 10% failure rate (a very high one!) ends up with 1%, which is normally negligible
Tip
It's advisable to use ART ONLY with lines with the same speed. In case of lines with different speeds, the packets are sent with the maximum speed of the slower line.
Backup over ISDN: in case of failure of the permanent VPN connection, the Abilis PV or AIPT tunnels may be instantaneously switched onto ISDN backup lines.

Link Check: it's a procedure used to detect end-to-end link (or emulated p-link) real functioning, regardless of the lower protocol layer states.

Encryption: it activates the cryptography of the data sent on the virtual VPN and define up to 63 256 bit cryptography key (exist also a default cryptography key that can be used in configuration).

MPX (Multiplexing): this owner protocol allows to share the same link (VPN) for transmission of data and packetized voice (also Link Check, if enabled).
VRED Protocol: Abilis “Voice Redundancy” duplicates VOICE and/or FAX packets by repeating a packet when the subsequent one has to be sent. This method is similar to the redundancy used in SIP for T38 packets. The receiving Abilis discards the packet which arrives second (out-of sequence). The probability that the same packet is lost in two different moments is therefore reduced.

LOG: activates/deactivates logging functionalities of meaningful events of the VPNs. These functionalities can be applied to IP tunnel or Link Level.

38.1.1. 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:

LLOG

Link Check logging activation/deactivation.

LMPX

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;

LC

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;

LCR

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].

LCRKEY

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.

LT1

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;

LT3

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;

LN2

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

	Tip
	Refer to chapter Section 38.5, “Appendix - LN2 parameter” to have more information about LN2 parameter.

LCOMP

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
                              FRAG:NO
       IPADD:000.000.000.000  MASK:255.255.255.255   NEIGH:000.000.000.000
       REDIS:YES     HIDE:NO         RP:NONE            IPSEC:NO       VRRP:NO
       NAT:NO                        DIFFSERV:NO        DDNS:NO
       OUTBUF:100    OUTQUEUE:FAIR   MTU:1500
       OUTSPL:NO
       INBUF:0                      mru:1500           SRCV:NO
       - TRFA section ---------------------------------------------------------
       TRFA:NO
       - 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
       MPX:NO
                     LOCPORT:2105     REMPORT:2100   CR:NO         CRKEY:DFT
       OUT-IP:AUTO
       LOCIPADD:R-ID (192.168.000.201)  REMIPADD:#

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.

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

	Tip
	It's advisable to use ART ONLY with lines with the same speed. In case of lines with different speeds, the packets are sent with the maximum speed of the slower line.


Chapter 38. Tunneling proprietary protocols		38.2. Configuring Packet Voice tunnels