13.2. Service Information 
- The feature “Signaling Survivability” is released for access points, OpenScape 4000 SoftGate and OpenScape Access/Branch.
- Up to 10 survivability routers can be configured in the system.
- Signaling survivability via PSTN network (modem) with OpenScape 4000 SoftGate (vNCUI) is supported for SoftGate 50 and SoftGate 500.
- Only valid for signaling survivability via PSTN network: Depending on the connection capacity, a survivability router can operate up to 30 access points/OpenScape 4000 SoftGates (router with S2 connection). As it cannot be foreseen precisely where in the IP network a fault will occur, the router capacity must be designed for the worst case scenario, i.e. failure of the link from the OpenScape 4000 LAN segment to the IP network of the customer. In such a case, alternative signaling routes will be needed immediately for all access points/OpenScape 4000 SoftGates with signaling survivability.
- Only valid for signaling survivability via PSTN network: If the modem connection goes over the public network, connection charges will accrue. The link to an access point/OpenScape 4000 SoftGate is used as long as the access point/OpenScape 4000 SoftGate is not accessible via the IP network. The configuration of the survivability router contains a setting for the period of “non-use“ after which this link is disconnected. This “hold-time” does not form part of the IPDA configuration. Accessibility of the access point/OpenScape 4000 SoftGate via the modem connection is checked on a cyclical basis (RTO). The check can also be started directly using the AMO TSU. In these cases too, charges for the link will accrue in the PSTN.
- The connection from the active processor (CC-A or CC-B) to the survivability router runs via the OpenScape 4000 LAN segment, just like the connection to the normal LAN router. If this LAN segment fails, for instance because a central L2 switch is faulty, the signaling survivability function will also fail. This “single point of failure” can be somewhat mitigated if CC-A and CC-B are connected to different L2 switches and, for example, half the survivability routers and half the HG 3500 are each connected to the relevant switches. This ensures that at least half of the system will still be available should one of the two L2 switches fail.
- The TCP stream (tcp.port=4000) has to be routed fully transparently through the customer's IP network (i.e. no manipulation of the SequenceNumber etc.), otherwise the "Signaling Survivability" will not work. Furthermore, any available firewalls have to be configured accordingly so that no SequenceNo and SYN check takes place for the tcp.port=4000. It this cannot be guaranteed, the "HSR over UDP" feature should be activated alternatively.
- Signaling survivability via PSTN network (modem) with OpenScape 4000 SoftGate (vNCUI) is tested and supported with OpenScape 4000 SoftGate 50 & OpenScape 4000 SoftGate 500. Both startup and basic scenarios with high load are tested (480 subscribers with > BHCA 6000) via modem, however the use of any large group Signaling features (e.g. AUN) may lead to Signaling delays. The delays are not one of the feature itself, however an issue of Bandwidth Limitation of the PPP connection (64kbit/s) that can lead to TCP Retransmission. If large groups with Signaling are in use, or OpenScape 4000 SoftGate 1000 is used, it is recommended to use "Signaling Survivability via alternate LAN" where there are lesser bandwidth concerns (i.e. ADSL access has much higher available bandwidth for Signaling). Other survivable options like APE, Survivable OpenScape 4000 SoftGate and BPOOL functions are also available, but not without interruption to telephony.
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Please also note:To assure signaling survivability at the OpenScape 40000 SoftGate a certain USB cable is necessary (Part number: C39195-Z7705-A3). If you are unsure, the correct type of cable will display "New USB device found, idVendor=067b, idProduct=2303" in \var\log\messages under Linux. An alternative cable from ATEN is known to cause problems. This has the vendor id "New USB device found, idVendor=0557, idProduct=2008".For signaling survivability at the OpenScape 40000 SoftGate functions with an external ISDN router, the ISDN modem must have a minimum firmware version of V7.019 to understand the AT**ACCM command. For further details, please see MSC24547 in G-DMS.
- Signaling Survivability with WAML-Replacement is only released for Common Gateway Boards (HG 3500). Thus, the WAML function can only be configured in a host shelf or in IPDA shelf (“direct link”), i.e. the functionality at an OpenScape 4000 SoftGate / OpenScape Access/Branch is not supported.
- Using L2 redundancy at access point for input of alternative router is only possible with OpenScape 4000 SoftGate.
- In case of signaling survivability via alternate LAN (AMO APRT, parameter SURVLAN) HSR over UDP must be configured.
- Restrictions and information with the deployment “Simply with integrated
SoftGate” (OpenScape 4000 SoftGate on same computer as host system):
- The integrated OpenScape 4000 SoftGate doesn’t support HSR over UDP.
- The integrated OpenScape 4000 SoftGate doesn’t support Signaling Survivability function for HSR connection.
- The integrated OpenScape 4000 SoftGate is allowed to accept a HSR Connection from an AP-CC (feature APE).
- Restrictions and information with the deployment “Survivable SoftGate”
(OpenScape 4000 SoftGate and APE on the same computer):
- APE doesn’t support Signaling Survivability function for HSR connection.
- OpenScape 4000 SoftGate supports HSR over UDP to the host system.
- OpenScape 4000 SoftGate supports Signaling Survivability function for HSR connection to the host system.
- The golden load loadware of the NCUI board doesn’t support UDP functionality which is necessary for signaling survivability via alternate LAN. Thus, follow the instructions in Section 3.2.4, “Replacement of a defect NCUI Board with a new NCUI Board” when replacing a board.