36 VoIP Subscriber Gateways
- Service-Name – Service-Name tag value in PADI message for PPPoE connection
initialization (this field is optional: set the parameter if it is required by provider);
- MTU size – maximum block size for data transmitted via the network. 1492 is
recommended;
PPTP – operation mode when the Internet access is established via a special channel—a
tunnel—using VPN;
L2TP – protocol for VPN implementation.
PPTP and L2TP allow establishing secure communication link over the Internet between the
remote user's computer and organization's private network. PPTP and L2TP are based on Point-to-
Point Protocol (PPP) and act as its extension. First, the OSI model higher level data is encapsulated into
PPP, and then into PPTP or L2TP for tunnel transmission via public data networks. PPTP and L2TP
functionality differs. L2TP may be used not only in IP networks, service messages for tunnel creation
and data transfer use the same format and protocols. PPTP may be used only in IP networks, it
requires a dedicated TCP connection for tunnel creation and usage. L2TP over IPSec
allows for the
higher security level compared to PPTP and provides the higher level of protection for business-critical
data.
Due to its characteristics, L2TP is an attractive protocol for building virtual networks.
During the selection PPTP or L2TP, the following parameters will be available for changing:
- Primary access for VoIP – when checked, interface of the primary access will be used for
operation VoIP application; flag is active only when VoIP is disabled;
- Access type – access type to PPTP-server. Two variant is possible: dynamic access, when
IP-address and other required parameters are obtained via DHCP protocol and static
access in this case IP address, subnet mask, DNS server, gateway and other required
parameters for access to PPTP server are assigned manually;
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IPSec support has been implemented in firmware version 1.6.0 and higher
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