Point-to-Point Connection Technology
134
PBX Networking
Example of a PBX network
Various line types and transmission protocols can be used for point-to-point
connections. The required network topology (distance, connection capacity)
determines which type of point-to-point connection is most suitable.
An IP network connection with Q.SIG-IP or SIP tie line can be established
either with a direct LAN connection or via a fast VPN connection (see also
starting on page 83). Q.SIG-IP or SIP tie line cannot be operated
using a connection with NAT. When the connection is via VPN, encryption is
advisable for security reasons.
Point-to-Point Connection
Technology
Protocol: Q.SIG or DSS1
The Q.SIG protocol, designed for ISDN point-to-point connections, is the pref-
erable choice as the transmission protocol; alternatively, the DSS1 protocol,
designed for ISDN dial-up connections in the Euro-ISDN, can be used. Certain
PBX networking features can only be used with the Q.SIG protocol, however.
In particular, the connection designation as internal or external call and also
the name of the caller cannot be transmitted via the DSS1 protocol.
Both protocols implement communication on several protocol layers:
●
L1: Layer 1 defines the physical line properties and the electrical coding of
signals.
●
L2: Layer 2 enables communication via individual error-protected channels
that are independent of each other.
●
L3: Layer 3 defines the administration of the individual channels and
implements the features designed for ISDN.
Point-to-point
connection
Trunk line
PBX
PBX
PBX
PBX
PBX
Summary of Contents for forum 523
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