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CE 450 IP R / IM-Ost english / A31008-M1817-R601_1-7619 / glossary.fm / 02.03.2007
S
Server
Provides a service to other Network subscribers (Clients). The term can indicate a com-
puter/PC or an application. A server is addressed via IP address/Domain name and Port.
SIP (Session Initiation Protocol)
Signalling protocol independent of voice communication. Used for establishing and
ending a call. It is also possible to define parameters for voice transmission.
SIP address
See URI.
SIP port/Local SIP port
(Local) Port which is used to send and receive SIP signalling data for VoIP.
SIP provider
See VoIP provider.
SIP proxy server
IP address of your VoIP provider's gateway server.
Static IP address
A static IP address is assigned to a network component manually during network con-
figuration. Unlike a Dynamic IP Address, a static (fixed) IP address never changes.
STUN
Simple Traversal of UDP over NAT
NAT control mechanism.
STUN is a data protocol for VoIP telephones. STUN replaces the private IP address in the
data packets of the VoIP telephone with the public address of the secure private net-
work. To control data transfer, a STUN server is also required on the Internet. STUN can-
not be implemented with symmetric NATs.
See also: ALG, Firewall, NAT, Outbound proxy.
Subnet
Segment of a Network.
Subnet mask
IP addresses consist of a fixed network number and a variable subscriber number. The
network number is identical for all Network subscribers. The proportion of the IP
address made up of the network number is determined in the subnet mask. For the sub-
net mask 255.255.255.0, for example,the first three parts of the IP address are the net-
work number and the last part is the subscriber number.
Switch
Connects different network elements (see also Hub). A switch forwards data packets
straight to the network subscriber to which they are addressed.
Symmetric NAT
A symmetric NAT assigns different external IP addresses and port numbers to the same
internal IP address and port number – depending on the external target address. Your
router has a symmetric NAT.
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