Glossary – Siemens Gigaset C450IP User Manual

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Glossary

Gigaset C450 IP / Greek eng / A31008-M1713-T151-3-8U19 / glossary.fm / 24.9.07

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Glossary

ADSL

Asymmetric Digital Subscriber Line

Special form of DSL.

ALG

Application Layer Gateway

NAT control mechanism of a router.
Many routers with integrated NAT use

ALG. ALG lets the data packets in a VoIP

connection pass and adds the public IP

address of the secure private network.
The router's ALG should be deactivated

if the VoIP provider offers a STUN server

or an outbound proxy.
See also: Firewall, NAT, Outbound

proxy, STUN.

Authentication

Restriction of access to a network/serv-

ice by use of a password to log in.

Automatic ringback

See Ringback when the number is

busy.

Block dialling

Enter the complete phone number, and

correct it if necessary. Then pick up the

receiver or press the handsfree key to

dial the phone number.

Broadband Internet access

See DSL.

Call forwarding

Automatic forwarding of a call to a dif-

ferent telephone number. There are

three kinds of call forwarding:
– CFU, Call Forwarding Unconditional
– CFB, Call Forwarding Busy
– CFNR, Call Forwarding No Reply

Call waiting

VoIP provider feature. A beep during a

call indicates that another caller is wait-

ing. You can accept or reject the second

call. You can activate/deactivate the

feature.

Call Forwarding

See Call forwarding.

Client

Application that requests a service

from a server.

Codec

Coder/decoder

Codec is a procedure that digitises and

compresses analogue voice before it is

sent via the Internet and decodes –

i.e.translates into analogue voice – dig-

ital data when voice packets are

received. There are different codecs

that vary, for instance, according to the

level of compression.
Both parties involved in the telephone

connection (caller/sender and recipi-

ent) must use the same codec. This is

negotiated between the sender and the

recipient when establishing a connec-

tion.
The choice of codec is a compromise

between voice quality, transmission

speed and the necessary bandwidth. A

high level of compression, for example,

means that the bandwidth required for

each voice connection is low. However,

it also means that the time needed to

compress/decompress the data is

greater, which increases execution

time for data in the network and thus

impairs voice quality. The time required

increases the delay between the sender

speaking and the recipient hearing

what has been said.