SS-16 VoIP-2-GSM USER MANUAL
DOC. NO: SS-16-14 (REV. 02)
Page 82 of 84
Control Protocol, manages the assembling of a message or file into smaller packets
that are transmitted over the Internet and received by a TCP layer that reassembles
the packets into the original message. The lower layer, Internet Protocol, handles the
address part of each packet so that it gets to the right destination. For details see the
definitions of those protocols that Access -LAN supports.
TCP
– Acronym for Transmission Control Protocol. In TCP/IP, the TCP part is the one
that takes care of keeping track of the individual units of data (packets) that a
message was divided into for efficient routing through the Internet. TCP is known as a
connection-oriented protocol, which means that a connection is established and
maintained until the message or messages to be exchanged by the application
programs at each end have been exchanged. TCP is responsible for ensuring that a
message is divided into the packets that IP manages and for reassembling the
packets back into the complete message at the other end.
At the destination, TCP reassembles the individual packets and waits until they have
all arrived to forward them to you as a single file. It also checks the received packets.
TCP acts at the transport level (level 4) of the ISO/OSI model. See also ISO/OSI
model, packet, TCP/IP.
TDM
– Acronym for
Time Division Multiplexing
- is a type of digital multiplexing in
which two or more apparently simultaneous channels are derived from a given
frequency spectrum by interleaving pulses representing bits from different channels.
In some TDM systems, successive pulses represent bits from successive channels. In
other systems different channels take turns using the channels for a group of
successive pulse-times (a so-called "time slot"), such as voice channels in E1/T1
landline systems or wireless GSM systems. What distinguishes coarse time-division
multiplexing from packet switching is that the time-slots are pre-allocated to the
channels, rather than arbitrated on a per-time slot basis. Since it interfaces between
VoIP and GSM networks, SS-16 VOIP-2-GSM also performs conversion between
TDM and packet-switching!
UDP
– Acronym for User Datagram Protocol. It is a simpler protocol than TCP/IP that
corresponds to the transport layer of the ISO/OSI model. UDP converts the messages
generated by the application into data packets to be sent through IP, but does not
check if the messages have been transmitted correctly or not.
UDP allows individual packets to be dropped (with no retries) and UDP packets to be
received in a different order than they were sent. Consequently UDP is more efficient
but less reliable than TCP and is used to different purposes - primarily for
broadcasting messages over a network. With UDP, reliability is wholly in charge of the
application that generates the message.
UDP is used often in applications such as videoconferencing or games where optimal
performance is preferred over guaranteed message delivery.
VoIP
- Acronym for
Voice over IP
. It describes the hardware or software category
which allows people to make phone calls over the Internet. The voice signals are
converted in data packets and these are sent on the public telephonic lines, avoiding
the costs of the PSTN network. The VoIP applications can be used with a regular
microphone and computer speakers, but IP phones or VoIP speakers can also can be
used, providing an identical experience like the regular telephony. The quality and the
reliability of the VoIP technology improved so much that many users completely
renounced the standard telephony contracts for VoIP technology.
