Technical data

Chapter 4 Deployment Manual VIPA System 300S SPEED7
4-8 HB140E - CP - RE_343-1EX71 - Rev. 09/46
TCP/IP protocols are available on all major systems. At the bottom end this
applies to simple PCs, through to the typical mini-computer up to
mainframes.
For the wide spread of Internet accesses and connections, TCP/IP is often
used to assemble heterogeneous system pools.
TCP/IP, standing for Transmission Control Protocol and Internet Protocol,
collects a various range of protocols and functions.
TCP and IP are only two of the protocols required for the assembly of a
complete architecture. The application layer provides programs like "FTP"
and "Telnet" for the PC.
The application layer of the Ethernet CP 343S-NET - SPEED-Bus is
defined with the user application using the standard handling blocks.
These user applications use the transport layer with the protocols TCP and
UDP for the data transfer which themselves communicate via the IP
protocol with the Internet layer.
The Internet protocol covers the network layer (Layer 3) of the ISO/OSI
layer model.
The purpose of IP is to send data packages from on PC to another passing
several other PCs. These data packages are referred to as datagrams.
The IP doesn't neither guarantee the correct sequence of the datagrams
nor the delivery at the receiver.
For the unambiguous identification between sender and receiver 32Bit
addresses (IP addresses) are used that are normally written as four octets
(exactly 8Bit), e.g. 172.16.192.11.
These Internet addresses are defined and assigned worldwide from the
DDN network (Defense Department Network), thus every user may
communicate with all other TCP/IP users.
One part of the address specifies the network; the rest serves the
identification of the participants inside the network. The boarder between
the network and the host part is variable and depends on the size of the
network.
To save IP addresses, so called
NAT router are used that have one official
IP address and cover the network. Then the network can use any IP
address.
The TCP (
Transmission Control Protocol) bases directly on the IP and
thus covers the transport layer (layer 4) of the ISO/OSI layer model. TCP is
a connection orientated end-to-end protocol and serves the logic
connection between two partners.
TCP guarantees the correct sequence and reliability of the data transfer.
Therefore you need a relatively large protocol overhead that slows down
the transfer speed.
Every datagram gets a header of at least 20Byte. This header also
contains a sequence number identifying the series. This has the
consequence that the single datagrams may reach the destination on
different ways through the network.
Using TCP connections, the telegram length is not transmitted. This means
that the recipient has to know how many bytes belong to a message. To
transfer data with variable length you may begin the user data with the
length information and evaluate this at the counter station.
TCP/IP
IP
TCP