IM01-Industrial communications
Unit 5 Industrial Ethernet
Industrial Ethernet is now the most important system of
communications. Its use as a standard for internet
communications is actually also the system which is
used by the new industrial equipment, including in field
bus applications.
TO KNOW MORE
If you want to learn more, you can check the following information about this.
http://www.automation.siemens.com/mcms/automation/en/industrialrofibus/pages/default.aspx
1.1. The wire
The cable connector Ethernet uses 4 pairs of twisted together (UTP) cables. In industry, this
cable is reinforced with wire mesh and a more resistant coating (STP)
1.2. The connections
The connector used in Ethernet bus is the showed in the figure: the RJ45 connector. It has 8
points of connexion and each one should be used with a cable in the correct order.
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We need a special tool for the connection of the RJ-45 with the
cable: the crimper.
The distribution of the Ethernet net is always in
star. The hub is the most basic device
connection. It is used in local networks with a
limited number of machines. It is more than a
multiple RJ45 jack that amplifies the signal from
the network (base 10/100).
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1.3. Ethernet (Internet) protocol
The Internet protocol family is a set of network protocols on which the Internet is based and
which allows the transmission of data between computer networks. It is sometimes called the
TCP / IP protocols, referring to the two most important protocols that compose it: the
Transmission Control Protocol (TCP) and Internet Protocol (IP).
An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g.,
computer, printer) participating in a computer network that uses the Internet Protocol for
communication. An IP address serves two principal functions: host or network
interface identification and location addressing. Its role has been characterized as follows:
"A name indicates what we seek. An address indicates where it is. A route indicates how to get
there."
The designers of the Internet Protocol defined an IP address as a 32-bit number consisting of 4
octets and this system, known as Internet Protocol Version 4 (IPv4), is still in use today.
However, due to the enormous growth of the Internet and the predicted depletion of available
addresses, a new version of IP (IPv6), using 128 bits for the address, was developed in
1995. IPv6 was standardized as RFC 2460 in 1998, and its deployment has been ongoing since
the mid-2000s.
IP addresses are binary numbers, but they are usually stored in text files and displayed
in human-readable notations, such as 172.16.254.1 (for IPv4), and 2001:db8:0:1234:0:567:8:1
(for IPv6).
The Internet Assigned Numbers Authority (IANA) manages the IP address space allocations
globally and delegates five regional Internet registries (RIRs) to allocate IP address blocks
to local Internet registries (Internet service providers) and other entities.
IP subnetworks.
IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP
address is logically recognized as consisting of two parts: the network prefix and the host
identifier, or interface identifier (IPv6). The subnet mask or the CIDR prefix determines how the
IP address is divided into network and host parts.
The term subnet mask is only used within IPv4. Both IP versions however use the CIDR concept
and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits
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used for the network part, also called the routing prefix. For example, an IPv4 address and its
subnet mask may be 192.0.2.1 and 255.255.255.0, respectively. The CIDR notation for the
same IP address and subnet is 192.0.2.1/24, because the first 24 bits of the IP address
indicates the network and subnet.
IP address assignment
Internet Protocol addresses are assigned to host either a new at the time of booting, or
permanently by fixed configuration of its hardware or software. Persistent configuration is also
known as using a static IP address. In contrast, in situations when the computer's IP address is
assigned newly each time, this is known as using a dynamic IP address.
Methods
Static IP addresses are manually assigned to a computer by an administrator. The exact
procedure varies according to platform. This contrasts with dynamic IP addresses, which are
assigned either by the computer interface or host software itself, as in Zero conf, or assigned by
a server using Dynamic Host Configuration Protocol (DHCP). Even though IP addresses
assigned using DHCP may stay the same for long periods of time, they can generally change. In
some cases, a network administrator may implement dynamically assigned static IP addresses.
In this case, a DHCP server is used, but it is specifically configured to always assign the same
IP address to a particular computer. This allows static IP addresses to be configured centrally,
without having to specifically configure each computer on the network in a manual procedure.
In the absence or failure of static or stateful (DHCP) address configurations, an operating
system may assign an IP address to a network interface using state-less auto-configuration
methods, such as Zero configuration.
Uses of dynamic address assignment
IP addresses are most frequently assigned dynamically on LANs and broadband networks by
the Dynamic Host Configuration Protocol (DHCP). They are used because it avoids the
administrative burden of assigning specific static addresses to each device on a network. It also
allows many devices to share limited address space on a network if only some of them will be
online at a particular time. In most current desktop operating systems, dynamic IP configuration
is enabled by default so that a user does not need to manually enter any settings to connect to a
network with a DHCP server. DHCP is not the only technology used to assign IP addresses
dynamically. Dialup and some broadband networks use dynamic address features of the Pointto-Point Protocol.
HIGHLIGHTS

Ethernet uses 8 cables, 4 pairs twisted together.

Each cable finishes in a RJ45 connector.

All the distribution of Ethernet is in star. The key element in this distribution is the
HUB.

Ethernet uses the IP address. Each element has an IP address and a subnet
mask. Both determine the elements connected in a specific net.

IP is a 32 bits number, 4 bytes, expressed as a decimal number (IPv4).

Subnet mask has the same structure as IP address.

IP address can be given by the administrator (manual assignment) or
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automatically by the Host.
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