Automation Networking, IP Address, Class of IP Address, Protocols, RS-232, RS-422, RS-485

1. SHIVAM SINGH
PROJECT ENGINEER
+91-8527199116
shivam.technisys@gmail.com

2. Network Architecture
Network architecture is a blueprint of the complete computer
communication network, which provides a framework and technology
foundation for designing, building and managing a communication
network.

Anyone is free to design hardware and software based on the network
architecture.

The TCP/IP network architecture, which the Internet is based on, is such
as open network architecture and it is adopted as a worldwide network
standard and widely deployed in local area network (LAN), wide area
network (WAN), small and large enterprises, and last but not the
least, the Internet.

Open Systems Interconnection (OSI) network architecture, developed by
International Organization for Standardization, is an open standard for
communication in the network across different equipment and
applications by different vendors.

Network architecture provides only a conceptual framework for
communications between computers. Actual communication is defined by
various communications protocols.

3. OSI 7 Layers Model
Open Systems Interconnection (OSI) model is a reference model
developed by ISO (International Organization for Standardization) in
1984, as a conceptual framework of standards for communication in
the network across different equipment and applications by different
vendors.

4. OSI 7 Layers Model……

The OSI model defines the communications process into 7 layers, dividing the
tasks involved with moving information between networked computers into
seven smaller, more manageable task groups.

Basically, layers 7 through 4 deals with end to end communications between
data source and destinations, while layers 3 to 1 deal with communications
between network devices.

On the other hand, the seven layers of the OSI model can be divided into two
groups:
Upper layers (layers 7, 6 & 5) and
Lower layers (layers 4, 3, 2, 1).

The upper layers of the OSI model deal with application issues and generally
are implemented only in software. The highest layer, the application layer, is
closest to the end user.

The lower layers of the OSI model handle data transport issues. The physical
layer and the data link layer are implemented in hardware and software. The
lowest layer, the physical layer, is closest to the physical network medium (the
wires, for example) and is responsible for placing data on the medium.

5. OSI 7 Layers Model……

Layer 7: Application Layer
• Defines interface to user processes for communication and data transfer in network.
• Provides standardized services such as virtual terminal, file and job transfer and
operations.

Layer 6: Presentation Layer
• Masks the differences of data formats between dissimilar systems.
• Specifies architecture-independent data transfer format.
• Encodes and decodes data; encrypts and decrypts data; compresses and
decompresses data.

Layer 5: Session Layer
• Manages user sessions and dialogues.
• Controls establishment and termination of logic links between users.
• Reports upper layer errors.

Layer 4: Transport Layer
• Provides reliable and sequential packet delivery through error recovery and flow
control mechanisms.
• Provides connectionless oriented packet delivery and Manages end-to-end message
delivery in network.

6. OSI 7 Layers Model……

Layer 3: Network Layer
• Determines how data are transferred between network devices
• Routes packets according to unique network device addresses
• Provides flow and congestion control to prevent network resource depletion

Layer 2: Data Link Layer
• Defines procedures for operating the communication links
• Frames packets
• Detects and corrects packets transmit errors

Layer 1: Physical Layer
• Defines physical means of sending data over network devices
• Interfaces between network medium and devices
• Defines optical, electrical and mechanical characteristics

7. Internet Protocol (IP)
The Internet protocols are the world’s most popular opensystem (nonproprietary) protocol suite because they can be
used to communicate across any set of interconnected
networks and are equally well suited for LAN and WAN
communications.

The Internet protocols consist of a suite of communication
protocols, of which the two best known are the
Transmission Control Protocol (TCP) and the Internet
Protocol (IP).

The Internet protocol suite not only includes lower-layer
protocols (such as TCP and IP), but it also specifies common
applications such as electronic mail, terminal emulation,
and file transfer.

9. IP Addressing
As with any other network-layer protocol, the IP addressing scheme is
integral to the process of routing IP datagrams through an
internetwork.

Each IP address has specific components and follows a basic format.

Each host on a TCP/IP network is assigned a unique 32-bit logical
address that is divided into two main parts: the network number and
the host number.

The network number identifies a network and must be assigned by the
Internet Network Information Center (InterNIC) if the network is to be
part of the Internet.

An Internet Service Provider (ISP) can obtain blocks of network
addresses from the InterNIC and can itself assign address space as
necessary.

The host number identifies a host on a network and is assigned by the
local network administrator.

10. IP Address Format
The 32-bit IP address is grouped eight bits at a time, separated by
dots, and represented in decimal format (known as dotted decimal
notation).

Each bit in the octet has a binary weight (128, 64, 32, 16, 8, 4, 2, and
1). The minimum value for an octet is 0, and the maximum value for an
octet is 255.

11. IP Address ClassesIP addressing supports five different address classes: A, B, C, D, and
E. Only classes A, B, and C are available for commercial use. The
left-most (high-order) bits indicate the network class.

12. IP Address Classes……

13. IP Subnet Addressing
IP networks can be divided into smaller networks called
sub-networks (or subnets).

Sub-netting provides the network administrator with
several benefits, including extra flexibility, more efficient
use of network addresses, and the capability to contain
broadcast traffic (a broadcast will not cross a router).

Subnets are under local administration. As such, the
outside world sees an organization as a single network and
has no detailed knowledge of the organization’s internal
structure.

A given network address can be broken up into many subnetworks.
For
example,
172.16.1.0,
172.16.2.0,
172.16.3.0, and 172.16.4.0 are all subnets within network
171.16.0.0. (All 0s in the host portion of an address
specifies the entire network.)

14. Transmission Control Protocol (TCP)
The TCP provides reliable transmission of data in an IP environment.
TCP corresponds to the transport layer (Layer 4) of the OSI reference
model. Among the services TCP provides are stream data
transfer, reliability, efficient flow control, full-duplex operation, and
multiplexing.

TCP offers reliability by providing connection-oriented, end-to-end
reliable packet delivery through an internetwork. It does this by
sequencing bytes with a forwarding acknowledgment number that
indicates to the destination the next byte the source expects to
receive.

TCP offers efficient flow control, which means that, when sending
acknowledgments back to the source, the receiving TCP process
indicates the highest sequence number it can receive without
overflowing its internal buffers.

Full-duplex operation means that TCP processes can both send and
receive at the same time. Finally, TCP’s multiplexing means that
numerous simultaneous upper-layer conversations can be multiplexed
over a single connection.

15. User Datagram Protocol (UDP)
The User Datagram Protocol (UDP) is a connectionless transport-layer
protocol (Layer 4) that belongs to the Internet protocol family.

UDP is basically an interface between IP and upper-layer processes.
UDP protocol ports distinguish multiple applications running on a single
device from one another.

Unlike the TCP, UDP adds no reliability, flow-control, or error-recovery
functions to IP. Because of UDP’s simplicity, UDP headers contain fewer
bytes and consume less network overhead than TCP.

UDP is useful in situations where the reliability mechanisms of TCP are
not necessary, such as in cases where a higher-layer protocol might
provide error and flow control.

UDP is the transport protocol for several well-known application-layer
protocols, including Network File System (NFS), Simple Network
Management Protocol (SNMP), Domain Name System (DNS), and Trivial
File Transfer Protocol (TFTP).

17. Serial Communication
The RS stands for Recommended Standard. Nothing was really agreed upon or
official. At least not in the sense of the "made-by-committee" standards like IEEE1284 and IEEE-1394.

Simplex can be viewed as a communications "one-way street". Data only flows in
one direction. That is to say, a device can be a receiver or a transmitter
exclusively. A simplex device is not a transceiver. A good example of simplex
communications is an FM radio station and your car radio

Duplex communications overcome the limits of Simplex communications by
allowing the devices to act as transceivers. Duplex communication data flows in
both directions thereby allowing verification and control of data
reception/transmission.

Full Duplex devices can transmit and receive data at the same time. RS232 is a
fine example of Full Duplex communications. There are separate transmit and
receive signal lines that allow data to flow in both directions simultaneously.
RS422 devices also operate Full Duplex.

Half Duplex devices have the dubious honor of allowing both transmission and
receiving, but not at the same time. Essentially only one device can transmit at a
time while all other half duplex devices receive. Devices operate as transceivers,
but not simultaneous transmit and receive

18. DCE and DTE Devices
DTE stands for Data Terminal Equipment, and DCE stands for Data
Communications Equipment.

These terms are used to indicate the pin-out for the connectors
on a device and the direction of the signals on the pins.

Your computer is a DTE device, while most other devices such as
modem and other serial devices are usually DCE devices.
DTE
DCE
25 pin male pin-out
25 pin female pin-out
Pin 1 - Shield Ground
Pin 1 - Shield Ground
Pin 2 - Transmitted Data (TD) output
Pin 2 - Transmitted Data (TD) input
Pin 3 - Receive Data (RD) input
Pin 3 - Receive Data (RD) output
Pin 4 - Request To Send (RTS) output
Pin 4 - Request To Send (RTS) input
Pin 5 - Clear To Send (CTS) input
Pin 5 - Clear To Send (CTS) output
Pin 6 - Data Set Ready (DSR) input
Pin 6 - Data Set Ready (DSR) output
Pin 7 - Signal Ground
Pin 7 - Signal Ground
Pin 8 - Carrier Detect (CD) input
Pin 8 - Carrier Detect (CD) output
Pin
20
(DTR) output
Data
Terminal
Pin 22 - Ring Indicator (RI) input
Ready Pin
20
(DTR) input
Data
Terminal
Pin 22 - Ring Indicator (RI) output
Ready

19. Synchronous Data Transfer-

In program-to-program communication, synchronous
communication requires that each end of an exchange of
communication respond in turn without initiating a new
communication.

A typical activity that might use a synchronous protocol
would be a transmission of files from one point to another.

As each transmission is received, a response is returned
indicating success or the need to resend.

20. Asynchronous Data Transfer
The term asynchronous is usually used to describe
communications in which data can be transmitted intermittently
rather than in a steady stream.

For example, a telephone conversation is asynchronous because
both parties can talk whenever they like.

If the communication were synchronous, each party would be
required to wait a specified interval before speaking.

The difficulty with asynchronous communications is that the
receiver must have a way to distinguish between valid data and
noise.

In computer communications, this is usually accomplished
through a special start bit and stop bit at the beginning and end
of each piece of data. For this reason, asynchronous
communication is sometimes called Start-Stop Transmission.

21. Handshaking
Handshaking is a procedure used to check the link between DTE
& DCE before transmitting of data.

Data is transmitted and received on pins 2 and 3 respectively (for
both types 25 & 9 pin).
1. DTE would request to send data to DCE (RTS).
2. The DCE will indicate to DTE that it is ready and clear to send
data (CTS).

Both RTS and CTS therefore used to control data flow between
DTE & DCE. Data Set Ready (DSR) is an indication from the DCE
(i.e., the modem) that it is ON.

Similarly, DTR (i.e., the PC) indicates to the Data Set that the
DTE is on. Data Carrier Detect (CD) indicates that a good carrier
is being received from the remote modem.

22. RS-232
RS-232 (Recommended standard-232) is a standard interface
approved by the Electronic Industries Association (EIA) for
connecting serial devices.

In other words, RS-232 is a long established standard that
describes the physical interface and protocol for relatively lowspeed serial data communication between computers and related
devices.

An industry trade group, the EIA, defined it originally for
teletypewriter devices. In 1987, the EIA released a new version
of the standard and changed the name to EIA-232-D. Many
people, however, still refer to the standard as RS-232C, or just
RS- 232.

RS-232 is the interface that your computer uses to talk to and
exchange data with your modem and other serial devices. The
serial ports on most computers use a subset of the RS- 232C
standard.

23. RS-232…….
9-pin D-type connector Pin assignment

24. RS-232…….
25-pin D-type connector
Pin assignment

25. RS-232…….
Type of Cables-
(A) Modem Cable:

A normal modem cable runs straight through with pin 1 to pin 1,
pin 2 to pin 2 etc. The end that will be connected to the terminal
or PC is a female connector, and the end that will be connected
to the modem is male connector.

26. RS-232…….
(B) Null Modem Cables:

When you need to connect two equipment with both (DTE) or
both (DCE), for example connecting two PC's, then in this case
you have to use the cable with below pin connection (25 to 25).
And this is called Null modem cable.
“Connecting 25 pin to 25 pin for Null modem”

27. RS-232…….
“Connecting 9 pin to 9 pin for Null Modem”

28. RS-232…….
“Connecting 9 pin to 25 pin for Null Modem”

29. RS-485
RS-485 allows multiple devices (up to 32) to communicate at
half-duplex on a single pair of wires, plus a ground wire (more on
that later), at distances up to 1200 meters (4000 feet). Both the
length of the network and the number of nodes can easily be
extended using a variety of repeater products on the market.

Data is transmitted differentially on two wires twisted together,
referred to as a “twisted pair.” The properties of differential
signals provide high noise immunity and long distance
capabilities. A 485 network can be configured two ways, “twowire” or “four-wire.”

In a “two-wire” network the transmitter and receiver of each
device are connected to a twisted pair.

“Four-wire” networks have one master port with the transmitter
connected to each of the “slave” receivers on one twisted pair.
The “slave” transmitters are all connected to the “master”
receiver on a second twisted pair.

30. RS-485……

The EIA RS- 485 Specification labels the data wires “A” and
“B”, but many manufacturers label their wires “+” and “-”.

In our experience, the “-” wire should be connected to the “A”
line, and the “+” wire to the “B” line.

Reversing the polarity will not damage a 485 device, but it will
not communicate. This said, the rest is easy: always connect A to
A and B to B.

31. RS-422
The TIA/EIA-422 standard, known as RS422, describes a
communication interface that uses balanced data transmission
over multiple pairs of wires to establish communication from one
transmitter to up to 10 receivers.

At least two twisted pairs of wires are used, one for
communication from the transmitter (usually the master) to the
receivers (usually the slaves), and the other for transmission
from the slaves back to the master.

RS-422 is similar to RS-232, and can be programmed in the same
way, however, offers a few advantages and disadvantages. One
problem is that you need to purchase an RS-422 port or at least
an RS-422 to RS-232 converter, since PC's don't come standard
with this interface. Also, you may find that there are fewer
devices supporting RS-422.

32. RS-422…….
Some advantages are:

1. Long Distance Runs - Up to 500 feet is
generally supported, and with repeaters, even
further distances can be achieved.

2. Multi-Drop - Usually, up to 32 devices can be
connected per port, and even more using
repeaters. Devices are distinguished by unique
addresses that are assigned to each device.

3. Noise Resistant - Since it uses a separate
FLOATING transmit and receive pair (four wires),
it offers better noise immunity than RS-232.

33. Comparison-