Data Communications and

Networks

Abdul-Rahman Mahmood

http://alphapeeler.sourceforge.net

http://pk.linkedin.com/in/armahmood

abdulmahmood-sss twitter.com/alphapeeler

alphapeeler.sourceforge.net/pubkeys/pkey.htm

VC++, VB, ASP

About the instructor –

Roles / Skills

ROLES # Y ORGANIZATIONS

Chief Technology Officer 4.2 Riysoft PVT LTD

Consultant / Head Crypto Div– MOD 3.0 Ministry of Defense , RikSof, SecureBytes, RT Japan, Pyntail, SSS

Proj Manager, Team Lead, OG-I 1.5 National Bank – Head Office (IT Group)

Proj Coord / Analyst / Tech Lead 2.5 Plexus (Global Partner - WSI International, Canada.)

QMR / Proj / Process / HR Manager 1.5 Softech Worldwide L.L.C. (A US based software house )

IT Manager (Computer Engineer) 1.5 Peritech Intl.– Nagoya, Japan

Sr. Software Engineer 3.5 Infinilogic Pvt. Ltd. (A UK based software house)

TECHNICAL SKILLS DETAILS

Languages & Tools C++, C#, ObjectiveC, PHP,ASP,VC,VB,COM,MTS,ATL,HTML,JScript,Qt

Mobile App Development Tools X-Code 3.2/4.0, Titanium. ADT, MS Silverlight 4, Expression Blend

Project Management Dot project, MS Project, Mind manager 6 pro, net office.

Software Architecture Rational rose, Design for databases, Erwin modeler, MS Visio 2003

Quality Assurance Testog, PVCS tracker, Requisite pro, Mantus BT

Configuration & Content Mgmt. Subversion, CVS, VSS, Git, SharePoint, Mambo Server, Wordpress, Durpal

Databases / RDBMS Mysql, Postgres, Oracle, MSSQL, MS Access, SQLite

Server Administration Win server, SUSE Linux, Apache / IIS, postfix, openxpki, samba, privoxy

Reporting Tools Crystal Reports 8.5, Microsoft SQL server reporting Services.

CERTIFICATIONS /

WORKSHOPS

CERTIFICATIONS YEAR INSTITUTION DETAILS

QMR certification 2005 Softech worldwide L.L.C (USA) Quality Management Rep.

Quality Auditing 2005 Pakistan Institute of Quality Control ISO 9001:200

Brainbench CertificationsMS Visual C++, ASP, MS Visual Basic

2001 Brainbench Corporation, 14425 Penrose Place, Suite 150, Chantilly, VA 20151, U.S.A.

VC Transcript ID: 2574319VB Transcript ID: 2574319ASP Transcript ID: 2574319

Microsoft Certified System Engineer 1999 Microsoft Certified System Engineer, training at SSUET Network Admin, IIS , Tech. Support, Internetworking,

Microsoft Certified Professional 1998 Microsoft Corporation, Redmond, WA 98052-6399, U.S.A.

MS Win ServerMCP ID: 1270382

AutoCAD certification 1993 Computer Guide Institute Release 10

WORKSHOPS YEAR INSTITUTION DETAILS

Performance & Load Testing 2009 NUST – SEECS, Islamabad School of Electrical Engineering & Computer Science, NUST,17-1-2009

Network Security 2008 Networkers Society of Pak Sheraton Hotel, Karachi, 7-10-2008.

Microsoft PDC 2007 Microsoft – Pakistan SQL server 2008

AWARD / RECOGNITION

TRAININGSAWARD/RECOGNITION YEAR INSTITUTION DETAILS URL

Revised Embedded OS in Operating Systems book by Dr. William

2011 Prentice Hall – USAISBN-10: 013230998XISBN-13: 9780132309981

Acknowledged by Dr. William Stallings in book preface (7th Edition).(Embedded OS : TinyOS & ECOS)

AlphaPeeler - packaged with Cryptography & Network Security book

2010 Prentice Hall – USADeveloped at SSUET, Karachi –Pakistan

Author of book Dr. William Stallings included this educational tool in his book of cryptography 5th

Edition.

NBP Excellence Award 2007 National Bank of Pakistan Awarded on meritorious achievements.

Certification for Professional Engineer

2000 Pakistan Engineering Council. Reg. # COMP/1343

SOFTEC 98 Award 1998 FAST – ICS, Lahore Implementation of DesignoCAD

PROCOM 98 Award 1998 FAST – ICS, Karachi Implementation of DesignoCAD

AlphaPeeler – Classical cryptography tool

1998-2011

Developed at SSUET - Karachi Most popular educational crypto toolhttp://alphapeeler.sourceforge.net

TEACHING/TRAINING YEAR ORGANIZATION DETAILS URL

Documentation, Linux 2010 Ministry of Defense- Islamabad Delivered training for employees

Decision Making, 360 Employee Evaluations

2008 The Shams Group (Shams Software Services) – USA.

Conducted internal training: Decision Making, 360° evaluations.

Req. Elicitation, RN, Coding Standards

2006 Plexus PVT. LTD. - Karachi SDLC, Development standards & secure coding techniques & tips

PHP, Linux, MySQL 2005 Softech Worldwide LLC - USA open-source technology trainings

Data Communications and

Networks

Chapter 1

Introduction

Definitions

The scope of this course is broad, covering three general areas:

datacommunications,

networking, and

protocols;

Data communications deals with the transmission of signals in a reliable and efficient manner.

Networking deals with the technology and architecture of the communications networks used to interconnect communicating devices.

Definitions

This field is generally divided into the topics of local area networks : (LANs) and (WANs).

1970s - 1980s : merger of the fields of computer science and data communications:

There is no fundamental difference between data processing (computers) and data communications (transmission and switching equipment).

There are no fundamental differences among data, voice, and video communications

The distinction among single-processor computer, multiprocessor computer, local network, metropolitan network, and long-haul network has blurred

Trends Traffic growth, development of new services, and advances in technology.

Service vs throughput rates:

A Communications Model

Source

generates data to be transmitted

Transmitter

Converts data into transmittable signals

Transmission System

Carries data

Receiver

Converts received signal into data

Destination

Takes incoming data

Simplified Communications

Model - Diagram

Key Communications Tasks

Transmission System Utilization (Congestion control)

Interfacing (device with comm. sys)

Signal Generation (form, intensity, interpretable at the receiver)

Synchronization (b/t receiver and transmitter)

Exchange Management

Error detection and correction

Flow control

Addressing and routing

Recovery

Message formatting

Security

Network Management

Simplified Data

Communications Model

Networking

Point to point communication not usually practical

Devices are too far apart

Large set of devices would need impractical number of connections

Solution is a communications network

Simplified Network Model

Wide Area Networks

Large geographical area

Crossing public rights of way

Rely in part on common carrier circuits

Alternative technologies

Circuit switching

Packet switching

Frame relay

Asynchronous Transfer Mode (ATM)

Circuit Switching

Dedicated communications path established for the duration of the conversation

e.g. telephone network

Packet Switching

Data sent out of sequence

Small chunks (packets) of data at a time

Packets passed from node to node between source and destination

Used for terminal to computer and computer to computer communications

Frame Relay

Packet switching systems have large overheads to compensate for errors

Modern systems are more reliable

Errors can be caught in end system

Most overhead for error control is stripped out

Frame Relay is a standardized wide area network technology that specifies the physical and logical link layers of digital telecommunications channels using a packet switching methodology.

Uses variable length packets called frames

Asynchronous Transfer Mode

ATM : sometimes referred to as cell relay, is a culmination of developments in circuit switching and packet switching.

Evolution of frame relay

Little overhead for error control

frame relay uses variable-length packets, called frames, and ATM uses fixed-length packets, called cells.

Range of 10s and 100s of Mbps, and in the Gbps range.

Constant data rate using packet switching technique. ATM can also be viewed as an evolution from circuit switching.With circuit switching, only fixed-data-rate circuits are available to the end system.

Integrated Services Digital

Network

Integrated Services Digital Network (ISDN) is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network.

Designed to replace public telecom system

Wide variety of services

Entirely digital domain

Local Area Networks

Smaller scope

Building or small campus

Usually owned by same organization as attached devices

Data rates much higher

Usually broadcast systems

Now some switched systems and ATM are being introduced

THE INTERNET

ARPANET, which was developed in 1969 by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense.

It was the first operational packet-switching network.

ARPANET began operations in four locations.

Today the number of hosts is in the hundreds of millions, the number of users in the billions, and the number of countries participating nearing 200.

TCP : Vint Cerf and Bob Kahn - May of 1974

TCP/IP protocol suite. This provided the foundation for the Internet.

Key Elements of the Internet

Key Elements of the Internet

The purpose of the Internet, of course, is to interconnect end systems, called hosts;

Network, routers, WAN, LAN, IP datagrams or IP packets, IP address.

LANs are connected to an Internet service provider (ISP) through a point of presence (POP).

The connection is made in a series of steps starting with the customer premises equipment (CPE). The CPE is the communications equipment located onsite with the host.

For home users, the CPE is a 56-kbps modem, DSL, cable modem, and satellite

PROTOCOL

ARCHITECTURE,TCP/IP,

AND INTERNET-BASED

APPLICATIONS

To destroy communication completely, there must be no

rules in common between transmitter and receiver—

neither of alphabet nor of syntax.

—On Human Communication, Colin Cherry

Protocol architecture

A protocol architecture is the layered structure of hardware and software that supports the exchange of data between systems and supports distributed applications, such as electronic mail and file transfer

The most widely used protocol architecture is the TCP/IP protocol suite, which consists of the following layers: physical, network access, internet, transport, and application.

Another important protocol architecture is the seven-layer OSI model. (Open Systems Interconnection)

Protocols

Used for communications between entities in a system

Must speak the same language

Entities

User applications

e-mail facilities

terminals

Systems

Computer

Terminal

Remote sensor

Key Elements of a Protocol

Communication is achieved by having the corresponding, or peer, layers in two systems. The peer layers communicate by means of formatted blocks of data that obey a set of rules known as a protocol. The key features of a protocol are as follows:

Syntax

Data formats

Signal levels

Semantics

Control information

Error handling

Timing

Speed matching

Sequencing

Protocol Architecture

Task of communication broken up into modules

For example file transfer could use three modules

File transfer application

Communication service module

Network access module

Simplified File Transfer

Architecture

A Three Layer Model

Network Access Layer

Transport Layer

Application Layer

Network Access Layer

Exchange of data between the computer and the network

Sending computer provides address of destination

May invoke levels of service

Dependent on type of network used (LAN, packet switched etc.)

Transport Layer

Reliable data exchange

Independent of network being used

Independent of application

Application Layer

Support for different user applications

e.g. e-mail, file transfer

Addressing Requirements

Two levels of addressing required

Each computer needs unique network address

Each application on a (multi-tasking) computer needs a unique address within the computer

The service access point or SAP

Protocol Data Units (PDU)

At each layer, protocols are used to communicate

Control information is added to user data at each layer

Transport layer may fragment user data

Each fragment has a transport header added

Destination SAP

Sequence number

Error detection code

This gives a transport protocol data unit

Network PDU

Adds network header

network address for destination computer

Facilities requests

Operation of a Protocol

Architecture

TCP/IP Protocol Architecture

Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET)

Used by the global Internet

No official model but a working one.

Application layer

Host to host or transport layer

Internet layer

Network access layer

Physical layer

TCP / IP Layers

Physical layer (physical interface of a device and transmission media)

Network access layer (exchange of data between an end system and the network to which it Is attached)

Internet layer (provide the routing function across multiple networks)

Host-to-host, or transport layer (manages reliability of data)

Application layer (contains the logic needed to support the various user applications)

TCP/IP Protocol Architecture

Model

Need For Protocol Architecture

data exchange can involve complex procedures, cf. file transfer example

better if task broken into subtasks

implemented separately in layers in stack

each layer provides functions needed to perform comms for layers above

using functions provided by layers below

peer layers communicate with a protocol

Key Elements of a Protocol

syntax - data format

semantics - control info & error handling

timing - speed matching & sequencing

TCP/IP Protocol Architecture

developed by US Defense Advanced Research Project Agency (DARPA)

for ARPANET packet switched network

used by the global Internet

protocol suite comprises a large collection of standardized protocols

Simplified Network

Architecture

TCP/IP Layers

no official model but a working one Application layer

Host-to-host, or transport layer

Internet layer

Network access layer

Physical layer

Physical Layer

concerned with physical interface between computer and network

concerned with issues like:

characteristics of transmission medium

signal levels

data rates

other related matters

Network Access Layer

exchange of data between an end system and attached network

concerned with issues like :destination address provision

invoking specific services like priority

access to & routing data across a network link between two attached systems

allows layers above to ignore link specifics

Internet Layer (IP)

routing functions across multiple networks

for systems attached to different networks

using IP protocol

implemented in end systems and routers

routers connect two networks and relays data between them

Transport Layer (TCP)

common layer shared by all applications

provides reliable delivery of data

in same order as sent

commonly uses TCP

Application Layer

provide support for user applications

need a separate module for each type of application

Operation of TCP and IP

Addressing Requirements

two levels of addressing required

each host on a subnet needs a unique global network address

its IP address

each application on a (multi-tasking) host needs a unique address within the host

known as a port

Operation of TCP/IP

Transmission Control

Protocol (TCP)

usual transport layer is (TCP)

provides a reliable connection for transfer of data between applications

a TCP segment is the basic protocol unit

TCP tracks segments between entities for duration of each connection

TCP Header

User Datagram Protocol

(UDP)

an alternative to TCP

no guaranteed delivery

no preservation of sequence

no protection against duplication

minimum overhead

adds port addressing to IP

Applications : SNMP

UDP Header

IP Header

IPv6 Header

TCP/IP Applications

have a number of standard TCP/IP applications such as

Simple Mail Transfer Protocol (SMTP)

File Transfer Protocol (FTP)

Telnet

Some TCP/IP Protocols

OSI

Open Systems Interconnection

developed by the International Organization for Standardization (ISO)

has seven layers

is a theoretical system delivered too late!

TCP/IP is the de facto standard

OSI Layers

OSI v TCP/IP

Standardized Protocol

Architectures

Layer Specific Standards

Service Primitives and

Parameters

define services between adjacent layers using:

primitives to specify function performed

parameters to pass data and control info

Primitive TypesREQUEST A primitive issued by a service user to invoke some

service and to pass the parameters needed to specify

fully the requested service

INDICATION A primitive issued by a service provider either to:

indicate that a procedure has been invoked by the peer

service user on the connection and to provide the

associated parameters, or

notify the service user of a provider-initiated action

RESPONSE A primitive issued by a service user to acknowledge or

complete some procedure previously invoked by an

indication to that user

CONFIRM A primitive issued by a service provider to acknowledge

or complete some procedure previously invoked by a

request by the service user

Traditional vs Multimedia

Applications

traditionally Internet dominated by info retrieval applications

typically using text and image transfer

eg. email, file transfer, web

see increasing growth in multimedia applications

involving massive amounts of data

such as streaming audio and video

Elastic and Inelastic Traffic

elastic traffic

can adjust to delay & throughput changes over a wide range

eg. traditional “data” style TCP/IP traffic

some applications more sensitive though

inelastic traffic

does not adapt to such changes

eg. “real-time” voice & video traffic

need minimum requirements on net arch

Multimedia Technologies

Summary

introduced need for protocol architecture

TCP/IP protocol architecture

OSI Model & protocol architecture standardization

traditional vs multimedia application needs

Further Reading

Stallings, W. Data and Computer Communications (6th edition), Prentice Hall 1999 chapter 1

Web site for Stallings book

www.shore.net/~ws/DCC6e.html

Web sites for IETF, IEEE, ITU-T, ISO

Internet Requests for Comment (RFCs)

Usenet News groups

comp.dcom.*

comp.protocols.tcp-ip