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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